Fix String.equals() for moveable String.class.

If the String.class is moveable (i.e. running without boot
image), the instanceof check emitted by the JIT in the
String.equals() intrinsic would require read barriers.
As we do not really care about the performance of running
without the boot image, disable the intrinsic in this case.

Test: 669-moveable-string-class-equals (--jit)
Bug: 68181300
Change-Id: I39c9f9935e0482b3b30f1ae5cd23515cbda0603b

1 files changed, 14 insertions, 0 deletions

diff --git a/compiler/optimizing/instruction_simplifier.cc b/compiler/optimizing/instruction_simplifier.cc
index 2bd2d5f0a1..fbfee12be9 100644
--- a/compiler/optimizing/instruction_simplifier.cc
+++ b/compiler/optimizing/instruction_simplifier.cc
@@ -2024,6 +2024,20 @@ void InstructionSimplifierVisitor::SimplifyStringEquals(HInvoke* instruction) {
     ReferenceTypeInfo argument_rti = argument->GetReferenceTypeInfo();
     if (argument_rti.IsValid() && argument_rti.IsStringClass()) {
       optimizations.SetArgumentIsString();
+    } else if (kUseReadBarrier) {
+      DCHECK(instruction->GetResolvedMethod() != nullptr);
+      DCHECK(instruction->GetResolvedMethod()->GetDeclaringClass()->IsStringClass());
+      Runtime* runtime = Runtime::Current();
+      // For AOT, we always assume that the boot image shall contain the String.class and
+      // we do not need a read barrier for boot image classes as they are non-moveable.
+      // For JIT, check if we actually have a boot image; if we do, the String.class
+      // should also be non-moveable.
+      if (runtime->IsAotCompiler() || runtime->GetHeap()->HasBootImageSpace()) {
+        DCHECK(runtime->IsAotCompiler() ||
+               !runtime->GetHeap()->IsMovableObject(
+                   instruction->GetResolvedMethod()->GetDeclaringClass()));
+        optimizations.SetNoReadBarrierForStringClass();
+      }
     }
   }
 }