// selfhost/cmd/wcc/cgenutil.ww — split out of cgen.ww.
//
// General helpers used across cgenexpr / cgenstmt / cgendecl:
//   - pushargsrev: per-call arg pushing
//   - type predicates: isstr*/isslice*/istagged*/nodeis* families
//   - field ops:    fieldloadop, fieldstoreop
//   - index helpers: indexbaseesz, dotinnerstructptr, elemsizeof
//   - slot sizing:  structlookup, primsize, slotsize, fieldsize,
//                   registerstruct, collectstructs
//   - rhs helpers:  rhstargetname, taggedvariantindex
//
// Bundler pulls this in transitively via cgen.ww; consumers don't
// need to `use cgenutil;` directly.

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

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

// pushargsrev — 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 pushargsrev(c: *cgen, arg: *node) i32 = {
	if (arg == nil) { return 0; };
	let rest: i32 = pushargsrev(c, arg.next);
	// nkind.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 == nkind.N_SLICE) {
		let base: *node = arg.lhs;
		let lo: *node = arg.rhs;
		let hi: *node = arg.cond;
		let baselocal: *local = nil;
		if (base != nil) {
			if (base.kind == nkind.N_IDENT) {
				let bn: str = base.str;
				baselocal = localfindnode(c, bn);
			};
		};
		// base address → push
		if (baselocal != nil) {
			let tn: *node = baselocal.tnode;
			if (tn != nil) {
				if (tn.kind == nkind.N_TARRAY) {
					emitline("\tLEAQ\t");
					emitoff(baselocal.off: i64);
					emitline("(BP), AX\n");
				} else {
					emitline("\tMOVQ\t");
					emitoff(baselocal.off: i64);
					emitline("(BP), AX\n");
				};
			} else {
				emitline("\tMOVQ\t");
				emitoff(baselocal.off: i64);
				emitline("(BP), AX\n");
			};
		} else {
			cgexpr(c, base);
		};
		emitline("\tPUSHQ\tAX\n");
		// hi (default base length) → push
		if (hi != nil) {
			cgexpr(c, hi);
		} else { if (baselocal != nil) {
			let tn: *node = baselocal.tnode;
			if (tn != nil) {
				if (tn.kind == nkind.N_TARRAY) {
					let lenn: *node = tn.rhs;
					if (lenn != nil) {
						if (lenn.kind == nkind.N_INTLIT) {
							emitline("\tMOVQ\t$");
							emituint(lenn.uval);
							emitline(", AX\n");
						};
					};
				} else { if (tn.kind == nkind.N_TSLICE) {
					emitline("\tMOVQ\t");
					emitoff((baselocal.off + 8): i64);
					emitline("(BP), AX\n");
				} else { if (tn.kind == nkind.N_TNAME) {
					if (streq(tn.str, "str")) {
						emitline("\tMOVQ\t");
						emitoff((baselocal.off + 8): i64);
						emitline("(BP), AX\n");
					};
				};};};
			};
		} else {
			emitline("\tMOVQ\t$0, AX\n");
		};};
		emitline("\tPUSHQ\tAX\n");
		// lo (default 0) → AX
		if (lo != nil) { cgexpr(c, lo); }
		else { emitline("\tMOVQ\t$0, AX\n"); };
		emitline("\tPOPQ\tBX\n");           // hi
		emitline("\tPOPQ\tCX\n");           // base
		emitline("\tMOVQ\tBX, DX\n");       // DX = hi
		emitline("\tSUBQ\tAX, DX\n");       // DX = hi - lo = len
		emitline("\tADDQ\tAX, CX\n");       // CX = base + lo = ptr
		emitline("\tPUSHQ\tDX\n");          // cap
		emitline("\tPUSHQ\tDX\n");          // len
		emitline("\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 == nkind.N_IDENT) {
		let nm: str = arg.str;
		let lc: *local = localfindnode(c, nm);
		if (lc != nil) {
			let off: i32 = lc.off;
			if (isslicetype(c, lc.tnode) || istaggedtype(lc.tnode)) {
				emitline("\tMOVQ\t");
				emitoff((off + 16): i64);
				emitline("(BP), AX\n");
				emitline("\tPUSHQ\tAX\n");
				emitline("\tMOVQ\t");
				emitoff((off + 8): i64);
				emitline("(BP), AX\n");
				emitline("\tPUSHQ\tAX\n");
				emitline("\tMOVQ\t");
				emitoff(off: i64);
				emitline("(BP), AX\n");
				emitline("\tPUSHQ\tAX\n");
				return rest + 3;
			};
		};
	};
	// Float arg: cgexpr leaves the value in X0. Push 8 bytes from
	// X0 via SUBQ+MOVSD so cgcall's pop side can drain into the
	// XMM stream (X0..X7). f32 still occupies 8B on the stack —
	// the MOVSS load on the pop side touches only the low 4.
	let fk: i32 = exprfloatkind(c, arg);
	if (fk != 0) {
		cgexpr(c, arg);
		let mov: str = "MOVSD";
		if (fk == 1) { mov = "MOVSS"; };
		emitline("\tSUBQ\t$8, SP\n");
		emitline("\t");
		emitline(mov);
		emitline("\tX0, (SP)\n");
		return rest + 1;
	};
	cgexpr(c, arg);
	if (nodeisslice(c, arg)) {
		emitline("\tPUSHQ\tCX\n");
		emitline("\tPUSHQ\tBX\n");
		emitline("\tPUSHQ\tAX\n");
		return rest + 3;
	};
	if (nodeisstr(c, arg)) {
		emitline("\tPUSHQ\tBX\n");
		emitline("\tPUSHQ\tAX\n");
		return rest + 2;
	};
	emitline("\tPUSHQ\tAX\n");
	return rest + 1;
};

