Check that the String class is not movable in String.equals intrinsics.

Test: art/test.py
Bug: 68181300
Bug: 67628039
Change-Id: I66afa3ea010f758125f8aec79509f0255cb5ea03

1 files changed, 8 insertions, 0 deletions

diff --git a/compiler/optimizing/intrinsics_mips64.cc b/compiler/optimizing/intrinsics_mips64.cc
index 2eb252908c..cbe3b42cbf 100644
--- a/compiler/optimizing/intrinsics_mips64.cc
+++ b/compiler/optimizing/intrinsics_mips64.cc
@@ -1429,8 +1429,16 @@ void IntrinsicCodeGeneratorMIPS64::VisitStringEquals(HInvoke* invoke) {
     // All string objects must have the same type since String cannot be subclassed.
     // Receiver must be a string object, so its class field is equal to all strings' class fields.
     // If the argument is a string object, its class field must be equal to receiver's class field.
+    //
+    // As the String class is expected to be non-movable, we can read the class
+    // field from String.equals' arguments without read barriers.
+    AssertNonMovableStringClass();
+    // /* HeapReference<Class> */ temp1 = str->klass_
     __ Lw(temp1, str, class_offset);
+    // /* HeapReference<Class> */ temp2 = arg->klass_
     __ Lw(temp2, arg, class_offset);
+    // Also, because we use the previously loaded class references only in the
+    // following comparison, we don't need to unpoison them.
     __ Bnec(temp1, temp2, &return_false);
   }