cmd/compile: fix OpArg decomposer for registers in expandCalls

Includes test taken from
https://github.com/golang/go/issues/44816#issuecomment-791618179
and improved debugging output.

Updates #44816

Change-Id: I94aeb9c5255f175fe80727be29d218bad54bf7ea
Reviewed-on: https://go-review.googlesource.com/c/go/+/299389
Trust: David Chase <drchase@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

4 files changed, 39 insertions, 8 deletions

diff --git a/test/abi/double_nested_struct.go b/test/abi/double_nested_struct.go
index 70d8ea4bce..814341e701 100644
--- a/test/abi/double_nested_struct.go
+++ b/test/abi/double_nested_struct.go
@@ -8,7 +8,7 @@
 // license that can be found in the LICENSE file.
 
 // wasm is excluded because the compiler chatter about register abi pragma ends up
-// on stdout, and causes the expected output to not match. 
+// on stdout, and causes the expected output to not match.
 
 package main
 
@@ -37,13 +37,12 @@ func H(spp stringPairPair) string {
 
 //go:registerparams
 //go:noinline
-func G(a,b,c,d string) stringPairPair {
-	return stringPairPair{stringPair{a,b},stringPair{c,d}}
+func G(a, b, c, d string) stringPairPair {
+	return stringPairPair{stringPair{a, b}, stringPair{c, d}}
 }
 
-
 func main() {
-	spp := G("this","is","a","test")
+	spp := G("this", "is", "a", "test")
 	s := H(spp)
 	gotVsWant(s, "this is a test")
 }
diff --git a/test/abi/struct_lower_1.go b/test/abi/struct_lower_1.go
new file mode 100644
index 0000000000..b20de9be4b
--- /dev/null
+++ b/test/abi/struct_lower_1.go
@@ -0,0 +1,30 @@
+// run
+
+//go:build !wasm
+// +build !wasm
+
+// Copyright 2021 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
+
+import "fmt"
+
+//go:registerparams
+//go:noinline
+func passStruct6(a Struct6) Struct6 {
+	return a
+}
+
+type Struct6 struct {
+	Struct1
+}
+
+type Struct1 struct {
+	A, B, C uint
+}
+
+func main() {
+	fmt.Println(passStruct6(Struct6{Struct1{1, 2, 3}}))
+}
diff --git a/test/abi/struct_lower_1.out b/test/abi/struct_lower_1.out
new file mode 100644
index 0000000000..d326cb6119
--- /dev/null
+++ b/test/abi/struct_lower_1.out
@@ -0,0 +1 @@
+{{1 2 3}}
diff --git a/test/abi/too_big_to_ssa.go b/test/abi/too_big_to_ssa.go
index a5c6abb0e4..6c55d31419 100644
--- a/test/abi/too_big_to_ssa.go
+++ b/test/abi/too_big_to_ssa.go
@@ -1,5 +1,6 @@
 // run
 
+//go:build !wasm
 // +build !wasm
 
 // Copyright 2021 The Go Authors. All rights reserved.
@@ -16,7 +17,7 @@ var sink *string
 
 type toobig struct {
 	// 6 words will not SSA but will fit in registers
-	a,b,c string
+	a, b, c string
 }
 
 //go:registerparams
@@ -27,8 +28,8 @@ func H(x toobig) string {
 
 //go:registerparams
 //go:noinline
-func I(a,b,c string) toobig {
-	return toobig{a,b,c}
+func I(a, b, c string) toobig {
+	return toobig{a, b, c}
 }
 
 func main() {