// selfhost/cmd/wcc/cgenstmt.ww — split out of cgen.ww.
//
// cgstmt is a thin dispatcher over n.kind; each branch defers to a
// per-kind helper: cgblock, cgreturn, cgexprstmt, cglet, cgif, cgfor,
// cgmassign, cgbreak, cgcontinue.
//
// The expression generator (cgexpr) lives in cgenexpr.ww; the
// foundation (types, emit primitives, collect* tables, FFI/module
// maps) lives in cgen.ww.

package wcc;

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

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

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

	if (k == nkind.N_BLOCK) { cgblock(c, n); return; };

	if (k == nkind.N_RETURN) { cgreturn(c, n); return; };

	if (k == nkind.N_EXPRSTMT) { cgexprstmt(c, n); return; };

	if (k == nkind.N_LET) { cglet(c, n); return; };

	if (k == nkind.N_IF) { cgif(c, n); return; };

	if (k == nkind.N_FOR) { cgfor(c, n); return; };

	if (k == nkind.N_FORRANGE) { cgforrange(c, n); return; };

	if (k == nkind.N_SWITCH) { cgswitch(c, n); return; };

	if (k == nkind.N_MASSIGN) { cgmassign(c, n); return; };

	if (k == nkind.N_MLET) { cgmlet(c, n); return; };

	if (k == nkind.N_BREAK) { cgbreak(c, n); return; };
	if (k == nkind.N_CONTINUE) { cgcontinue(c, n); return; };

	if (k == nkind.N_YIELD) { cgyield(c, n); return; };

	if (k == nkind.N_DEFER) {
		if (c.defertop < DEFER_MAX) {
			c.deferbuf[c.defertop] = n.lhs;
			c.defertop += 1;
		};
		return;
	};

	c.lastwasreturn = 0;
};

fn cgyield(c: *cgen, n: *node) void = {
	// Evaluate the value into AX (and BX for str), then JMP to the
	// enclosing match's end label. Falls through silently if there
	// is no active match — should be a checker error eventually.
	if (n.lhs != nil) { cgexpr(c, n.lhs); };
	if (c.yieldtop > 0) {
		let tgt: str = c.yieldbuf[c.yieldtop - 1];
		emitline("\tJMP\t");
		emitline(tgt);
		emitline("\n");
	};
	c.lastwasreturn = 0;
	return;
};

fn cgblock(c: *cgen, n: *node) void = {
	// Save/restore the locals head across the block (post-#27).
	// Inner-scope `let` bindings prepend to c.locals via localadd;
	// without this restore, the prepended stubs leak into sibling
	// and ancestor scopes, and localfind (head-first) returns the
	// inner binding's offset for an identifier that semantically
	// belongs to the outer scope. The frame is left grown — we
	// don't reclaim popped slots, matching cstage's lowering.
	//
	// cgfn iterates fn_.body.list directly to bypass this save/
	// restore at the function's outermost block — defers (and the
	// implicit-return epilogue) need locals intact.
	let saved: *local = c.locals;
	let s: *node = n.list;
	for (s != nil) {
		cgstmt(c, s);
		s = s.next;
	};
	c.locals = saved;
	return;
};

// rundefers — emit cgexpr for every queued defer in LIFO order.
// Called from cgreturn and the cgfn implicit-return path.
fn rundefers(c: *cgen) void = {
	let i: i32 = c.defertop - 1;
	for (i >= 0) {
		cgexpr(c, c.deferbuf[i]);
		i -= 1;
	};
	return;
};

