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cmd/compile: avoid applying ARM CMP->CMN rewrite in unsigned context

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Fixes #41780.

Change-Id: I1dc7c19a9f057650905da3a96214c2ff4abb51be
Reviewed-on: https://go-review.googlesource.com/c/go/+/259450
Trust: David Chase <drchase@google.com>
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
This commit is contained in:
David Chase 2020-10-05 12:07:00 -04:00
parent 5d12434eee
commit 694025e74f
3 changed files with 257 additions and 29 deletions
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4
src/cmd/compile/internal/ssa/gen/ARM.rules
View File

@ -1263,8 +1263,8 @@
(SRLconst (SLLconst x [c]) [d]) && objabi.GOARM==7 && uint64(d)>=uint64(c) && uint64(d)<=31 => (BFXU [(d-c)|(32-d)<<8] x)
// comparison simplification
(CMP x (RSBconst [0] y)) => (CMN x y)
(CMN x (RSBconst [0] y)) => (CMP x y)
((LT|LE|EQ|NE|GE|GT) (CMP x (RSBconst [0] y))) => ((LT|LE|EQ|NE|GE|GT) (CMN x y)) // sense of carry bit not preserved
((LT|LE|EQ|NE|GE|GT) (CMN x (RSBconst [0] y))) => ((LT|LE|EQ|NE|GE|GT) (CMP x y)) // sense of carry bit not preserved
(EQ (CMPconst [0] l:(SUB x y)) yes no) && l.Uses==1 => (EQ (CMP x y) yes no)
(EQ (CMPconst [0] l:(MULS x y a)) yes no) && l.Uses==1 => (EQ (CMP a (MUL <x.Type> x y)) yes no)
(EQ (CMPconst [0] l:(SUBconst [c] x)) yes no) && l.Uses==1 => (EQ (CMPconst [c] x) yes no)