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

// nodeisstr — 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 nodeisstr(c: *cgen, n: *node) bool = {
	if (n == nil) { return false; };
	let k: nkind = n.kind;
	if (k == nkind.N_STRLIT) { return true; };
	if (k == nkind.N_IDENT) {
		let nm: str = n.str;
		let lc: *local = localfindnode(c, nm);
		if (lc != nil) {
			let tn: *node = lc.tnode;
			if (tn != nil) {
				if (tn.kind == nkind.N_TNAME) {
					let tnm: str = tn.str;
					if (streq(tnm, "str")) { return true; };
				};
			};
		};
		return false;
	};
	if (k == nkind.N_CALL) {
		let callee: *node = n.lhs;
		if (callee != nil) {
			if (callee.kind == nkind.N_IDENT) {
				let cnm: str = callee.str;
				let rt: *node = fnretlookup(c, cnm);
				return isstrtype(c, rt);
			};
		};
		return false;
	};
	if (k == nkind.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 == nkind.N_IDENT) {
				let lc: *local = localfindnode(c, base.str);
				if (lc != nil) {
					let tn: *node = lc.tnode;
					let lkind: nkind = nkind.N_NONE;
					if (tn != nil) { lkind = tn.kind; };
					if (lkind == nkind.N_TNAME) { sname = tn.str; };
					if (lkind == nkind.N_TPTR) {
						let inner: *node = tn.lhs;
						if (inner != nil) {
							if (inner.kind == nkind.N_TNAME) { sname = inner.str; };
						};
					};
				};
			};
			// Chained dot (`p.foo.bar`): use dotinnerstructptr
			// to resolve the inner chain to the *struct it lands
			// on, then look up `fld` in that struct.
			if (base.kind == nkind.N_DOT) {
				let innert: *node = dotinnerstructptr(c, base);
				if (innert != nil) {
					if (innert.kind == nkind.N_TNAME) { sname = innert.str; };
				};
			};
			if (sname.len > 0) {
				let si: *structinfo = structlookup(c, sname);
				if (si != nil) {
					let fi: *fieldinfo = si.fields;
					for (fi != nil) {
						let fn_: str = fi.fname;
						if (streq(fn_, fld)) {
							return isstrtype(c, fi.tnode);
						};
						fi = fi.finext;
					};
				};
			};
		};
		return false;
	};
	if (k == nkind.N_CAST) {
		return isstrtype(c, n.rhs);
	};
	return false;
};

// typenameisunsigned — true for u8/u16/u32/u64/uint/uintptr.
fn typenameisunsigned(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;
};

