Catch non-string subject in RegExpExecStub.

src/arm/code-stubs-arm.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 4547 matching lines @@
   // Check the representation and encoding of the subject string.
   Label seq_string;
   __ ldr(r0, FieldMemOperand(subject, HeapObject::kMapOffset));
   __ ldrb(r0, FieldMemOperand(r0, Map::kInstanceTypeOffset));
   // First check for flat string.
   __ and_(r1, r0, Operand(kIsNotStringMask | kStringRepresentationMask), SetCC);
   STATIC_ASSERT((kStringTag | kSeqStringTag) == 0);
   __ b(eq, &seq_string);
 
   // subject: Subject string
   // regexp_data: RegExp data (FixedArray)

[Lasse Reichstein, 2011/11/24 09:31:57]

If r1 contains the instance type, then make a comment about it here with the
other register invariants.

   // 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
   // string. Also in this case the first part of the cons string is known to be
   // a sequential string or an external string.
   // In the case of a sliced string its offset has to be taken into account.
   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).
+  __ tst(ebx, Immediate(kIsNotStringMask));

[Lasse Reichstein, 2011/11/24 09:31:57]

If it should have been guarded against, then make this an Assert check guarded
by FLAG_debug_code.
And if it there is actually a way to get here with a non-string, it should be
found and eliminated. We control the arguments to stubs completely, and are
expected to handle them safely.
If it's called from %_RegExpExec, then the test should be performed there (all
%-functions must check their arguments thoroughly).

+  __ b(eq, &runtime);
+
   // String is sliced.
   __ ldr(r9, FieldMemOperand(subject, SlicedString::kOffsetOffset));
   __ mov(r9, Operand(r9, ASR, kSmiTagSize));
   __ ldr(subject, FieldMemOperand(subject, SlicedString::kParentOffset));
   // r9: offset of sliced string, smi-tagged.
   __ jmp(&check_encoding);
   // String is a cons string, check whether it is flat.
   __ bind(&cons_string);
   __ ldr(r0, FieldMemOperand(subject, ConsString::kSecondOffset));
   __ LoadRoot(r1, Heap::kEmptyStringRootIndex);
@@ skipping 2587 matching lines @@
   __ StoreNumberToDoubleElements(r0, r3, r1, r5, r6, r7, r9, r10,
                                  &slow_elements);
   __ Ret();
 }
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM