cmd/internal/obj/x86: clean up byteswapreg
Make byteswapreg more Go like.
Change-Id: Ibdf3603cae9cad2b3465b4c224a28a4c4c745c2e
Reviewed-on: https://go-review.googlesource.com/38615
Run-TryBot: Dave Cheney <dave@cheney.net>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/src/cmd/internal/obj/x86/asm6.go b/src/cmd/internal/obj/x86/asm6.go
index fff17e5..86dfb28 100644
--- a/src/cmd/internal/obj/x86/asm6.go
+++ b/src/cmd/internal/obj/x86/asm6.go
@@ -4317,68 +4317,53 @@
// If a is empty, it returns BX to account for MULB-like instructions
// that might use DX and AX.
func byteswapreg(ctxt *obj.Link, a *obj.Addr) int {
- cand := 1
- canc := cand
- canb := canc
- cana := canb
-
+ cana, canb, canc, cand := true, true, true, true
if a.Type == obj.TYPE_NONE {
- cand = 0
- cana = cand
+ cana, cand = false, false
}
if a.Type == obj.TYPE_REG || ((a.Type == obj.TYPE_MEM || a.Type == obj.TYPE_ADDR) && a.Name == obj.NAME_NONE) {
switch a.Reg {
case REG_NONE:
- cand = 0
- cana = cand
-
+ cana, cand = false, false
case REG_AX, REG_AL, REG_AH:
- cana = 0
-
+ cana = false
case REG_BX, REG_BL, REG_BH:
- canb = 0
-
+ canb = false
case REG_CX, REG_CL, REG_CH:
- canc = 0
-
+ canc = false
case REG_DX, REG_DL, REG_DH:
- cand = 0
+ cand = false
}
}
if a.Type == obj.TYPE_MEM || a.Type == obj.TYPE_ADDR {
switch a.Index {
case REG_AX:
- cana = 0
-
+ cana = false
case REG_BX:
- canb = 0
-
+ canb = false
case REG_CX:
- canc = 0
-
+ canc = false
case REG_DX:
- cand = 0
+ cand = false
}
}
- if cana != 0 {
+ switch {
+ case cana:
return REG_AX
- }
- if canb != 0 {
+ case canb:
return REG_BX
- }
- if canc != 0 {
+ case canc:
return REG_CX
- }
- if cand != 0 {
+ case cand:
return REG_DX
+ default:
+ ctxt.Diag("impossible byte register")
+ log.Fatalf("bad code")
+ return 0
}
-
- ctxt.Diag("impossible byte register")
- log.Fatalf("bad code")
- return 0
}
func isbadbyte(a *obj.Addr) bool {