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

// typeis8byteprimitive — 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 nkind.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 typeis8byteprimitive(c: *cgen, t: *node) bool = {
	if (t == nil) { return false; };
	let k: nkind = t.kind;
	if (k == nkind.N_TPTR)   { return true; };
	if (k == nkind.N_TFN)    { return true; };
	if (k == nkind.N_TCHAN)  { return true; };
	if (k == nkind.N_TSLICE) { return false; };
	if (k == nkind.N_TARRAY) {
		// C cgen (cmd/w6c/cgen.c:3317) zero-inits TY_ARRAY whenever
		// its raw byte size is 8 — e.g. `[8]bool`, `[2]i32`, `[4]i16`,
		// `[1]i64`. Mirror that here so the wwstage matches.
		let lenn: *node = t.rhs;
		let elemn: *node = t.lhs;
		if (lenn == nil) { return false; };
		if (lenn.kind != nkind.N_INTLIT) { return false; };
		let elen: i64 = lenn.uval: i64;
		let esz: i32 = 8;
		if (elemn != nil) {
			if (elemn.kind == nkind.N_TNAME) {
				let ps: i32 = primsize(elemn.str);
				if (ps > 0) { esz = ps; };
			};
		};
		return (esz: i64 * elen) == 8i64;
	};
	if (k == nkind.N_TTUPLE) { return false; };
	if (k == nkind.N_TTAGGED){ return false; };
	if (k == nkind.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 (structlookup(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 (primsize(nm) > 0) { return true; };
		return false;
	};
	return false;
};

// elemissigned — given an indexable type (`*T`, `[]T`, `[N]T`), is
// its element a signed narrow primitive (i8/i16/i32/rune)? Used by
// cgindex to pick MOVSXD vs MOVL at esz=4. Mirrors C cgen's
// `signed_elem` check.
fn elemissigned(t: *node) bool = {
	if (t == nil) { return false; };
	let elem: *node = nil;
	let k: nkind = t.kind;
	if (k == nkind.N_TPTR)   { elem = t.lhs; };
	if (k == nkind.N_TSLICE) { elem = t.lhs; };
	if (k == nkind.N_TARRAY) { elem = t.lhs; };
	if (elem == nil) { return false; };
	if (elem.kind != nkind.N_TNAME) { return false; };
	return typenameissigned(elem.str);
};

// typenameissigned — true for i8/i16/i32/i64/int/rune.
fn typenameissigned(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;
};

// fieldloadop — 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 fieldloadop(f: *fieldinfo) 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 == nkind.N_TNAME) {
				if (typenameissigned(t.str)) { return "MOVSXD"; };
			};
		};
		return "MOVL";
	};
	return "MOVQ";
};

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

// indexbaseesz — 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 indexbaseesz(c: *cgen, base: *node) i32 = {
	if (base == nil) { return 8; };
	if (base.kind != nkind.N_DOT) { return 8; };
	let fld: str = base.str;
	let inner: *node = base.lhs;
	if (inner == nil) { return 8; };
	if (inner.kind != nkind.N_IDENT) { return 8; };
	let nm: str = inner.str;
	let lc: *local = localfindnode(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 innert: *node = tn;
		if (tn.kind == nkind.N_TPTR) { innert = tn.lhs; };
		if (innert == nil) { return 8; };
		if (innert.kind == nkind.N_TNAME) {
			if (streq(innert.str, "str")) { return 1; };
		};
		if (innert.kind == nkind.N_TSLICE) { return elemsizeof(innert); };
		return 8;
	};

	// Generic struct field: if it's *T, element size is T's size.
	let lkind: nkind = tn.kind;
	let sname: str;
	sname.ptr = nil; sname.len = 0;
	if (lkind == nkind.N_TNAME) { sname = tn.str; };
	if (lkind == nkind.N_TPTR) {
		let pinner: *node = tn.lhs;
		if (pinner != nil) {
			if (pinner.kind == nkind.N_TNAME) { sname = pinner.str; };
		};
	};
	if (sname.len == 0) { return 8; };
	let si: *structinfo = structlookup(c, sname);
	if (si == nil) { return 8; };
	let fi: *fieldinfo = 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 == nkind.N_TPTR) {
				let elem: *node = ft.lhs;
				if (elem != nil) {
					if (elem.kind == nkind.N_TNAME) {
						if (streq(elem.str, "str")) { return 16; };
						let ps: i32 = primsize(elem.str);
						if (ps > 0) { return ps; };
					};
				};
				return 8;
			};
			if (ft.kind == nkind.N_TSLICE) { return elemsizeof(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 == nkind.N_TNAME) {
				if (streq(ft.str, "str")) { return 1; };
			};
			return 8;
		};
		fi = fi.finext;
	};
	return 8;
};