fn cgreturn(c: *cgen, n: *node) void = {
	rundefers(c);
	let rhs: *node = n.lhs;
	if (rhs != nil) {
		// Tuple return `return a, b;`:
		//   (scalar, scalar) — AX = v0, DX = v1.
		//   (scalar, str) / (str, scalar) — AX = scalar elem,
		//                                   DX = str.ptr, CX = str.len.
		// 24B convention mirrors the tagged-union return below; receive
		// sites destructure off the same regs regardless of position.
		if (rhs.kind == nkind.N_TUPLE) {
			let v: *node = rhs.list;
			if (v != nil) {
				let v2: *node = v.next;
				if (v2 != nil) {
					let v0_is_str: bool = nodeisstr(c, v);
					let v1_is_str: bool = nodeisstr(c, v2);
					if ((v0_is_str || v1_is_str) && !(v0_is_str && v1_is_str)) {
						let strn: *node = v;
						let scaln: *node = v2;
						if (v1_is_str) { strn = v2; scaln = v; };
						cgexpr(c, scaln);
						emitline("\tPUSHQ\tAX\n");
						cgexpr(c, strn);
						emitline("\tMOVQ\tBX, CX\n");
						emitline("\tMOVQ\tAX, DX\n");
						emitline("\tPOPQ\tAX\n");
					} else {
						cgexpr(c, v2);
						emitline("\tPUSHQ\tAX\n");
						cgexpr(c, v);
						emitline("\tPOPQ\tDX\n");
					};
				} else {
					cgexpr(c, v);
				};
			};
			emitline("\tMOVQ\tBP, SP\n");
			emitline("\tPOPQ\tBP\n");
			emitline("\tRET\n");
			c.lastwasreturn = 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.
		// Nullable folded `(*T | void)`: just one word; AX is
		// already the pointer (or 0). No shuffle, no tag.
		if (istaggedtype(c, c.fnret)) {
			// Forwarding a fallible call: `return f();` where f
			// also returns a tagged union. The result is already
			// in (AX=tag, DX=v0, CX=v1) — no shuffle, no tag.
			// Mirrors the rhsreturnstagged path in cglet and the
			// !type_istagged guard in C cgen's N_RETURN.
			let forwardtagged: bool = false;
			if (rhs.kind == nkind.N_CALL) {
				let callee: *node = rhs.lhs;
				if (callee != nil) {
					let calleename: str;
					calleename.ptr = nil; calleename.len = 0;
					let cmod: str;
					cmod.ptr = nil; cmod.len = 0;
					if (callee.kind == nkind.N_IDENT) {
						calleename = callee.str;
						cmod = c.curmod;
					};
					if (callee.kind == nkind.N_DOT) {
						calleename = callee.str;
						if (callee.lhs != nil) {
							if (callee.lhs.kind == nkind.N_IDENT) {
								cmod = callee.lhs.str;
							};
						};
					};
					if (calleename.len > 0) {
						let rtyp: *node = fnretlookupmod(c, calleename, cmod);
						if (istaggedtype(c, rtyp)) { forwardtagged = true; };
					};
				};
			};
			// Struct payload or tagged-subset return — materialise
			// the widened value in scratch via cgwidentaggedstore
			// (handles tag remap and zero pad), then load AX/DX/CX
			// from the slot.
			let needswiden: bool = false;
			if (!isnullabletype(c.fnret)) {
				if (!forwardtagged) {
					let sname: str = rhsstructpayload(c, rhs);
					if (sname.len > 0) { needswiden = true; };
					if (rhstaggedident(c, rhs) != nil) {
						needswiden = true;
					};
				};
			};
			if (needswiden) {
				let rsz: i32 = slotsize(c, c.fnret);
				// @retscr (not @tagscr) for the return materialise
				// path. Cstage cmd/w6c/cgen.c cgreturn uses
				// `@retscr` here and reserves the @tagscr SSoT
				// for arg-widen / non-BP-base store / N_INDEX
				// tagged-element write. Sharing the name in a fn
				// that BOTH returns a 32B tagged AND pushes a
				// smaller tagged arg fatals localadd's @-prefix
				// size-grow guard (rule 7); routing returns
				// through their own slot keeps each cache
				// monotonic. Hardcoding 24 truncated 32B-slot
				// returns and overwrote adjacent locals during
				// the pre-zero loop (#38).
				let scroff: i32 = localadd(c, "@retscr", rsz, nil);
				emitline("\tXORQ\tAX, AX\n");
				let zz: i32 = 0;
				for (zz < rsz) {
					emitline("\tMOVQ\tAX, ");
					emitoff((scroff + zz): i64);
					emitline("(BP)\n");
					zz += 8;
				};
				cgwidentaggedstore(c, c.fnret, rhs, "BP",
				    scroff, rsz);
				emitline("\tMOVQ\t");
				emitoff(scroff: i64);
				emitline("(BP), AX\n");
				if (rsz > 8) {
					emitline("\tMOVQ\t");
					emitoff((scroff + 8): i64);
					emitline("(BP), DX\n");
				};
				if (rsz > 16) {
					emitline("\tMOVQ\t");
					emitoff((scroff + 16): i64);
					emitline("(BP), CX\n");
				};
				if (rsz > 24) {
					emitline("\tMOVQ\t");
					emitoff((scroff + 24): i64);
					emitline("(BP), R8\n");
				};
				emitline("\tMOVQ\tBP, SP\n");
				emitline("\tPOPQ\tBP\n");
				emitline("\tRET\n");
				c.lastwasreturn = 1;
				return;
			};
			cgexpr(c, rhs);
			if (isnullabletype(c.fnret)) {
				emitline("\tMOVQ\tBP, SP\n");
				emitline("\tPOPQ\tBP\n");
				emitline("\tRET\n");
				c.lastwasreturn = 1;
				return;
			};
			if (forwardtagged) {
				emitline("\tMOVQ\tBP, SP\n");
				emitline("\tPOPQ\tBP\n");
				emitline("\tRET\n");
				c.lastwasreturn = 1;
				return;
			};
			let idx: i32 = taggedvariantindex(c, c.fnret, rhs);
			// Tagged-return ABI: AX=tag, DX=word0, CX=word1,
			// R8=word2. Receiver (cgwidentaggedstore call-source
			// arm) writes AX/DX/CX/R8 unconditionally sized by the
			// dst slot; unused ABI words must be zeroed here so a
			// stale CX/R8 from the caller (e.g. a slice-stride
			// IMULQ before the call) does not land in slot+16 /
			// slot+24. (Task #18.)
			let rsz: i32 = slotsize(c, c.fnret);
			if (nodeisslice(c, rhs)) {
				// cgexpr leaves (AX=ptr, BX=len, CX=cap).
				// Shuffle into return ABI: DX=ptr, CX=len,
				// R8=cap.
				emitline("\tMOVQ\tCX, R8\n");
				emitline("\tMOVQ\tBX, CX\n");
				emitline("\tMOVQ\tAX, DX\n");
			} else { if (nodeisstr(c, rhs)) {
				emitline("\tMOVQ\tBX, CX\n");
				emitline("\tMOVQ\tAX, DX\n");
				// str fills DX,CX. Zero R8 if dst covers slot+24.
				if (rsz > 24) {
					emitline("\tMOVQ\t$0, R8\n");
				};
			} else {
				emitline("\tMOVQ\tAX, DX\n");
				// scalar fills DX only. Zero CX / R8 if dst
				// covers slot+16 / slot+24.
				if (rsz > 16) {
					emitline("\tMOVQ\t$0, CX\n");
				};
				if (rsz > 24) {
					emitline("\tMOVQ\t$0, R8\n");
				};
			};};
			emitline("\tMOVQ\t$");
			if (idx < 0) { idx = 0; };
			emitint(idx: i64);
			emitline(", AX\n");
			emitline("\tMOVQ\tBP, SP\n");
			emitline("\tPOPQ\tBP\n");
			emitline("\tRET\n");
			c.lastwasreturn = 1;
			return;
		};
		// sret return (#23): plain TY_STRUCT > 24B. Callee writes
		// through *(@sretarg) (the caller-prealloc dest saved at
		// the prologue), then loads @sretarg into RAX and rets —
		// the SysV "return the pointer" discipline. Two rhs shapes
		// are wired: N_IDENT (word-copy from rhs slot to *(dest))
		// and N_STRUCTLIT (cgstructlitfill with mode=1 PTR_LOCAL).
		let sretargoff: i32 = localfind(c, "@sretarg");
		if (sretargoff != 0) {
			let scs: i32 = sretretsize(c, c.fnret);
			if (scs > 0) {
				// sret return-forwarding (task #9 follow-up to
				// #23): `return f();` where outer + inner both
				// return the same >24B struct shape. Outer's
