Add external strings support to regexp in generated code.

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 9e6f7596e7fc60131cdaf956d07567854514e74b..3f85d6bc2f27617c58cbca3aee3e35ff25cb41d5 100644
--- a/src/arm/code-stubs-arm.cc
+++ b/src/arm/code-stubs-arm.cc
@@ -4572,12 +4572,12 @@ void RegExpExecStub::Generate(MacroAssembler* masm) {
   // 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;
+  Label cons_string, external_string, check_encoding;
   STATIC_ASSERT(kConsStringTag < kExternalStringTag);
   STATIC_ASSERT(kSlicedStringTag > kExternalStringTag);
   __ cmp(r1, Operand(kExternalStringTag));
   __ b(lt, &cons_string);
-  __ b(eq, &runtime);
+  __ b(eq, &external_string);
 
   // String is sliced.
   __ ldr(r9, FieldMemOperand(subject, SlicedString::kOffsetOffset));
@@ -4588,8 +4588,7 @@ void RegExpExecStub::Generate(MacroAssembler* masm) {
   // String is a cons string, check whether it is flat.
   __ bind(&cons_string);
   __ ldr(r0, FieldMemOperand(subject, ConsString::kSecondOffset));
-  __ LoadRoot(r1, Heap::kEmptyStringRootIndex);
-  __ cmp(r0, r1);
+  __ CompareRoot(r0, Heap::kEmptyStringRootIndex);
   __ b(ne, &runtime);
   __ ldr(subject, FieldMemOperand(subject, ConsString::kFirstOffset));
   // Is first part of cons or parent of slice a flat string?
@@ -4598,7 +4597,8 @@ void RegExpExecStub::Generate(MacroAssembler* masm) {
   __ ldrb(r0, FieldMemOperand(r0, Map::kInstanceTypeOffset));
   STATIC_ASSERT(kSeqStringTag == 0);
   __ tst(r0, Operand(kStringRepresentationMask));
-  __ b(ne, &runtime);
+  __ b(ne, &external_string);
+
   __ bind(&seq_string);
   // subject: Subject string
   // regexp_data: RegExp data (FixedArray)
@@ -4806,6 +4806,31 @@ void RegExpExecStub::Generate(MacroAssembler* masm) {
   __ add(sp, sp, Operand(4 * kPointerSize));
   __ Ret();
 
+  // String is external.
+  // r0: scratch
+  __ bind(&external_string);
+  if (FLAG_debug_code) {
+    // Assert that we do not have a cons or slice (indirect strings) here.
+    // Sequential strings have already been ruled out.
+    __ ldr(r0, FieldMemOperand(subject, HeapObject::kMapOffset));
+    __ ldrb(r0, FieldMemOperand(r0, Map::kInstanceTypeOffset));
+    __ tst(r0, Operand(kIsIndirectStringMask));
+    __ Assert(eq, "unexpected indirect string encountered");
+  }
+  __ ldr(r0, FieldMemOperand(subject, HeapObject::kMapOffset));
+  __ ldr(subject,
+         FieldMemOperand(subject, ExternalString::kResourceDataOffset));
+  // Assert that the data pointer cache is valid.
+  __ tst(subject, subject);
+  __ b(eq, &runtime);
+  // Move the pointer so that offset-wise, it looks like a sequential string.
+  STATIC_ASSERT(SeqTwoByteString::kHeaderSize == SeqAsciiString::kHeaderSize);
+  __ sub(subject,
+         subject,
+         Operand(SeqTwoByteString::kHeaderSize - kHeapObjectTag));
+  __ ldrb(r0, FieldMemOperand(r0, Map::kInstanceTypeOffset));
+  __ jmp(&seq_string);
+
   // Do the runtime call to execute the regexp.
   __ bind(&runtime);
   __ TailCallRuntime(Runtime::kRegExpExec, 4, 1);