// selfhost/cmd/wwc/cgen.ww — port of cmd/6c/cgen.c.
//
// Status: GROWING. Each subsystem we add is verified by `wwdump_ww -c`
// producing byte-identical output to C-side `6c` for the same source,
// then by assembling + linking + running the result.
//
// Current coverage:
//   - decls:  N_FILE, N_FNDECL (params, frame for locals, prologue
//             + dual-epilogue suppression; FFI body-less fn skipped)
//   - stmts:  N_BLOCK, N_RETURN, N_EXPRSTMT, N_LET (no init),
//             N_LET (int-literal / ident / call / N_BIN init),
//             N_IF (with optional else), N_FOR (cond-only and full
//             init/cond/post), N_BREAK, N_CONTINUE
//   - exprs:  N_INTLIT, N_IDENT (local/param), N_BIN with full op
//             coverage (+/-/*/// %, &/|/^, <</>>, comparisons with
//             signed-vs-unsigned dispatch, &&/||), N_UN (- ! ~ &amp; *),
//             N_CALL (recursive R-to-L push, pop into argregs L-to-R),
//             N_ASSIGN to local idents (plain and compound +=/-=)
//
// Type info is shallow — frame slots are 8 bytes per local, all loads
// /stores are MOVQ. Programs that mix i8/i32/i64 locals work but spill
// 8 bytes per local. Float, str, slice, struct, match, defer, alloc,
// tagged-union return — none of those are wired yet.

use os;
use mem;
use ast;
use tok;
use typ;
use sym;
use strconv;

// ---- typedef alias registry -----------------------------------------
//
// `type error = str;` makes `error` a struct-shape alias. We track
// alias→target so is_str_type / is_slice_type / struct_lookup can
// resolve through the chain. Only direct N_TNAME aliases are mapped;
// `type p = struct {...}` is handled by collect_structs.

type alias_ent = struct {
	aname:   str,
	target:  *node,	// the rhs type expr
	aanext:  *alias_ent,
};

fn collect_aliases(c: *cgen, file: *node) void = {
	c.aliases = nil;
	let d: *node = file.list;
	for (d != nil) {
		if (d.kind == N_TYPEDECL) {
			let body: *node = d.lhs;
			if (body != nil) {
				if (body.kind != N_TSTRUCT) {
					let a: *alias_ent = amalloc(c.a, 32u64): *alias_ent;
					a.aname = d.str;
					a.target = body;
					a.aanext = c.aliases;
					c.aliases = a;
				};
			};
		};
		d = d.next;
	};
};

fn alias_lookup(c: *cgen, name: str) *node = {
	let a: *alias_ent = c.aliases;
	for (a != nil) {
		let an: str = a.aname;
		if (streq(an, name)) { return a.target; };
		a = a.aanext;
	};
	return nil;
};

// resolve_type — follow typedef alias chains to a "canonical" type
// expr (str/slice/array/struct/...). Stops on cycles via depth limit.
fn resolve_type(c: *cgen, t: *node) *node = {
	let cur: *node = t;
	let depth: i32 = 0;
	for (depth < 16) {
		if (cur == nil) { return nil; };
		if (cur.kind != N_TNAME) { return cur; };
		let nm: str = cur.str;
		let next: *node = alias_lookup(c, nm);
		if (next == nil) { return cur; };
		cur = next;
		depth += 1;
	};
	return cur;
};

// ---- struct registry ------------------------------------------------
//
// Per-file map from struct name → list of fields with computed offsets
// and sizes. Built when cg_file walks N_TYPEDECL with N_TSTRUCT lhs.
// N_DOT and N_ASSIGN consult this to resolve `s.field` for struct or
// *struct bases.

type field_info = struct {
	fname: str,
	foff:  i32,
	fsz:   i32,
	tnode: *node,	// the field type expr, for nested struct lookups
	finext: *field_info,
};

type struct_info = struct {
	sname:    str,
	fields:   *field_info,
	tot_size: i32,
	sinext:   *struct_info,
};

// ---- locals / frame --------------------------------------------------

type local = struct {
	name:  str,
	off:   i32,
	tnode: *node,	// declared type expr (N_TNAME / N_TPTR / ...) or nil
	lnext: *local,
};

// strlit — interned string literal record. Emitted as a DATA directive
// after all functions; cgexpr N_STRLIT loads (LEAQ ptr, MOVQ len).
type strlit = struct {
	label: str,	// "_S_<seq>"
	bytes: str,
	slnext: *strlit,
};

// ffi — `@symbol("name")` mapping. Body-less fn `foo` with this attr
// gets its CALL target rewritten to `name`.
type ffi = struct {
	ident:  str,
	symbol: str,
	fnext:  *ffi,
};

def LOOP_MAX: i32 = 16;

type cgen = struct {
	a:        *arena,
	locals:   *local,
	frame:    i32,
	last_was_return: i32,
	labelseq: i32,
	strlit_seq: i32,
	strlits: *strlit,
	ffis:    *ffi,
	defs:    *def_ent,
	fnrets:  *fnret,
	aliases: *alias_ent,
	structs: *struct_info,
	fn_name:  str,
	fn_ret:   *node,	// declared return type of current fn (or nil)
	loop_top: i32,
	loop_end_buf:  *str,	// stack of end labels for break
	loop_cont_buf: *str,	// stack of cont labels for continue
};

fn cgen_init(c: *cgen, a: *arena) void = {
	c.a = a;
	c.locals = nil;
	c.frame = 0;
	c.last_was_return = 0;
	c.labelseq = 0;
	// Note: strlit_seq, strlits, ffis are *not* reset here; they
	// persist across cgfn calls within one file. cg_file resets them
	// at the start of each compilation unit.
	c.loop_top = 0;
	c.loop_end_buf  = amalloc(a, (LOOP_MAX: u64) * 16u64): *str;
	c.loop_cont_buf = amalloc(a, (LOOP_MAX: u64) * 16u64): *str;
};

// local_alloc — append a slot for `name` without dedup. Used for
// match-arm bindings, which C cgen allocates via cgexpr's by-value
// `locals` list — so two separate matches each get fresh slots even
// when their bind names collide. scan_locals follows the same rule
// for N_MCASE.
fn local_alloc(c: *cgen, name: str, sz: i32, tnode: *node) i32 = {
	let asz: i32 = sz;
	if (asz < 8) { asz = 8; };
	if ((asz & 7) != 0) { asz = (asz + 7) & ~7; };
	c.frame += asz;
	let off: i32 = 0 - c.frame;
	let l: *local = amalloc(c.a, 48u64): *local;
	l.name = name;
	l.off = off;
	l.tnode = tnode;
	l.lnext = c.locals;
	c.locals = l;
	return off;
};

fn local_add(c: *cgen, name: str, sz: i32, tnode: *node) i32 = {
	// Name-based slot reuse for N_LETs and params: if `name` is
	// already declared in this function, return its existing
	// offset. Mirrors C cgen (cmd/6c/cgen.c:localoff). Two
	// disjoint scopes that declare the same name share one slot —
	// so `escape` in wwdump (three `let cp: pos;` across separate
	// branches) reserves one slot, not three. scan_locals does
	// the matching dedup at prologue time so the SUBQ stays in
	// sync.
	//
	// On a dedup hit we also overwrite the stored tnode to match
	// the new declaration's type. C reads `n->lhs->type` (filled
	// by the checker) at every N_DOT/N_CAST site; we read
	// `lc.tnode`, so it must follow source order. Without this,
	// a later `let m: *node` inside a branch keeps an earlier
	// `let m: i32`'s tnode and `m.next` falls into the SB fallback.
	let cur: *local = c.locals;
	for (cur != nil) {
		let cn: str = cur.name;
		if (streq(cn, name)) {
			cur.tnode = tnode;
			return cur.off;
		};
		cur = cur.lnext;
	};
	return local_alloc(c, name, sz, tnode);
};

// scan_seen_mark — called by scan_locals on every let / match-bind
// site. Returns true if `name` is already tracked in c.locals (so
// the slot will be shared at emission time — no new frame bump).
// Otherwise appends a name-only stub and returns false. Stubs are
// thrown away when cgfn resets c.locals before emission.
fn scan_seen_mark(c: *cgen, name: str) bool = {
	if (local_find_node(c, name) != nil) { return true; };
	let l: *local = amalloc(c.a, 48u64): *local;
	l.name = name;
	l.off = 0;
	l.tnode = nil;
	l.lnext = c.locals;
	c.locals = l;
	return false;
};

fn local_find_node(c: *cgen, name: str) *local = {
	let l: *local = c.locals;
	for (l != nil) {
		let ln: str = l.name;
		if (streq(ln, name)) { return l; };
		l = l.lnext;
	};
	return nil;
};

fn local_find(c: *cgen, name: str) i32 = {
	let l: *local = c.locals;
	for (l != nil) {
		let ln: str = l.name;
		if (ln.len == name.len) {
			let i: i32 = 0;
			let eq: bool = true;
			for (i < name.len) {
				if (ln[i] != name[i]) { eq = false; i = name.len; }
				else { i += 1; };
			};
			if (eq) { return l.off; };
		};
		l = l.lnext;
	};
	return 0;
};

// ---- emit helpers ---------------------------------------------------

fn emit_line(s: str) void = { os.write(1, s.ptr, s.len: u64); };

fn emit_int(v: i64) void = {
	let buf: [32]u8;
	let n: i32 = strconv.i64toa(buf[0:32], v);
	os.write(1, buf.ptr, n: u64);
};

fn emit_uint(v: u64) void = {
	let buf: [32]u8;
	let n: i32 = strconv.u64toa(buf[0:32], v);
	os.write(1, buf.ptr, n: u64);
};

// emit_disp_reg — print "disp(reg)" or "(reg)" when disp == 0, the
// way Plan 9 6c/6a do.
fn emit_disp_reg(off: i64, reg: str) void = {
	if (off != 0i64) { emit_int(off); };
	emit_line("(");
	emit_line(reg);
	emit_line(")");
};

// emit_off — print an integer offset, suppressing it entirely when 0.
// Use before any emit_line("(BP)...") or emit_line("(SB)...") sequence.
// Plan 9 cc convention: "(BP)" not "0(BP)".
fn emit_off(v: i64) void = {
	if (v != 0i64) { emit_int(v); };
};

// mklabel — fresh label "<fnname>_<base>_<seq>". Returns an
// arena-owned str. Mirrors C cgen's mklabel so diffs match.
fn mklabel(c: *cgen, base: str) str = {
	let buf: [128]u8;
	let i: i32 = 0;
	let fname: str = c.fn_name;
	let j: i32 = 0;
	for (j < fname.len) {
		buf[i] = fname[j];
		i += 1; j += 1;
	};
	buf[i] = 95u8; i += 1;	// '_'
	j = 0;
	for (j < base.len) {
		buf[i] = base[j];
		i += 1; j += 1;
	};
	buf[i] = 95u8; i += 1;	// '_'
	let n: i32 = strconv.i64toa(buf[i:128], c.labelseq: i64);
	c.labelseq += 1;
	let total: i32 = i + n;
	let p: *u8 = amalloc(c.a, (total: u64) + 1u64): *u8;
	let k: i32 = 0;
	for (k < total) {
		p[k] = buf[k];
		k += 1;
	};
	p[total] = 0u8;
	let r: str;
	r.ptr = p;
	r.len = total;
	return r;
};

fn emit_label(s: str) void = {
	os.write(1, s.ptr, s.len: u64);
	emit_line(":\n");
};

// ---- string interning ------------------------------------------------
//
// streq is provided by sym.ww and reused here.

// intern_strlit — return a stable label for `bytes`. Dedups by content
// so identical literals share storage.
fn intern_strlit(c: *cgen, bytes: str) str = {
	let s: *strlit = c.strlits;
	for (s != nil) {
		let bs: str = s.bytes;
		if (streq(bs, bytes)) {
			return s.label;
		};
		s = s.slnext;
	};
	// New label "_S_<seq>".
	let buf: [32]u8;
	buf[0] = 95u8; buf[1] = 83u8; buf[2] = 95u8;	// "_S_"
	let n: i32 = strconv.i64toa(buf[3:32], c.strlit_seq: i64);
	c.strlit_seq += 1;
	let total: i32 = 3 + n;
	let p: *u8 = amalloc(c.a, (total: u64) + 1u64): *u8;
	let i: i32 = 0;
	for (i < total) { p[i] = buf[i]; i += 1; };
	p[total] = 0u8;
	let lab: str;
	lab.ptr = p;
	lab.len = total;
	let nw: *strlit = amalloc(c.a, 48u64): *strlit;
	nw.label = lab;
	nw.bytes = bytes;
	nw.slnext = c.strlits;
	c.strlits = nw;
	return lab;
};