				// @sretarg already holds its caller's prealloc
				// dest; pass it to inner in RDI (set by cgcall
				// via c.sretforward), inner writes directly
				// there, inner's RAX (dest pointer) is already
				// outer's return value. The trailing MOVQ
				// @sretarg(BP), AX is redundant after inner's
				// RET but kept for byte-id symmetry with the
				// N_IDENT / N_STRUCTLIT arms below.
				if (rhs.kind == nkind.N_CALL) {
					c.sretforward = 1;
					cgexpr(c, rhs);
					emitline("\tMOVQ\t");
					emitoff(sretargoff: i64);
					emitline("(BP), AX\n");
					emitline("\tMOVQ\tBP, SP\n");
					emitline("\tPOPQ\tBP\n");
					emitline("\tRET\n");
					c.lastwasreturn = 1;
					return;
				};
				let okrhs: bool = false;
				if (rhs.kind == nkind.N_IDENT) { okrhs = true; };
				if (rhs.kind == nkind.N_STRUCTLIT) { okrhs = true; };
				if (okrhs) {
					if (rhs.kind == nkind.N_STRUCTLIT) {
						let trefn: *node = rhs.lhs;
						let sname: str;
						sname.ptr = nil; sname.len = 0;
						if (trefn != nil) {
							if (trefn.kind == nkind.N_IDENT) { sname = trefn.str; }
							else { if (trefn.kind == nkind.N_TNAME) { sname = trefn.str; }; };
						};
						let sret_si: *structinfo = structlookup(c, sname);
						if (sret_si != nil) {
							let emptys: str;
							emptys.ptr = nil; emptys.len = 0;
							// mode=1 (PTR_LOCAL): base reg = BX,
							// reloaded from @sretarg(BP) before
							// each field store. disp = 0 because
							// the dest pointer IS the struct base.
							cgstructlitfill(c, sret_si, rhs,
							    1, sretargoff, emptys,
							    0, scs);
						};
					} else {
						let rl: *local = localfindnode(c, rhs.str);
						if (rl != nil) {
							emitline("\tMOVQ\t");
							emitoff(sretargoff: i64);
							emitline("(BP), BX\n");
							let k: i32 = 0;
							for (k + 8 <= scs) {
								emitline("\tMOVQ\t");
								emitoff((rl.off + k): i64);
								emitline("(BP), AX\n");
								emitline("\tMOVQ\tAX, ");
								emitoff(k: i64);
								emitline("(BX)\n");
								k += 8;
							};
							for (k + 4 <= scs) {
								emitline("\tMOVL\t");
								emitoff((rl.off + k): i64);
								emitline("(BP), AX\n");
								emitline("\tMOVL\tAX, ");
								emitoff(k: i64);
								emitline("(BX)\n");
								k += 4;
							};
							for (k < scs) {
								emitline("\tMOVB\t");
								emitoff((rl.off + k): i64);
								emitline("(BP), AX\n");
								emitline("\tMOVB\tAX, ");
								emitoff(k: i64);
								emitline("(BX)\n");
								k += 1;
							};
						};
					};
					// sret return: RAX = dest pointer.
					emitline("\tMOVQ\t");
					emitoff(sretargoff: i64);
					emitline("(BP), AX\n");
					emitline("\tMOVQ\tBP, SP\n");
					emitline("\tPOPQ\tBP\n");
					emitline("\tRET\n");
					c.lastwasreturn = 1;
					return;
				};
			};
		};
		// Whole-struct return for sizes <= 24B. ABI: AX=bytes[0..7],
		// DX=bytes[8..15], CX=bytes[16..23]. Mirrors cstage cgen.c
		// N_RETURN TY_STRUCT branch. Two rhs shapes are wired:
		// N_IDENT (word-copy from rhs local slot) and N_STRUCTLIT
		// (field-by-field store at scratch+foff, with tagged fields
		// delegated to cgwidentaggedstore). Call-result chain return
		// is deferred to #5's receive side. Sizes > 24B route through
		// the sret arm above.
		let rname: str;
		rname.ptr = nil; rname.len = 0;
		if (c.fnret != nil) {
			if (c.fnret.kind == nkind.N_TNAME) {
				rname = c.fnret.str;
			};
		};
		if (rname.len > 0) {
			let rsi: *structinfo = structlookup(c, rname);
			if (rsi != nil) {
				let rsz: i32 = rsi.totsize;
				if (rsz <= 24) {
					let okrhs: bool = false;
					if (rhs.kind == nkind.N_IDENT) {
						okrhs = true;
					};
					if (rhs.kind == nkind.N_STRUCTLIT) {
						okrhs = true;
					};
					if (okrhs) {
						let scroff: i32 = localadd(c,
						    "@retscr", 24, nil);
						emitline("\tXORQ\tAX, AX\n");
						emitline("\tMOVQ\tAX, ");
						emitoff(scroff: i64);
						emitline("(BP)\n");
						emitline("\tMOVQ\tAX, ");
						emitoff((scroff + 8): i64);
						emitline("(BP)\n");
						emitline("\tMOVQ\tAX, ");
						emitoff((scroff + 16): i64);
						emitline("(BP)\n");
						if (rhs.kind == nkind.N_STRUCTLIT) {
							// Delegate to the shared BP-relative
							// structlit fill helper. Same store
							// sequence the inline pre-#17 walk
							// emitted (tagged + float + scalar),
							// plus nested struct-typed structlit
							// values recurse instead of dropping
							// trailing bytes.
							cgstructlitfillbp(c, rsi, rhs, scroff);
						} else {
							// N_IDENT: word-copy from rhs slot
							// to scratch. Whole 8B words via
							// MOVQ; tail via MOVL/MOVB so we
							// read no further than the source
							// slot's declared size.
							let rl: *local = localfindnode(c, rhs.str);
							if (rl != nil) {
								let k: i32 = 0;
								for (k + 8 <= rsz) {
									emitline("\tMOVQ\t");
									emitoff((rl.off + k): i64);
									emitline("(BP), AX\n");
									emitline("\tMOVQ\tAX, ");
									emitoff((scroff + k): i64);
									emitline("(BP)\n");
									k += 8;
								};
								for (k + 4 <= rsz) {
									emitline("\tMOVL\t");
									emitoff((rl.off + k): i64);
									emitline("(BP), AX\n");
									emitline("\tMOVL\tAX, ");
									emitoff((scroff + k): i64);
									emitline("(BP)\n");
									k += 4;
								};
								for (k < rsz) {
									emitline("\tMOVB\t");
									emitoff((rl.off + k): i64);
									emitline("(BP), AX\n");
									emitline("\tMOVB\tAX, ");
									emitoff((scroff + k): i64);
									emitline("(BP)\n");
									k += 1;
								};
							};
						};
						emitline("\tMOVQ\t");
						emitoff(scroff: i64);
						emitline("(BP), AX\n");
						emitline("\tMOVQ\t");
						emitoff((scroff + 8): i64);
						emitline("(BP), DX\n");
						emitline("\tMOVQ\t");
						emitoff((scroff + 16): i64);
						emitline("(BP), CX\n");
						emitline("\tMOVQ\tBP, SP\n");
						emitline("\tPOPQ\tBP\n");
						emitline("\tRET\n");
						c.lastwasreturn = 1;
						return;
					};
				};
			};
		};
		cgexpr(c, rhs);
	} else {
		// Bare `return;` from a tagged-union-returning fn is
		// the void variant: emit its tag. Payload is undefined
		// (void has size 0). Otherwise zero AX for determinism.
		if (istaggedtype(c, c.fnret)) {
			if (isnullabletype(c.fnret)) {
				// null = void variant; AX = 0.
				emitline("\tMOVQ\t$0, AX\n");
			} else {
				let idx: i32 = voidvariantindex(c.fnret);
				if (idx < 0) { idx = 0; };
				emitline("\tMOVQ\t$");
				emitint(idx: i64);
				emitline(", AX\n");
			};
			emitline("\tMOVQ\tBP, SP\n");
			emitline("\tPOPQ\tBP\n");
			emitline("\tRET\n");
			c.lastwasreturn = 1;
			return;
		};
		emitline("\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 (isstrtype(c, c.fnret)) {
		emitline("\tMOVQ\tBX, DX\n");
	};
	emitline("\tMOVQ\tBP, SP\n");
	emitline("\tPOPQ\tBP\n");
	emitline("\tRET\n");
	c.lastwasreturn = 1;
	return;
};

