Revert "Remove unnecessary check in RegExpExecStub."

src/arm/code-stubs-arm.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #if V8_TARGET_ARCH_ARM
 
 #include "src/bootstrapper.h"
 #include "src/code-stubs.h"
@@ skipping 2502 matching lines @@
   __ cmp(r0, Operand(1));
   // We expect exactly one result since we force the called regexp to behave
   // as non-global.
   __ b(eq, &success);
   Label failure;
   __ cmp(r0, Operand(NativeRegExpMacroAssembler::FAILURE));
   __ b(eq, &failure);
   __ cmp(r0, Operand(NativeRegExpMacroAssembler::EXCEPTION));
   // If not exception it can only be retry. Handle that in the runtime system.
   __ b(ne, &runtime);
-
-  // Result must now be exception.
+  // Result must now be exception. If there is no pending exception already a
+  // stack overflow (on the backtrack stack) was detected in RegExp code but
+  // haven't created the exception yet. Handle that in the runtime system.
+  // TODO(592): Rerunning the RegExp to get the stack overflow exception.
   __ mov(r1, Operand(isolate()->factory()->the_hole_value()));
   __ mov(r2, Operand(ExternalReference(Isolate::kPendingExceptionAddress,
                                        isolate())));
   __ ldr(r0, MemOperand(r2, 0));
+  __ cmp(r0, r1);
+  __ b(eq, &runtime);
+
   __ str(r1, MemOperand(r2, 0));  // Clear pending exception.
 
   // Check if the exception is a termination. If so, throw as uncatchable.
   __ CompareRoot(r0, Heap::kTerminationExceptionRootIndex);
 
   Label termination_exception;
   __ b(eq, &termination_exception);
 
   __ Throw(r0);
 
@@ skipping 2532 matching lines @@
                               MemOperand(fp, 6 * kPointerSize),
                               NULL);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM