From 7b3abf0ec5fcb2e2bf5d286b042eedc6f17ba762 Mon Sep 17 00:00:00 2001
From: Hojun-Cho <ghwns6743@gmail.com>
Date: Mon, 25 May 2026 13:48:31 +0900
Subject: [PATCH] cgen: wwstage fnretlookup resolves cross-module callee f64
 return type (#98/#101)
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exprfloatkind's N_CALL arm only set the callee name for an N_IDENT
callee, so a module-qualified `mod.g()` callee never reached any
return-type lookup and fell through to integer (kind 0). Both f64
consumers then took the integer path for an imported f64-returning
fn: cgcast emitted MOVSXD instead of CVTTSD2SI (#101), and pushargsrev
spilled the call result as a GPR PUSHQ/POPQ instead of the MOVSD float
spill (#98) — one root, two symptoms.

Route the N_DOT callee through fnretlookupmod with the module
qualifier, mirroring nodeisslice / nodeisstr's #34 N_DOT arm, so a
cross-module f64 call resolves to kind 2 exactly like same-module
already does. This aligns wwstage UP to cstage, whose cg_isfloat reads
the resolved call result type directly (cmd/w6c/cgen.c:117,155) and is
correct for both cases. Consumers (cgcast, pushargsrev) unchanged.
---
 selfhost/cmd/wcc/cgenutil.ww | 37 ++++++++++++++++++++++++++----------
 1 file changed, 27 insertions(+), 10 deletions(-)

diff --git a/selfhost/cmd/wcc/cgenutil.ww b/selfhost/cmd/wcc/cgenutil.ww
index 38f4762b..67ef2aca 100644
--- a/selfhost/cmd/wcc/cgenutil.ww
+++ b/selfhost/cmd/wcc/cgenutil.ww
@@ -1889,18 +1889,35 @@ export fn exprfloatkind(c: *cgen, n: *node) i32 = {
 		return 0;
 	};
 	if (k == nkind.N_CALL) {
-		// Look up the callee's declared return type — fnretlookup
+		// Look up the callee's declared return type — fnretlookupmod
 		// 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 rtyp: *node = fnretlookup(c, nm);
-			if (isf32type(c, rtyp)) { return 1; };
-			if (isfloattype(c, rtyp)) { return 2; };
+		// N_DOT (cross-module callee, #98/#101): without the explicit
+		// arm a module-qualified `myf.g()` callee never reaches any
+		// lookup, so an imported f64-returning fn fell through to
+		// integer (0) — cgcast then emitted MOVSXD not CVTTSD2SI
+		// (#101) and pushargsrev spilled the result as a GPR not
+		// MOVSD (#98). Mirror nodeisslice / nodeisstr's #34 N_DOT arm
+		// so cross-module resolves to kind 2 like same-module does.
+		let callee: *node = n.lhs;
+		if (callee != nil) {
+			if (callee.kind == nkind.N_IDENT) {
+				let rtyp: *node = fnretlookupmod(c, callee.str, c.curmod);
+				if (isf32type(c, rtyp)) { return 1; };
+				if (isfloattype(c, rtyp)) { return 2; };
+			};
+			if (callee.kind == nkind.N_DOT) {
+				let cmod: str;
+				cmod.ptr = nil; cmod.len = 0;
+				if (callee.lhs != nil) {
+					if (callee.lhs.kind == nkind.N_IDENT) {
+						cmod = callee.lhs.str;
+					};
+				};
+				let rtyp: *node = fnretlookupmod(c, callee.str, cmod);
+				if (isf32type(c, rtyp)) { return 1; };
+				if (isfloattype(c, rtyp)) { return 2; };
+			};
 		};
 		return 0;
 	};