// dotinnerstructptr — for an nkind.N_DOT whose lhs is a chain of dots
// or an nkind.N_IDENT, walk the chain and return the nkind.N_TNAME tnode of the
// struct that the chain dereferences to (i.e., for `r.sym` where
// .sym is *lsym, return nkind.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 dotinnerstructptr(c: *cgen, n: *node) *node = {
	if (n == nil) { return nil; };
	if (n.kind != nkind.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 baset: *node = nil;
	if (base.kind == nkind.N_IDENT) {
		let lc: *local = localfindnode(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 (nkind.N_TNAME) or *struct (nkind.N_TPTR).
		if (tn.kind == nkind.N_TNAME) { baset = tn; };
		if (tn.kind == nkind.N_TPTR)  { baset = tn.lhs; };
	} else { if (base.kind == nkind.N_DOT) {
		baset = dotinnerstructptr(c, base);
	};};
	if (baset == nil) { return nil; };
	if (baset.kind != nkind.N_TNAME) { return nil; };

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

// elemsizeof — 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 elemsizeof(t: *node) i32 = {
	if (t == nil) { return 1; };
	let k: nkind = t.kind;
	let elem: *node = nil;
	if (k == nkind.N_TPTR)   { elem = t.lhs; };
	if (k == nkind.N_TSLICE) { elem = t.lhs; };
	if (k == nkind.N_TARRAY) { elem = t.lhs; };
	if (k == nkind.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 = primsize(nm);
		if (ps > 0) { return ps; };
		return 1;
	};
	if (elem == nil) { return 1; };
	if (elem.kind == nkind.N_TNAME) {
		let nm: str = elem.str;
		// str element is 16B (ptr+len). primsize returns 0 for it.
		if (streq(nm, "str")) { return 16; };
		let ps: i32 = primsize(nm);
		if (ps > 0) { return ps; };
	};
	return 8;
};

// nodeisunsigned — best-effort cgen-time inference from the AST. We
// don't have a typed AST yet, so we walk surface nodes:
//   nkind.N_INTLIT      — never marked unsigned (no tsuffix plumbing yet)
//   nkind.N_IDENT       — look up the local's declared type
//   nkind.N_DOT         — look up the field's declared type via struct reg
//   nkind.N_BIN / nkind.N_UN  — recurse: unsigned if either operand is unsigned
//   nkind.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 nodeisunsigned(c: *cgen, n: *node) bool = {
	if (n == nil) { return false; };
	let k: nkind = n.kind;
	if (k == nkind.N_IDENT) {
		let nm: str = n.str;
		let lc: *local = localfindnode(c, nm);
		if (lc != nil) { return typenodeisunsigned(lc.tnode); };
		return false;
	};
	if (k == nkind.N_DOT) {
		let base: *node = n.lhs;
		let fld: str = n.str;
		if (base != nil) {
			if (base.kind == nkind.N_IDENT) {
				let bn: str = base.str;
				let lc: *local = localfindnode(c, bn);
				if (lc != nil) {
					let tn: *node = lc.tnode;
					let lkind: nkind = nkind.N_NONE;
					if (tn != nil) { lkind = tn.kind; };
					let sname: str;
					sname.ptr = nil; sname.len = 0;
					if (lkind == nkind.N_TPTR) {
						let inner: *node = tn.lhs;
						if (inner != nil) {
							if (inner.kind == nkind.N_TNAME) { sname = inner.str; };
						};
					};
					if (lkind == nkind.N_TNAME) { sname = tn.str; };
					if (sname.len > 0) {
						let si: *structinfo = structlookup(c, sname);
						if (si != nil) {
							let fi: *fieldinfo = si.fields;
							for (fi != nil) {
								let fn_: str = fi.fname;
								if (streq(fn_, fld)) {
									return typenodeisunsigned(fi.tnode);
								};
								fi = fi.finext;
							};
						};
					};
				};
			};
		};
		return false;
	};
	if (k == nkind.N_CAST) { return typenodeisunsigned(n.rhs); };
	if (k == nkind.N_BIN) {
		if (nodeisunsigned(c, n.lhs)) { return true; };
		return nodeisunsigned(c, n.rhs);
	};
	if (k == nkind.N_UN) { return nodeisunsigned(c, n.lhs); };
	// nkind.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 w6c on byte indexing.
	if (k == nkind.N_INDEX) {
		let base: *node = n.lhs;
		if (base != nil) {
			if (base.kind == nkind.N_IDENT) {
				let lc: *local = localfindnode(c, base.str);
				if (lc != nil) {
					let tn: *node = lc.tnode;
					if (tn != nil) {
						let elem: *node = nil;
						if (tn.kind == nkind.N_TPTR)   { elem = tn.lhs; };
						if (tn.kind == nkind.N_TARRAY) { elem = tn.lhs; };
						if (tn.kind == nkind.N_TSLICE) { elem = tn.lhs; };
						if (elem != nil) {
							return typenodeisunsigned(elem);
						};
					};
				};
			};
		};
		return false;
	};
	return false;
};
// ---- type-driven slot sizing ----------------------------------------