243
src/cmd/compile/internal/ssa/rewriteARM.go
View File

@ -3362,21 +3362,6 @@ func rewriteValueARM_OpARMCMN(v *Value) bool {
}
break
}
// match: (CMN x (RSBconst [0] y))
// result: (CMP x y)
for {
for _i0 := 0; _i0 <= 1; _i0, v_0, v_1 = _i0+1, v_1, v_0 {
x := v_0
if v_1.Op != OpARMRSBconst || auxIntToInt32(v_1.AuxInt) != 0 {
continue
}
y := v_1.Args[0]
v.reset(OpARMCMP)
v.AddArg2(x, y)
return true
}
break
}
return false
}
func rewriteValueARM_OpARMCMNconst(v *Value) bool {
@ -3938,18 +3923,6 @@ func rewriteValueARM_OpARMCMP(v *Value) bool {
v.AddArg(v0)
return true
}
// match: (CMP x (RSBconst [0] y))
// result: (CMN x y)
for {
x := v_0
if v_1.Op != OpARMRSBconst || auxIntToInt32(v_1.AuxInt) != 0 {
break
}
y := v_1.Args[0]
v.reset(OpARMCMN)
v.AddArg2(x, y)
return true
}
return false
}
func rewriteValueARM_OpARMCMPD(v *Value) bool {
@ -16002,6 +15975,42 @@ func rewriteBlockARM(b *Block) bool {
b.resetWithControl(BlockARMEQ, cmp)
return true
}
// match: (EQ (CMP x (RSBconst [0] y)))
// result: (EQ (CMN x y))
for b.Controls[0].Op == OpARMCMP {
v_0 := b.Controls[0]
_ = v_0.Args[1]
x := v_0.Args[0]
v_0_1 := v_0.Args[1]
if v_0_1.Op != OpARMRSBconst || auxIntToInt32(v_0_1.AuxInt) != 0 {
break
}
y := v_0_1.Args[0]
v0 := b.NewValue0(v_0.Pos, OpARMCMN, types.TypeFlags)
v0.AddArg2(x, y)
b.resetWithControl(BlockARMEQ, v0)
return true
}
// match: (EQ (CMN x (RSBconst [0] y)))
// result: (EQ (CMP x y))
for b.Controls[0].Op == OpARMCMN {
v_0 := b.Controls[0]
_ = v_0.Args[1]
v_0_0 := v_0.Args[0]
v_0_1 := v_0.Args[1]
for _i0 := 0; _i0 <= 1; _i0, v_0_0, v_0_1 = _i0+1, v_0_1, v_0_0 {
x := v_0_0
if v_0_1.Op != OpARMRSBconst || auxIntToInt32(v_0_1.AuxInt) != 0 {
continue
}
y := v_0_1.Args[0]
v0 := b.NewValue0(v_0.Pos, OpARMCMP, types.TypeFlags)
v0.AddArg2(x, y)
b.resetWithControl(BlockARMEQ, v0)
return true
}
break
}
// match: (EQ (CMPconst [0] l:(SUB x y)) yes no)
// cond: l.Uses==1
// result: (EQ (CMP x y) yes no)
@ -16848,6 +16857,42 @@ func rewriteBlockARM(b *Block) bool {
b.resetWithControl(BlockARMLE, cmp)
return true
}
// match: (GE (CMP x (RSBconst [0] y)))
// result: (GE (CMN x y))
for b.Controls[0].Op == OpARMCMP {
v_0 := b.Controls[0]
_ = v_0.Args[1]
x := v_0.Args[0]
v_0_1 := v_0.Args[1]
if v_0_1.Op != OpARMRSBconst || auxIntToInt32(v_0_1.AuxInt) != 0 {
break
}
y := v_0_1.Args[0]
v0 := b.NewValue0(v_0.Pos, OpARMCMN, types.TypeFlags)
v0.AddArg2(x, y)
b.resetWithControl(BlockARMGE, v0)
return true
}
// match: (GE (CMN x (RSBconst [0] y)))
// result: (GE (CMP x y))
for b.Controls[0].Op == OpARMCMN {
v_0 := b.Controls[0]
_ = v_0.Args[1]
v_0_0 := v_0.Args[0]
v_0_1 := v_0.Args[1]
for _i0 := 0; _i0 <= 1; _i0, v_0_0, v_0_1 = _i0+1, v_0_1, v_0_0 {
x := v_0_0
if v_0_1.Op != OpARMRSBconst || auxIntToInt32(v_0_1.AuxInt) != 0 {
continue
}
y := v_0_1.Args[0]
v0 := b.NewValue0(v_0.Pos, OpARMCMP, types.TypeFlags)
v0.AddArg2(x, y)
b.resetWithControl(BlockARMGE, v0)
return true
}
break
}
// match: (GE (CMPconst [0] l:(SUB x y)) yes no)
// cond: l.Uses==1
// result: (GEnoov (CMP x y) yes no)
@ -17728,6 +17773,42 @@ func rewriteBlockARM(b *Block) bool {
b.resetWithControl(BlockARMLT, cmp)
return true
}
// match: (GT (CMP x (RSBconst [0] y)))
// result: (GT (CMN x y))
for b.Controls[0].Op == OpARMCMP {
v_0 := b.Controls[0]
_ = v_0.Args[1]
x := v_0.Args[0]
v_0_1 := v_0.Args[1]
if v_0_1.Op != OpARMRSBconst || auxIntToInt32(v_0_1.AuxInt) != 0 {
break
}
y := v_0_1.Args[0]
v0 := b.NewValue0(v_0.Pos, OpARMCMN, types.TypeFlags)
v0.AddArg2(x, y)
b.resetWithControl(BlockARMGT, v0)
return true
}
// match: (GT (CMN x (RSBconst [0] y)))
// result: (GT (CMP x y))
for b.Controls[0].Op == OpARMCMN {
v_0 := b.Controls[0]
_ = v_0.Args[1]
v_0_0 := v_0.Args[0]
v_0_1 := v_0.Args[1]
for _i0 := 0; _i0 <= 1; _i0, v_0_0, v_0_1 = _i0+1, v_0_1, v_0_0 {
x := v_0_0
if v_0_1.Op != OpARMRSBconst || auxIntToInt32(v_0_1.AuxInt) != 0 {
continue
}
y := v_0_1.Args[0]
v0 := b.NewValue0(v_0.Pos, OpARMCMP, types.TypeFlags)
v0.AddArg2(x, y)
b.resetWithControl(BlockARMGT, v0)
return true
}
break
}
// match: (GT (CMPconst [0] l:(SUB x y)) yes no)
// cond: l.Uses==1
