Revert "Remove unnecessary check in RegExpExecStub."

src/ia32/code-stubs-ia32.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_IA32
 
 #include "src/bootstrapper.h"
 #include "src/code-stubs.h"
@@ skipping 1578 matching lines @@
   __ cmp(eax, 1);
   // We expect exactly one result since we force the called regexp to behave
   // as non-global.
   __ j(equal, &success);
   Label failure;
   __ cmp(eax, NativeRegExpMacroAssembler::FAILURE);
   __ j(equal, &failure);
   __ cmp(eax, NativeRegExpMacroAssembler::EXCEPTION);
   // If not exception it can only be retry. Handle that in the runtime system.
   __ j(not_equal, &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.
   ExternalReference pending_exception(Isolate::kPendingExceptionAddress,
                                       isolate());
   __ mov(edx, Immediate(isolate()->factory()->the_hole_value()));
   __ mov(eax, Operand::StaticVariable(pending_exception));
+  __ cmp(edx, eax);
+  __ j(equal, &runtime);
+  // For exception, throw the exception again.
 
-  // Clear pending exception.
+  // Clear the pending exception variable.
   __ mov(Operand::StaticVariable(pending_exception), edx);
 
   // Special handling of termination exceptions which are uncatchable
   // by javascript code.
   __ cmp(eax, factory->termination_exception());
   Label throw_termination_exception;
   __ j(equal, &throw_termination_exception, Label::kNear);
 
   // Handle normal exception by following handler chain.
   __ Throw(eax);
@@ skipping 3366 matching lines @@
                               Operand(ebp, 7 * kPointerSize),
                               NULL);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32