// emit_def_constants — DATA directive per top-level int-literal `def`.
// 8 bytes little-endian to match what the C cgen emits.
fn emit_def_constants(c: *cgen, file: *node) void = {
	let d: *node = file.list;
	for (d != nil) {
		if (d.kind == N_DEF) {
			let r: *node = d.rhs;
			let v: u64 = 0u64;
			let ok: bool = false;
			if (r != nil) {
				if (r.kind == N_INTLIT)  { v = r.uval; ok = true; };
				if (r.kind == N_RUNELIT) { v = r.uval; ok = true; };
				if (r.kind == N_TRUE)    { v = 1u64;   ok = true; };
				if (r.kind == N_FALSE)   { v = 0u64;   ok = true; };
				if (r.kind == N_NIL)     { v = 0u64;   ok = true; };
			};
			if (ok) {
				emit_line("DATA ");
				let nm: str = d.str;
				os.write(1, nm.ptr, nm.len: u64);
				emit_line("(SB),\"");
				let i: i32 = 0;
				let n: u64 = v;
				for (i < 8) {
					let b: u8 = (n & 255u64): u8;
					n = n >> 8u64;
					// C emit_defs only special-cases " and \;
					// every other non-printable goes as \xHH.
					if (b == 34u8) { emit_line("\\\""); }
					else { if (b == 92u8) { emit_line("\\\\"); }
					else {
						if (b < 32u8) {
							emit_line("\\x");
							let hi: u8 = b >> 4u8;
							let lo: u8 = b & 15u8;
							let bb: [2]u8;
							if (hi < 10u8) { bb[0] = hi + 48u8; }
							else { bb[0] = (hi - 10u8) + 97u8; };
							if (lo < 10u8) { bb[1] = lo + 48u8; }
							else { bb[1] = (lo - 10u8) + 97u8; };
							os.write(1, bb.ptr, 2u64);
						} else {
							if (b >= 127u8) {
								emit_line("\\x");
								let hi: u8 = b >> 4u8;
								let lo: u8 = b & 15u8;
								let bb: [2]u8;
								if (hi < 10u8) { bb[0] = hi + 48u8; }
								else { bb[0] = (hi - 10u8) + 97u8; };
								if (lo < 10u8) { bb[1] = lo + 48u8; }
								else { bb[1] = (lo - 10u8) + 97u8; };
								os.write(1, bb.ptr, 2u64);
							} else {
								let bb: [1]u8;
								bb[0] = b;
								os.write(1, bb.ptr, 1u64);
							};
						};
					};};
					i += 1;
				};
				emit_line("\"\n");
			};
		};
		d = d.next;
	};
};

// emit_data_section — DATA directives for every interned strlit.
// Trailing NUL appended so .ptr can be used as a C string by syscalls.
fn emit_data_section(c: *cgen) void = {
	let s: *strlit = c.strlits;
	for (s != nil) {
		emit_line("DATA ");
		let lab: str = s.label;
		os.write(1, lab.ptr, lab.len: u64);
		emit_line("(SB),\"");
		let bs: str = s.bytes;
		let i: i32 = 0;
		for (i < bs.len) {
			let b: u8 = bs[i];
			if (b == 34u8) { emit_line("\\\""); }	// "
			else { if (b == 92u8) { emit_line("\\\\"); }	// \
			else { if (b == 10u8) { emit_line("\\n"); }
			else { if (b == 9u8)  { emit_line("\\t"); }
			else { if (b == 13u8) { emit_line("\\r"); }
			else {
				if (b < 32u8) {
					emit_line("\\x");
					let hi: u8 = b >> 4u8;
					let lo: u8 = b & 15u8;
					let bb: [2]u8;
					if (hi < 10u8) { bb[0] = hi + 48u8; }
					else { bb[0] = (hi - 10u8) + 97u8; };
					if (lo < 10u8) { bb[1] = lo + 48u8; }
					else { bb[1] = (lo - 10u8) + 97u8; };
					os.write(1, bb.ptr, 2u64);
				} else {
					if (b >= 127u8) {
						emit_line("\\x");
						let hi: u8 = b >> 4u8;
						let lo: u8 = b & 15u8;
						let bb: [2]u8;
						if (hi < 10u8) { bb[0] = hi + 48u8; }
						else { bb[0] = (hi - 10u8) + 97u8; };
						if (lo < 10u8) { bb[1] = lo + 48u8; }
						else { bb[1] = (lo - 10u8) + 97u8; };
						os.write(1, bb.ptr, 2u64);
					} else {
						let bb: [1]u8;
						bb[0] = b;
						os.write(1, bb.ptr, 1u64);
					};
				};
			};};};};};
			i += 1;
		};
		emit_line("\\x00\"\n");
		s = s.slnext;
	};
};

// ---- fn return-type map ---------------------------------------------
//
// Per-file: ident → ret-type-node. Used to decide whether to shuffle
// (AX, DX) → (AX, BX) after a CALL — needed for str-returning fns so
// the value flows through cgen as the canonical (AX, BX) str pair.

type fnret = struct {
	fname: str,
	rtype: *node,
	frnext: *fnret,
};

fn collect_fnrets(c: *cgen, file: *node) void = {
	c.fnrets = nil;
	let d: *node = file.list;
	for (d != nil) {
		if (d.kind == N_FNDECL) {
			let f: *fnret = amalloc(c.a, 32u64): *fnret;
			f.fname = d.str;
			f.rtype = d.lhs;
			f.frnext = c.fnrets;
			c.fnrets = f;
		};
		d = d.next;
	};
};

fn fnret_lookup(c: *cgen, name: str) *node = {
	let f: *fnret = c.fnrets;
	for (f != nil) {
		let fn_: str = f.fname;
		if (streq(fn_, name)) { return f.rtype; };
		f = f.frnext;
	};
	return nil;
};

// ---- def-constant registry ------------------------------------------
//
// `def NAME: T = LIT;` becomes a DATA symbol the C-side 6c emits; an
// ident reference loads it via `MOVQ NAME(SB), AX`. We collect them at
// file load and consult on N_IDENT lookup.

type def_ent = struct {
	dname: str,
	dnext: *def_ent,
};

fn collect_defs(c: *cgen, file: *node) void = {
	c.defs = nil;
	let d: *node = file.list;
	for (d != nil) {
		if (d.kind == N_DEF) {
			let e: *def_ent = amalloc(c.a, 32u64): *def_ent;
			e.dname = d.str;
			e.dnext = c.defs;
			c.defs = e;
		};
		d = d.next;
	};
};

fn def_lookup(c: *cgen, name: str) bool = {
	let e: *def_ent = c.defs;
	for (e != nil) {
		let dn: str = e.dname;
		if (streq(dn, name)) { return true; };
		e = e.dnext;
	};
	return false;
};

// ---- FFI map ---------------------------------------------------------

fn ffi_collect(c: *cgen, file: *node) void = {
	c.ffis = nil;
	if (file == nil) { return; };
	let d: *node = file.list;
	for (d != nil) {
		if (d.kind == N_FNDECL) {
			let a: *node = d.attr;
			for (a != nil) {
				if (a.kind == N_ATTR) {
					let aname: str = a.str;
					if (streq(aname, "symbol")) {
						let sym_node: *node = a.list;
						if (sym_node != nil) {
							if (sym_node.kind == N_STRLIT) {
								let f: *ffi = amalloc(c.a, 48u64): *ffi;
								f.ident  = d.str;
								f.symbol = sym_node.str;
								f.fnext  = c.ffis;
								c.ffis   = f;
							};
						};
					};
				};
				a = a.next;
			};
		};
		d = d.next;
	};
};

fn ffi_resolve(c: *cgen, ident: str) str = {
	let f: *ffi = c.ffis;
	for (f != nil) {
		let id: str = f.ident;
		if (streq(id, ident)) { return f.symbol; };
		f = f.fnext;
	};
	return ident;
};

// ---- ABI argreg helpers ---------------------------------------------

fn argreg_name(i: i32) str = {
	if (i == 0) { return "DI"; };
	if (i == 1) { return "SI"; };
	if (i == 2) { return "DX"; };
	if (i == 3) { return "CX"; };
	if (i == 4) { return "R8"; };
	if (i == 5) { return "R9"; };
	return "?";
};

// ---- expression cgen -------------------------------------------------

// push_args_rev — recursively walks the arg list, evaluates rightmost
// first, and pushes. str args take two slots (ptr in AX, len in BX);
// the order on the stack so a left-to-right pop into argregs lands
// (ptr, len) correctly is: PUSHQ BX (top), PUSHQ AX (above) — the
// pop sequence then yields AX, then BX.
fn push_args_rev(c: *cgen, arg: *node) i32 = {
	if (arg == nil) { return 0; };
	let rest: i32 = push_args_rev(c, arg.next);
	// N_SLICE expression as arg: `buf[lo:hi]` builds a slice header
	// on the stack matching C cgen's sequence — push base, push hi,
	// compute lo, pop into BX/CX, derive len/ptr, push (cap, len, ptr).
	if (arg.kind == N_SLICE) {
		let base: *node = arg.lhs;
		let lo: *node = arg.rhs;
		let hi: *node = arg.cond;
		let base_local: *local = nil;
		if (base != nil) {
			if (base.kind == N_IDENT) {
				let bn: str = base.str;
				base_local = local_find_node(c, bn);
			};
		};
		// base address → push
		if (base_local != nil) {
			let tn: *node = base_local.tnode;
			if (tn != nil) {
				if (tn.kind == N_TARRAY) {
					emit_line("\tLEAQ\t");
					emit_off(base_local.off: i64);
					emit_line("(BP), AX\n");
				} else {
					emit_line("\tMOVQ\t");
					emit_off(base_local.off: i64);
					emit_line("(BP), AX\n");
				};
			} else {
				emit_line("\tMOVQ\t");
				emit_off(base_local.off: i64);
				emit_line("(BP), AX\n");
			};
		} else {
			cgexpr(c, base);
		};
		emit_line("\tPUSHQ\tAX\n");
		// hi (default base length) → push
		if (hi != nil) {
			cgexpr(c, hi);
		} else { if (base_local != nil) {
			let tn: *node = base_local.tnode;
			if (tn != nil) {
				if (tn.kind == N_TARRAY) {
					let len_n: *node = tn.rhs;
					if (len_n != nil) {
						if (len_n.kind == N_INTLIT) {
							emit_line("\tMOVQ\t$");
							emit_uint(len_n.uval);
							emit_line(", AX\n");
						};
					};
				} else { if (tn.kind == N_TSLICE) {
					emit_line("\tMOVQ\t");
					emit_off((base_local.off + 8): i64);
					emit_line("(BP), AX\n");
				} else { if (tn.kind == N_TNAME) {
					if (streq(tn.str, "str")) {
						emit_line("\tMOVQ\t");
						emit_off((base_local.off + 8): i64);
						emit_line("(BP), AX\n");
					};
				};};};
			};
		} else {
			emit_line("\tMOVQ\t$0, AX\n");
		};};
		emit_line("\tPUSHQ\tAX\n");
		// lo (default 0) → AX
		if (lo != nil) { cgexpr(c, lo); }
		else { emit_line("\tMOVQ\t$0, AX\n"); };
		emit_line("\tPOPQ\tBX\n");           // hi
		emit_line("\tPOPQ\tCX\n");           // base
		emit_line("\tMOVQ\tBX, DX\n");       // DX = hi
		emit_line("\tSUBQ\tAX, DX\n");       // DX = hi - lo = len
		emit_line("\tADDQ\tAX, CX\n");       // CX = base + lo = ptr
		emit_line("\tPUSHQ\tDX\n");          // cap
		emit_line("\tPUSHQ\tDX\n");          // len
		emit_line("\tPUSHQ\tCX\n");          // ptr (top)
		return rest + 3;
	};
	// Slice/tagged ident args: emit per-register MOVQ+PUSHQ pairs in
	// reverse order (cap/v1, len/v0, ptr/tag) so a left-to-right pop
	// into argregs lands the canonical (ptr/tag, len/v0, cap/v1).
	if (arg.kind == N_IDENT) {
		let nm: str = arg.str;
		let lc: *local = local_find_node(c, nm);
		if (lc != nil) {
			let off: i32 = lc.off;
			if (is_slice_type(c, lc.tnode) || is_tagged_type(lc.tnode)) {
				emit_line("\tMOVQ\t");
				emit_off((off + 16): i64);
				emit_line("(BP), AX\n");
				emit_line("\tPUSHQ\tAX\n");
				emit_line("\tMOVQ\t");
				emit_off((off + 8): i64);
				emit_line("(BP), AX\n");
				emit_line("\tPUSHQ\tAX\n");
				emit_line("\tMOVQ\t");
				emit_off(off: i64);
				emit_line("(BP), AX\n");
				emit_line("\tPUSHQ\tAX\n");
				return rest + 3;
			};
		};
	};
	cgexpr(c, arg);
	if (node_isslice(c, arg)) {
		emit_line("\tPUSHQ\tCX\n");
		emit_line("\tPUSHQ\tBX\n");
		emit_line("\tPUSHQ\tAX\n");
		return rest + 3;
	};
	if (node_isstr(c, arg)) {
		emit_line("\tPUSHQ\tBX\n");
		emit_line("\tPUSHQ\tAX\n");
		return rest + 2;
	};
	emit_line("\tPUSHQ\tAX\n");
	return rest + 1;
};

fn node_isslice(c: *cgen, n: *node) bool = {
	if (n == nil) { return false; };
	let k: i32 = n.kind;
	if (k == N_IDENT) {
		let nm: str = n.str;
		let lc: *local = local_find_node(c, nm);
		if (lc != nil) { return is_slice_type(c, lc.tnode); };
		return false;
	};
	if (k == N_SLICE) { return true; };
	return false;
};