fn cgexprstmt(c: *cgen, n: *node) void = {
	if (n.lhs != nil) { cgexpr(c, n.lhs); };
	c.lastwasreturn = 0;
	return;
};

fn cglet(c: *cgen, n: *node) void = {
	let nm: str = n.str;
	let sz: i32 = letslotsize(c, n);
	// `let x = f()?` has no annotation but the cgen's struct-field
	// paths need a tnode to dispatch off. Infer from f's tagged
	// success variant — see inferletcalltype.
	let tn: *node = n.lhs;
	if (tn == nil) { tn = inferletcalltype(c, n.rhs); };
	let off: i32 = localadd(c, nm, sz, tn);
	if (n.rhs != nil) {
		let rhs: *node = n.rhs;
		// `let s: []T = alloc([], n)!;` / `?` shortcut (#32, #45).
		// Mirror of cstage cgen.c N_LET arrlit-empty branch: allocate
		// n*esz bytes via rt_alloc, then build the {ptr, 0, n} slice
		// header in the let slot. The `!`/`?` wraps the builtin's
		// `([]T | nomem)` return; walk into the N_TRYUNW / N_TRYPROP
		// to keep the direct-store fast path rather than falling
		// through to cgalloc (which models scalar alloc and would
		// land an 8B region and a junk slice header). `?` propagates
		// nomem via AX = tag of nomem in c.fnret, then epilogue RET.
		{
			let scall: *node = nil;
			let viatryunw: bool = false;
			let viatryprop: bool = false;
			if (rhs.kind == nkind.N_TRYUNW) {
				if (rhs.lhs != nil) {
					if (rhs.lhs.kind == nkind.N_CALL) {
						scall = rhs.lhs;
						viatryunw = true;
					};
				};
			} else { if (rhs.kind == nkind.N_TRYPROP) {
				if (rhs.lhs != nil) {
					if (rhs.lhs.kind == nkind.N_CALL) {
						scall = rhs.lhs;
						viatryprop = true;
					};
				};
			}; };
			let shapeok: bool = false;
			// #43: route the slice-shape size guard through SSoT.
			// The N_TSLICE kind gate already discriminates here, so
			// this is belt-and-suspenders, but the literal would
			// silently miss after #1 if check.ww's astsize ever
			// drifted from this dispatch.
			if (scall != nil && tn != nil
			    && tn.kind == nkind.N_TSLICE && sz == tyslicesize(): i32) {
				let callee: *node = scall.lhs;
				let a0: *node = scall.list;
				let a1: *node = nil;
				let a2: *node = nil;
				if (a0 != nil) { a1 = a0.next; };
				if (a1 != nil) { a2 = a1.next; };
				if (callee != nil && a0 != nil && a1 != nil
				    && a2 == nil) {
					if (callee.kind == nkind.N_IDENT
					    && streq(callee.str, "alloc")
					    && a0.kind == nkind.N_ARRLIT
					    && a0.list == nil) {
						shapeok = true;
					};
				};
			};
			if (shapeok) {
				// #32: cstage uses `lu->sub->size` (cgen.c:6387), so
				// the element width must resolve struct/tagged/alias
				// names too — not just primitives. elemsizeofc follows
				// TNAME through structlookup/aliaslookup, matching the
				// cstage path byte-identically. A bare primsize/slotsize
				// fork would silently land esz=1 on `[]point`.
				let esz: i32 = elemsizeofc(c, tn);
				let count: *node = scall.list.next;
				cgexpr(c, count);
				emitline("\tPUSHQ\tAX\n");
				if (esz > 1) {
					emitline("\tMOVQ\t$");
					emitint(esz: i64);
					emitline(", BX\n");
					emitline("\tIMULQ\tBX, AX\n");
				};
				emitline("\tMOVQ\tAX, DI\n");
				emitline("\tCALL\t");
				emitline(ffiresolve(c, "alloc"));
				emitline("(SB)\n");
				if (viatryunw) {
					let okl: str = mklabel(c, "tryunw_ok");
					emitline("\tCMPQ\t$0, AX\n");
					emitline("\tJNE\t");
					emitline(okl);
					emitline("\n");
					emitline("\tMOVQ\t$1, DI\n");
					emitline("\tMOVQ\t$60, AX\n");
					emitline("\tSYSCALL\n");
					emitlabel(okl);
				};
				if (viatryprop) {
					// #45: null = nomem; propagate to the
					// enclosing fn's tagged return. AX = tag
					// of nomem variant in c.fnret, epilogue
					// RETs to caller.
					let okl: str = mklabel(c, "tryprop_ok");
					emitline("\tCMPQ\t$0, AX\n");
					emitline("\tJNE\t");
					emitline(okl);
					emitline("\n");
					let nidx: i32 = flatvariantidx(c, c.fnret, "nomem");
					if (nidx < 0) { nidx = 1; };
					emitline("\tMOVQ\t$");
					emitint(nidx: i64);
					emitline(", AX\n");
					emitline("\tMOVQ\tBP, SP\n\tPOPQ\tBP\n\tRET\n");
					emitlabel(okl);
				};
				emitline("\tPOPQ\tBX\n");
				emitline("\tMOVQ\tAX, ");
				emitoff(off: i64);
				emitline("(BP)\n");
				emitline("\tMOVQ\t$0, ");
				emitoff((off + 8): i64);
				emitline("(BP)\n");
				emitline("\tMOVQ\tBX, ");
				emitoff((off + 16): i64);
				emitline("(BP)\n");
				c.lastwasreturn = 0;
				return;
			};
		};
		// Tagged-union init: delegate to cgwidentaggedstore, which
		// handles nullable fold, tagged source (ident or AX/DX/CX
		// ABI call), struct payload (literal/ident), str payload,
		// scalar payload — with tag remap for tagged-subset widening.
		if (istaggedtype(c, tn)) {
			cgwidentaggedstore(c, tn, rhs, "BP", off, sz);
			c.lastwasreturn = 0;
			return;
		};
		// 24B tuple init for `let t: (scalar, str) = call()` /
		// `let t: (str, scalar) = call()`. Per the AX:DX:CX return
		// convention: AX = scalar elem, DX = str.ptr, CX = str.len.
		// Layout is positional, so we route each register to the
		// slot dictated by element type, not by AX/DX position.
		if (n.lhs != nil) {
			if (n.lhs.kind == nkind.N_TTUPLE) {
				let p0: *node = n.lhs.list;
				let p1: *node = nil;
				if (p0 != nil) { p1 = p0.next; };
				let s0_is_str: bool = isstrtyperaw(p0);
				let s1_is_str: bool = isstrtyperaw(p1);
				if (p0 != nil) {
					if (p1 != nil) {
						if (s0_is_str != s1_is_str) {
							cgexpr(c, rhs);
							if (s0_is_str) {
								emitline("\tMOVQ\tDX, ");
								emitoff(off: i64);
								emitline("(BP)\n");
								emitline("\tMOVQ\tCX, ");
								emitoff((off + 8): i64);
								emitline("(BP)\n");
								emitline("\tMOVQ\tAX, ");
								emitoff((off + 16): i64);
								emitline("(BP)\n");
							} else {
								emitline("\tMOVQ\tAX, ");
								emitoff(off: i64);
								emitline("(BP)\n");
								emitline("\tMOVQ\tDX, ");
								emitoff((off + 8): i64);
								emitline("(BP)\n");
								emitline("\tMOVQ\tCX, ");
								emitoff((off + 16): i64);
								emitline("(BP)\n");
							};
							c.lastwasreturn = 0;
							return;
						};
					};
				};
			};
		};
		// Array literal init: `let xs: [N]T = [a, b, c];` (or [_]T).
		// Walk elements in declaration order, store each at off + i*esz
		// using the right width for the element type. Trailing `...`
		// after the last value (an nkind.N_FIELD with str=="...") fills the
		// remaining slots up to the declared length with that value.
		//
		// str element (16B = ptr+len) needs both halves stored. cgstrlit
		// / cgident leave a str as (AX=ptr, BX=len) and a single MOVQ
		// from AX would leave .len as whatever the stack held — silent
		// miscompile. Worse, primsize("str") returns 0 so esz would fall
		// back to 8, also collapsing the per-element stride (element i+1
		// would overwrite element i's would-be .len half). Detect the
		// str-element case up front so both esz and the store path are
		// right. (primsize's default-to-8-on-zero pattern is brittle for
		// composites generally; same gap blocks slice / struct / tuple /
		// tagged element arrays — tracked as a follow-up.)
		if (rhs.kind == nkind.N_ARRLIT) {
			let elemn: *node = n.lhs.lhs;
			let esz: i32 = 8;
			let isstrel: bool = false;
			if (elemn != nil) {
				if (elemn.kind == nkind.N_TNAME) {
					if (streq(elemn.str, "str")) {
						esz = primtypesize("str"): i32;
						isstrel = true;
					} else {
						let ps: i32 = primsize(elemn.str);
						if (ps > 0) { esz = ps; };
					};
				};
			};
			let mop: str = tnodestoreop(c, elemn, esz);
			let idx: i32 = 0;
			let repeat: bool = false;
			let e: *node = rhs.list;
			for (e != nil) {
				let isellip: bool = false;
				if (e.kind == nkind.N_FIELD) {
					if (streq(e.str, "...")) {
						repeat = true;
						isellip = true;
					};
				};
				if (isellip) {
					e = nil;
				} else {
					cgexpr(c, e);
					if (isstrel) {
						emitline("\tMOVQ\tAX, ");
						emitoff((off + idx * esz): i64);
						emitline("(BP)\n");
						emitline("\tMOVQ\tBX, ");
						emitoff((off + idx * esz + 8): i64);
						emitline("(BP)\n");
					} else {
						emitline("\t");
						emitline(mop);
						emitline("\tAX, ");
						emitoff((off + idx * esz): i64);
						emitline("(BP)\n");
					};
					idx += 1;
					e = e.next;
				};
			};
			// AX (and BX for str) still holds the last stored value;
			// fill remaining slots up to the declared length with it.
			if (repeat) {
				let total: i32 = idx;
				if (n.lhs != nil) {
					if (n.lhs.kind == nkind.N_TARRAY) {
						if (n.lhs.rhs != nil) {
							if (n.lhs.rhs.kind == nkind.N_INTLIT) {
