MIPS: Catch non-string subject in RegExpExecStub.

src/mips/code-stubs-mips.cc

Index: src/mips/code-stubs-mips.cc
diff --git a/src/mips/code-stubs-mips.cc b/src/mips/code-stubs-mips.cc
index b26e0b435e9e4b0808491d189259b05a0347e873..679b23fffa39f8215282bb1dc018dfac2f7d0e22 100644
--- a/src/mips/code-stubs-mips.cc
+++ b/src/mips/code-stubs-mips.cc
@@ -4746,7 +4746,8 @@ void RegExpExecStub::Generate(MacroAssembler* masm) {
   Label seq_string;
   __ lw(a0, FieldMemOperand(subject, HeapObject::kMapOffset));
   __ lbu(a0, FieldMemOperand(a0, Map::kInstanceTypeOffset));
-  // First check for flat string.
+  // First check for flat string.  None of the following string type tests will
+  // succeed if kIsNotStringTag is set.
   __ And(a1, a0, Operand(kIsNotStringMask | kStringRepresentationMask));
   STATIC_ASSERT((kStringTag | kSeqStringTag) == 0);
   __ Branch(&seq_string, eq, a1, Operand(zero_reg));
@@ -4754,6 +4755,7 @@ void RegExpExecStub::Generate(MacroAssembler* masm) {
   // subject: Subject string
   // a0: instance type if Subject string
   // regexp_data: RegExp data (FixedArray)
+  // a1: 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
@@ -4763,9 +4765,15 @@ void RegExpExecStub::Generate(MacroAssembler* masm) {
   Label cons_string, check_encoding;
   STATIC_ASSERT(kConsStringTag < kExternalStringTag);
   STATIC_ASSERT(kSlicedStringTag > kExternalStringTag);
+  STATIC_ASSERT(kIsNotStringMask > kExternalStringTag);
   __ Branch(&cons_string, lt, a1, Operand(kExternalStringTag));
   __ Branch(&runtime, eq, a1, Operand(kExternalStringTag));
 
+  // Catch non-string subject (should already have been guarded against).
+  STATIC_ASSERT(kNotStringTag != 0);
+  __ And(at, a1, Operand(kIsNotStringMask));
+  __ Branch(&runtime, ne, at, Operand(zero_reg));
+
   // String is sliced.
   __ lw(t0, FieldMemOperand(subject, SlicedString::kOffsetOffset));
   __ sra(t0, t0, kSmiTagSize);