// node_isstr — best-effort surface check: does this expression
// evaluate to a str value? Used to drive the call-arg push convention
// (str args take two slots: ptr + len).
fn node_isstr(c: *cgen, n: *node) bool = {
	if (n == nil) { return false; };
	let k: i32 = n.kind;
	if (k == N_STRLIT) { return true; };
	if (k == N_IDENT) {
		let nm: str = n.str;
		let lc: *local = local_find_node(c, nm);
		if (lc != nil) {
			let tn: *node = lc.tnode;
			if (tn != nil) {
				if (tn.kind == N_TNAME) {
					let tnm: str = tn.str;
					if (streq(tnm, "str")) { return true; };
				};
			};
		};
		return false;
	};
	if (k == N_CALL) {
		let callee: *node = n.lhs;
		if (callee != nil) {
			if (callee.kind == N_IDENT) {
				let cnm: str = callee.str;
				let rt: *node = fnret_lookup(c, cnm);
				return is_str_type(c, rt);
			};
		};
		return false;
	};
	if (k == N_DOT) {
		let base: *node = n.lhs;
		let fld: str = n.str;
		// `<expr>.ptr` is *u8 not str; `<expr>.len` is i32 not str.
		if (streq(fld, "ptr")) { return false; };
		if (streq(fld, "len")) { return false; };
		if (streq(fld, "cap")) { return false; };
		if (base != nil) {
			let sname: str;
			sname.ptr = nil; sname.len = 0;
			if (base.kind == N_IDENT) {
				let lc: *local = local_find_node(c, base.str);
				if (lc != nil) {
					let tn: *node = lc.tnode;
					let lkind: i32 = -1;
					if (tn != nil) { lkind = tn.kind; };
					if (lkind == N_TNAME) { sname = tn.str; };
					if (lkind == N_TPTR) {
						let inner: *node = tn.lhs;
						if (inner != nil) {
							if (inner.kind == N_TNAME) { sname = inner.str; };
						};
					};
				};
			};
			// Chained dot (`p.foo.bar`): use dot_inner_struct_ptr
			// to resolve the inner chain to the *struct it lands
			// on, then look up `fld` in that struct.
			if (base.kind == N_DOT) {
				let inner_t: *node = dot_inner_struct_ptr(c, base);
				if (inner_t != nil) {
					if (inner_t.kind == N_TNAME) { sname = inner_t.str; };
				};
			};
			if (sname.len > 0) {
				let si: *struct_info = struct_lookup(c, sname);
				if (si != nil) {
					let fi: *field_info = si.fields;
					for (fi != nil) {
						let fn_: str = fi.fname;
						if (streq(fn_, fld)) {
							return is_str_type(c, fi.tnode);
						};
						fi = fi.finext;
					};
				};
			};
		};
		return false;
	};
	if (k == N_CAST) {
		return is_str_type(c, n.rhs);
	};
	return false;
};

// type_name_isunsigned — true for u8/u16/u32/u64/uint/uintptr.
fn type_name_isunsigned(nm: str) bool = {
	if (streq(nm, "u8"))   { return true; };
	if (streq(nm, "u16"))  { return true; };
	if (streq(nm, "u32"))  { return true; };
	if (streq(nm, "u64"))  { return true; };
	if (streq(nm, "uint")) { return true; };
	if (streq(nm, "uintptr")) { return true; };
	return false;
};

// type_node_isunsigned — recurse through TNAME / TPTR / TSLICE etc.
fn type_node_isunsigned(t: *node) bool = {
	if (t == nil) { return false; };
	if (t.kind == N_TNAME) { return type_name_isunsigned(t.str); };
	return false;
};

// type_is_8byte_primitive — does this type take exactly one 8-byte
// slot (pointer / fn-ptr / 64-bit int / chan / scalar primitive
// padded up to 8) rather than a wider aggregate? Used by N_LET
// zero-init to mirror C cgen's "only zero if sz == 8 at the type
// level" rule. Strings (16), slices (24), tagged unions (>=16),
// tuples (16), structs (varies), arrays — all fall through to
// false here even when their *slot* rounds up to 8.
fn type_is_8byte_primitive(c: *cgen, t: *node) bool = {
	if (t == nil) { return false; };
	let k: i32 = t.kind;
	if (k == N_TPTR)   { return true; };
	if (k == N_TFN)    { return true; };
	if (k == N_TCHAN)  { return true; };
	if (k == N_TSLICE) { return false; };
	if (k == N_TARRAY) { return false; };
	if (k == N_TTUPLE) { return false; };
	if (k == N_TTAGGED){ return false; };
	if (k == N_TNAME) {
		let nm: str = t.str;
		if (streq(nm, "str")) { return false; };
		// Struct alias: not a primitive even if the slot is 8B.
		if (struct_lookup(c, nm) != nil) { return false; };
		// Primitive (i8/u8/.../i64/u64/bool/rune/f32/f64/int/...).
		// All of these get slot-padded to 8 and zero-init in C.
		if (prim_size(nm) > 0) { return true; };
		return false;
	};
	return false;
};

// type_name_issigned — true for i8/i16/i32/i64/int/rune.
fn type_name_issigned(nm: str) bool = {
	if (streq(nm, "i8"))   { return true; };
	if (streq(nm, "i16"))  { return true; };
	if (streq(nm, "i32"))  { return true; };
	if (streq(nm, "i64"))  { return true; };
	if (streq(nm, "int"))  { return true; };
	if (streq(nm, "rune")) { return true; };
	return false;
};

// field_load_op — pick the load instruction for a non-str struct
// field by its declared size + signedness. Mirrors the C cgen op
// dispatch (MOVZBQ for u8/bool/i8, MOVSXD for i32, MOVL for u32, MOVQ
// for 8-byte). f might be nil for fields outside our struct registry.
fn field_load_op(f: *field_info) str = {
	if (f == nil) { return "MOVQ"; };
	let sz: i32 = f.fsz;
	if (sz == 1) { return "MOVZBQ"; };
	if (sz == 4) {
		let t: *node = f.tnode;
		if (t != nil) {
			if (t.kind == N_TNAME) {
				if (type_name_issigned(t.str)) { return "MOVSXD"; };
			};
		};
		return "MOVL";
	};
	return "MOVQ";
};

// field_store_op — pick the store instruction for a non-str struct
// field by its declared size. MOVB for 1, MOVL for 4, MOVQ for 8.
fn field_store_op(f: *field_info) str = {
	if (f == nil) { return "MOVQ"; };
	let sz: i32 = f.fsz;
	if (sz == 1) { return "MOVB"; };
	if (sz == 4) { return "MOVL"; };
	return "MOVQ";
};

// index_base_esz — element size for `arr[i]` where the base is a
// chained-dot pseudo-field `s.ptr` (s being str/*str/slice/*slice).
// For str the element is one byte; for `[]T` / `*[]T` we drill into
// the slice element type.
fn index_base_esz(c: *cgen, base: *node) i32 = {
	if (base == nil) { return 8; };
	if (base.kind != N_DOT) { return 8; };
	let fld: str = base.str;
	let inner: *node = base.lhs;
	if (inner == nil) { return 8; };
	if (inner.kind != N_IDENT) { return 8; };
	let nm: str = inner.str;
	let lc: *local = local_find_node(c, nm);
	if (lc == nil) { return 8; };
	let tn: *node = lc.tnode;
	if (tn == nil) { return 8; };

	// `.ptr` pseudo-field on str/slice → element of the str/slice.
	if (streq(fld, "ptr")) {
		let inner_t: *node = tn;
		if (tn.kind == N_TPTR) { inner_t = tn.lhs; };
		if (inner_t == nil) { return 8; };
		if (inner_t.kind == N_TNAME) {
			if (streq(inner_t.str, "str")) { return 1; };
		};
		if (inner_t.kind == N_TSLICE) { return elem_size_of(inner_t); };
		return 8;
	};

	// Generic struct field: if it's *T, element size is T's size.
	let lkind: i32 = tn.kind;
	let sname: str;
	sname.ptr = nil; sname.len = 0;
	if (lkind == N_TNAME) { sname = tn.str; };
	if (lkind == N_TPTR) {
		let pinner: *node = tn.lhs;
		if (pinner != nil) {
			if (pinner.kind == N_TNAME) { sname = pinner.str; };
		};
	};
	if (sname.len == 0) { return 8; };
	let si: *struct_info = struct_lookup(c, sname);
	if (si == nil) { return 8; };
	let fi: *field_info = si.fields;
	for (fi != nil) {
		let fn_: str = fi.fname;
		if (streq(fn_, fld)) {
			let ft: *node = fi.tnode;
			if (ft == nil) { return 8; };
			if (ft.kind == N_TPTR) {
				let elem: *node = ft.lhs;
				if (elem != nil) {
					if (elem.kind == N_TNAME) {
						if (streq(elem.str, "str")) { return 16; };
						let ps: i32 = prim_size(elem.str);
						if (ps > 0) { return ps; };
					};
				};
				return 8;
			};
			if (ft.kind == N_TSLICE) { return elem_size_of(ft); };
			// str-typed field: indexing yields one byte
			// (`n.s[i]` where .s is str — matches C cgen's
			// MOVZBQ for byte indexing).
			if (ft.kind == N_TNAME) {
				if (streq(ft.str, "str")) { return 1; };
			};
			return 8;
		};
		fi = fi.finext;
	};
	return 8;
};

// dot_inner_struct_ptr — for an N_DOT whose lhs is a chain of dots
// or an N_IDENT, walk the chain and return the N_TNAME tnode of the
// struct that the chain dereferences to (i.e., for `r.sym` where
// .sym is *lsym, return N_TNAME("lsym")). Returns nil if the chain
// doesn't resolve to a *struct.
//
// Used by the chained-DOT cgen path so `r.sym.val` knows the outer
// is a field of `lsym`.
fn dot_inner_struct_ptr(c: *cgen, n: *node) *node = {
	if (n == nil) { return nil; };
	if (n.kind != N_DOT) { return nil; };
	let base: *node = n.lhs;
	let fld: str = n.str;
	if (base == nil) { return nil; };

	// Resolve base's struct tnode.
	let base_t: *node = nil;
	if (base.kind == N_IDENT) {
		let lc: *local = local_find_node(c, base.str);
		if (lc == nil) { return nil; };
		let tn: *node = lc.tnode;
		if (tn == nil) { return nil; };
		// base could be either struct-by-value (N_TNAME) or *struct (N_TPTR).
		if (tn.kind == N_TNAME) { base_t = tn; };
		if (tn.kind == N_TPTR)  { base_t = tn.lhs; };
	} else { if (base.kind == N_DOT) {
		base_t = dot_inner_struct_ptr(c, base);
	};};
	if (base_t == nil) { return nil; };
	if (base_t.kind != N_TNAME) { return nil; };

	// Look up the struct, find the field, return the field's *struct.
	let si: *struct_info = struct_lookup(c, base_t.str);
	if (si == nil) { return nil; };
	let fi: *field_info = si.fields;
	for (fi != nil) {
		if (streq(fi.fname, fld)) {
			let ft: *node = fi.tnode;
			if (ft == nil) { return nil; };
			if (ft.kind != N_TPTR) { return nil; };
			let inner: *node = ft.lhs;
			if (inner == nil) { return nil; };
			if (inner.kind != N_TNAME) { return nil; };
			return inner;
		};
		fi = fi.finext;
	};
	return nil;
};

// elem_size_of — given the type node of an indexable (`*T`, `[]T`,
// `[N]T`, `str`), return the byte size of one element (1 for u8/i8/
// bool/str-byte, 8 otherwise — same shape as C cgen's esz fallback).
fn elem_size_of(t: *node) i32 = {
	if (t == nil) { return 1; };
	let k: i32 = t.kind;
	let elem: *node = nil;
	if (k == N_TPTR)   { elem = t.lhs; };
	if (k == N_TSLICE) { elem = t.lhs; };
	if (k == N_TARRAY) { elem = t.lhs; };
	if (k == N_TNAME) {
		let nm: str = t.str;
		if (streq(nm, "str")) { return 1; };
		// Indexing a primitive name (rare): element size = the prim.
		let ps: i32 = prim_size(nm);
		if (ps > 0) { return ps; };
		return 1;
	};
	if (elem == nil) { return 1; };
	if (elem.kind == N_TNAME) {
		let nm: str = elem.str;
		// str element is 16B (ptr+len). prim_size returns 0 for it.
		if (streq(nm, "str")) { return 16; };
		let ps: i32 = prim_size(nm);
		if (ps > 0) { return ps; };
	};
	return 8;
};

// node_isunsigned — best-effort cgen-time inference from the AST. We
// don't have a typed AST yet, so we walk surface nodes:
//   N_INTLIT      — never marked unsigned (no tsuffix plumbing yet)
//   N_IDENT       — look up the local's declared type
//   N_DOT         — look up the field's declared type via struct reg
//   N_BIN / N_UN  — recurse: unsigned if either operand is unsigned
//   N_CAST        — use the cast target type
//
// Conservative: if we can't tell, return false (signed). The cost of
// being wrong here is byte-different asm vs C, not bad runtime.
fn node_isunsigned(c: *cgen, n: *node) bool = {
	if (n == nil) { return false; };
	let k: i32 = n.kind;
	if (k == N_IDENT) {
		let nm: str = n.str;
		let lc: *local = local_find_node(c, nm);
		if (lc != nil) { return type_node_isunsigned(lc.tnode); };
		return false;
	};
	if (k == N_DOT) {
		let base: *node = n.lhs;
		let fld: str = n.str;
		if (base != nil) {
			if (base.kind == N_IDENT) {
				let bn: str = base.str;
				let lc: *local = local_find_node(c, bn);
				if (lc != nil) {
					let tn: *node = lc.tnode;
					let lkind: i32 = -1;
					if (tn != nil) { lkind = tn.kind; };
					let sname: str;
					sname.ptr = nil; sname.len = 0;
					if (lkind == N_TPTR) {
						let inner: *node = tn.lhs;
						if (inner != nil) {
							if (inner.kind == N_TNAME) { sname = inner.str; };
						};
					};
					if (lkind == N_TNAME) { sname = tn.str; };
					if (sname.len > 0) {
						let si: *struct_info = struct_lookup(c, sname);
						if (si != nil) {
							let fi: *field_info = si.fields;
							for (fi != nil) {
								let fn_: str = fi.fname;
								if (streq(fn_, fld)) {
									return type_node_isunsigned(fi.tnode);
								};
								fi = fi.finext;
							};
						};
					};
				};
			};
		};
		return false;
	};
	if (k == N_CAST) { return type_node_isunsigned(n.rhs); };
	if (k == N_BIN) {
		if (node_isunsigned(c, n.lhs)) { return true; };
		return node_isunsigned(c, n.rhs);
	};
	if (k == N_UN) { return node_isunsigned(c, n.lhs); };
	// N_INDEX: `p[i]` is unsigned iff p's element type is unsigned.
	// Walks the base local's declared type and pulls the element
	// out — *u8 → u8, [N]u32 → u32, []u64 → u64. Without this the
	// compare-codegen for `p[i] >= 48u8` falls back to signed JGE
	// instead of JAE, diverging from C 6c on byte indexing.
	if (k == N_INDEX) {
		let base: *node = n.lhs;
		if (base != nil) {
			if (base.kind == N_IDENT) {
				let lc: *local = local_find_node(c, base.str);
				if (lc != nil) {
					let tn: *node = lc.tnode;
					if (tn != nil) {
						let elem: *node = nil;
						if (tn.kind == N_TPTR)   { elem = tn.lhs; };
						if (tn.kind == N_TARRAY) { elem = tn.lhs; };
						if (tn.kind == N_TSLICE) { elem = tn.lhs; };
						if (elem != nil) {
							return type_node_isunsigned(elem);
						};
					};
				};
			};
		};
		return false;
	};
	return false;
};