								total = n.lhs.rhs.uval: i32;
							};
						};
					};
				};
				for (idx < total) {
					if (isstrel) {
						emitline("\tMOVQ\tAX, ");
						emitoff((off + idx * esz): i64);
						emitline("(BP)\n");
						emitline("\tMOVQ\tBX, ");
						emitoff((off + idx * esz + 8): i64);
						emitline("(BP)\n");
					} else {
						emitline("\t");
						emitline(mop);
						emitline("\tAX, ");
						emitoff((off + idx * esz): i64);
						emitline("(BP)\n");
					};
					idx += 1;
				};
			};
			c.lastwasreturn = 0;
			return;
		};
		// Struct literal init: `let p: point = point{x=..., y=...};`.
		// Delegates to the shared cgstructlitfillbp helper: TK_ELLIPSIS
		// autofill + per-field walk, with nested struct-typed structlit
		// values recursing into the helper instead of landing only AX
		// (the #17 silent-zero fix). Mirror of cstage cgen.c N_LET
		// structlit branch.
		if (rhs.kind == nkind.N_STRUCTLIT) {
			let trefn: *node = rhs.lhs;
			let sname: str;
			sname.ptr = nil; sname.len = 0;
			if (trefn != nil) {
				if (trefn.kind == nkind.N_IDENT) { sname = trefn.str; }
				else { if (trefn.kind == nkind.N_TNAME) { sname = trefn.str; }; };
			};
			let si: *structinfo = structlookup(c, sname);
			if (si != nil) {
				cgstructlitfillbp(c, si, rhs, off);
				c.lastwasreturn = 0;
				return;
			};
		};
		// sret receive (#23): plain TY_STRUCT > 24B from a call.
		// The let's own slot IS the caller-prealloc dest; the
		// nested cgexpr → cgcall path emits `LEAQ off(BP), DI`
		// before the CALL and the callee writes through it. No
		// AX/DX/CX shuffle; AX returns the dest pointer per SysV
		// sret discipline (irrelevant here).
		if (rhs.kind == nkind.N_CALL) {
			let scs: i32 = callsretsize(c, rhs);
			if (scs > 0) {
				c.sretdestoff = off;
				cgexpr(c, rhs);
				c.sretdestoff = 0;
				c.lastwasreturn = 0;
				return;
			};
		};
		// Whole-struct receive for sizes <=24B (call-result rhs).
		// Counterpart of #4's cgreturn ABI: cgexpr leaves
		// AX=bytes[0..7], DX=bytes[8..15], CX=bytes[16..23],
		// zero-padded to 24B by the producer.
		//
		// ASYMMETRY (do NOT mirror the sender): producer emits three
		// uniform MOVQs into a zero-padded 24B scratch slot; the
		// receiver writes only `sz` bytes — MOVQ for full 8B chunks
		// plus a sized tail (MOVL/MOVW/MOVB) by the *declared*
		// struct size. Otherwise a trailing 1..7-byte chunk would
		// overrun into the next local slot.
		//
		// Tail chunks in {3,5,6,7} (unreachable under WW struct
		// alignment rules — field aligns force size%align==0) fall
		// through to the generic scalar store rather than emit a
		// stomping MOVQ tail. Sizes >24B also fall through (sret
		// deferred, same constraint as #4). Mirrors the cstage
		// cgen.c N_LET receive branch.
		if (rhs.kind == nkind.N_CALL) {
			let sname: str;
			sname.ptr = nil; sname.len = 0;
			if (tn != nil) {
				if (tn.kind == nkind.N_TNAME) {
					sname = tn.str;
				};
			};
			if (sname.len > 0) {
				let lsi: *structinfo = structlookup(c, sname);
				if (lsi != nil) {
					// si.totsize is slot-padded (rounded to 8) for
					// stack-slot use; the receive ABI needs the
					// TYPE's natural size — see structnaturalsize.
					let lsz: i32 = structnaturalsize(lsi);
					let tlm: i32 = lsz - (lsz / 8) * 8;
					if (lsz <= 24) {
						if (tlm == 0 || tlm == 1
						    || tlm == 2 || tlm == 4) {
							cgexpr(c, rhs);
							let full: i32 = lsz / 8;
							let i: i32 = 0;
							for (i < full) {
								let reg: str = "AX";
								if (i == 1) { reg = "DX"; };
								if (i == 2) { reg = "CX"; };
								emitline("\tMOVQ\t");
								emitline(reg);
								emitline(", ");
								emitoff((off + i * 8): i64);
								emitline("(BP)\n");
								i += 1;
							};
							if (tlm > 0) {
								let top: str = "MOVB";
								if (tlm == 4) { top = "MOVL"; };
								if (tlm == 2) { top = "MOVW"; };
								let treg: str = "AX";
								if (full == 1) { treg = "DX"; };
								if (full == 2) { treg = "CX"; };
								emitline("\t");
								emitline(top);
								emitline("\t");
								emitline(treg);
								emitline(", ");
								emitoff((off + full * 8): i64);
								emitline("(BP)\n");
							};
							c.lastwasreturn = 0;
							return;
						};
					};
				};
			};
		};
		// Struct ident copy: `let p2: T = p1;` where T is a struct
		// >8B and rhs is a local ident. Per-qword MOVQ from src
		// slot to dst slot, with a sized tail (MOVL/MOVB) for
		// natural sizes that aren't 8-aligned (e.g. `struct
		// { i32, i32, i32 }` is 12B). Pre-fix this path fell
		// through to `cgexpr + MOVQ AX, off(BP)` which stored
		// only the first qword (and a stale BX for sz==16 lets
		// via the str-init tail) — silent partial copy. Mirrors
		// cstage cgen.c N_LET struct-ident branch (Task #32).
		if (rhs.kind == nkind.N_IDENT) {
			let sname: str;
			sname.ptr = nil; sname.len = 0;
			if (tn != nil) {
				if (tn.kind == nkind.N_TNAME) { sname = tn.str; };
			};
			if (sname.len > 0) {
				let lsi: *structinfo = structlookup(c, sname);
				if (lsi != nil) {
					let lsz: i32 = structnaturalsize(lsi);
					if (lsz > 8) {
						let lc: *local = localfindnode(c, rhs.str);
						if (lc != nil) {
							let soff: i32 = lc.off;
							let ki: i32 = 0;
							for (ki + 8 <= lsz) {
								emitline("\tMOVQ\t");
								emitoff((soff + ki): i64);
								emitline("(BP), AX\n");
								emitline("\tMOVQ\tAX, ");
								emitoff((off + ki): i64);
								emitline("(BP)\n");
								ki += 8;
							};
							if (ki < lsz) {
								let tail: i32 = lsz - ki;
								let lop: str = "MOVQ";
								if (tail == 4) { lop = "MOVL"; }
								else { if (tail == 1) { lop = "MOVB"; }; };
								emitline("\t");
								emitline(lop);
								emitline("\t");
								emitoff((soff + ki): i64);
								emitline("(BP), AX\n");
								emitline("\t");
								emitline(lop);
								emitline("\tAX, ");
								emitoff((off + ki): i64);
								emitline("(BP)\n");
							};
							c.lastwasreturn = 0;
							return;
						};
					};
				};
			};
		};
		cgexpr(c, rhs);
		// Float local: cgexpr leaves the value in X0. Spill via
		// MOVSS (f32, 4B) or MOVSD (f64, 8B).
		if (isfloattype(c, n.lhs)) {
			let mov: str = "MOVSD";
			if (isf32type(c, n.lhs)) { mov = "MOVSS"; };
			emitline("\t");
			emitline(mov);
			emitline("\tX0, ");
			emitoff(off: i64);
			emitline("(BP)\n");
			c.lastwasreturn = 0;
			return;
		};
		emitline("\tMOVQ\tAX, ");
		emitoff(off: i64);
		emitline("(BP)\n");
		// str init: cgexpr also leaves len in BX; store both.
		// #60: gate by kind too — under #1's str=24 bump, sizeof(str)
		// and sizeof(slice) collide, so a bare `sz ==` check fires
		// both branches for one let. Mirrors cstage cgen.c:6439's
		// `type_isstr(lt) && sz == ty_str->size` shape.
		if (isstrtype(c, tn) && sz == primtypesize("str"): i32) {
			emitline("\tMOVQ\tBX, ");
			emitoff((off + 8): i64);
			emitline("(BP)\n");
		};
		// slice init: ptr/len/cap in AX/BX/CX. Same kind+size gate as
		// the str arm — without the kind check this fires on a str let
		// once sz==24 (#60).
		if (isslicetype(c, tn) && sz == tyslicesize(): i32) {
			emitline("\tMOVQ\tBX, ");
			emitoff((off + 8): i64);
			emitline("(BP)\n");
			emitline("\tMOVQ\tCX, ");
			emitoff((off + 16): i64);
			emitline("(BP)\n");
		};
	} else {
		// Bare `let x: T;` with no initializer. C cgen
		// (cmd/w6c/cgen.c N_LET no-rhs branch) zero-inits in two
		// shapes:
		//   - 8B primitives (scalar/ptr/fn/chan/`[8]bool` etc.):
		//     single `MOVQ $0, off(BP)`.
		//   - multi-word composites (str/slice/tuple/struct/tagged):
		//     `XORQ AX,AX` + a run of `MOVQ AX, ...` over the slot
		//     so reads after the bare let see {0...} rather than
		//     stack garbage.
		// `[N]T` arrays of size != 8 keep the per-index-write
		// contract — they're left uninit.
		let isarr: bool = false;
		if (n.lhs != nil) {
			if (n.lhs.kind == nkind.N_TARRAY) { isarr = true; };
		};
		if (typeis8byteprimitive(c, n.lhs)) {
			emitline("\tMOVQ\t$0, ");
			emitoff(off: i64);
			emitline("(BP)\n");
		} else { if (!isarr) { if (sz > 8) {
			emitline("\tXORQ\tAX, AX\n");
			let zi: i32 = 0;
			for (zi + 8 <= sz) {
				emitline("\tMOVQ\tAX, ");
				emitoff((off + zi): i64);
				emitline("(BP)\n");
				zi += 8;
			};
			for (zi + 4 <= sz) {
				emitline("\tMOVL\tAX, ");
				emitoff((off + zi): i64);
				emitline("(BP)\n");
				zi += 4;
			};
			for (zi < sz) {
				emitline("\tMOVB\tAX, ");
				emitoff((off + zi): i64);
				emitline("(BP)\n");
				zi += 1;
			};
		}; }; };
	};
	c.lastwasreturn = 0;
	return;
};

