cmd/compile: mark MOVQconvert as resultInArg0 on x86 architectures

This prevents unnecessary reg-reg moves during pointer arithmetic.

This change reduces the size of the full hello world binary by 0.4%.

Updates #21572

Change-Id: Ia0427021e5c94545a0dbd83a6801815806e5b12d
Reviewed-on: https://go-review.googlesource.com/58371
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Run-TryBot: Martin Möhrmann <moehrmann@google.com>
Reviewed-by: Keith Randall <khr@golang.org>

src/cmd/compile/internal/ssa/gen/386Ops.go

@@ -448,7 +448,7 @@ func init() {
 		// (particularly stack maps).  It takes a memory arg so it
 		// gets correctly ordered with respect to GC safepoints.
 		// arg0=ptr/int arg1=mem, output=int/ptr
-		{name: "MOVLconvert", argLength: 2, reg: gp11, asm: "MOVL"},
+		{name: "MOVLconvert", argLength: 2, reg: gp11, asm: "MOVL", resultInArg0: true},
 
 		// Constant flag values. For any comparison, there are 5 possible
 		// outcomes: the three from the signed total order (<,==,>) and the

src/cmd/compile/internal/ssa/gen/AMD64Ops.go

@@ -538,8 +538,8 @@ func init() {
 		// (particularly stack maps).  It takes a memory arg so it
 		// gets correctly ordered with respect to GC safepoints.
 		// arg0=ptr/int arg1=mem, output=int/ptr
-		{name: "MOVQconvert", argLength: 2, reg: gp11, asm: "MOVQ"},
-		{name: "MOVLconvert", argLength: 2, reg: gp11, asm: "MOVL"}, // amd64p32 equivalent
+		{name: "MOVQconvert", argLength: 2, reg: gp11, asm: "MOVQ", resultInArg0: true},
+		{name: "MOVLconvert", argLength: 2, reg: gp11, asm: "MOVL", resultInArg0: true}, // amd64p32 equivalent
 
 		// Constant flag values. For any comparison, there are 5 possible
 		// outcomes: the three from the signed total order (<,==,>) and the

src/cmd/compile/internal/ssa/gen/main.go

@@ -177,10 +177,10 @@ func genOp() {
 			if v.resultInArg0 {
 				fmt.Fprintln(w, "resultInArg0: true,")
 				if v.reg.inputs[0] != v.reg.outputs[0] {
-					log.Fatalf("input[0] and output[0] must use the same registers for %s", v.name)
+					log.Fatalf("%s: input[0] and output[0] must use the same registers for %s", a.name, v.name)
 				}
 				if v.commutative && v.reg.inputs[1] != v.reg.outputs[0] {
-					log.Fatalf("input[1] and output[0] must use the same registers for %s", v.name)
+					log.Fatalf("%s: input[1] and output[0] must use the same registers for %s", a.name, v.name)
 				}
 			}
 			if v.resultNotInArgs {

src/cmd/compile/internal/ssa/opGen.go

@@ -4273,6 +4273,7 @@ var opcodeTable = [...]opInfo{
 	{
 		name:         "MOVLconvert",
 		argLen:       2,
+		resultInArg0: true,
 		asm:          x86.AMOVL,
 		reg: regInfo{
 			inputs: []inputInfo{
@@ -7822,6 +7823,7 @@ var opcodeTable = [...]opInfo{
 	{
 		name:         "MOVQconvert",
 		argLen:       2,
+		resultInArg0: true,
 		asm:          x86.AMOVQ,
 		reg: regInfo{
 			inputs: []inputInfo{
@@ -7835,6 +7837,7 @@ var opcodeTable = [...]opInfo{
 	{
 		name:         "MOVLconvert",
 		argLen:       2,
+		resultInArg0: true,
 		asm:          x86.AMOVL,
 		reg: regInfo{
 			inputs: []inputInfo{