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

// primsize — size in bytes of a primitive type name (or 0 if not
// recognised as a primitive — the caller falls back to other paths).
// fldnumidx — parse a tuple field name like "0" / "1" / "12" into an
// index, or -1 if not all-digits. Used by cgdot to dispatch
// `t.0` / `t.1` against an nkind.N_TTUPLE local without pulling in strconv.
fn fldnumidx(s: str) i32 = {
	if (s.len == 0) { return -1; };
	let r: i32 = 0;
	let i: i32 = 0;
	for (i < s.len) {
		let b: u8 = s[i];
		if (b < 48u8) { return -1; };
		if (b > 57u8) { return -1; };
		r = r * 10 + ((b - 48u8): i32);
		i += 1;
	};
	return r;
};

fn primsize(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;
};

// letslotsize — slot size for a `let` binding. Like slotsize, but
// detects `[_]T = arrlit;` (the type-AST has rhs == nil as the
// length-inferred sentinel) and computes count × element-size from
// the initialiser. Used by both scanlocals (prologue sizing) and
// cglet (slot alloc) so they agree on the frame layout.
export fn letslotsize(c: *cgen, n: *node) i32 = {
	// `[_]T = arrlit;` — inferred-length array. slotsize would
	// return elem_size * 1 (treating missing length as 1); intercept
	// and compute the real count first.
	if (n.lhs != nil) {
		if (n.lhs.kind == nkind.N_TARRAY) {
			if (n.lhs.rhs == nil) {
				if (n.rhs != nil) {
					if (n.rhs.kind == nkind.N_ARRLIT) {
						let elemn: *node = n.lhs.lhs;
						let esz: i32 = 8;
						if (elemn != nil) {
							if (elemn.kind == nkind.N_TNAME) {
								let ps: i32 = primsize(elemn.str);
								if (ps > 0) { esz = ps; };
							};
						};
						let cnt: i32 = 0;
						let e: *node = n.rhs.list;
						for (e != nil) {
							let adv: bool = true;
							if (e.kind == nkind.N_FIELD) {
								if (streq(e.str, "...")) {
									e = nil;
									adv = false;
								};
							};
							if (adv) {
								cnt += 1;
								e = e.next;
							};
						};
						return esz * cnt;
					};
				};
			};
		};
	};
	return slotsize(c, n.lhs);
};

