atomicbitops package cleanups

- Redocument memory ordering from "no ordering" to "acquire-release". (No
  functional change: both LOCK WHATEVER on x86, and LDAXR/STLXR loops on ARM64,
  already have this property.)

- Remove IncUnlessZeroInt32 and DecUnlessOneInt32, which were only faster than
  the equivalent loops using sync/atomic before the Go compiler inlined
  non-unsafe.Pointer atomics many releases ago.

PiperOrigin-RevId: 295811743

1 files changed, 105 insertions, 0 deletions

diff --git a/pkg/atomicbitops/atomicbitops_arm64.s b/pkg/atomicbitops/atomicbitops_arm64.s
new file mode 100644
index 000000000..5c780851b
--- /dev/null
+++ b/pkg/atomicbitops/atomicbitops_arm64.s
@@ -0,0 +1,105 @@
+// Copyright 2019 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build arm64
+
+#include "textflag.h"
+
+TEXT ·AndUint32(SB),$0-12
+  MOVD    ptr+0(FP), R0
+  MOVW    val+8(FP), R1
+again:
+  LDAXRW  (R0), R2
+  ANDW    R1, R2
+  STLXRW  R2, (R0), R3
+  CBNZ    R3, again
+  RET
+
+TEXT ·OrUint32(SB),$0-12
+  MOVD    ptr+0(FP), R0
+  MOVW    val+8(FP), R1
+again:
+  LDAXRW  (R0), R2
+  ORRW    R1, R2
+  STLXRW  R2, (R0), R3
+  CBNZ    R3, again
+  RET
+
+TEXT ·XorUint32(SB),$0-12
+  MOVD    ptr+0(FP), R0
+  MOVW    val+8(FP), R1
+again:
+  LDAXRW  (R0), R2
+  EORW    R1, R2
+  STLXRW  R2, (R0), R3
+  CBNZ    R3, again
+  RET
+
+TEXT ·CompareAndSwapUint32(SB),$0-20
+  MOVD addr+0(FP), R0
+  MOVW old+8(FP), R1
+  MOVW new+12(FP), R2
+again:
+  LDAXRW (R0), R3
+  CMPW R1, R3
+  BNE done
+  STLXRW R2, (R0), R4
+  CBNZ R4, again
+done:
+  MOVW R3, prev+16(FP)
+  RET
+
+TEXT ·AndUint64(SB),$0-16
+  MOVD    ptr+0(FP), R0
+  MOVD    val+8(FP), R1
+again:
+  LDAXR   (R0), R2
+  AND     R1, R2
+  STLXR   R2, (R0), R3
+  CBNZ    R3, again
+  RET
+
+TEXT ·OrUint64(SB),$0-16
+  MOVD    ptr+0(FP), R0
+  MOVD    val+8(FP), R1
+again:
+  LDAXR   (R0), R2
+  ORR     R1, R2
+  STLXR   R2, (R0), R3
+  CBNZ    R3, again
+  RET
+
+TEXT ·XorUint64(SB),$0-16
+  MOVD    ptr+0(FP), R0
+  MOVD    val+8(FP), R1
+again:
+  LDAXR   (R0), R2
+  EOR     R1, R2
+  STLXR   R2, (R0), R3
+  CBNZ    R3, again
+  RET
+
+TEXT ·CompareAndSwapUint64(SB),$0-32
+  MOVD addr+0(FP), R0
+  MOVD old+8(FP), R1
+  MOVD new+16(FP), R2
+again:
+  LDAXR (R0), R3
+  CMP R1, R3
+  BNE done
+  STLXR R2, (R0), R4
+  CBNZ R4, again
+done:
+  MOVD R3, prev+24(FP)
+  RET