fn cgexpr(c: *cgen, n: *node) void = {
	if (n == nil) { return; };
	let k: i32 = n.kind;

	if (k == N_INTLIT) {
		// Print signed (i64), not unsigned (u64). C cgen uses
		// `$%lld` so 64-bit constants with bit 63 set show up as
		// negative — e.g. FNV-1a's offset basis prints as
		// $-3750763034362895579, not $14695981039346656037.
		emit_line("\tMOVQ\t$");
		emit_int(n.uval: i64);
		emit_line(", AX\n");
		return;
	};
	if (k == N_RUNELIT) {
		emit_line("\tMOVQ\t$");
		emit_int(n.uval: i64);
		emit_line(", AX\n");
		return;
	};
	if (k == N_STRLIT) {
		// Result is the (ptr, len) pair: ptr in AX, len in BX. Call
		// sites that expect a str arg pick these up directly.
		let nstr: str = n.str;
		let lab: str = intern_strlit(c, nstr);
		emit_line("\tLEAQ\t");
		os.write(1, lab.ptr, lab.len: u64);
		emit_line("(SB), AX\n");
		emit_line("\tMOVQ\t$");
		emit_int(nstr.len: i64);
		emit_line(", BX\n");
		return;
	};
	if (k == N_TRUE) {
		emit_line("\tMOVQ\t$1, AX\n");
		return;
	};
	if (k == N_FALSE) {
		emit_line("\tMOVQ\t$0, AX\n");
		return;
	};
	if (k == N_NIL) {
		emit_line("\tMOVQ\t$0, AX\n");
		return;
	};

	if (k == N_IDENT) {
		let nm: str = n.str;
		let lc: *local = local_find_node(c, nm);
		if (lc != nil) {
			let off: i32 = lc.off;
			emit_line("\tMOVQ\t");
			emit_off(off: i64);
			emit_line("(BP), AX\n");
			// str local: also load the len half into BX.
			if (is_str_type(c, lc.tnode)) {
				emit_line("\tMOVQ\t");
				emit_off((off + 8): i64);
				emit_line("(BP), BX\n");
			};
			// slice local: load (ptr, len, cap) into (AX, BX, CX).
			if (is_slice_type(c, lc.tnode)) {
				emit_line("\tMOVQ\t");
				emit_off((off + 8): i64);
				emit_line("(BP), BX\n");
				emit_line("\tMOVQ\t");
				emit_off((off + 16): i64);
				emit_line("(BP), CX\n");
			};
			return;
		};
		// Top-level `def` constant — load from its DATA symbol.
		if (def_lookup(c, nm)) {
			emit_line("\tMOVQ\t");
			os.write(1, nm.ptr, nm.len: u64);
			emit_line("(SB), AX\n");
			return;
		};
		// Fn-name used as a value (e.g. `let f = some_fn;` or
		// `... = some_fn;`). LEAQ the symbol address into AX —
		// resolved through ffi_resolve so a body-less FFI binding
		// emits the C symbol it was declared with via @symbol(),
		// not the ww-side ident.
		let rt: *node = fnret_lookup(c, nm);
		if (rt != nil) {
			let resolved: str = ffi_resolve(c, nm);
			emit_line("\tLEAQ\t");
			os.write(1, resolved.ptr, resolved.len: u64);
			emit_line("(SB), AX\n");
			return;
		};
		return;
	};

	if (k == N_INDEX) {
		// Element-size-aware load: u8-element bases use MOVZBQ,
		// everything else MOVQ. Fast path when the base is a bare
		// ident (mem.ww shape).
		let base: *node = n.lhs;
		let idx: *node = n.rhs;
		let esz: i32 = 8;
		let base_local: *local = nil;
		if (base != nil) {
			if (base.kind == N_IDENT) {
				let bn: str = base.str;
				base_local = local_find_node(c, bn);
				if (base_local != nil) { esz = elem_size_of(base_local.tnode); };
			} else { if (base.kind == N_DOT) {
				esz = index_base_esz(c, base);
			};};
		};
		cgexpr(c, idx);
		if (esz > 1) {
			emit_line("\tMOVQ\t$");
			emit_int(esz: i64);
			emit_line(", CX\n");
			emit_line("\tIMULQ\tCX, AX\n");
		};
		if (base_local != nil) {
			let tn: *node = base_local.tnode;
			let is_array: bool = false;
			if (tn != nil) { if (tn.kind == N_TARRAY) { is_array = true; }; };
			if (is_array) {
				emit_line("\tLEAQ\t");
				emit_off(base_local.off: i64);
				emit_line("(BP), BX\n");
			} else {
				emit_line("\tMOVQ\t");
				emit_off(base_local.off: i64);
				emit_line("(BP), BX\n");
			};
			emit_line("\tADDQ\tAX, BX\n");
			// str element (16B): load (ptr, len) into (AX, BX) so
			// the value flows through the str-rhs convention.
			if (esz == 16) {
				emit_line("\tMOVQ\t8(BX), CX\n");
				emit_line("\tMOVQ\t(BX), AX\n");
				emit_line("\tMOVQ\tCX, BX\n");
				return;
			};
			if (esz == 1) { emit_line("\tMOVZBQ\t(BX), AX\n"); }
			else          { emit_line("\tMOVQ\t(BX), AX\n"); };
			return;
		};
		// Generic fallback when base isn't a plain ident.
		emit_line("\tPUSHQ\tAX\n");
		cgexpr(c, base);
		emit_line("\tPOPQ\tBX\n");
		emit_line("\tADDQ\tBX, AX\n");
		if (esz == 16) {
			emit_line("\tMOVQ\t8(AX), BX\n");
			emit_line("\tMOVQ\t(AX), AX\n");
			return;
		};
		if (esz == 1) { emit_line("\tMOVZBQ\t(AX), AX\n"); }
		else          { emit_line("\tMOVQ\t(AX), AX\n"); };
		return;
	};

	if (k == N_MATCH) {
		// match (e) { case let v: T => stmt; ... }
		//
		// Read the tagged-union slot and dispatch by tag. Slot
		// layout: [+0]=tag, [+8]=value0, [+16]=value1. Bindings
		// (`case let v: T =>`) get a fresh local slot loaded from
		// slot+8 (and slot+16 for str-typed payload).
		let scrut: *node = n.lhs;
		let scrut_off: i32 = 0;
		let scrut_t: *node = nil;
		if (scrut != nil) {
			if (scrut.kind == N_IDENT) {
				let lc: *local = local_find_node(c, scrut.str);
				if (lc != nil) {
					scrut_off = lc.off;
					scrut_t = resolve_type(c, lc.tnode);
				};
			};
		};
		let endl: str = mklabel(c, "match_end");
		let cs: *node = n.list;
		for (cs != nil) {
			let nxt: str = mklabel(c, "match_next");
			let pat: *node = cs.lhs;
			// Compute the variant tag for this arm. Default arm
			// (no pattern) skips the tag check.
			if (pat != nil) {
				let want: i32 = 0;
				if (scrut_t != nil) {
					if (scrut_t.kind == N_TTAGGED) {
						let pat_name: str;
						pat_name.ptr = nil; pat_name.len = 0;
						if (pat.kind == N_TNAME) { pat_name = pat.str; };
						let v: *node = scrut_t.list;
						let idx: i32 = 0;
						let found: bool = false;
						for (v != nil) {
							if (v.kind == N_TNAME) {
								if (streq(v.str, pat_name)) {
									want = idx;
									found = true;
									v = nil;
								};
							};
							if (v != nil) {
								v = v.next;
								idx += 1;
							};
						};
						if (!found) { want = 0; };
					};
				};
				emit_line("\tMOVQ\t");
				emit_off(scrut_off: i64);
				emit_line("(BP), AX\n");
				emit_line("\tCMPQ\t$");
				emit_int(want: i64);
				emit_line(", AX\n");
				emit_line("\tJNE\t");
				emit_line(nxt);
				emit_line("\n");
			};
			// Bind `let v: T` from the slot, if requested.
			let bn: str = cs.str;
			if (bn.len > 0) {
				if (pat != nil) {
					let bsz: i32 = 8;
					if (is_str_type(c, pat)) { bsz = 16; };
					// local_alloc (not local_add): match-arm
					// binds don't dedup with same-named binds
					// in *other* matches, since C's cgexpr
					// allocates a fresh slot per match expr.
					let voff: i32 = local_alloc(c, bn, bsz, pat);
					emit_line("\tMOVQ\t");
					emit_off((scrut_off + 8): i64);
					emit_line("(BP), AX\n");
					emit_line("\tMOVQ\tAX, ");
					emit_off(voff: i64);
					emit_line("(BP)\n");
					if (bsz == 16) {
						emit_line("\tMOVQ\t");
						emit_off((scrut_off + 16): i64);
						emit_line("(BP), AX\n");
						emit_line("\tMOVQ\tAX, ");
						emit_off((voff + 8): i64);
						emit_line("(BP)\n");
					};
				};
			};
			// Body. Match arms are statements; we cgstmt them.
			if (cs.body != nil) { cgstmt(c, cs.body); };
			emit_line("\tJMP\t");
			emit_line(endl);
			emit_line("\n");
			emit_label(nxt);
			cs = cs.next;
		};
		emit_label(endl);
		return;
	};

	if (k == N_CAST) {
		// Type casts are mostly no-ops at the asm level for our
		// integer-shaped operands. Evaluate the source; AX holds
		// the bits unchanged. (Sign- or zero-extending narrow loads
		// to wider types is the loader's job, not cast's, in this
		// minimal cgen.)
		cgexpr(c, n.lhs);
		return;
	};

