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cmd/compile: fix precedence order bug

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&^ and << have equal precedence.  Add some parentheses to make sure
we shift before we andnot.

Fixes #27829

Change-Id: Iba8576201f0f7c52bf9795aaa75d15d8f9a76811
Reviewed-on: https://go-review.googlesource.com/136899
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
This commit is contained in:
Keith Randall 2018-09-24 10:23:53 -07:00 committed by Keith Randall
parent 8d6a455df4
commit 9774fa6f40
3 changed files with 37 additions and 10 deletions
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4
src/cmd/compile/internal/ssa/gen/AMD64.rules
View file

@ -709,8 +709,8 @@
(ANDL x (MOVLconst [c])) -> (ANDLconst [c] x)
(AND(L|Q)const [c] (AND(L|Q)const [d] x)) -> (AND(L|Q)const [c & d] x)
(BTR(L|Q)const [c] (AND(L|Q)const [d] x)) -> (AND(L|Q)const [d &^ 1<<uint32(c)] x)
(AND(L|Q)const [c] (BTR(L|Q)const [d] x)) -> (AND(L|Q)const [c &^ 1<<uint32(d)] x)
(BTR(L|Q)const [c] (AND(L|Q)const [d] x)) -> (AND(L|Q)const [d &^ (1<<uint32(c))] x)
(AND(L|Q)const [c] (BTR(L|Q)const [d] x)) -> (AND(L|Q)const [c &^ (1<<uint32(d))] x)
(BTR(L|Q)const [c] (BTR(L|Q)const [d] x)) -> (AND(L|Q)const [^(1<<uint32(c) | 1<<uint32(d))] x)
(XOR(L|Q)const [c] (XOR(L|Q)const [d] x)) -> (XOR(L|Q)const [c ^ d] x)
(BTC(L|Q)const [c] (XOR(L|Q)const [d] x)) -> (XOR(L|Q)const [d ^ 1<<uint32(c)] x)

16
src/cmd/compile/internal/ssa/rewriteAMD64.go
View file

@ -3620,7 +3620,7 @@ func rewriteValueAMD64_OpAMD64ANDLconst_0(v *Value) bool {
}
// match: (ANDLconst [c] (BTRLconst [d] x))
// cond:
// result: (ANDLconst [c &^ 1<<uint32(d)] x)
// result: (ANDLconst [c &^ (1<<uint32(d))] x)
for {
c := v.AuxInt
v_0 := v.Args[0]
@ -3630,7 +3630,7 @@ func rewriteValueAMD64_OpAMD64ANDLconst_0(v *Value) bool {
d := v_0.AuxInt
x := v_0.Args[0]
v.reset(OpAMD64ANDLconst)
v.AuxInt = c &^ 1 << uint32(d)
v.AuxInt = c &^ (1 << uint32(d))
v.AddArg(x)
return true
}
@ -4147,7 +4147,7 @@ func rewriteValueAMD64_OpAMD64ANDQconst_0(v *Value) bool {
}
// match: (ANDQconst [c] (BTRQconst [d] x))
// cond:
// result: (ANDQconst [c &^ 1<<uint32(d)] x)
// result: (ANDQconst [c &^ (1<<uint32(d))] x)
for {
c := v.AuxInt
v_0 := v.Args[0]
@ -4157,7 +4157,7 @@ func rewriteValueAMD64_OpAMD64ANDQconst_0(v *Value) bool {
d := v_0.AuxInt
x := v_0.Args[0]
v.reset(OpAMD64ANDQconst)
v.AuxInt = c &^ 1 << uint32(d)
v.AuxInt = c &^ (1 << uint32(d))
v.AddArg(x)
return true
}
@ -5019,7 +5019,7 @@ func rewriteValueAMD64_OpAMD64BTRLconst_0(v *Value) bool {
}
// match: (BTRLconst [c] (ANDLconst [d] x))
// cond:
// result: (ANDLconst [d &^ 1<<uint32(c)] x)
// result: (ANDLconst [d &^ (1<<uint32(c))] x)
for {
c := v.AuxInt
v_0 := v.Args[0]
@ -5029,7 +5029,7 @@ func rewriteValueAMD64_OpAMD64BTRLconst_0(v *Value) bool {
d := v_0.AuxInt
x := v_0.Args[0]
v.reset(OpAMD64ANDLconst)
v.AuxInt = d &^ 1 << uint32(c)
v.AuxInt = d &^ (1 << uint32(c))
v.AddArg(x)
return true
}
@ -5212,7 +5212,7 @@ func rewriteValueAMD64_OpAMD64BTRQconst_0(v *Value) bool {
}
// match: (BTRQconst [c] (ANDQconst [d] x))
// cond:
// result: (ANDQconst [d &^ 1<<uint32(c)] x)
// result: (ANDQconst [d &^ (1<<uint32(c))] x)
for {
c := v.AuxInt
v_0 := v.Args[0]
@ -5222,7 +5222,7 @@ func rewriteValueAMD64_OpAMD64BTRQconst_0(v *Value) bool {
d := v_0.AuxInt
x := v_0.Args[0]
v.reset(OpAMD64ANDQconst)
v.AuxInt = d &^ 1 << uint32(c)
v.AuxInt = d &^ (1 << uint32(c))
v.AddArg(x)
return true
}

27
test/fixedbugs/issue27829.go Normal file
View file

@ -0,0 +1,27 @@
// 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.
// Bad AND/BTR combination rule.
package main
import "fmt"
//go:noinline
func f(x uint64) uint64 {
return (x >> 48) &^ (uint64(0x4000))
}
func main() {
bad := false
if got, want := f(^uint64(0)), uint64(0xbfff); got != want {
fmt.Printf("got %x, want %x\n", got, want)
bad = true
}
if bad {
panic("bad")
}
}