From 1493dd3cfc34dbf18d30ff551bfaf3996430c38a Mon Sep 17 00:00:00 2001
From: David Chase <drchase@google.com>
Date: Tue, 10 Oct 2023 12:18:43 -0400
Subject: [PATCH] cmd/compile: get rid of zero-sized values in call expansion

Do this by removing all stores of zero-sized anything.

Fixes #63433.

Change-Id: I5d8271edab992d15d02005fa3fe31835f2eff8fa
Reviewed-on: https://go-review.googlesource.com/c/go/+/534296
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Run-TryBot: David Chase <drchase@google.com>
Reviewed-by: Keith Randall <khr@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
---
 src/cmd/compile/internal/ssa/_gen/dec.rules |  2 ++
 src/cmd/compile/internal/ssa/rewritedec.go  | 12 +++++++
 test/fixedbugs/issue63490.go                | 36 +++++++++++++++++++++
 3 files changed, 50 insertions(+)
 create mode 100644 test/fixedbugs/issue63490.go

diff --git a/src/cmd/compile/internal/ssa/_gen/dec.rules b/src/cmd/compile/internal/ssa/_gen/dec.rules
index 4484cd7e28..2adf061874 100644
--- a/src/cmd/compile/internal/ssa/_gen/dec.rules
+++ b/src/cmd/compile/internal/ssa/_gen/dec.rules
@@ -7,6 +7,8 @@
 // types.  These rules work together with the decomposeBuiltIn
 // pass which handles phis of these types.
 
+(Store {t} _ _ mem) && t.Size() == 0 => mem
+
 // complex ops
 (ComplexReal (ComplexMake real _  )) => real
 (ComplexImag (ComplexMake _ imag )) => imag
diff --git a/src/cmd/compile/internal/ssa/rewritedec.go b/src/cmd/compile/internal/ssa/rewritedec.go
index fbfe15c0c5..7468518246 100644
--- a/src/cmd/compile/internal/ssa/rewritedec.go
+++ b/src/cmd/compile/internal/ssa/rewritedec.go
@@ -583,6 +583,18 @@ func rewriteValuedec_OpStore(v *Value) bool {
 	b := v.Block
 	config := b.Func.Config
 	typ := &b.Func.Config.Types
+	// match: (Store {t} _ _ mem)
+	// cond: t.Size() == 0
+	// result: mem
+	for {
+		t := auxToType(v.Aux)
+		mem := v_2
+		if !(t.Size() == 0) {
+			break
+		}
+		v.copyOf(mem)
+		return true
+	}
 	// match: (Store {t} dst (ComplexMake real imag) mem)
 	// cond: t.Size() == 8
 	// result: (Store {typ.Float32} (OffPtr <typ.Float32Ptr> [4] dst) imag (Store {typ.Float32} dst real mem))
diff --git a/test/fixedbugs/issue63490.go b/test/fixedbugs/issue63490.go
new file mode 100644
index 0000000000..740ce9b634
--- /dev/null
+++ b/test/fixedbugs/issue63490.go
@@ -0,0 +1,36 @@
+// compile
+
+// Copyright 2023 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+type ResourceFunc struct {
+	junk [8]int
+	base assignmentBaseResource
+}
+
+type SubscriptionAssignmentResource struct {
+	base assignmentBaseResource
+}
+
+type assignmentBaseResource struct{}
+
+//go:noinline
+func (a assignmentBaseResource) f(s string) ResourceFunc {
+	println(s)
+	return ResourceFunc{}
+}
+
+//go:noinline
+func (r SubscriptionAssignmentResource) Hi() ResourceFunc {
+	rf := r.base.f("Hello world")
+	rf.base = r.base
+	return rf
+}
+
+func main() {
+	var r SubscriptionAssignmentResource
+	r.Hi()
+}
-- 
2.44.0