fn slotsize(c: *cgen, typn: *node) i32 = {
	if (typn == nil) { return 8; };
	let k: nkind = typn.kind;
	if (k == nkind.N_TPTR)   { return 8; };
	if (k == nkind.N_TFN)    { return 8; };
	if (k == nkind.N_TCHAN)  { return 8; };
	if (k == nkind.N_TSLICE) { return 24; };
	if (k == nkind.N_TTUPLE) {
		// Sum element sizes. Mirrors C cgen which uses raw type
		// sizes; padding to 8 happens inside slotsize for primitives,
		// so a `(i64, str)` resolves to 8 + 16 = 24 (matches the C
		// cgen 24B init / positional-access layout).
		let total: i32 = 0;
		let p: *node = typn.list;
		for (p != nil) {
			total += slotsize(c, p);
			p = p.next;
		};
		return total;
	};
	if (k == nkind.N_TTAGGED){
		// Nullable `(*T | void)` collapses to a single 8B pointer.
		if (isnullabletype(typn)) { return 8; };
		// Slot = 8 (tag) + max(variant payload sizes), rounded up
		// to an 8-byte multiple so the reg-passing ABI (size/8
		// words) doesn't drop the last value register. Mirrors C
		// cgen's resolve_type for nkind.N_TTAGGED.
		let v: *node = typn.list;
		let maxsz: i32 = 0;
		for (v != nil) {
			let sz: i32 = slotsize(c, v);
			if (sz > maxsz) { maxsz = sz; };
			v = v.next;
		};
		let pad: i32 = (maxsz + 7) & ~7;
		return 8 + pad;
	};
	if (k == nkind.N_TNAME) {
		let nm: str = typn.str;
		if (streq(nm, "str")) { return 16; };
		let ps: i32 = primsize(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: *structinfo = structlookup(c, nm);
		if (si != nil) { return si.totsize; };
		return 8;
	};
	if (k == nkind.N_TARRAY) {
		let lenn: *node = typn.rhs;
		let elemn: *node = typn.lhs;
		let elen: i64 = 1i64;
		if (lenn != nil) {
			if (lenn.kind == nkind.N_INTLIT) { elen = lenn.uval: i64; };
		};
		let esz: i32 = 8;
		if (elemn != nil) {
			if (elemn.kind == nkind.N_TNAME) {
				let en: str = elemn.str;
				let ps: i32 = primsize(en);
				if (ps > 0) { esz = ps; };
			};
		};
		return (esz: i64 * elen): i32;
	};
	if (k == nkind.N_TSTRUCT) {
		// Inline anonymous struct — sum of field sizes.
		let f: *node = typn.list;
		let total: i32 = 0;
		for (f != nil) {
			if (f.kind == nkind.N_TFIELD) {
				total += slotsize(c, f.lhs);
			};
			f = f.next;
		};
		return total;
	};
	return 8;
};

// registerstruct — compute field offsets + total size for a struct
// type-decl, store in c.structs. Field type sizes use the same
// slotsize logic (with primitives kept at their natural width — we
// only round to 8 for stack slots, not struct interiors).
fn fieldsize(c: *cgen, tnode: *node) i32 = {
	if (tnode == nil) { return 8; };
	let k: nkind = tnode.kind;
	if (k == nkind.N_TNAME) {
		let nm: str = tnode.str;
		if (streq(nm, "str")) { return 16; };
		let ps: i32 = primsize(nm);
		if (ps > 0) { return ps; };
		let si: *structinfo = structlookup(c, nm);
		if (si != nil) { return si.totsize; };
		// Enum: size of its storage type. Mirrors the C cgen, which
		// reads Type.size off the TY_ENUM (which inherits from .sub).
		let en: *enumtype = enumlookup(c, nm);
		if (en != nil) {
			if (en.storage != nil) {
				if (en.storage.kind == nkind.N_TNAME) {
					let sps: i32 = primsize(en.storage.str);
					if (sps > 0) { return sps; };
				};
			};
			return 4;	// default storage is i32
		};
		return 8;
	};
	if (k == nkind.N_TPTR)   { return 8; };
	if (k == nkind.N_TSLICE) { return 24; };
	if (k == nkind.N_TARRAY) {
		// Same shape as slotsize's TARRAY branch.
		let lenn: *node = tnode.rhs;
		let elemn: *node = tnode.lhs;
		let elen: i64 = 1i64;
		if (lenn != nil) {
			if (lenn.kind == nkind.N_INTLIT) { elen = lenn.uval: i64; };
		};
		let esz: i32 = fieldsize(c, elemn);
		return (esz: i64 * elen): i32;
	};
	return 8;
};

fn registerstruct(c: *cgen, name: str, tstruct: *node) void = {
	let si: *structinfo = amalloc(c.a, 64u64): *structinfo;
	si.sname = name;
	si.fields = nil;
	si.totsize = 0;
	let head: *fieldinfo = nil;
	let tail: *fieldinfo = nil;
	let off: i32 = 0;
	let f: *node = tstruct.list;
	for (f != nil) {
		if (f.kind == nkind.N_TFIELD) {
			let sz: i32 = fieldsize(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: *fieldinfo = amalloc(c.a, 48u64): *fieldinfo;
			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.totsize = off;
	si.sinext = c.structs;
	c.structs = si;
};

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

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

fn isstrtype(c: *cgen, t: *node) bool = {
	if (isstrtyperaw(t)) { return true; };
	if (c == nil) { return false; };
	let r: *node = resolvetype(c, t);
	return isstrtyperaw(r);
};