fn cgif(c: *cgen, n: *node) void = {
	let els: str = mklabel(c, "else");
	let endl: str = mklabel(c, "end");
	cgexpr(c, n.cond);
	emitline("\tCMPQ\t$0, AX\n");
	emitline("\tJE\t");
	if (n.els != nil) { emitline(els); }
	else              { emitline(endl); };
	emitline("\n");
	if (n.body != nil) { cgstmt(c, n.body); };
	if (n.els != nil) {
		emitline("\tJMP\t"); emitline(endl); emitline("\n");
		emitlabel(els);
		cgstmt(c, n.els);
	};
	emitlabel(endl);
	c.lastwasreturn = 0;
	return;
};

fn cgfor(c: *cgen, n: *node) void = {
	// 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");
	// `else` runs at natural cond-false exit; break skips it. When
	// present, branch the cond-fail edge to a separate natural_exit
	// label so the else body sits between it and the break target.
	let naturall: str = endl;
	if (n.els != nil) { naturall = mklabel(c, "elseloop"); };

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

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

	c.loopendbuf[c.looptop]  = endl;
	c.loopcontbuf[c.looptop] = topl;
	c.looptop += 1;

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

	c.looptop -= 1;

	if (n.rhs != nil) { cgexpr(c, n.rhs); };
	emitline("\tJMP\t"); emitline(topl); emitline("\n");
	if (n.els != nil) {
		emitlabel(naturall);
		cgstmt(c, n.els);
	};
	emitlabel(endl);
	c.lastwasreturn = 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/w6c/cgen.c:2424-2440. Lvalues beyond two are dropped (same
// as C — no fixture uses >2 today).
fn cgmassign(c: *cgen, n: *node) void = {
	if (n.rhs != nil) { cgexpr(c, n.rhs); };
	emitline("\tPUSHQ\tDX\n");
	let l0: *node = n.list;
	let l1: *node = nil;
	if (l0 != nil) { l1 = l0.next; };
	if (l0 != nil) {
		if (l0.kind == nkind.N_IDENT) {
			let off: i32 = localfind(c, l0.str);
			if (off != 0) {
				emitline("\tMOVQ\tAX, ");
				emitoff(off: i64);
				emitline("(BP)\n");
			};
		};
	};
	emitline("\tPOPQ\tDX\n");
	if (l1 != nil) {
		if (l1.kind == nkind.N_IDENT) {
			let off: i32 = localfind(c, l1.str);
			if (off != 0) {
				emitline("\tMOVQ\tDX, ");
				emitoff(off: i64);
				emitline("(BP)\n");
			};
		};
	};
	c.lastwasreturn = 0;
	return;
};

