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cmd/compile/internal/ssa: fix endless compile loop on AMD64

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We currently rewrite
(TESTQ (MOVQconst [c] x)) into (TESTQconst [c] x)
and (TESTQconst [-1] x) into (TESTQ x x)
if x is a (MOVQconst [-1]) we will be stuck in the endless rewrite loop.
Don't perform the rewrite in such cases.

Fixes #25006

Change-Id: I77f561ba2605fc104f1e5d5c57f32e9d67a2c000
Reviewed-on: https://go-review.googlesource.com/108879
Run-TryBot: Ilya Tocar <ilya.tocar@intel.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
This commit is contained in:
Ilya Tocar 2018-04-23 14:11:40 -05:00
parent cd037bce09
commit fb017c60bc
3 changed files with 50 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
src/cmd/compile/internal/ssa/gen/AMD64.rules
View File

@ -1443,10 +1443,10 @@
(CMPLconst x [0]) -> (TESTL x x)
(CMPWconst x [0]) -> (TESTW x x)
(CMPBconst x [0]) -> (TESTB x x)
(TESTQconst [-1] x) -> (TESTQ x x)
(TESTLconst [-1] x) -> (TESTL x x)
(TESTWconst [-1] x) -> (TESTW x x)
(TESTBconst [-1] x) -> (TESTB x x)
(TESTQconst [-1] x) && x.Op != OpAMD64MOVQconst -> (TESTQ x x)
(TESTLconst [-1] x) && x.Op != OpAMD64MOVLconst -> (TESTL x x)
(TESTWconst [-1] x) && x.Op != OpAMD64MOVLconst -> (TESTW x x)
(TESTBconst [-1] x) && x.Op != OpAMD64MOVLconst -> (TESTB x x)
// Combining byte loads into larger (unaligned) loads.
// There are many ways these combinations could occur. This is

20
src/cmd/compile/internal/ssa/rewriteAMD64.go
View File

@ -49732,13 +49732,16 @@ func rewriteValueAMD64_OpAMD64TESTB_0(v *Value) bool {
}
func rewriteValueAMD64_OpAMD64TESTBconst_0(v *Value) bool {
// match: (TESTBconst [-1] x)
// cond:
// cond: x.Op != OpAMD64MOVLconst
// result: (TESTB x x)
for {
if v.AuxInt != -1 {
break
}
x := v.Args[0]
if !(x.Op != OpAMD64MOVLconst) {
break
}
v.reset(OpAMD64TESTB)
v.AddArg(x)
v.AddArg(x)
@ -49841,13 +49844,16 @@ func rewriteValueAMD64_OpAMD64TESTL_0(v *Value) bool {
}
func rewriteValueAMD64_OpAMD64TESTLconst_0(v *Value) bool {
// match: (TESTLconst [-1] x)
// cond:
// cond: x.Op != OpAMD64MOVLconst
// result: (TESTL x x)
for {
if v.AuxInt != -1 {
break
}
x := v.Args[0]
if !(x.Op != OpAMD64MOVLconst) {
break
}
v.reset(OpAMD64TESTL)
v.AddArg(x)
v.AddArg(x)
@ -49956,13 +49962,16 @@ func rewriteValueAMD64_OpAMD64TESTQ_0(v *Value) bool {
}
func rewriteValueAMD64_OpAMD64TESTQconst_0(v *Value) bool {
// match: (TESTQconst [-1] x)
// cond:
// cond: x.Op != OpAMD64MOVQconst
// result: (TESTQ x x)
for {
if v.AuxInt != -1 {
break
}
x := v.Args[0]
if !(x.Op != OpAMD64MOVQconst) {
break
}
v.reset(OpAMD64TESTQ)
v.AddArg(x)
v.AddArg(x)
@ -50065,13 +50074,16 @@ func rewriteValueAMD64_OpAMD64TESTW_0(v *Value) bool {
}
func rewriteValueAMD64_OpAMD64TESTWconst_0(v *Value) bool {
// match: (TESTWconst [-1] x)
// cond:
// cond: x.Op != OpAMD64MOVLconst
// result: (TESTW x x)
for {
if v.AuxInt != -1 {
break
}
x := v.Args[0]
if !(x.Op != OpAMD64MOVLconst) {
break
}
v.reset(OpAMD64TESTW)
v.AddArg(x)
v.AddArg(x)

30
test/fixedbugs/issue25006.go Normal file
View File

@ -0,0 +1,30 @@
// compile
// 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.
package p
func spin() {
var i int
var b bool
switch 1 {
case 0:
i = 1
}
switch 1 {
case i:
default:
i = 1
b = !b && (b && !b) && b
}
switch false {
case false:
i = 3 + -i
switch 0 {
case 1 - i:
}
}
}