	if (k == N_DOT) {
		let lhs: *node = n.lhs;
		let fld: str = n.str;
		if (lhs != nil) {
			if (lhs.kind == N_IDENT) {
				let nm: str = lhs.str;
				let lc: *local = local_find_node(c, nm);
				if (lc != nil) {
					let tn: *node = lc.tnode;
					let lkind: i32 = -1;
					if (tn != nil) { lkind = tn.kind; };
					// Pointer-to-struct: deref then field load.
					if (lkind == N_TPTR) {
						let inner: *node = tn.lhs;
						let sname: str;
						sname.ptr = nil; sname.len = 0;
						if (inner != nil) {
							if (inner.kind == N_TNAME) {
								sname = inner.str;
							};
						};
						if (sname.len > 0) {
							let si: *struct_info = struct_lookup(c, sname);
							if (si != nil) {
								let fi: *field_info = si.fields;
								for (fi != nil) {
									let fn_: str = fi.fname;
									if (streq(fn_, fld)) {
										// str field via *struct: load len into a
										// scratch first (so loading ptr into AX
										// last leaves (AX=ptr, BX=len)).
										emit_line("\tMOVQ\t");
										emit_off(lc.off: i64);
										emit_line("(BP), BX\n");
										if (is_str_type(c, fi.tnode)) {
											emit_line("\tMOVQ\t");
											emit_disp_reg((fi.foff + 8): i64, "BX");
											emit_line(", CX\n");
											emit_line("\tMOVQ\t");
											emit_disp_reg(fi.foff: i64, "BX");
											emit_line(", AX\n");
											emit_line("\tMOVQ\tCX, BX\n");
										} else {
											let op: str = field_load_op(fi);
											emit_line("\t");
											emit_line(op);
											emit_line("\t");
											emit_disp_reg(fi.foff: i64, "BX");
											emit_line(", AX\n");
										};
										return;
									};
									fi = fi.finext;
								};
							};
						};
					};
					// Direct struct local: field load at off+foff.
					if (lkind == N_TNAME) {
						let sname: str = tn.str;
						let si: *struct_info = struct_lookup(c, sname);
						if (si != nil) {
							let fi: *field_info = si.fields;
							for (fi != nil) {
								let fn_: str = fi.fname;
								if (streq(fn_, fld)) {
									// str field: load both halves so chained
									// `.ptr` / `.len` see (AX=ptr, BX=len).
									if (is_str_type(c, fi.tnode)) {
										emit_line("\tMOVQ\t");
										emit_off((lc.off + fi.foff): i64);
										emit_line("(BP), AX\n");
										emit_line("\tMOVQ\t");
										emit_off((lc.off + fi.foff + 8): i64);
										emit_line("(BP), BX\n");
									} else {
										let op: str = field_load_op(fi);
										emit_line("\t");
										emit_line(op);
										emit_line("\t");
										emit_off((lc.off + fi.foff): i64);
										emit_line("(BP), AX\n");
									};
									return;
								};
								fi = fi.finext;
							};
						};
					};
					// Array pseudo-fields: `.ptr` is the array's
					// address (LEAQ); `.len` is the static element
					// count (immediate).
					if (lkind == N_TARRAY) {
						if (streq(fld, "ptr")) {
							emit_line("\tLEAQ\t");
							emit_off(lc.off: i64);
							emit_line("(BP), AX\n");
							return;
						};
						if (streq(fld, "len")) {
							let len_n: *node = tn.rhs;
							let alen: i64 = 0i64;
							if (len_n != nil) {
								if (len_n.kind == N_INTLIT) { alen = len_n.uval: i64; };
							};
							emit_line("\tMOVQ\t$");
							emit_int(alen);
							emit_line(", AX\n");
							return;
						};
					};
					// str/slice pseudo-fields .ptr/.len/.cap on a
					// direct local: load at slot+delta.
					let delta: i32 = -1;
					if (streq(fld, "ptr")) { delta = 0; };
					if (streq(fld, "len")) { delta = 8; };
					if (streq(fld, "cap")) { delta = 16; };
					if (delta >= 0) {
						// Pointer to str/slice (`*[]u8`, `*str`):
						// deref, then load at delta within the
						// pointed-to header. C cgen does the same.
						if (lkind == N_TPTR) {
							let inner: *node = tn.lhs;
							let inner_kind: i32 = -1;
							if (inner != nil) { inner_kind = inner.kind; };
							let inner_str: bool = false;
							if (inner_kind == N_TNAME) {
								if (streq(inner.str, "str")) { inner_str = true; };
							};
							if (inner_kind == N_TSLICE) { inner_str = true; };
							if (inner_str) {
								emit_line("\tMOVQ\t");
								emit_off(lc.off: i64);
								emit_line("(BP), BX\n");
								emit_line("\tMOVQ\t");
								emit_disp_reg(delta: i64, "BX");
								emit_line(", AX\n");
								return;
							};
						};
						emit_line("\tMOVQ\t");
						emit_off((lc.off + delta): i64);
						emit_line("(BP), AX\n");
						return;
					};
				};
			};
		};
		// Module-qualified value reference: `mod.name` where `mod`
		// is N_IDENT bound as SK_USE and the leaf isn't a local.
		// Treat as a SB symbol — `MOVQ leaf(SB), AX`. Same fallback
		// the C cgen takes when bt is NULL/ty_err.
		if (lhs != nil) {
			if (lhs.kind == N_IDENT) {
				emit_line("\tMOVQ\t");
				emit_line(fld);
				emit_line("(SB), AX\n");
				return;
			};
		};
		// Non-ident base pseudo-field: e.g. `"abc".ptr` / `"abc".len`.
		// Evaluate the str-producing expression — that leaves
		// (AX=ptr, BX=len). Then `.ptr` returns AX as is; `.len`
		// shuffles BX→AX. Mirrors what C cgen does (it just evaluates
		// the literal and picks the half it wants).
		if (streq(fld, "ptr")) { cgexpr(c, lhs); return; };
		if (streq(fld, "len")) {
			cgexpr(c, lhs);
			emit_line("\tMOVQ\tBX, AX\n");
			return;
		};
		// Chained struct-field-via-ptr-via-ptr access:
		//   r.sym.val   where r: *lrel, .sym: *lsym, .val: u64
		// Inner DOT (`r.sym`) returns a *struct (a pointer-to-struct
		// field). Outer DOT dereferences and reads `val`. Without this
		// path the cgen falls through and AX retains whatever the
		// inner expression left there — typically the *struct pointer
		// itself, so reads silently get the pointer value instead of
		// the field. (Showed up porting 6l/pass.ww.)
		if (lhs != nil) {
			if (lhs.kind == N_DOT) {
				let inner_t: *node = dot_inner_struct_ptr(c, lhs);
				if (inner_t != nil) {
					let sname: str = inner_t.str;
					let si: *struct_info = struct_lookup(c, sname);
					if (si != nil) {
						let fi: *field_info = si.fields;
						for (fi != nil) {
							if (streq(fi.fname, fld)) {
								cgexpr(c, lhs);	// AX = ptr to inner struct
								let lop: str = field_load_op(fi);
								// str field: load both halves.
								if (is_str_type(c, fi.tnode)) {
									emit_line("\tMOVQ\t");
									emit_disp_reg((fi.foff + 8): i64, "AX");
									emit_line(", BX\n");
									emit_line("\tMOVQ\t");
									emit_disp_reg(fi.foff: i64, "AX");
									emit_line(", AX\n");
									return;
								};
								emit_line("\t");
								emit_line(lop);
								emit_line("\t");
								emit_disp_reg(fi.foff: i64, "AX");
								emit_line(", AX\n");
								return;
							};
							fi = fi.finext;
						};
					};
				};
			};
		};
		return;
	};

	if (k == N_UN) {
		// Match C cgen ordering: evaluate operand first (load into AX),
		// then apply the unary op. AMP / STAR override AX with the
		// address / deref. The wasted load before AMP keeps our asm
		// byte-identical to the C version.
		cgexpr(c, n.lhs);
		if (n.op == TK_MINUS) { emit_line("\tNEGQ\tAX\n"); return; };
		if (n.op == TK_TILDE) { emit_line("\tNOTQ\tAX\n"); return; };
		if (n.op == TK_STAR)  { emit_line("\tMOVQ\t(AX), AX\n"); return; };
		if (n.op == TK_AMP) {
			let opnd: *node = n.lhs;
			if (opnd != nil) {
				if (opnd.kind == N_IDENT) {
					let nm: str = opnd.str;
					let off: i32 = local_find(c, nm);
					if (off != 0) {
						emit_line("\tLEAQ\t");
						emit_off(off: i64);
						emit_line("(BP), AX\n");
						return;
					};
				};
			};
			return;
		};
		if (n.op == TK_NOT) {
			let t: str = mklabel(c, "tt");
			let e: str = mklabel(c, "te");
			emit_line("\tCMPQ\t$0, AX\n");
			emit_line("\tJE\t");   emit_line(t); emit_line("\n");
			emit_line("\tMOVQ\t$0, AX\n");
			emit_line("\tJMP\t");  emit_line(e); emit_line("\n");
			emit_label(t);
			emit_line("\tMOVQ\t$1, AX\n");
			emit_label(e);
			return;
		};
		return;
	};

	if (k == N_BIN) {
		let unsignd: bool = node_isunsigned(c, n.lhs);
		if (!unsignd) { unsignd = node_isunsigned(c, n.rhs); };

		cgexpr(c, n.rhs);
		emit_line("\tPUSHQ\tAX\n");
		cgexpr(c, n.lhs);
		emit_line("\tPOPQ\tBX\n");
		if (n.op == TK_PLUS)    { emit_line("\tADDQ\tBX, AX\n"); return; };
		if (n.op == TK_MINUS)   { emit_line("\tSUBQ\tBX, AX\n"); return; };
		if (n.op == TK_STAR)    { emit_line("\tIMULQ\tBX, AX\n"); return; };
		if (n.op == TK_SLASH) {
			emit_line("\tMOVQ\t$0, DX\n");
			if (unsignd) { emit_line("\tDIVQ\tBX\n"); }
			else         { emit_line("\tIDIVQ\tBX\n"); };
			return;
		};
		if (n.op == TK_PERCENT) {
			emit_line("\tMOVQ\t$0, DX\n");
			if (unsignd) { emit_line("\tDIVQ\tBX\n"); }
			else         { emit_line("\tIDIVQ\tBX\n"); };
			emit_line("\tMOVQ\tDX, AX\n");
			return;
		};
		if (n.op == TK_AMP)   { emit_line("\tANDQ\tBX, AX\n"); return; };
		if (n.op == TK_PIPE)  { emit_line("\tORQ\tBX, AX\n");  return; };
		if (n.op == TK_CARET) { emit_line("\tXORQ\tBX, AX\n"); return; };
		if (n.op == TK_LSHIFT) {
			emit_line("\tMOVQ\tBX, CX\n");
			emit_line("\tSHLQ\tCX, AX\n");
			return;
		};
		if (n.op == TK_RSHIFT) {
			emit_line("\tMOVQ\tBX, CX\n");
			emit_line("\tSHRQ\tCX, AX\n");
			return;
		};
		if (n.op == TK_AND) { emit_line("\tANDQ\tBX, AX\n"); return; };
		if (n.op == TK_OR)  { emit_line("\tORQ\tBX, AX\n");  return; };

		// Comparison: emit CMPQ, jump on signed/unsigned variant,
		// materialise 0/1 in AX. Same shape as the C cgen.
		let is_cmp: bool = false;
		let jcc: str = "";
		if (n.op == TK_EQ)  { is_cmp = true; jcc = "JE"; };
		if (n.op == TK_NEQ) { is_cmp = true; jcc = "JNE"; };
		if (n.op == TK_LT)  { is_cmp = true; if (unsignd) { jcc = "JB"; } else { jcc = "JL"; }; };
		if (n.op == TK_LE)  { is_cmp = true; if (unsignd) { jcc = "JBE"; } else { jcc = "JLE"; }; };
		if (n.op == TK_GT)  { is_cmp = true; if (unsignd) { jcc = "JA"; } else { jcc = "JG"; }; };
		if (n.op == TK_GE)  { is_cmp = true; if (unsignd) { jcc = "JAE"; } else { jcc = "JGE"; }; };
		if (is_cmp) {
			let t: str = mklabel(c, "ct");
			let e: str = mklabel(c, "ce");
			emit_line("\tCMPQ\tBX, AX\n");
			emit_line("\t"); emit_line(jcc); emit_line("\t"); emit_line(t); emit_line("\n");
			emit_line("\tMOVQ\t$0, AX\n");
			emit_line("\tJMP\t"); emit_line(e); emit_line("\n");
			emit_label(t);
			emit_line("\tMOVQ\t$1, AX\n");
			emit_label(e);
			return;
		};
		return;
	};

	if (k == N_CALL) {
		let nargs: i32 = push_args_rev(c, n.list);
		let i: i32 = 0;
		for (i < nargs) {
			emit_line("\tPOPQ\t");
			emit_line(argreg_name(i));
			emit_line("\n");
			i += 1;
		};
		let callee: *node = n.lhs;
		let callee_name: str;
		callee_name.ptr = nil; callee_name.len = 0;
		// Detect fn-pointer field call: `w.emit(args)` where `w` is
		// a struct local and `emit` is an N_TFN field. Load the
		// field value into AX and CALL through it. Also detect a
		// bare `fp(args)` where `fp` is a local holding a function
		// pointer — mirror C cgen's localfind dispatch (commit
		// 635818e). Without this the call emits `CALL fp(SB)` and
		// the linker rightly fails.
		let is_fnptr_call: bool = false;
		if (callee != nil) {
			if (callee.kind == N_IDENT) {
				let cn: str = callee.str;
				if (local_find_node(c, cn) != nil) {
					is_fnptr_call = true;
				};
			};
			if (callee.kind == N_DOT) {
				let base: *node = callee.lhs;
				let fld: str = callee.str;
				if (base != nil) {
					if (base.kind == N_IDENT) {
						let bn: str = base.str;
						let lc: *local = local_find_node(c, bn);
						if (lc != nil) {
							let tn: *node = lc.tnode;
							if (tn != nil) {
								let lkind: i32 = tn.kind;
								let sname: str;
								sname.ptr = nil; sname.len = 0;
								if (lkind == N_TNAME) { sname = tn.str; };
								if (lkind == N_TPTR) {
									let inner: *node = tn.lhs;
									if (inner != nil) {
										if (inner.kind == N_TNAME) { sname = inner.str; };
									};
								};
								if (sname.len > 0) {
									let si: *struct_info = struct_lookup(c, sname);
									if (si != nil) {
										let fi: *field_info = si.fields;
										for (fi != nil) {
											let fn_: str = fi.fname;
											if (streq(fn_, fld)) {
												let ft: *node = fi.tnode;
												if (ft != nil) {
													if (ft.kind == N_TFN) {
														is_fnptr_call = true;
													};
												};
												fi = nil;
											} else {
												fi = fi.finext;
											};
										};
									};
								};
							};
						};
					};
				};
			};
		};
		if (is_fnptr_call) {
			// Load fn-ptr field value into AX; CALL AX. We emit the
			// load AFTER the args have been popped (so AX/BX/etc
			// don't get clobbered by the field load before the pops).
			// `popped args` left DI/SI/etc set; AX is free.
			cgexpr(c, callee);
			emit_line("\tCALL\tAX\n");
		} else {
			emit_line("\tCALL\t");
			if (callee != nil) {
				if (callee.kind == N_IDENT) {
					callee_name = callee.str;
					let resolved: str = ffi_resolve(c, callee_name);
					os.write(1, resolved.ptr, resolved.len: u64);
				} else { if (callee.kind == N_DOT) {
					callee_name = callee.str;
					let resolved: str = ffi_resolve(c, callee_name);
					os.write(1, resolved.ptr, resolved.len: u64);
				};};
			};
			emit_line("(SB)\n");
		};
		// SysV returns 16-byte aggregates in (AX, DX). Our str
		// convention is (AX, BX), so shuffle for str-returning calls.
		if (callee_name.len > 0) {
			let rt: *node = fnret_lookup(c, callee_name);
			if (is_str_type(c, rt)) {
				emit_line("\tMOVQ\tDX, BX\n");
			};
		};
		return;
	};

