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

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>

diff --git a/src/cmd/compile/internal/ssa/gen/AMD64.rules b/src/cmd/compile/internal/ssa/gen/AMD64.rules
index cab0f660799d7ac01488fa05c718ad1d76885dcb..f589d00631f91a94b625d8f0cd070483331f6f16 100644 (file)
--- a/src/cmd/compile/internal/ssa/gen/AMD64.rules
+++ b/src/cmd/compile/internal/ssa/gen/AMD64.rules
@@ -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

diff --git a/src/cmd/compile/internal/ssa/rewriteAMD64.go b/src/cmd/compile/internal/ssa/rewriteAMD64.go
index 313b6bef9c39dfdb2f074b041dae98280cf7a3c6..052646a2b78d983856cc4a20b31f14cf2433338d 100644 (file)
--- a/src/cmd/compile/internal/ssa/rewriteAMD64.go
+++ b/src/cmd/compile/internal/ssa/rewriteAMD64.go
@@ -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)

diff --git a/test/fixedbugs/issue25006.go b/test/fixedbugs/issue25006.go
new file mode 100644 (file)
index 0000000..570fdca
--- /dev/null
+++ b/test/fixedbugs/issue25006.go
@@ -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:
+               }
+       }
+}