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

fn isslicetype(c: *cgen, t: *node) bool = {
	if (isslicetyperaw(t)) { return true; };
	if (c == nil) { return false; };
	let r: *node = resolvetype(c, t);
	return isslicetyperaw(r);
};

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

// isf32typeraw / isf64typeraw — bare TNAME check, no alias resolution.
fn isf32typeraw(t: *node) bool = {
	if (t == nil) { return false; };
	if (t.kind != nkind.N_TNAME) { return false; };
	return streq(t.str, "f32");
};

fn isf64typeraw(t: *node) bool = {
	if (t == nil) { return false; };
	if (t.kind != nkind.N_TNAME) { return false; };
	return streq(t.str, "f64");
};

// isfloattype — f32 / f64 (and aliases of those). Used by cglet,
// cgident, cgassign, cgbin, cgcast, cgcall, cgreturn, fn-prologue to
// dispatch the MOVSS/MOVSD-shaped paths.
export fn isfloattype(c: *cgen, t: *node) bool = {
	if (isf32typeraw(t)) { return true; };
	if (isf64typeraw(t)) { return true; };
	if (c == nil) { return false; };
	let r: *node = resolvetype(c, t);
	if (isf32typeraw(r)) { return true; };
	if (isf64typeraw(r)) { return true; };
	return false;
};

// isf32type — narrower predicate: true only for f32 (after alias
// resolution). f64 returns false. Used to pick MOVSS vs MOVSD and
// the SS-variant arithmetic / cast opcodes.
export fn isf32type(c: *cgen, t: *node) bool = {
	if (isf32typeraw(t)) { return true; };
	if (c == nil) { return false; };
	let r: *node = resolvetype(c, t);
	return isf32typeraw(r);
};

// exprfloatkind — classify an expression's value-class so callers can
// pick float vs integer codegen without a full type system. Returns:
//   0  — integer-like (or unknown — same fallback the existing cgen
//        takes today)
//   1  — f32
//   2  — f64
// Recognises: float literals, idents bound to float lets/locals,
// chained casts whose target is float, and (recursively) the inner
// expr of a non-narrowing wrapping construct. Anything we can't
// pin down conservatively reports integer — the worst case is that
// CVT* is skipped for an exotic case the user can still spell with
// an explicit local.
export fn exprfloatkind(c: *cgen, n: *node) i32 = {
	if (n == nil) { return 0; };
	let k: nkind = n.kind;
	if (k == nkind.N_FLOATLIT) { return 2; };
	if (k == nkind.N_CAST) {
		if (isf32type(c, n.rhs)) { return 1; };
		if (isfloattype(c, n.rhs)) { return 2; };
		return 0;
	};
	if (k == nkind.N_IDENT) {
		let lc: *local = localfindnode(c, n.str);
		if (lc != nil) {
			if (isf32type(c, lc.tnode)) { return 1; };
			if (isfloattype(c, lc.tnode)) { return 2; };
			return 0;
		};
		let lv: *letvar = c.lets;
		for (lv != nil) {
			if (streq(lv.name, n.str)) {
				if (isf32type(c, lv.tnode)) { return 1; };
				if (isfloattype(c, lv.tnode)) { return 2; };
				return 0;
			};
			lv = lv.lvnext;
		};
		return 0;
	};
	if (k == nkind.N_UN) {
		// Unary on a float (TK_MINUS) returns float; everything
		// else is integer-coded.
		if (n.op == tkind.TK_MINUS) {
			return exprfloatkind(c, n.lhs);
		};
		return 0;
	};
	if (k == nkind.N_BIN) {
		// Arithmetic binops inherit the operands' kind. Comparison
		// (eq/ne/lt/...) returns bool — integer.
		let op: tkind = n.op;
		if (op == tkind.TK_PLUS)  { return exprfloatkind(c, n.lhs); };
		if (op == tkind.TK_MINUS) { return exprfloatkind(c, n.lhs); };
		if (op == tkind.TK_STAR)  { return exprfloatkind(c, n.lhs); };
		if (op == tkind.TK_SLASH) { return exprfloatkind(c, n.lhs); };
		return 0;
	};
	if (k == nkind.N_CALL) {
		// Look up the callee's declared return type — fnretlookup
		// returns the type-AST. Routes float-returning fns through
		// the X0 ABI so cglet / cgassign know to spill from X0.
		let nm: str;
		nm.ptr = nil; nm.len = 0;
		if (n.lhs != nil) {
			if (n.lhs.kind == nkind.N_IDENT) { nm = n.lhs.str; };
		};
		if (nm.len > 0) {
			let rt: *node = fnretlookup(c, nm);
			if (isf32type(c, rt)) { return 1; };
			if (isfloattype(c, rt)) { return 2; };
		};
		return 0;
	};
	return 0;
};