// Multi-let from a tuple-returning call: `let n, s = call();` or
// `let (n, s) = call();`. wwstage has no checker, so each binding's
// type is taken from its explicit annotation (l.lhs) when present
// or inferred from the called fn's return-type tuple element.
//
// Per the AX:DX:CX return convention (mirrors C cgen nkind.N_MLET):
//   (scalar, scalar) — AX → l0, DX → l1.
//   (scalar, str)    — AX → scalar slot, (DX, CX) → str slot
//                      as (.ptr, .len). Position-agnostic — the
//                      regs are routed by element type, not by AX/DX.
fn cgmlet(c: *cgen, n: *node) void = {
	let rhs: *node = n.rhs;
	if (rhs == nil) { return; };

	let p0t: *node = nil;
	let p1t: *node = nil;
	if (rhs.kind == nkind.N_CALL) {
		let callee: *node = rhs.lhs;
		if (callee != nil) {
			let cnm: str;
			cnm.ptr = nil; cnm.len = 0;
			let cmod: str;
			cmod.ptr = nil; cmod.len = 0;
			if (callee.kind == nkind.N_IDENT) {
				cnm = callee.str;
				cmod = c.curmod;
			};
			if (callee.kind == nkind.N_DOT) {
				cnm = callee.str;
				if (callee.lhs != nil) {
					if (callee.lhs.kind == nkind.N_IDENT) {
						cmod = callee.lhs.str;
					};
				};
			};
			if (cnm.len > 0) {
				let rtyp: *node = fnretlookupmod(c, cnm, cmod);
				if (rtyp != nil) {
					if (rtyp.kind == nkind.N_TTUPLE) {
						p0t = rtyp.list;
						if (p0t != nil) { p1t = p0t.next; };
					};
				};
			};
		};
	};

	let l0: *node = n.list;
	let l1: *node = nil;
	if (l0 != nil) { l1 = l0.next; };

	let t0: *node = nil;
	let t1: *node = nil;
	if (l0 != nil) { t0 = l0.lhs; };
	if (l1 != nil) { t1 = l1.lhs; };
	if (t0 == nil) { t0 = p0t; };
	if (t1 == nil) { t1 = p1t; };

	let s0_is_str: bool = isstrtyperaw(t0);
	let s1_is_str: bool = isstrtyperaw(t1);

	cgexpr(c, rhs);

	if (l0 != nil) {
		if (l1 != nil) {
			if (s0_is_str != s1_is_str) {
				let sz0: i32 = 8;
				let sz1: i32 = 8;
				if (s0_is_str) { sz0 = primtypesize("str"): i32; };
				if (s1_is_str) { sz1 = primtypesize("str"): i32; };
				let off0: i32 = localadd(c, l0.str, sz0, t0);
				let off1: i32 = localadd(c, l1.str, sz1, t1);
				if (s0_is_str) {
					emitline("\tMOVQ\tDX, ");
					emitoff(off0: i64);
					emitline("(BP)\n");
					emitline("\tMOVQ\tCX, ");
					emitoff((off0 + 8): i64);
					emitline("(BP)\n");
					emitline("\tMOVQ\tAX, ");
					emitoff(off1: i64);
					emitline("(BP)\n");
				} else {
					emitline("\tMOVQ\tAX, ");
					emitoff(off0: i64);
					emitline("(BP)\n");
					emitline("\tMOVQ\tDX, ");
					emitoff(off1: i64);
					emitline("(BP)\n");
					emitline("\tMOVQ\tCX, ");
					emitoff((off1 + 8): i64);
					emitline("(BP)\n");
				};
				c.lastwasreturn = 0;
				return;
			};
		};
	};

	if (l0 != nil) {
		let off: i32 = localadd(c, l0.str, 8, t0);
		emitline("\tMOVQ\tAX, ");
		emitoff(off: i64);
		emitline("(BP)\n");
	};
	if (l1 != nil) {
		let off: i32 = localadd(c, l1.str, 8, t1);
		emitline("\tMOVQ\tDX, ");
		emitoff(off: i64);
		emitline("(BP)\n");
	};
	c.lastwasreturn = 0;
	return;
};

// paramfieldsize — raw byte size of a tuple-field type. Mirrors the
// `tp->type->size` read in C cgen N_FORRANGE: 1 for i8/u8/bool, 4 for
// i32/u32, 8 for i64/u64/*T/fn/slice-elt, 16 for str, default 8.
fn paramfieldsize(t: *node) i32 = {
	if (t == nil) { return 8; };
	let k: nkind = t.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_TNAME)  {
		let nm: str = t.str;
		if (streq(nm, "str")) { return primtypesize("str"): i32; };
		let ps: i32 = primsize(nm);
		if (ps > 0) { return ps; };
	};
	return 8;
};

// paramissigned — does this type need sign-extending on a sub-word
// (1/2/4B) load? Mirrors cstage's signed_field check via
// fieldissignedc (resolves TBANG / TENUM / alias chains).
fn paramissigned(c: *cgen, t: *node) bool = {
	return fieldissignedc(c, t);
};

// cgforrange — lower `for (let x .. slice) body` (and the tuple-
// destructure cousin `for (let (a, b) .. slice) body`). The body is
// wrapped in a counted loop driven by stack-spilled `.rgi`/`.rgl`.
// Each iteration computes the element address `s.ptr + i*esz` and
// either loads the whole element into the named local or pulls each
// tuple field into its own local. Mirrors cmd/w6c/cgen.c N_FORRANGE
// byte-for-byte (label names + labelseq consumption order).
fn cgforrange(c: *cgen, n: *node) void = {
	let slc: *node = n.lhs;
	let slclocal: *local = nil;
	let slctn: *node = nil;
	if (slc != nil) {
		if (slc.kind == nkind.N_IDENT) {
			slclocal = localfindnode(c, slc.str);
			if (slclocal != nil) { slctn = slclocal.tnode; };
		};
	};
	// Element type — peek through TSLICE/TARRAY for the tuple param walk.
	let elemt: *node = nil;
	if (slctn != nil) {
		let sk: nkind = slctn.kind;
		if (sk == nkind.N_TSLICE) { elemt = slctn.lhs; };
		if (sk == nkind.N_TARRAY) { elemt = slctn.lhs; };
	};
	// esz: raw elem byte size. For tuple-element slices `[](T0, T1)`,
	// C cgen reads the resolved tuple's size (sum of raw param sizes,
	// no slot-padding) so e.g. `(i64, i64)` is 16, `(i32, i32)` is 8.
	// elemsizeof returns 8 for non-primitive elem, which would be
	// wrong here — compute from the tuple param walk instead.
	let esz: i32 = elemsizeof(slctn);
	if (elemt != nil) {
		if (elemt.kind == nkind.N_TTUPLE) {
			let total: i32 = 0;
			let p: *node = elemt.list;
			for (p != nil) {
				total += paramfieldsize(p);
				p = p.next;
			};
			esz = total;
		};
	};
	let destruct: bool = (n.list != nil);

	// .rgi (counter) + .rgl (length) scratch slots.
	let iname: str = mkscratchname(c, "rgi");
	let lname: str = mkscratchname(c, "rgl");
	let ioff: i32 = localalloc(c, iname, 8, nil);
	let loff: i32 = localalloc(c, lname, 8, nil);

	// Per-binding (up to 8 — matches the C array). Parallel arrays so
	// we don't depend on local-struct cgen.
	let bind_off:    [8]i32;
	let bind_sz:     [8]i32;
	let bind_foff:   [8]i32;
	let bind_signed: [8]bool;
	let nbinds: i32 = 0;

	if (destruct) {
		let tp: *node = nil;
		if (elemt != nil) {
			if (elemt.kind == nkind.N_TTUPLE) { tp = elemt.list; };
		};
		let field_off: i32 = 0;
		let m: *node = n.list;
		for (m != nil) {
			if (nbinds >= 8) { m = nil; }
			else {
				let fsz: i32 = 8;
				let signf: bool = false;
				if (tp != nil) {
					fsz = paramfieldsize(tp);
					signf = paramissigned(c, tp);
				};
				let slot_sz: i32 = fsz;
				if (slot_sz < 8) { slot_sz = 8; };
				bind_sz[nbinds] = fsz;
				bind_foff[nbinds] = field_off;
				bind_signed[nbinds] = signf;
				let bnm: str = m.str;
				if (bnm.len > 0) {
					bind_off[nbinds] = localadd(c, bnm, slot_sz, tp);
				} else {
					bind_off[nbinds] = localalloc(c, mkscratchname(c, "fr"), slot_sz, tp);
				};
				field_off += fsz;
				nbinds += 1;
				if (tp != nil) { tp = tp.next; };
				m = m.next;
			};
		};
	} else {
		let slot_sz: i32 = esz;
		if (slot_sz < 8) { slot_sz = 8; };
		bind_sz[0] = esz;
		bind_foff[0] = 0;
		// Single-binding signed-narrow detection: mirror C which
		// reads `u->sub->kind` for the elem type.
		bind_signed[0] = false;
		if (elemt != nil) {
			bind_signed[0] = paramissigned(c, elemt);
		};
		if (n.str.len > 0) {
			// Register with elem tnode so x.field on a loop
			// var resolves through the standard local-typed
			// path instead of falling into the SB fallback.
			bind_off[0] = localadd(c, n.str, slot_sz, elemt);
		} else {
			bind_off[0] = localalloc(c, mkscratchname(c, "fr"), slot_sz, elemt);
		};
		nbinds = 1;
	};

