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cmd/compile: fix an arm64's comparison bug

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The arm64 backend generates "TST" for "if uint32(a)&uint32(b) == 0",
which should be "TSTW".

fixes #26438

Change-Id: I7d64c30e3a840b43486bcd10eea2e3e75aaa4857
Reviewed-on: https://go-review.googlesource.com/124637
Run-TryBot: Ben Shi <powerman1st@163.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
This commit is contained in:
Ben Shi 2018-07-18 11:16:47 +00:00 committed by Cherry Zhang
parent 07b81912d4
commit f6ce1e2aa5
3 changed files with 32 additions and 6 deletions
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4
src/cmd/compile/internal/ssa/gen/ARM64.rules
View file

@ -574,8 +574,8 @@
(EQ (CMPconst [0] z:(AND x y)) yes no) && z.Uses == 1 -> (EQ (TST x y) yes no)
(NE (CMPconst [0] z:(AND x y)) yes no) && z.Uses == 1 -> (NE (TST x y) yes no)
(EQ (CMPWconst [0] z:(AND x y)) yes no) && z.Uses == 1 -> (EQ (TST x y) yes no)
(NE (CMPWconst [0] z:(AND x y)) yes no) && z.Uses == 1 -> (NE (TST x y) yes no)
(EQ (CMPWconst [0] z:(AND x y)) yes no) && z.Uses == 1 -> (EQ (TSTW x y) yes no)
(NE (CMPWconst [0] z:(AND x y)) yes no) && z.Uses == 1 -> (NE (TSTW x y) yes no)
(EQ (CMPconst [0] x:(ANDconst [c] y)) yes no) && x.Uses == 1 -> (EQ (TSTconst [c] y) yes no)
(NE (CMPconst [0] x:(ANDconst [c] y)) yes no) && x.Uses == 1 -> (NE (TSTconst [c] y) yes no)

8
src/cmd/compile/internal/ssa/rewriteARM64.go
View file

@ -32192,7 +32192,7 @@ func rewriteBlockARM64(b *Block) bool {
}
// match: (EQ (CMPWconst [0] z:(AND x y)) yes no)
// cond: z.Uses == 1
// result: (EQ (TST x y) yes no)
// result: (EQ (TSTW x y) yes no)
for {
v := b.Control
if v.Op != OpARM64CMPWconst {
@ -32212,7 +32212,7 @@ func rewriteBlockARM64(b *Block) bool {
break
}
b.Kind = BlockARM64EQ
v0 := b.NewValue0(v.Pos, OpARM64TST, types.TypeFlags)
v0 := b.NewValue0(v.Pos, OpARM64TSTW, types.TypeFlags)
v0.AddArg(x)
v0.AddArg(y)
b.SetControl(v0)
@ -33290,7 +33290,7 @@ func rewriteBlockARM64(b *Block) bool {
}
// match: (NE (CMPWconst [0] z:(AND x y)) yes no)
// cond: z.Uses == 1
// result: (NE (TST x y) yes no)
// result: (NE (TSTW x y) yes no)
for {
v := b.Control
if v.Op != OpARM64CMPWconst {
@ -33310,7 +33310,7 @@ func rewriteBlockARM64(b *Block) bool {
break
}
b.Kind = BlockARM64NE
v0 := b.NewValue0(v.Pos, OpARM64TST, types.TypeFlags)
v0 := b.NewValue0(v.Pos, OpARM64TSTW, types.TypeFlags)
v0.AddArg(x)
v0.AddArg(y)
b.SetControl(v0)

26
test/fixedbugs/issue26438.go Normal file
View file

@ -0,0 +1,26 @@
// run
// Copyright 2018 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Issue 26438: arm64 backend may use 64-bit TST for
// "if uint32(a)&uint32(b) == 0", which should be
// 32-bit TSTW
package main
//go:noinline
func tstw(a, b uint64) uint64 {
if uint32(a)&uint32(b) == 0 {
return 100
} else {
return 200
}
}
func main() {
if tstw(0xff00000000, 0xaa00000000) == 200 {
panic("impossible")
}
}