cmd/gc: record argument size for all indirect function calls

This is required to properly unwind reflect.methodValueCall/makeFuncStub.
Fixes #5954.
Stats for 'go install std':
61849 total INSTCALL
24655 currently have ArgSize metadata
27278 have ArgSize metadata with this change
godoc size before: 11351888, after: 11364288

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/12163043

src/cmd/5g/ggen.c

@@ -81,7 +81,12 @@ ginscall(Node *f, int proc)
 		setmaxarg(f->type);
 
 	arg = -1;
-	if(f->type != T && ((f->sym != S && f->sym->pkg == runtimepkg) || proc == 1 || proc == 2)) {
+	// Most functions have a fixed-size argument block, so traceback uses that during unwind.
+	// Not all, though: there are some variadic functions in package runtime,
+	// and for those we emit call-specific metadata recorded by caller.
+	// Reflect generates functions with variable argsize (see reflect.methodValueCall/makeFuncStub),
+	// so we do this for all indirect calls as well.
+	if(f->type != T && (f->sym == S || (f->sym != S && f->sym->pkg == runtimepkg) || proc == 1 || proc == 2)) {
 		arg = f->type->argwid;
 		if(proc == 1 || proc == 2)
 			arg += 3*widthptr;

src/cmd/6g/ggen.c

@@ -79,7 +79,12 @@ ginscall(Node *f, int proc)
 		setmaxarg(f->type);
 
 	arg = -1;
-	if(f->type != T && ((f->sym != S && f->sym->pkg == runtimepkg) || proc == 1 || proc == 2)) {
+	// Most functions have a fixed-size argument block, so traceback uses that during unwind.
+	// Not all, though: there are some variadic functions in package runtime,
+	// and for those we emit call-specific metadata recorded by caller.
+	// Reflect generates functions with variable argsize (see reflect.methodValueCall/makeFuncStub),
+	// so we do this for all indirect calls as well.
+	if(f->type != T && (f->sym == S || (f->sym != S && f->sym->pkg == runtimepkg) || proc == 1 || proc == 2)) {
 		arg = f->type->argwid;
 		if(proc == 1 || proc == 2)
 			arg += 2*widthptr;

src/cmd/8g/ggen.c

@@ -123,7 +123,12 @@ ginscall(Node *f, int proc)
 		setmaxarg(f->type);
 
 	arg = -1;
-	if(f->type != T && ((f->sym != S && f->sym->pkg == runtimepkg) || proc == 1 || proc == 2)) {
+	// Most functions have a fixed-size argument block, so traceback uses that during unwind.
+	// Not all, though: there are some variadic functions in package runtime,
+	// and for those we emit call-specific metadata recorded by caller.
+	// Reflect generates functions with variable argsize (see reflect.methodValueCall/makeFuncStub),
+	// so we do this for all indirect calls as well.
+	if(f->type != T && (f->sym == S || (f->sym != S && f->sym->pkg == runtimepkg) || proc == 1 || proc == 2)) {
 		arg = f->type->argwid;
 		if(proc == 1 || proc == 2)
 			arg += 2*widthptr;

src/pkg/reflect/asm_386.s

@@ -5,6 +5,7 @@
 // makeFuncStub is the code half of the function returned by MakeFunc.
 // See the comment on the declaration of makeFuncStub in makefunc.go
 // for more details.
+// No argsize here, gc generates argsize info at call site.
 TEXT ·makeFuncStub(SB),7,$8
 	MOVL	DX, 0(SP)
 	LEAL	argframe+0(FP), CX
@@ -15,6 +16,7 @@ TEXT ·makeFuncStub(SB),7,$8
 // methodValueCall is the code half of the function returned by makeMethodValue.
 // See the comment on the declaration of methodValueCall in makefunc.go
 // for more details.
+// No argsize here, gc generates argsize info at call site.
 TEXT ·methodValueCall(SB),7,$8
 	MOVL	DX, 0(SP)
 	LEAL	argframe+0(FP), CX

src/pkg/reflect/asm_amd64.s

@@ -5,6 +5,7 @@
 // makeFuncStub is the code half of the function returned by MakeFunc.
 // See the comment on the declaration of makeFuncStub in makefunc.go
 // for more details.
+// No argsize here, gc generates argsize info at call site.
 TEXT ·makeFuncStub(SB),7,$16
 	MOVQ	DX, 0(SP)
 	LEAQ	argframe+0(FP), CX
@@ -15,6 +16,7 @@ TEXT ·makeFuncStub(SB),7,$16
 // methodValueCall is the code half of the function returned by makeMethodValue.
 // See the comment on the declaration of methodValueCall in makefunc.go
 // for more details.
+// No argsize here, gc generates argsize info at call site.
 TEXT ·methodValueCall(SB),7,$16
 	MOVQ	DX, 0(SP)
 	LEAQ	argframe+0(FP), CX

src/pkg/reflect/asm_arm.s

@@ -5,6 +5,7 @@
 // makeFuncStub is jumped to by the code generated by MakeFunc.
 // See the comment on the declaration of makeFuncStub in makefunc.go
 // for more details.
+// No argsize here, gc generates argsize info at call site.
 TEXT ·makeFuncStub(SB),7,$8
 	MOVW	R7, 4(R13)
 	MOVW	$argframe+0(FP), R1
@@ -15,6 +16,7 @@ TEXT ·makeFuncStub(SB),7,$8
 // methodValueCall is the code half of the function returned by makeMethodValue.
 // See the comment on the declaration of methodValueCall in makefunc.go
 // for more details.
+// No argsize here, gc generates argsize info at call site.
 TEXT ·methodValueCall(SB),7,$8
 	MOVW	R7, 4(R13)
 	MOVW	$argframe+0(FP), R1

src/pkg/runtime/traceback_arm.c

@@ -102,7 +102,7 @@ runtime·gentraceback(uintptr pc0, uintptr sp0, uintptr lr0, G *gp, int32 skip,
 		// Most functions have a fixed-size argument block,
 		// so we can use metadata about the function f.
 		// Not all, though: there are some variadic functions
-		// in package runtime, and for those we use call-specific
+		// in package runtime and reflect, and for those we use call-specific
 		// metadata recorded by f's caller.
 		if(callback != nil || printing) {
 			frame.argp = (byte*)frame.fp + sizeof(uintptr);

src/pkg/runtime/traceback_x86.c

@@ -118,7 +118,7 @@ runtime·gentraceback(uintptr pc0, uintptr sp0, uintptr lr0, G *gp, int32 skip,
 		// Most functions have a fixed-size argument block,
 		// so we can use metadata about the function f.
 		// Not all, though: there are some variadic functions
-		// in package runtime, and for those we use call-specific
+		// in package runtime and reflect, and for those we use call-specific
 		// metadata recorded by f's caller.
 		if(callback != nil || printing) {
 			frame.argp = (byte*)frame.fp;