cmd/compile: use inc/dec for bytes, too

Change-Id: Ib2890ab1983cbef7c1c1ee5a10204ba3ace19b53
Reviewed-on: https://go-review.googlesource.com/21312
Run-TryBot: Alexandru Moșoi <alexandru@mosoi.ro>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

src/cmd/compile/internal/amd64/ssa.go

@@ -430,9 +430,7 @@ func ssaGenValue(s *gc.SSAGenState, v *ssa.Value) {
 				// and make a binary a little smaller.
 				case ssa.OpAMD64ADDQconst:
 					asm = x86.AINCQ
-				case ssa.OpAMD64ADDLconst:
-					asm = x86.AINCL
-				case ssa.OpAMD64ADDWconst:
+				case ssa.OpAMD64ADDLconst, ssa.OpAMD64ADDWconst, ssa.OpAMD64ADDBconst:
 					asm = x86.AINCL
 				}
 				p := gc.Prog(asm)
@@ -444,9 +442,7 @@ func ssaGenValue(s *gc.SSAGenState, v *ssa.Value) {
 				switch v.Op {
 				case ssa.OpAMD64ADDQconst:
 					asm = x86.ADECQ
-				case ssa.OpAMD64ADDLconst:
-					asm = x86.ADECL
-				case ssa.OpAMD64ADDWconst:
+				case ssa.OpAMD64ADDLconst, ssa.OpAMD64ADDWconst, ssa.OpAMD64ADDBconst:
 					asm = x86.ADECL
 				}
 				p := gc.Prog(asm)