// result: (GTnoov (CMP x y) yes no)
@ -18699,6 +18780,42 @@ func rewriteBlockARM(b *Block) bool {
b.resetWithControl(BlockARMGE, cmp)
return true
}
// match: (LE (CMP x (RSBconst [0] y)))
// result: (LE (CMN x y))
for b.Controls[0].Op == OpARMCMP {
v_0 := b.Controls[0]
_ = v_0.Args[1]
x := v_0.Args[0]
v_0_1 := v_0.Args[1]
if v_0_1.Op != OpARMRSBconst || auxIntToInt32(v_0_1.AuxInt) != 0 {
break
}
y := v_0_1.Args[0]
v0 := b.NewValue0(v_0.Pos, OpARMCMN, types.TypeFlags)
v0.AddArg2(x, y)
b.resetWithControl(BlockARMLE, v0)
return true
}
// match: (LE (CMN x (RSBconst [0] y)))
// result: (LE (CMP x y))
for b.Controls[0].Op == OpARMCMN {
v_0 := b.Controls[0]
_ = v_0.Args[1]
v_0_0 := v_0.Args[0]
v_0_1 := v_0.Args[1]
for _i0 := 0; _i0 <= 1; _i0, v_0_0, v_0_1 = _i0+1, v_0_1, v_0_0 {
x := v_0_0
if v_0_1.Op != OpARMRSBconst || auxIntToInt32(v_0_1.AuxInt) != 0 {
continue
}
y := v_0_1.Args[0]
v0 := b.NewValue0(v_0.Pos, OpARMCMP, types.TypeFlags)
v0.AddArg2(x, y)
b.resetWithControl(BlockARMLE, v0)
return true
}
break
}
// match: (LE (CMPconst [0] l:(SUB x y)) yes no)
// cond: l.Uses==1
// result: (LEnoov (CMP x y) yes no)
@ -19579,6 +19696,42 @@ func rewriteBlockARM(b *Block) bool {
b.resetWithControl(BlockARMGT, cmp)
return true
}
// match: (LT (CMP x (RSBconst [0] y)))
// result: (LT (CMN x y))
for b.Controls[0].Op == OpARMCMP {
v_0 := b.Controls[0]
_ = v_0.Args[1]
x := v_0.Args[0]
v_0_1 := v_0.Args[1]
if v_0_1.Op != OpARMRSBconst || auxIntToInt32(v_0_1.AuxInt) != 0 {
break
}
y := v_0_1.Args[0]
v0 := b.NewValue0(v_0.Pos, OpARMCMN, types.TypeFlags)
v0.AddArg2(x, y)
b.resetWithControl(BlockARMLT, v0)
return true
}
// match: (LT (CMN x (RSBconst [0] y)))
// result: (LT (CMP x y))
for b.Controls[0].Op == OpARMCMN {
v_0 := b.Controls[0]
_ = v_0.Args[1]
v_0_0 := v_0.Args[0]
v_0_1 := v_0.Args[1]
for _i0 := 0; _i0 <= 1; _i0, v_0_0, v_0_1 = _i0+1, v_0_1, v_0_0 {
x := v_0_0
if v_0_1.Op != OpARMRSBconst || auxIntToInt32(v_0_1.AuxInt) != 0 {
continue
}
y := v_0_1.Args[0]
v0 := b.NewValue0(v_0.Pos, OpARMCMP, types.TypeFlags)
v0.AddArg2(x, y)
b.resetWithControl(BlockARMLT, v0)
return true
}
break
}
// match: (LT (CMPconst [0] l:(SUB x y)) yes no)
// cond: l.Uses==1
// result: (LTnoov (CMP x y) yes no)
@ -20609,6 +20762,42 @@ func rewriteBlockARM(b *Block) bool {
b.resetWithControl(BlockARMNE, cmp)
return true
}
// match: (NE (CMP x (RSBconst [0] y)))
// result: (NE (CMN x y))
for b.Controls[0].Op == OpARMCMP {
v_0 := b.Controls[0]
_ = v_0.Args[1]
x := v_0.Args[0]
v_0_1 := v_0.Args[1]
if v_0_1.Op != OpARMRSBconst || auxIntToInt32(v_0_1.AuxInt) != 0 {
break
}
y := v_0_1.Args[0]
v0 := b.NewValue0(v_0.Pos, OpARMCMN, types.TypeFlags)
v0.AddArg2(x, y)
b.resetWithControl(BlockARMNE, v0)
return true
}
// match: (NE (CMN x (RSBconst [0] y)))
// result: (NE (CMP x y))
for b.Controls[0].Op == OpARMCMN {
v_0 := b.Controls[0]
_ = v_0.Args[1]
v_0_0 := v_0.Args[0]
v_0_1 := v_0.Args[1]
for _i0 := 0; _i0 <= 1; _i0, v_0_0, v_0_1 = _i0+1, v_0_1, v_0_0 {
x := v_0_0
if v_0_1.Op != OpARMRSBconst || auxIntToInt32(v_0_1.AuxInt) != 0 {
continue
}
y := v_0_1.Args[0]
v0 := b.NewValue0(v_0.Pos, OpARMCMP, types.TypeFlags)
v0.AddArg2(x, y)
b.resetWithControl(BlockARMNE, v0)
return true
}
break
}
// match: (NE (CMPconst [0] l:(SUB x y)) yes no)
// cond: l.Uses==1
// result: (NE (CMP x y) yes no)

39
test/fixedbugs/issue41780.go Normal file
View File

@ -0,0 +1,39 @@
// run
// Copyright 2020 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.
// Checks that conversion of CMP(x,-y) -> CMN(x,y) is only applied in correct context.
package main
type decimal struct {
d [8]byte // digits, big-endian representation
dp int // decimal point
}
var powtab = []int{1, 3, 6, 9, 13, 16, 19, 23, 26}
//go:noinline
func foo(d *decimal) int {
exp := int(d.d[1])
if d.dp < 0 || d.dp == 0 && d.d[0] < '5' {
var n int
if -d.dp >= len(powtab) {
n = 27
} else {
n = powtab[-d.dp] // incorrect CMP -> CMN substitution causes indexing panic.
}
exp += n
}
return exp
}
func main() {
var d decimal
d.d[0] = '1'
if foo(&d) != 1 {
println("FAILURE (though not the one this test was written to catch)")
}
}