	if (k == N_ASSIGN) {
		let lhs: *node = n.lhs;
		// `*p = v` — deref-assign. Element width comes from the
		// pointer's declared type. Mirrors C cgen: eval rhs (AX,
		// and BX if str), push, eval pointer, pop value, store.
		// We default to MOVQ (8B) since most fixtures use it; for
		// `*bool` / `*u8` / `*i32` we narrow via the local's tnode.
		if (lhs != nil) {
			if (lhs.kind == N_UN) {
				if (lhs.op == TK_STAR) {
					if (n.op == TK_ASSIGN) {
						let inner: *node = lhs.lhs;
						let elem_str: bool = false;
						let store_op: str = "MOVQ";
						if (inner != nil) {
							if (inner.kind == N_IDENT) {
								let lc: *local = local_find_node(c, inner.str);
								if (lc != nil) {
									let tn: *node = lc.tnode;
									if (tn != nil) {
										if (tn.kind == N_TPTR) {
											let pe: *node = tn.lhs;
											if (pe != nil) {
												if (pe.kind == N_TNAME) {
													if (streq(pe.str, "str")) { elem_str = true; }
													else {
														let ps: i32 = prim_size(pe.str);
														if (ps == 1) { store_op = "MOVB"; }
														else { if (ps == 4) { store_op = "MOVL"; }; };
													};
												};
											};
										};
									};
								};
							};
						};
						cgexpr(c, n.rhs);
						// Push order matches C cgen
						// (cmd/6c/cgen.c:1033-1041): PUSHQ AX
						// (ptr) first, then PUSHQ BX (len) if
						// str, so the pop sequence is POP CX
						// (len) → POP AX (ptr) → MOVQ AX,
						// (BX) → MOVQ CX, 8(BX).
						emit_line("\tPUSHQ\tAX\n");
						if (elem_str) { emit_line("\tPUSHQ\tBX\n"); };
						cgexpr(c, inner);
						emit_line("\tMOVQ\tAX, BX\n");
						if (elem_str) {
							emit_line("\tPOPQ\tCX\n");
							emit_line("\tPOPQ\tAX\n");
							emit_line("\tMOVQ\tAX, (BX)\n");
							emit_line("\tMOVQ\tCX, 8(BX)\n");
							return;
						};
						emit_line("\tPOPQ\tAX\n");
						emit_line("\t");
						emit_line(store_op);
						emit_line("\tAX, (BX)\n");
						return;
					};
				};
			};
		};
		// Array/slice/ptr index store: `arr[i] = v;`. Element size
		// from base.tnode picks MOVB vs MOVQ.
		if (lhs != nil) {
			if (lhs.kind == N_INDEX) {
				if (n.op == TK_ASSIGN) {
					let base: *node = lhs.lhs;
					let idx: *node = lhs.rhs;
					let esz: i32 = 8;
					let base_local: *local = nil;
					if (base != nil) {
						if (base.kind == N_IDENT) {
							let bn: str = base.str;
							base_local = local_find_node(c, bn);
							if (base_local != nil) {
								esz = elem_size_of(base_local.tnode);
							};
						} else { if (base.kind == N_DOT) {
							esz = index_base_esz(c, base);
						};};
					};
					cgexpr(c, n.rhs);            // value → AX
						if (esz == 16) { emit_line("\tPUSHQ\tBX\n"); };
					emit_line("\tPUSHQ\tAX\n");
					cgexpr(c, idx);              // idx → AX
					if (esz > 1) {
						emit_line("\tMOVQ\t$");
						emit_int(esz: i64);
						emit_line(", CX\n");
						emit_line("\tIMULQ\tCX, AX\n");
					};
					emit_line("\tPUSHQ\tAX\n");  // scaled idx
					if (base_local != nil) {
						let tn: *node = base_local.tnode;
						let is_array: bool = false;
						if (tn != nil) { if (tn.kind == N_TARRAY) { is_array = true; }; };
						if (is_array) {
							emit_line("\tLEAQ\t");
							emit_off(base_local.off: i64);
							emit_line("(BP), BX\n");
						} else {
							emit_line("\tMOVQ\t");
							emit_off(base_local.off: i64);
							emit_line("(BP), BX\n");
						};
					} else {
						cgexpr(c, base);
						emit_line("\tMOVQ\tAX, BX\n");
					};
					emit_line("\tPOPQ\tAX\n");   // scaled idx
					emit_line("\tADDQ\tAX, BX\n");
					emit_line("\tPOPQ\tAX\n");   // value
						if (esz == 16) {
							emit_line("\tMOVQ\tAX, (BX)\n");
							emit_line("\tPOPQ\tCX\n");
							emit_line("\tMOVQ\tCX, 8(BX)\n");
							return;
						};
					if (esz == 1) { emit_line("\tMOVB\tAX, (BX)\n"); }
					else          { emit_line("\tMOVQ\tAX, (BX)\n"); };
					return;
				};
			};
		};
		// Struct/ptr-to-struct field assignment: `s.f = expr;` or
		// `p.f = expr;`. Only plain `=` is wired (compound on field
		// is rare and not yet needed by our fixtures).
		if (lhs != nil) {
			if (lhs.kind == N_DOT) {
				let base: *node = lhs.lhs;
				let fld: str = lhs.str;
				if (base != nil) {
					if (base.kind == N_IDENT) {
						let bn: str = base.str;
						let lc: *local = local_find_node(c, bn);
						if (lc != nil) {
							let tn: *node = lc.tnode;
							let lkind: i32 = -1;
							if (tn != nil) { lkind = tn.kind; };
							// Pointer-to-struct: deref then store.
							if (lkind == N_TPTR) {
								let inner: *node = tn.lhs;
								let sname: str;
								sname.ptr = nil; sname.len = 0;
								if (inner != nil) {
									if (inner.kind == N_TNAME) { sname = inner.str; };
								};
								if (sname.len > 0) {
									let si: *struct_info = struct_lookup(c, sname);
									if (si != nil) {
										let fi: *field_info = si.fields;
										for (fi != nil) {
											let fn_: str = fi.fname;
											if (streq(fn_, fld)) {
												if (n.op != TK_ASSIGN) {
													// compound: load current value
													emit_line("\tMOVQ\t");
													emit_off(lc.off: i64);
													emit_line("(BP), BX\n");
													let lop: str = field_load_op(fi);
													emit_line("\t");
													emit_line(lop);
													emit_line("\t");
													emit_disp_reg(fi.foff: i64, "BX");
													emit_line(", BX\n");
													emit_line("\tPUSHQ\tBX\n");
												};
												cgexpr(c, n.rhs);
												if (n.op != TK_ASSIGN) {
													emit_line("\tPOPQ\tBX\n");
													// PLUSEQ is commutative; MINUSEQ
													// needs lhs - rhs (BX is old lhs,
													// AX is rhs).
													if (n.op == TK_PLUSEQ)  { emit_line("\tADDQ\tBX, AX\n"); };
													if (n.op == TK_MINUSEQ) {
														emit_line("\tSUBQ\tAX, BX\n");
														emit_line("\tMOVQ\tBX, AX\n");
													};
												};
												// str field via *struct: rhs left
												// (AX=ptr, BX=len). Use CX as the
												// address scratch so we don't clobber
												// the len half before storing it.
												if (n.op == TK_ASSIGN) {
													if (is_str_type(c, fi.tnode)) {
														emit_line("\tMOVQ\t");
														emit_off(lc.off: i64);
														emit_line("(BP), CX\n");
														emit_line("\tMOVQ\tAX, ");
														emit_disp_reg(fi.foff: i64, "CX");
														emit_line("\n");
														emit_line("\tMOVQ\tBX, ");
														emit_disp_reg((fi.foff + 8): i64, "CX");
														emit_line("\n");
														return;
													};
												};
												emit_line("\tMOVQ\t");
												emit_off(lc.off: i64);
												emit_line("(BP), BX\n");
												let sop: str = field_store_op(fi);
												emit_line("\t");
												emit_line(sop);
												emit_line("\tAX, ");
												emit_disp_reg(fi.foff: i64, "BX");
												emit_line("\n");
												return;
											};
											fi = fi.finext;
										};
									};
								};
							};
								// Direct struct local: store at off+foff.
								if (lkind == N_TNAME) {
									let sname: str = tn.str;
									let si: *struct_info = struct_lookup(c, sname);
									if (si != nil) {
										let fi: *field_info = si.fields;
										for (fi != nil) {
											let fn_: str = fi.fname;
											if (streq(fn_, fld)) {
												cgexpr(c, n.rhs);
												let sop: str = field_store_op(fi);
												emit_line("\t");
												emit_line(sop);
												emit_line("\tAX, ");
												emit_off((lc.off + fi.foff): i64);
												emit_line("(BP)\n");
												return;
											};
											fi = fi.finext;
										};
									};
								};
								// str/slice pseudo-field assignment.
								let delta: i32 = -1;
								if (streq(fld, "ptr")) { delta = 0; };
								if (streq(fld, "len")) { delta = 8; };
								if (streq(fld, "cap")) { delta = 16; };
								if (delta >= 0) {
									if (lkind == N_TPTR) {
										let inner: *node = tn.lhs;
										let inner_kind: i32 = -1;
										if (inner != nil) { inner_kind = inner.kind; };
										let inner_str: bool = false;
										if (inner_kind == N_TNAME) {
											if (streq(inner.str, "str")) { inner_str = true; };
										};
										if (inner_kind == N_TSLICE) { inner_str = true; };
										if (inner_str) {
											if (n.op != TK_ASSIGN) {
												// Compound on `(*str|*slice).field`: load
												// current → push → eval rhs → combine → store.
												emit_line("\tMOVQ\t");
												emit_off(lc.off: i64);
												emit_line("(BP), BX\n");
												emit_line("\tMOVQ\t");
												emit_disp_reg(delta: i64, "BX");
												emit_line(", BX\n");
												emit_line("\tPUSHQ\tBX\n");
												cgexpr(c, n.rhs);
												emit_line("\tPOPQ\tBX\n");
												// PLUSEQ is commutative; MINUSEQ
												// needs lhs - rhs.
												if (n.op == TK_PLUSEQ)  { emit_line("\tADDQ\tBX, AX\n"); };
												if (n.op == TK_MINUSEQ) {
													emit_line("\tSUBQ\tAX, BX\n");
													emit_line("\tMOVQ\tBX, AX\n");
												};
												emit_line("\tMOVQ\t");
												emit_off(lc.off: i64);
												emit_line("(BP), BX\n");
												emit_line("\tMOVQ\tAX, ");
												emit_disp_reg(delta: i64, "BX");
												emit_line("\n");
												return;
											};
											cgexpr(c, n.rhs);
											emit_line("\tMOVQ\t");
											emit_off(lc.off: i64);
											emit_line("(BP), BX\n");
											emit_line("\tMOVQ\tAX, ");
											emit_disp_reg(delta: i64, "BX");
											emit_line("\n");
											return;
										};
									};
									cgexpr(c, n.rhs);
									emit_line("\tMOVQ\tAX, ");
									emit_off((lc.off + delta): i64);
									emit_line("(BP)\n");
									return;
								};
							};
						};
					};
				};
			};
		// Local-ident target — plain `=` and the simple compound
		// forms (+= -= *= /=); other compounds fall back to
		// "evaluate rhs, replace". Mirrors C cgen's IDENT-assign path.
		if (lhs != nil) {
			if (lhs.kind == N_IDENT) {
				let nm: str = lhs.str;
				let off: i32 = local_find(c, nm);
				if (off == 0) { return; };
				// Detect str-typed local — assignment must store both
				// halves (AX=ptr at +0, BX=len at +8).
				let lc_str: bool = false;
				let lcn: *local = local_find_node(c, nm);
				if (lcn != nil) { lc_str = is_str_type(c, lcn.tnode); };
				cgexpr(c, n.rhs);
				if (n.op == TK_ASSIGN) {
					emit_line("\tMOVQ\tAX, ");
					emit_off(off: i64);
					emit_line("(BP)\n");
					if (lc_str) {
						emit_line("\tMOVQ\tBX, ");
						emit_off((off + 8): i64);
						emit_line("(BP)\n");
					};
					return;
				};
				if (n.op == TK_PLUSEQ) {
					emit_line("\tADDQ\tAX, ");
					emit_off(off: i64);
					emit_line("(BP)\n");
					return;
				};
				if (n.op == TK_MINUSEQ) {
					emit_line("\tSUBQ\tAX, ");
					emit_off(off: i64);
					emit_line("(BP)\n");
					return;
				};
				// Generic compound: load → combine in BX → store.
				emit_line("\tMOVQ\t");
				emit_off(off: i64);
				emit_line("(BP), BX\n");
				if (n.op == TK_STAREQ)   { emit_line("\tIMULQ\tAX, BX\n"); };
				if (n.op == TK_AMPEQ)    { emit_line("\tANDQ\tAX, BX\n"); };
				if (n.op == TK_PIPEEQ)   { emit_line("\tORQ\tAX, BX\n"); };
				if (n.op == TK_CARETEQ)  { emit_line("\tXORQ\tAX, BX\n"); };
				if (n.op == TK_LSHIFTEQ) {
					emit_line("\tMOVQ\tAX, CX\n");
					emit_line("\tSHLQ\tCX, BX\n");
				};
				if (n.op == TK_RSHIFTEQ) {
					emit_line("\tMOVQ\tAX, CX\n");
					emit_line("\tSHRQ\tCX, BX\n");
				};
				emit_line("\tMOVQ\tBX, ");
				emit_off(off: i64);
				emit_line("(BP)\n");
				return;
			};
		};
		return;
	};
};

// ---- type-driven slot sizing ----------------------------------------

fn struct_lookup(c: *cgen, name: str) *struct_info = {
	let s: *struct_info = c.structs;
	for (s != nil) {
		let sn: str = s.sname;
		if (streq(sn, name)) { return s; };
		s = s.sinext;
	};
	return nil;
};

