commit 70102e618a82c41c0e0c790db6959bc58d4837de
author Ulya Trafimovich <skvadrik@google.com> Fri Jan 14 15:20:38 2022 +0000
committer Ulya Trofimovich <skvadrik@google.com> Mon Jan 17 14:52:07 2022 +0000
tree 03766b8b7fe4172c7421ea863ecbf03fcdf1ecd4
parent 27d4f33f6bb07c941f9082eb1b6d920540f98370

arm64: Implement Unsafe.compareAndSetObject intrinsic.

Also fix a few copy-paste errors in comments for x86/x86_64.

The implementation is the same as Unsafe.compareAndSwapObject, as the
latter operation has compare-and-set semantics.

Benchmarks improvements (using benchmarks provided by
https://android-review.googlesource.com/1420959):

  benchmark                              before   after
  -----------------------------------------------------
  UnsafeCompareAndSetStaticFieldString   3.908    0.014
  UnsafeCompareAndSetFieldString         3.917    0.014

Bug: 71781600
Bug: 202868177
Test: art/test.py --target -r -t 712-varhandle-invocations --64
Change-Id: I799f47210f8b70d6944418c05b985fe678f36208

compiler/optimizing/intrinsics_arm64.cc

diff --git a/compiler/optimizing/intrinsics_arm64.cc b/compiler/optimizing/intrinsics_arm64.cc
index 92776f1..77b55e4 100644
--- a/compiler/optimizing/intrinsics_arm64.cc
+++ b/compiler/optimizing/intrinsics_arm64.cc
@@ -1098,7 +1098,8 @@
 static void CreateUnsafeCASLocations(ArenaAllocator* allocator, HInvoke* invoke) {
   bool can_call = kEmitCompilerReadBarrier &&
       (invoke->GetIntrinsic() == Intrinsics::kUnsafeCASObject ||
-       invoke->GetIntrinsic() == Intrinsics::kJdkUnsafeCASObject);
+       invoke->GetIntrinsic() == Intrinsics::kJdkUnsafeCASObject ||
+       invoke->GetIntrinsic() == Intrinsics::kJdkUnsafeCompareAndSetObject);
   LocationSummary* locations =
       new (allocator) LocationSummary(invoke,
                                       can_call
@@ -1505,14 +1506,26 @@
 }
 
 void IntrinsicLocationsBuilderARM64::VisitJdkUnsafeCASInt(HInvoke* invoke) {
-  CreateUnsafeCASLocations(allocator_, invoke);
+  // `jdk.internal.misc.Unsafe.compareAndSwapInt` has compare-and-set semantics (see javadoc).
+  VisitJdkUnsafeCompareAndSetInt(invoke);
 }
 void IntrinsicLocationsBuilderARM64::VisitJdkUnsafeCASLong(HInvoke* invoke) {
-  CreateUnsafeCASLocations(allocator_, invoke);
+  // `jdk.internal.misc.Unsafe.compareAndSwapLong` has compare-and-set semantics (see javadoc).
+  VisitJdkUnsafeCompareAndSetLong(invoke);
 }
 void IntrinsicLocationsBuilderARM64::VisitJdkUnsafeCASObject(HInvoke* invoke) {
-  // The only read barrier implementation supporting the
-  // UnsafeCASObject intrinsic is the Baker-style read barriers. b/173104084
+  // `jdk.internal.misc.Unsafe.compareAndSwapObject` has compare-and-set semantics (see javadoc).
+  VisitJdkUnsafeCompareAndSetObject(invoke);
+}
+
+void IntrinsicLocationsBuilderARM64::VisitJdkUnsafeCompareAndSetInt(HInvoke* invoke) {
+  CreateUnsafeCASLocations(allocator_, invoke);
+}
+void IntrinsicLocationsBuilderARM64::VisitJdkUnsafeCompareAndSetLong(HInvoke* invoke) {
+  CreateUnsafeCASLocations(allocator_, invoke);
+}
+void IntrinsicLocationsBuilderARM64::VisitJdkUnsafeCompareAndSetObject(HInvoke* invoke) {
+  // The only supported read barrier implementation is the Baker-style read barriers.
   if (kEmitCompilerReadBarrier && !kUseBakerReadBarrier) {
     return;
   }
@@ -1536,12 +1549,6 @@
     }
   }
 }
-void IntrinsicLocationsBuilderARM64::VisitJdkUnsafeCompareAndSetInt(HInvoke* invoke) {
-  CreateUnsafeCASLocations(allocator_, invoke);
-}
-void IntrinsicLocationsBuilderARM64::VisitJdkUnsafeCompareAndSetLong(HInvoke* invoke) {
-  CreateUnsafeCASLocations(allocator_, invoke);
-}
 
 void IntrinsicCodeGeneratorARM64::VisitUnsafeCASInt(HInvoke* invoke) {
   VisitJdkUnsafeCASInt(invoke);
@@ -1554,20 +1561,30 @@
 }
 
 void IntrinsicCodeGeneratorARM64::VisitJdkUnsafeCASInt(HInvoke* invoke) {
-  GenUnsafeCas(invoke, DataType::Type::kInt32, codegen_);
+  // `jdk.internal.misc.Unsafe.compareAndSwapLong` has compare-and-set semantics (see javadoc).
+  VisitJdkUnsafeCompareAndSetInt(invoke);
 }
 void IntrinsicCodeGeneratorARM64::VisitJdkUnsafeCASLong(HInvoke* invoke) {
-  GenUnsafeCas(invoke, DataType::Type::kInt64, codegen_);
+  // `jdk.internal.misc.Unsafe.compareAndSwapLong` has compare-and-set semantics (see javadoc).
+  VisitJdkUnsafeCompareAndSetLong(invoke);
 }
 void IntrinsicCodeGeneratorARM64::VisitJdkUnsafeCASObject(HInvoke* invoke) {
-  GenUnsafeCas(invoke, DataType::Type::kReference, codegen_);
+  // `jdk.internal.misc.Unsafe.compareAndSwapObject` has compare-and-set semantics (see javadoc).
+  VisitJdkUnsafeCompareAndSetObject(invoke);
 }
+
 void IntrinsicCodeGeneratorARM64::VisitJdkUnsafeCompareAndSetInt(HInvoke* invoke) {
   GenUnsafeCas(invoke, DataType::Type::kInt32, codegen_);
 }
 void IntrinsicCodeGeneratorARM64::VisitJdkUnsafeCompareAndSetLong(HInvoke* invoke) {
   GenUnsafeCas(invoke, DataType::Type::kInt64, codegen_);
 }
+void IntrinsicCodeGeneratorARM64::VisitJdkUnsafeCompareAndSetObject(HInvoke* invoke) {
+  // The only supported read barrier implementation is the Baker-style read barriers.
+  DCHECK(!kEmitCompilerReadBarrier || kUseBakerReadBarrier);
+
+  GenUnsafeCas(invoke, DataType::Type::kReference, codegen_);
+}
 
 enum class GetAndUpdateOp {
   kSet,
@@ -5655,7 +5672,6 @@
 UNIMPLEMENTED_INTRINSIC(ARM64, JdkUnsafeGetAndSetInt)
 UNIMPLEMENTED_INTRINSIC(ARM64, JdkUnsafeGetAndSetLong)
 UNIMPLEMENTED_INTRINSIC(ARM64, JdkUnsafeGetAndSetObject)
-UNIMPLEMENTED_INTRINSIC(ARM64, JdkUnsafeCompareAndSetObject)
 
 UNREACHABLE_INTRINSICS(ARM64)