Catch non-string subject in RegExpExecStub.

src/arm/code-stubs-arm.cc

Index: src/arm/code-stubs-arm.cc
diff --git a/src/arm/code-stubs-arm.cc b/src/arm/code-stubs-arm.cc
index f471220332c187ea660afca64ea70ea0e867d1c6..65b6ed1b6d54af44d5b6f9c95209157e0479b449 100644
--- a/src/arm/code-stubs-arm.cc
+++ b/src/arm/code-stubs-arm.cc
@@ -4607,6 +4607,7 @@ void RegExpExecStub::Generate(MacroAssembler* masm) {
 
   // subject: Subject string
   // regexp_data: RegExp data (FixedArray)
+  // r1: whether subject is a string and if yes, its string representation
   // Check for flat cons string or sliced string.
   // A flat cons string is a cons string where the second part is the empty
   // string. In that case the subject string is just the first part of the cons
@@ -4616,10 +4617,16 @@ void RegExpExecStub::Generate(MacroAssembler* masm) {
   Label cons_string, check_encoding;
   STATIC_ASSERT(kConsStringTag < kExternalStringTag);
   STATIC_ASSERT(kSlicedStringTag > kExternalStringTag);
+  STATIC_ASSERT(kIsNotStringMask > kExternalStringTag);
   __ cmp(r1, Operand(kExternalStringTag));
   __ b(lt, &cons_string);
   __ b(eq, &runtime);
 
+  // Catch non-string subject (should already have been guarded against).
+  STATIC_ASSERT(kIsNotStringTag != 0);
+  __ tst(r1, Immediate(kIsNotStringMask));
+  __ b(ne, &runtime);
+
   // String is sliced.
   __ ldr(r9, FieldMemOperand(subject, SlicedString::kOffsetOffset));
   __ mov(r9, Operand(r9, ASR, kSmiTagSize));