cmd/compile: fix an arm64's comparison bug

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>

diff --git a/src/cmd/compile/internal/ssa/gen/ARM64.rules b/src/cmd/compile/internal/ssa/gen/ARM64.rules
index d9e614f61a2832abd9d8b558f7cc3135953cfd8b..4c5f8c75024d9695ccaa17dc652b5f5c419b62ca 100644 (file)
--- a/src/cmd/compile/internal/ssa/gen/ARM64.rules
+++ b/src/cmd/compile/internal/ssa/gen/ARM64.rules
@@ -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)

diff --git a/src/cmd/compile/internal/ssa/rewriteARM64.go b/src/cmd/compile/internal/ssa/rewriteARM64.go
index cea9d03a9d51678e71473a44a507227bfe137a1d..0715a5347de22db8238616143f76479b23edfa33 100644 (file)
--- a/src/cmd/compile/internal/ssa/rewriteARM64.go
+++ b/src/cmd/compile/internal/ssa/rewriteARM64.go
@@ -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)

diff --git a/test/fixedbugs/issue26438.go b/test/fixedbugs/issue26438.go
new file mode 100644 (file)
index 0000000..d44da21
--- /dev/null
+++ b/test/fixedbugs/issue26438.go
@@ -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")
+       }
+}