Fixing a performance bug introduced in r4581.

src/ia32/codegen-ia32.cc

 // Copyright 2010 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 10938 matching lines @@
   // Get the length of the string to ebx.
   __ mov(ebx, FieldOperand(eax, String::kLengthOffset));
 
   // ebx: Length of subject string as a smi
   // ecx: RegExp data (FixedArray)
   // edx: Number of capture registers
   // Check that the third argument is a positive smi less than the subject
   // string length. A negative value will be greater (unsigned comparison).
   __ mov(eax, Operand(esp, kPreviousIndexOffset));
   __ test(eax, Immediate(kSmiTagMask));
-  __ j(zero, &runtime);
+  __ j(not_zero, &runtime);
   __ cmp(eax, Operand(ebx));
   __ j(above_equal, &runtime);
 
   // ecx: RegExp data (FixedArray)
   // edx: Number of capture registers
   // Check that the fourth object is a JSArray object.
   __ mov(eax, Operand(esp, kLastMatchInfoOffset));
   __ test(eax, Immediate(kSmiTagMask));
   __ j(zero, &runtime);
   __ CmpObjectType(eax, JS_ARRAY_TYPE, ebx);
@@ skipping 2145 matching lines @@
 
   // Call the runtime; it returns -1 (less), 0 (equal), or 1 (greater)
   // tagged as a small integer.
   __ bind(&runtime);
   __ TailCallRuntime(Runtime::kStringCompare, 2, 1);
 }
 
 #undef __
 
 } }  // namespace v8::internal