	// init: ioff(BP) = 0
	emitline("\tMOVQ\t$0, ");
	emitoff(ioff: i64);
	emitline("(BP)\n");

	// loff(BP) = len
	let isarr: bool = false;
	let isslicestr: bool = false;
	if (slctn != nil) {
		let tk: nkind = slctn.kind;
		if (tk == nkind.N_TSLICE) { isslicestr = true; };
		if (tk == nkind.N_TARRAY) { isarr = true; };
		if (tk == nkind.N_TNAME) {
			if (streq(slctn.str, "str")) { isslicestr = true; };
		};
	};
	if (isslicestr) {
		if (slc.kind == nkind.N_IDENT) {
			if (slclocal != nil) {
				emitline("\tMOVQ\t");
				emitoff((slclocal.off + 8): i64);
				emitline("(BP), AX\n");
				emitline("\tMOVQ\tAX, ");
				emitoff(loff: i64);
				emitline("(BP)\n");
			};
		};
	} else { if (isarr) {
		let alen: i64 = 0i64;
		if (slctn.rhs != nil) {
			if (slctn.rhs.kind == nkind.N_INTLIT) { alen = slctn.rhs.uval: i64; };
		};
		emitline("\tMOVQ\t$");
		emitint(alen);
		emitline(", ");
		emitoff(loff: i64);
		emitline("(BP)\n");
	} else {
		cgexpr(c, slc);
		emitline("\tMOVQ\tAX, ");
		emitoff(loff: i64);
		emitline("(BP)\n");
	};};

	let loopl: str = mklabel(c, "rloop");
	let endl: str  = mklabel(c, "rend");
	let naturall: str = endl;
	if (n.els != nil) { naturall = mklabel(c, "relseloop"); };

	c.loopcontbuf[c.looptop] = loopl;
	c.loopendbuf[c.looptop]  = endl;
	c.looptop += 1;

	emitlabel(loopl);
	emitline("\tMOVQ\t");
	emitoff(ioff: i64);
	emitline("(BP), AX\n");
	emitline("\tMOVQ\t");
	emitoff(loff: i64);
	emitline("(BP), BX\n");
	emitline("\tCMPQ\tBX, AX\n");
	emitline("\tJGE\t"); emitline(naturall); emitline("\n");

	// BX = base + i*esz
	if (esz > 1) {
		emitline("\tMOVQ\t$");
		emitint(esz: i64);
		emitline(", CX\n");
		emitline("\tIMULQ\tCX, AX\n");
	};
	if (slc.kind == nkind.N_IDENT) {
		if (slclocal != nil) {
			if (isarr) {
				emitline("\tLEAQ\t");
				emitoff(slclocal.off: i64);
				emitline("(BP), BX\n");
			} else {
				emitline("\tMOVQ\t");
				emitoff(slclocal.off: i64);
				emitline("(BP), BX\n");
			};
		};
	};
	emitline("\tADDQ\tAX, BX\n");

	// Per-binding load from BX+foff. Signedness comes from bind_signed
	// (set via paramissigned → fieldissignedc), so enum-aliased narrows
	// pick the right MOVS*Q without a literal-name gate.
	let b: i32 = 0;
	for (b < nbinds) {
		let op: str = loadopsz(bind_signed[b], bind_sz[b]);
		emitline("\t");
		emitline(op);
		emitline("\t");
		emitoff(bind_foff[b]: i64);
		emitline("(BX), AX\n");
		emitline("\tMOVQ\tAX, ");
		emitoff(bind_off[b]: i64);
		emitline("(BP)\n");
		b += 1;
	};

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

	c.looptop -= 1;

	emitline("\tADDQ\t$1, ");
	emitoff(ioff: i64);
	emitline("(BP)\n");
	emitline("\tJMP\t"); emitline(loopl); emitline("\n");
	if (n.els != nil) {
		emitlabel(naturall);
		cgstmt(c, n.els);
	};
	emitlabel(endl);
	c.lastwasreturn = 0;
	return;
};

// cgswitch — lower `switch (e) { case 1, 2: ...; case: default; }` to
// a chain of compares against the scrutinee. Scrutinee lands in a
// fresh 8B local slot so case bodies can spill SP without losing it.
// Cases are tried top-to-bottom; the `case:` arm with no exprs is the
// default and runs after all named arms fail. Mirrors cmd/w6c/cgen.c
// N_SWITCH: same labelseq consumption order so labels match byte-for-
// byte.
fn cgswitch(c: *cgen, n: *node) void = {
	let swname: str = mkscratchname(c, "sw");
	let sloff: i32 = localalloc(c, swname, 8, nil);

	if (n.lhs != nil) { cgexpr(c, n.lhs); };
	emitline("\tMOVQ\tAX, ");
	emitoff(sloff: i64);
	emitline("(BP)\n");

	let endl: str = mklabel(c, "swend");
	let defcase: *node = nil;

	let cs: *node = n.list;
	for (cs != nil) {
		if (cs.list == nil) {
			defcase = cs;
			cs = cs.next;
			continue;
		};
		let body: str = mklabel(c, "swcase");
		let nxt: str = mklabel(c, "swnext");
		let e: *node = cs.list;
		for (e != nil) {
			cgexpr(c, e);
			emitline("\tMOVQ\t");
			emitoff(sloff: i64);
			emitline("(BP), BX\n");
			emitline("\tCMPQ\tBX, AX\n");
			emitline("\tJE\t");
			emitline(body);
			emitline("\n");
			e = e.next;
		};
		emitline("\tJMP\t");
		emitline(nxt);
		emitline("\n");
		emitlabel(body);
		if (cs.body != nil) { cgstmt(c, cs.body); };
		emitline("\tJMP\t");
		emitline(endl);
		emitline("\n");
		emitlabel(nxt);
		cs = cs.next;
	};
	if (defcase != nil) {
		if (defcase.body != nil) { cgstmt(c, defcase.body); };
	};
	emitlabel(endl);
	c.lastwasreturn = 0;
	return;
};

fn cgbreak(c: *cgen, n: *node) void = {
	if (c.looptop > 0) {
		let lbl: str = c.loopendbuf[c.looptop - 1];
		emitline("\tJMP\t"); emitline(lbl); emitline("\n");
	};
	c.lastwasreturn = 0;
	return;
};

fn cgcontinue(c: *cgen, n: *node) void = {
	if (c.looptop > 0) {
		let lbl: str = c.loopcontbuf[c.looptop - 1];
		emitline("\tJMP\t"); emitline(lbl); emitline("\n");
	};
	c.lastwasreturn = 0;
	return;
};