Revert "Remove unnecessary check in RegExpExecStub."

src/mips/code-stubs-mips.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_MIPS
 
 #include "src/bootstrapper.h"
 #include "src/code-stubs.h"
@@ skipping 2652 matching lines @@
   // last_match_info_elements: Last match info elements (callee saved)
   // Check the result.
   Label success;
   __ Branch(&success, eq, v0, Operand(1));
   // We expect exactly one result since we force the called regexp to behave
   // as non-global.
   Label failure;
   __ Branch(&failure, eq, v0, Operand(NativeRegExpMacroAssembler::FAILURE));
   // If not exception it can only be retry. Handle that in the runtime system.
   __ Branch(&runtime, ne, v0, Operand(NativeRegExpMacroAssembler::EXCEPTION));
-
-  // 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.
   __ li(a1, Operand(isolate()->factory()->the_hole_value()));
   __ li(a2, Operand(ExternalReference(Isolate::kPendingExceptionAddress,
                                       isolate())));
   __ lw(v0, MemOperand(a2, 0));
+  __ Branch(&runtime, eq, v0, Operand(a1));
+
   __ sw(a1, MemOperand(a2, 0));  // Clear pending exception.
 
   // Check if the exception is a termination. If so, throw as uncatchable.
   __ LoadRoot(a0, Heap::kTerminationExceptionRootIndex);
   Label termination_exception;
   __ Branch(&termination_exception, eq, v0, Operand(a0));
 
   __ Throw(v0);
 
   __ bind(&termination_exception);
@@ skipping 2606 matching lines @@
                               MemOperand(fp, 6 * kPointerSize),
                               NULL);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_MIPS