// isnullabletype — nkind.N_TTAGGED with exactly two children, one *T and
// one `void`. Folds to a single 8-byte pointer slot per Hare's
// `(*T | null)` semantics. Mirrors check.c's resolve_type detection.
export fn isnullabletype(t: *node) bool = {
	if (t == nil) { return false; };
	if (t.kind != nkind.N_TTAGGED) { return false; };
	let a: *node = t.list;
	if (a == nil) { return false; };
	let b: *node = a.next;
	if (b == nil) { return false; };
	if (b.next != nil) { return false; };
	let aptr: bool = (a.kind == nkind.N_TPTR);
	let bptr: bool = (b.kind == nkind.N_TPTR);
	let avoid: bool = (a.kind == nkind.N_TNAME);
	if (avoid) { avoid = streq(a.str, "void"); };
	let bvoid: bool = (b.kind == nkind.N_TNAME);
	if (bvoid) { bvoid = streq(b.str, "void"); };
	if (aptr) { if (bvoid) { return true; }; };
	if (avoid) { if (bptr) { return true; }; };
	return false;
};

// nullableptrtag — 0-based index of the *T variant in a nullable
// union. The void variant takes the other slot (0 or 1).
export fn nullableptrtag(t: *node) i32 = {
	if (t == nil) { return 0; };
	if (t.kind != nkind.N_TTAGGED) { return 0; };
	let a: *node = t.list;
	if (a != nil) { if (a.kind == nkind.N_TPTR) { return 0; }; };
	return 1;
};

// voidvariantindex — find the 0-based index of the `void` variant in a
// tagged-union type expr, -1 if absent. Used by cgreturn to map bare
// `return;` in a tagged-union-returning fn to the void variant's tag.
fn voidvariantindex(tagged: *node) i32 = {
	if (tagged == nil) { return -1; };
	if (tagged.kind != nkind.N_TTAGGED) { return -1; };
	let v: *node = tagged.list;
	let idx: i32 = 0;
	for (v != nil) {
		if (v.kind == nkind.N_TNAME) {
			if (streq(v.str, "void")) { return idx; };
		};
		v = v.next;
		idx += 1;
	};
	return -1;
};

// rhstargetname — 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 rhstargetname(c: *cgen, rhs: *node) str = {
	let nm: str;
	nm.ptr = nil; nm.len = 0;
	if (rhs == nil) { return nm; };
	if (rhs.kind == nkind.N_CAST) {
		let t: *node = rhs.rhs;
		if (t != nil) {
			if (t.kind == nkind.N_TNAME) { return t.str; };
		};
		return nm;
	};
	if (rhs.kind == nkind.N_STRLIT) { return "str"; };
	if (rhs.kind == nkind.N_IDENT) {
		let lc: *local = localfindnode(c, rhs.str);
		if (lc != nil) {
			let tn: *node = lc.tnode;
			if (tn != nil) {
				if (tn.kind == nkind.N_TNAME) { return tn.str; };
			};
		};
	};
	return nm;
};

// taggedvariantindex — 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 taggedvariantindex(c: *cgen, tagged: *node, rhs: *node) i32 = {
	if (tagged == nil) { return -1; };
	if (rhs == nil)    { return -1; };
	let wantname: str = rhstargetname(c, rhs);
	if (wantname.len > 0) {
		let v: *node = tagged.list;
		let idx: i32 = 0;
		for (v != nil) {
			if (v.kind == nkind.N_TNAME) {
				if (streq(v.str, wantname)) { return idx; };
			};
			v = v.next;
			idx += 1;
		};
	};
	// Fallback: by str-shape (resolves aliases).
	let wantstr: bool = nodeisstr(c, rhs);
	let v: *node = tagged.list;
	let idx: i32 = 0;
	for (v != nil) {
		let visstr: bool = false;
		if (v.kind == nkind.N_TNAME) {
			if (isstrtype(c, v)) { visstr = true; };
		};
		if (visstr == wantstr) { return idx; };
		v = v.next;
		idx += 1;
	};
	return -1;
};