cmd/compile: mark LoweredGetCallerPC rematerializeable

The caller's PC is always available in the frame. We can just
load it when needed, no need to spill.

Change-Id: I9c0a525903e574bb4eec9fe53cbeb8c64321166a
Reviewed-on: https://go-review.googlesource.com/70710
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

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

@@ -444,7 +444,7 @@ func init() {
 		// I.e., if f calls g "calls" getcallerpc,
 		// the result should be the PC within f that g will return to.
 		// See runtime/stubs.go for a more detailed discussion.
-		{name: "LoweredGetCallerPC", reg: gp01},
+		{name: "LoweredGetCallerPC", reg: gp01, rematerializeable: true},
 		// LoweredGetCallerSP returns the SP of the caller of the current function.
 		{name: "LoweredGetCallerSP", reg: gp01, rematerializeable: true},
 		//arg0=ptr,arg1=mem, returns void.  Faults if ptr is nil.

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

@@ -555,7 +555,7 @@ func init() {
 		// I.e., if f calls g "calls" getcallerpc,
 		// the result should be the PC within f that g will return to.
 		// See runtime/stubs.go for a more detailed discussion.
-		{name: "LoweredGetCallerPC", reg: gp01},
+		{name: "LoweredGetCallerPC", reg: gp01, rematerializeable: true},
 		// LoweredGetCallerSP returns the SP of the caller of the current function.
 		{name: "LoweredGetCallerSP", reg: gp01, rematerializeable: true},
 		//arg0=ptr,arg1=mem, returns void.  Faults if ptr is nil.

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

@@ -4341,8 +4341,9 @@ var opcodeTable = [...]opInfo{
 		},
 	},
 	{
-		name:   "LoweredGetCallerPC",
-		argLen: 0,
+		name:              "LoweredGetCallerPC",
+		argLen:            0,
+		rematerializeable: true,
 		reg: regInfo{
 			outputs: []outputInfo{
 				{0, 239}, // AX CX DX BX BP SI DI
@@ -8118,8 +8119,9 @@ var opcodeTable = [...]opInfo{
 		},
 	},
 	{
-		name:   "LoweredGetCallerPC",
-		argLen: 0,
+		name:              "LoweredGetCallerPC",
+		argLen:            0,
+		rematerializeable: true,
 		reg: regInfo{
 			outputs: []outputInfo{
 				{0, 65519}, // AX CX DX BX BP SI DI R8 R9 R10 R11 R12 R13 R14 R15