// prim_size — size in bytes of a primitive type name (or 0 if not
// recognised as a primitive — the caller falls back to other paths).
fn prim_size(name: str) i32 = {
	if (streq(name, "u8"))   { return 1; };
	if (streq(name, "i8"))   { return 1; };
	if (streq(name, "bool")) { return 1; };
	if (streq(name, "u16"))  { return 2; };
	if (streq(name, "i16"))  { return 2; };
	if (streq(name, "u32"))  { return 4; };
	if (streq(name, "i32"))  { return 4; };
	if (streq(name, "f32"))  { return 4; };
	if (streq(name, "u64"))  { return 8; };
	if (streq(name, "i64"))  { return 8; };
	if (streq(name, "uint")) { return 8; };
	if (streq(name, "int"))  { return 8; };
	if (streq(name, "uintptr")) { return 8; };
	if (streq(name, "f64"))  { return 8; };
	if (streq(name, "rune")) { return 4; };
	if (streq(name, "void")) { return 0; };
	return 0;
};

fn slot_size(c: *cgen, typ_n: *node) i32 = {
	if (typ_n == nil) { return 8; };
	let k: i32 = typ_n.kind;
	if (k == N_TPTR)   { return 8; };
	if (k == N_TFN)    { return 8; };
	if (k == N_TCHAN)  { return 8; };
	if (k == N_TSLICE) { return 24; };
	if (k == N_TTUPLE) { return 16; };
	if (k == N_TTAGGED){ return 24; };
	if (k == N_TNAME) {
		let nm: str = typ_n.str;
		if (streq(nm, "str")) { return 16; };
		let ps: i32 = prim_size(nm);
		if (ps > 0) {
			// Pad to 8 for stack slots — matches C cgen which spills
			// every primitive into an 8-byte slot.
			return 8;
		};
		// Named struct lookup.
		let si: *struct_info = struct_lookup(c, nm);
		if (si != nil) { return si.tot_size; };
		return 8;
	};
	if (k == N_TARRAY) {
		let len_n: *node = typ_n.rhs;
		let elem_n: *node = typ_n.lhs;
		let elen: i64 = 1i64;
		if (len_n != nil) {
			if (len_n.kind == N_INTLIT) { elen = len_n.uval: i64; };
		};
		let esz: i32 = 8;
		if (elem_n != nil) {
			if (elem_n.kind == N_TNAME) {
				let en: str = elem_n.str;
				let ps: i32 = prim_size(en);
				if (ps > 0) { esz = ps; };
			};
		};
		return (esz: i64 * elen): i32;
	};
	if (k == N_TSTRUCT) {
		// Inline anonymous struct — sum of field sizes.
		let f: *node = typ_n.list;
		let total: i32 = 0;
		for (f != nil) {
			if (f.kind == N_TFIELD) {
				total += slot_size(c, f.lhs);
			};
			f = f.next;
		};
		return total;
	};
	return 8;
};

// register_struct — compute field offsets + total size for a struct
// type-decl, store in c.structs. Field type sizes use the same
// slot_size logic (with primitives kept at their natural width — we
// only round to 8 for stack slots, not struct interiors).
fn field_size(c: *cgen, tnode: *node) i32 = {
	if (tnode == nil) { return 8; };
	let k: i32 = tnode.kind;
	if (k == N_TNAME) {
		let nm: str = tnode.str;
		if (streq(nm, "str")) { return 16; };
		let ps: i32 = prim_size(nm);
		if (ps > 0) { return ps; };
		let si: *struct_info = struct_lookup(c, nm);
		if (si != nil) { return si.tot_size; };
		return 8;
	};
	if (k == N_TPTR)   { return 8; };
	if (k == N_TSLICE) { return 24; };
	if (k == N_TARRAY) {
		// Same shape as slot_size's TARRAY branch.
		let len_n: *node = tnode.rhs;
		let elem_n: *node = tnode.lhs;
		let elen: i64 = 1i64;
		if (len_n != nil) {
			if (len_n.kind == N_INTLIT) { elen = len_n.uval: i64; };
		};
		let esz: i32 = field_size(c, elem_n);
		return (esz: i64 * elen): i32;
	};
	return 8;
};

fn register_struct(c: *cgen, name: str, tstruct: *node) void = {
	let si: *struct_info = amalloc(c.a, 64u64): *struct_info;
	si.sname = name;
	si.fields = nil;
	si.tot_size = 0;
	let head: *field_info = nil;
	let tail: *field_info = nil;
	let off: i32 = 0;
	let f: *node = tstruct.list;
	for (f != nil) {
		if (f.kind == N_TFIELD) {
			let sz: i32 = field_size(c, f.lhs);
			// Align to 8 for any field >= 4 bytes (matches our other
			// cgen choices). i8/u8/bool may sit on odd byte offsets;
			// the C cgen does similar best-effort packing.
			let aln: i32 = 1;
			if (sz >= 8) { aln = 8; }
			else { if (sz >= 4) { aln = 4; }
			else { if (sz >= 2) { aln = 2; }; }; };
			if ((off & (aln - 1)) != 0) {
				off = (off + aln - 1) & ~(aln - 1);
			};
			let fi: *field_info = amalloc(c.a, 48u64): *field_info;
			fi.fname = f.str;
			fi.foff = off;
			fi.fsz  = sz;
			fi.tnode = f.lhs;
			if (head == nil) { head = fi; tail = fi; }
			else { tail.finext = fi; tail = fi; };
			off += sz;
		};
		f = f.next;
	};
	// Round total to 8 for stack-slot use.
	if ((off & 7) != 0) { off = (off + 7) & ~7; };
	si.fields = head;
	si.tot_size = off;
	si.sinext = c.structs;
	c.structs = si;
};

fn collect_structs(c: *cgen, file: *node) void = {
	c.structs = nil;
	if (file == nil) { return; };
	let d: *node = file.list;
	for (d != nil) {
		if (d.kind == N_TYPEDECL) {
			let body: *node = d.lhs;
			if (body != nil) {
				if (body.kind == N_TSTRUCT) {
					register_struct(c, d.str, body);
				};
			};
		};
		d = d.next;
	};
};

// ---- frame pre-scan --------------------------------------------------
//
// Recursively walks the body to count every local `let`. Each gets a
// slot sized by slot_size(typ); 8-byte default. Match-bindings + for-
// init lets count too. Params are added by the cgfn driver.

fn scan_locals(c: *cgen, n: *node) i32 = {
	if (n == nil) { return 0; };
	let total: i32 = 0;
	if (n.kind == N_LET) {
		// Match local_add's rounding: < 8 bumps to 8, then 8-align.
		// scan_locals must agree with local_add or the prologue
		// SUBQ undersizes the frame and lets overflow into the
		// caller's stack — corrupting whatever's at -frameSize..-1
		// of the caller. Same-name re-declarations share the first
		// slot (see scan_seen_mark / local_add).
		if (!scan_seen_mark(c, n.str)) {
			let sz: i32 = slot_size(c, n.lhs);
			if (sz < 8) { sz = 8; };
			if ((sz & 7) != 0) { sz = (sz + 7) & ~7; };
			total += sz;
		};
	};
	// Match-arm binding (`case let v: T => ...`) gets a slot too.
	// Crucially we do NOT dedup these against c.locals: C cgen
	// handles a match as an expression with a by-value locals copy,
	// so two separate matches in the same function each allocate
	// their `v`/`e` slots fresh. Treating these as deduped would
	// shrink the frame below what local_add then bumps it to.
	if (n.kind == N_MCASE) {
		let bn: str = n.str;
		if (bn.len > 0) {
			let pat: *node = n.lhs;
			if (pat != nil) {
				if (is_str_type(c, pat)) { total += 16; }
				else { total += 8; };
			};
		};
	};
	if (n.lhs  != nil) { total += scan_locals(c, n.lhs);  };
	if (n.rhs  != nil) { total += scan_locals(c, n.rhs);  };
	if (n.cond != nil) { total += scan_locals(c, n.cond); };
	if (n.body != nil) { total += scan_locals(c, n.body); };
	if (n.els  != nil) { total += scan_locals(c, n.els);  };
	if (n.list != nil) {
		let m: *node = n.list;
		for (m != nil) {
			total += scan_locals(c, m);
			m = m.next;
		};
	};
	return total;
};

// ---- statement cgen --------------------------------------------------

fn cgstmt(c: *cgen, n: *node) void = {
	if (n == nil) { return; };
	let k: i32 = n.kind;

	if (k == N_BLOCK) {
		let s: *node = n.list;
		for (s != nil) {
			cgstmt(c, s);
			s = s.next;
		};
		return;
	};

	if (k == N_RETURN) {
		let rhs: *node = n.lhs;
		if (rhs != nil) {
			// Tuple return `return a, b;` — pack as (AX=v0, DX=v1).
			// Matches C cgen: evaluate v1 first (PUSHQ), then v0
			// into AX, then POPQ DX. End state: AX = v0, DX = v1.
			if (rhs.kind == N_TUPLE) {
				let v: *node = rhs.list;
				if (v != nil) {
					let v2: *node = v.next;
					if (v2 != nil) {
						cgexpr(c, v2);
						emit_line("\tPUSHQ\tAX\n");
						cgexpr(c, v);
						emit_line("\tPOPQ\tDX\n");
					} else {
						cgexpr(c, v);
					};
				};
				emit_line("\tMOVQ\tBP, SP\n");
				emit_line("\tPOPQ\tBP\n");
				emit_line("\tRET\n");
				c.last_was_return = 1;
				return;
			};
			// Tagged-union return: pack as (AX=tag, DX=value0, CX=value1).
			// For str variant, cgexpr leaves (AX=ptr, BX=len), so we
			// shuffle DX←AX (ptr) and CX←BX (len), then load tag.
			// For other variants, cgexpr leaves AX, shuffle DX←AX.
			if (is_tagged_type(c.fn_ret)) {
				cgexpr(c, rhs);
				let idx: i32 = tagged_variant_index(c, c.fn_ret, rhs);
				if (node_isstr(c, rhs)) {
					emit_line("\tMOVQ\tBX, CX\n");
					emit_line("\tMOVQ\tAX, DX\n");
				} else {
					emit_line("\tMOVQ\tAX, DX\n");
				};
				emit_line("\tMOVQ\t$");
				if (idx < 0) { idx = 0; };
				emit_int(idx: i64);
				emit_line(", AX\n");
				emit_line("\tMOVQ\tBP, SP\n");
				emit_line("\tPOPQ\tBP\n");
				emit_line("\tRET\n");
				c.last_was_return = 1;
				return;
			};
			cgexpr(c, rhs);
		} else {
			// Bare `return;` in a void fn — zero AX so the caller
			// sees a deterministic value (matches C cgen, which
			// always falls through to `cgexpr_int(c, 0)`).
			emit_line("\tMOVQ\t$0, AX\n");
		};
		// SysV: 16-byte aggregates (str, 2-tuple) return in (AX, DX).
		// cgexpr leaves str in (AX, BX); shuffle BX→DX.
		if (is_str_type(c, c.fn_ret)) {
			emit_line("\tMOVQ\tBX, DX\n");
		};
		emit_line("\tMOVQ\tBP, SP\n");
		emit_line("\tPOPQ\tBP\n");
		emit_line("\tRET\n");
		c.last_was_return = 1;
		return;
	};

	if (k == N_EXPRSTMT) {
		if (n.lhs != nil) { cgexpr(c, n.lhs); };
		c.last_was_return = 0;
		return;
	};

	if (k == N_LET) {
		let nm: str = n.str;
		let sz: i32 = slot_size(c, n.lhs);
		let off: i32 = local_add(c, nm, sz, n.lhs);
		if (n.rhs != nil) {
			let rhs: *node = n.rhs;
			// Tagged-union init: `let r: (T | E) = expr;`.
			//   - If rhs is a CALL to a fn returning tagged-union,
			//     the result is already in (AX=tag, DX=v0, CX=v1);
			//     just spill all three.
			//   - Otherwise rhs is a bare variant value: pack tag +
			//     value(s).
			if (is_tagged_type(n.lhs)) {
				let rhs_returns_tagged: bool = false;
				if (rhs.kind == N_CALL) {
					let callee: *node = rhs.lhs;
					if (callee != nil) {
						let callee_name: str;
						callee_name.ptr = nil; callee_name.len = 0;
						if (callee.kind == N_IDENT) { callee_name = callee.str; };
						if (callee.kind == N_DOT)   { callee_name = callee.str; };
						if (callee_name.len > 0) {
							let rt: *node = fnret_lookup(c, callee_name);
							if (is_tagged_type(rt)) { rhs_returns_tagged = true; };
						};
					};
				};
				cgexpr(c, rhs);
				if (rhs_returns_tagged) {
					emit_line("\tMOVQ\tAX, ");
					emit_off(off: i64);
					emit_line("(BP)\n");
					emit_line("\tMOVQ\tDX, ");
					emit_off((off + 8): i64);
					emit_line("(BP)\n");
					emit_line("\tMOVQ\tCX, ");
					emit_off((off + 16): i64);
					emit_line("(BP)\n");
					c.last_was_return = 0;
					return;
				};
				let tag_idx: i32 = tagged_variant_index(c, n.lhs, rhs);
				if (tag_idx < 0) { tag_idx = 0; };
				if (node_isstr(c, rhs)) {
					emit_line("\tMOVQ\tAX, ");
					emit_off((off + 8): i64);
					emit_line("(BP)\n");
					emit_line("\tMOVQ\tBX, ");
					emit_off((off + 16): i64);
					emit_line("(BP)\n");
				} else {
					emit_line("\tMOVQ\tAX, ");
					emit_off((off + 8): i64);
					emit_line("(BP)\n");
				};
				emit_line("\tMOVQ\t$");
				emit_int(tag_idx: i64);
				emit_line(", ");
				emit_off(off: i64);
				emit_line("(BP)\n");
				c.last_was_return = 0;
				return;
			};
			// Struct literal init: `let p: point = point{x=..., y=...};`.
			// For each field in the lit, evaluate its value and store at
			// the field's offset within the slot. Field-name → offset
			// from the struct registry.
			if (rhs.kind == N_STRUCTLIT) {
				let trefn: *node = rhs.lhs;
				let sname: str;
				sname.ptr = nil; sname.len = 0;
				if (trefn != nil) {
					if (trefn.kind == N_IDENT) { sname = trefn.str; }
					else { if (trefn.kind == N_TNAME) { sname = trefn.str; }; };
				};
				let si: *struct_info = struct_lookup(c, sname);
				if (si != nil) {
					let field_node: *node = rhs.list;
					for (field_node != nil) {
						if (field_node.kind == N_FIELD) {
							let fname: str = field_node.str;
							let fi: *field_info = si.fields;
							for (fi != nil) {
								let fn_: str = fi.fname;
								if (streq(fn_, fname)) {
									cgexpr(c, field_node.lhs);
									let sop: str = field_store_op(fi);
									emit_line("\t");
									emit_line(sop);
									emit_line("\tAX, ");
									emit_off((off + fi.foff): i64);
									emit_line("(BP)\n");
									fi = nil;
								} else {
									fi = fi.finext;
								};
							};
						};
						field_node = field_node.next;
					};
					c.last_was_return = 0;
					return;
				};
			};
			cgexpr(c, rhs);
			emit_line("\tMOVQ\tAX, ");
			emit_off(off: i64);
			emit_line("(BP)\n");
			// str init: cgexpr also leaves len in BX; store both.
			if (sz == 16) {
				emit_line("\tMOVQ\tBX, ");
				emit_off((off + 8): i64);
				emit_line("(BP)\n");
			};
			// slice init: ptr/len/cap in AX/BX/CX.
			if (sz == 24) {
				emit_line("\tMOVQ\tBX, ");
				emit_off((off + 8): i64);
				emit_line("(BP)\n");
				emit_line("\tMOVQ\tCX, ");
				emit_off((off + 16): i64);
				emit_line("(BP)\n");
			};
		} else {
			// Bare `let x: T;` with no initializer. C cgen
			// (cmd/6c/cgen.c:2181-2183) zero-inits only when
			// the underlying type's natural size is 8 — pointers,
			// i64/u64, function pointers, ints. Structs/arrays/
			// slices/strings/tagged/tuples are left for per-field
			// writes. ww's slot_size pads struct slots up to 8,
			// so we can't just check sz == 8: walk the type AST
			// directly to make the same call.
			if (type_is_8byte_primitive(c, n.lhs)) {
				emit_line("\tMOVQ\t$0, ");
				emit_off(off: i64);
				emit_line("(BP)\n");
			};
		};
		c.last_was_return = 0;
		return;
	};

