[dev.ssa] cmd/compile: respect stack slot width when storing/loading registers

Prior to this, we were smashing our own stack,
which caused the crypto/sha256 tests to fail.

Change-Id: I7dd94cf466d175b3be0cd65f9c4fe8b1223081fe
Reviewed-on: https://go-review.googlesource.com/12660
Reviewed-by: Daniel Morsing <daniel.morsing@gmail.com>
Reviewed-by: Keith Randall <khr@golang.org>

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

@@ -1639,23 +1639,23 @@ func genValue(v *ssa.Value) {
 			p.To.Type = obj.TYPE_REG
 			p.To.Reg = y
 		}
-	case ssa.OpLoadReg8:
+	case ssa.OpLoadReg:
 		if v.Type.IsFlags() {
 			v.Unimplementedf("load flags not implemented: %v", v.LongString())
 			return
 		}
-		p := Prog(x86.AMOVQ)
+		p := Prog(movSize(v.Type.Size()))
 		p.From.Type = obj.TYPE_MEM
 		p.From.Reg = x86.REG_SP
 		p.From.Offset = localOffset(v.Args[0])
 		p.To.Type = obj.TYPE_REG
 		p.To.Reg = regnum(v)
-	case ssa.OpStoreReg8:
+	case ssa.OpStoreReg:
 		if v.Type.IsFlags() {
 			v.Unimplementedf("store flags not implemented: %v", v.LongString())
 			return
 		}
-		p := Prog(x86.AMOVQ)
+		p := Prog(movSize(v.Type.Size()))
 		p.From.Type = obj.TYPE_REG
 		p.From.Reg = regnum(v.Args[0])
 		p.To.Type = obj.TYPE_MEM
@@ -1711,6 +1711,23 @@ func genValue(v *ssa.Value) {
 	}
 }
 
+// movSize returns the MOV instruction of the given width.
+func movSize(width int64) (asm int) {
+	switch width {
+	case 1:
+		asm = x86.AMOVB
+	case 2:
+		asm = x86.AMOVW
+	case 4:
+		asm = x86.AMOVL
+	case 8:
+		asm = x86.AMOVQ
+	default:
+		panic(fmt.Errorf("bad movSize %d", width))
+	}
+	return asm
+}
+
 // movZero generates a register indirect move with a 0 immediate and keeps track of bytes left and next offset
 func movZero(as int, width int64, nbytes int64, offset int64, regnum int16) (nleft int64, noff int64) {
 	p := Prog(as)

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

@@ -178,10 +178,8 @@ var genericOps = []opData{
 	// semantically identical to OpCopy; they do not take/return
 	// stores like regular memory ops do.  We can get away without memory
 	// args because we know there is no aliasing of spill slots on the stack.
-	// TODO: remove these, make them arch-specific ops stored
-	// in the fields of Config instead.
-	{name: "StoreReg8"},
-	{name: "LoadReg8"},
+	{name: "StoreReg"},
+	{name: "LoadReg"},
 
 	// Used during ssa construction.  Like Copy, but the arg has not been specified yet.
 	{name: "FwdRef"},

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

@@ -243,8 +243,8 @@ const (
 	OpStringMake
 	OpStringPtr
 	OpStringLen
-	OpStoreReg8
-	OpLoadReg8
+	OpStoreReg
+	OpLoadReg
 	OpFwdRef
 )
 
@@ -1590,11 +1590,11 @@ var opcodeTable = [...]opInfo{
 		generic: true,
 	},
 	{
-		name:    "StoreReg8",
+		name:    "StoreReg",
 		generic: true,
 	},
 	{
-		name:    "LoadReg8",
+		name:    "LoadReg",
 		generic: true,
 	},
 	{

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

@@ -240,7 +240,7 @@ func regalloc(f *Func) {
 						c := regs[r].c
 						if regs[r].dirty && lastUse[x.ID] > idx {
 							// Write x back to home.  Its value is currently held in c.
-							x.Op = OpStoreReg8
+							x.Op = OpStoreReg
 							x.Aux = nil
 							x.resetArgs()
 							x.AddArg(c)
@@ -276,7 +276,7 @@ func regalloc(f *Func) {
 						c = b.NewValue1(w.Line, OpCopy, w.Type, regs[s].c)
 					} else {
 						// Load from home location
-						c = b.NewValue1(w.Line, OpLoadReg8, w.Type, w)
+						c = b.NewValue1(w.Line, OpLoadReg, w.Type, w)
 					}
 					home = setloc(home, c, &registers[r])
 					// Remember what we did
@@ -319,7 +319,7 @@ func regalloc(f *Func) {
 					c := regs[r].c
 					if regs[r].dirty && lastUse[x.ID] > idx {
 						// Write x back to home.  Its value is currently held in c.
-						x.Op = OpStoreReg8
+						x.Op = OpStoreReg
 						x.Aux = nil
 						x.resetArgs()
 						x.AddArg(c)
@@ -373,7 +373,7 @@ func regalloc(f *Func) {
 			}
 
 			// change v to be a copy of c
-			v.Op = OpStoreReg8
+			v.Op = OpStoreReg
 			v.Aux = nil
 			v.resetArgs()
 			v.AddArg(c)