	if (k == N_IF) {
		let els: str = mklabel(c, "else");
		let endl: str = mklabel(c, "end");
		cgexpr(c, n.cond);
		emit_line("\tCMPQ\t$0, AX\n");
		emit_line("\tJE\t");
		if (n.els != nil) { emit_line(els); }
		else              { emit_line(endl); };
		emit_line("\n");
		if (n.body != nil) { cgstmt(c, n.body); };
		if (n.els != nil) {
			emit_line("\tJMP\t"); emit_line(endl); emit_line("\n");
			emit_label(els);
			cgstmt(c, n.els);
		};
		emit_label(endl);
		c.last_was_return = 0;
		return;
	};

	if (k == N_FOR) {
		// Match C cgen's label scheme: <fn>_loop_N for the top,
		// <fn>_endloop_N for the post-body merge. No separate cont
		// label when there's no post-expression.
		let topl: str = mklabel(c, "loop");
		let endl: str = mklabel(c, "endloop");

		if (n.lhs != nil) { cgstmt(c, n.lhs); };

		emit_label(topl);
		if (n.cond != nil) {
			cgexpr(c, n.cond);
			emit_line("\tCMPQ\t$0, AX\n");
			emit_line("\tJE\t"); emit_line(endl); emit_line("\n");
		};

		c.loop_end_buf[c.loop_top]  = endl;
		c.loop_cont_buf[c.loop_top] = topl;
		c.loop_top += 1;

		if (n.body != nil) { cgstmt(c, n.body); };

		c.loop_top -= 1;

		if (n.rhs != nil) { cgexpr(c, n.rhs); };
		emit_line("\tJMP\t"); emit_line(topl); emit_line("\n");
		emit_label(endl);
		c.last_was_return = 0;
		return;
	};

	// Tuple-destructure assign: `a, b = call();`. The call's tuple
	// return lands in (AX, DX); push DX to free it, store AX into
	// the first lvalue, then pop DX into the second. Mirrors
	// cmd/6c/cgen.c:2424-2440. Lvalues beyond two are dropped (same
	// as C — no fixture uses >2 today).
	if (k == N_MASSIGN) {
		if (n.rhs != nil) { cgexpr(c, n.rhs); };
		emit_line("\tPUSHQ\tDX\n");
		let l0: *node = n.list;
		let l1: *node = nil;
		if (l0 != nil) { l1 = l0.next; };
		if (l0 != nil) {
			if (l0.kind == N_IDENT) {
				let off: i32 = local_find(c, l0.str);
				if (off != 0) {
					emit_line("\tMOVQ\tAX, ");
					emit_off(off: i64);
					emit_line("(BP)\n");
				};
			};
		};
		emit_line("\tPOPQ\tDX\n");
		if (l1 != nil) {
			if (l1.kind == N_IDENT) {
				let off: i32 = local_find(c, l1.str);
				if (off != 0) {
					emit_line("\tMOVQ\tDX, ");
					emit_off(off: i64);
					emit_line("(BP)\n");
				};
			};
		};
		c.last_was_return = 0;
		return;
	};

	if (k == N_BREAK) {
		if (c.loop_top > 0) {
			let lbl: str = c.loop_end_buf[c.loop_top - 1];
			emit_line("\tJMP\t"); emit_line(lbl); emit_line("\n");
		};
		c.last_was_return = 0;
		return;
	};
	if (k == N_CONTINUE) {
		if (c.loop_top > 0) {
			let lbl: str = c.loop_cont_buf[c.loop_top - 1];
			emit_line("\tJMP\t"); emit_line(lbl); emit_line("\n");
		};
		c.last_was_return = 0;
		return;
	};

	c.last_was_return = 0;
};

// ---- function-level cgen ---------------------------------------------

// is_str_type — true when the type expr resolves (through any
// `type X = str;` aliases) to `str`. Takes *cgen so it can walk the
// alias chain registered at file load.
fn is_str_type_raw(t: *node) bool = {
	if (t == nil) { return false; };
	if (t.kind == N_TNAME) {
		let nm: str = t.str;
		if (streq(nm, "str")) { return true; };
	};
	return false;
};

fn is_str_type(c: *cgen, t: *node) bool = {
	if (is_str_type_raw(t)) { return true; };
	if (c == nil) { return false; };
	let r: *node = resolve_type(c, t);
	return is_str_type_raw(r);
};

fn is_slice_type_raw(t: *node) bool = {
	if (t == nil) { return false; };
	if (t.kind == N_TSLICE) { return true; };
	return false;
};

fn is_slice_type(c: *cgen, t: *node) bool = {
	if (is_slice_type_raw(t)) { return true; };
	if (c == nil) { return false; };
	let r: *node = resolve_type(c, t);
	return is_slice_type_raw(r);
};

fn is_tagged_type(t: *node) bool = {
	if (t == nil) { return false; };
	if (t.kind == N_TTAGGED) { return true; };
	return false;
};

// rhs_target_name — for a returned value, what's its declared (or
// surface-inferred) type name? `expr: T` casts dictate T directly;
// bare strlit/intlit fall back to a primitive name.
fn rhs_target_name(c: *cgen, rhs: *node) str = {
	let nm: str;
	nm.ptr = nil; nm.len = 0;
	if (rhs == nil) { return nm; };
	if (rhs.kind == N_CAST) {
		let t: *node = rhs.rhs;
		if (t != nil) {
			if (t.kind == N_TNAME) { return t.str; };
		};
		return nm;
	};
	if (rhs.kind == N_STRLIT) { return "str"; };
	if (rhs.kind == N_IDENT) {
		let lc: *local = local_find_node(c, rhs.str);
		if (lc != nil) {
			let tn: *node = lc.tnode;
			if (tn != nil) {
				if (tn.kind == N_TNAME) { return tn.str; };
			};
		};
	};
	return nm;
};

// tagged_variant_index — given the tagged-union type expr and the
// returned value's surface type, find the matching variant's 0-based
// index. Compare by exact type name first; if no match, fall back to
// "any str-shape variant matches an str-typed value".
fn tagged_variant_index(c: *cgen, tagged: *node, rhs: *node) i32 = {
	if (tagged == nil) { return -1; };
	if (rhs == nil)    { return -1; };
	let want_name: str = rhs_target_name(c, rhs);
	if (want_name.len > 0) {
		let v: *node = tagged.list;
		let idx: i32 = 0;
		for (v != nil) {
			if (v.kind == N_TNAME) {
				if (streq(v.str, want_name)) { return idx; };
			};
			v = v.next;
			idx += 1;
		};
	};
	// Fallback: by str-shape (resolves aliases).
	let want_str: bool = node_isstr(c, rhs);
	let v: *node = tagged.list;
	let idx: i32 = 0;
	for (v != nil) {
		let v_is_str: bool = false;
		if (v.kind == N_TNAME) {
			if (is_str_type(c, v)) { v_is_str = true; };
		};
		if (v_is_str == want_str) { return idx; };
		v = v.next;
		idx += 1;
	};
	return -1;
};

fn cgfn_params(c: *cgen, params: *node) void = {
	let p: *node = params;
	let idx: i32 = 0;
	for (p != nil) {
		if (p.kind == N_PARAM) {
			let nm: str = p.str;
			if (is_tagged_type(p.lhs)) {
				// tagged-union param: passed in 3 regs (tag, v0, v1),
				// 24-byte slot.
				let off: i32 = local_add(c, nm, 24, p.lhs);
				emit_line("\tMOVQ\t");
				emit_line(argreg_name(idx));
				emit_line(", ");
				emit_off(off: i64);
				emit_line("(BP)\n");
				idx += 1;
				emit_line("\tMOVQ\t");
				emit_line(argreg_name(idx));
				emit_line(", ");
				emit_off((off + 8): i64);
				emit_line("(BP)\n");
				idx += 1;
				emit_line("\tMOVQ\t");
				emit_line(argreg_name(idx));
				emit_line(", ");
				emit_off((off + 16): i64);
				emit_line("(BP)\n");
				idx += 1;
			} else { if (is_slice_type(c, p.lhs)) {
				// slice param: 3 regs (ptr, len, cap), 24-byte slot.
				let off: i32 = local_add(c, nm, 24, p.lhs);
				emit_line("\tMOVQ\t");
				emit_line(argreg_name(idx));
				emit_line(", ");
				emit_off(off: i64);
				emit_line("(BP)\n");
				idx += 1;
				emit_line("\tMOVQ\t");
				emit_line(argreg_name(idx));
				emit_line(", ");
				emit_off((off + 8): i64);
				emit_line("(BP)\n");
				idx += 1;
				emit_line("\tMOVQ\t");
				emit_line(argreg_name(idx));
				emit_line(", ");
				emit_off((off + 16): i64);
				emit_line("(BP)\n");
				idx += 1;
			} else { if (is_str_type(c, p.lhs)) {
				// str param: passed in two regs (ptr, len).
				// Slot is 16 bytes; ptr at off+0, len at off+8.
				let off: i32 = local_add(c, nm, 16, p.lhs);
				emit_line("\tMOVQ\t");
				emit_line(argreg_name(idx));
				emit_line(", ");
				emit_off(off: i64);
				emit_line("(BP)\n");
				idx += 1;
				emit_line("\tMOVQ\t");
				emit_line(argreg_name(idx));
				emit_line(", ");
				emit_off((off + 8): i64);
				emit_line("(BP)\n");
				idx += 1;
			} else {
				let off: i32 = local_add(c, nm, 8, p.lhs);
				emit_line("\tMOVQ\t");
				emit_line(argreg_name(idx));
				emit_line(", ");
				emit_off(off: i64);
				emit_line("(BP)\n");
				idx += 1;
			};};};
		};
		p = p.next;
	};
};

fn cgfn(c: *cgen, fn_: *node) void = {
	cgen_init(c, c.a);
	c.fn_name = fn_.str;
	c.fn_ret  = fn_.lhs;

	emit_line("TEXT ");
	let nm: str = fn_.str;
	os.write(1, nm.ptr, nm.len: u64);
	emit_line(",$");

	// Pre-scan total frame: 24 bytes per slice param, 16 per str
	// param, 8 per other param, plus per-let from scan_locals.
	// Seed c.locals with param-name stubs so scan_locals dedups a
	// re-declared `let <name>` in the body against the param's
	// slot (matches C cgen). Stubs get cleared before emission.
	let scan_p: *node = fn_.list;
	let frame: i32 = 0;
	for (scan_p != nil) {
		if (scan_p.kind == N_PARAM) {
			if (is_tagged_type(scan_p.lhs)) { frame += 24; }
			else { if (is_slice_type(c, scan_p.lhs)) { frame += 24; }
			else { if (is_str_type(c, scan_p.lhs)) { frame += 16; }
			else { frame += 8; }; }; };
			scan_seen_mark(c, scan_p.str);
		};
		scan_p = scan_p.next;
	};
	if (fn_.body != nil) { frame += scan_locals(c, fn_.body); };
	// Drop the stubs so emission rebuilds c.locals with real offsets.
	c.locals = nil;
	if ((frame & 15) != 0) {
		frame = (frame + 15) & ~15;
	};
	emit_int(frame: i64);
	emit_line("\n");

	emit_line("\tPUSHQ\tBP\n");
	emit_line("\tMOVQ\tSP, BP\n");
	emit_line("\tSUBQ\t$");
	emit_int(frame: i64);
	emit_line(", SP\n");

	cgfn_params(c, fn_.list);
	c.last_was_return = 0;
	if (fn_.body != nil) { cgstmt(c, fn_.body); };

	if (c.last_was_return == 0) {
		// Zero AX before the fall-through return — matches C cgen,
		// which always emits this so void-returning fns don't leak
		// a stale callee value to their caller.
		emit_line("\tMOVQ\t$0, AX\n");
		emit_line("\tMOVQ\tBP, SP\n");
		emit_line("\tPOPQ\tBP\n");
		emit_line("\tRET\n");
	};
};

// ---- file-level entry ------------------------------------------------

export fn cg_file(c: *cgen, file: *node) void = {
	if (file == nil) { return; };
	c.strlits = nil;
	c.strlit_seq = 0;
	collect_aliases(c, file);
	collect_structs(c, file);
	collect_defs(c, file);
	collect_fnrets(c, file);
	ffi_collect(c, file);
	let d: *node = file.list;
	for (d != nil) {
		if (d.kind == N_FNDECL) {
			if (d.body != nil) {
				cgfn(c, d);
			};
		};
		d = d.next;
	};
	emit_data_section(c);
	emit_def_constants(c, file);
};