Use fucomi instruction to compare floats and put results directly into EFLAGS...

src/ia32/codegen-ia32.cc

 // Copyright 2006-2009 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 6491 matching lines @@
   __ shr(edx, String::kShortLengthShift);
   __ j(zero, &false_result);
   __ jmp(&true_result);
 
   __ bind(&not_string);
   // HeapNumber => false iff +0, -0, or NaN.
   __ cmp(edx, Factory::heap_number_map());
   __ j(not_equal, &true_result);
   __ fldz();
   __ fld_d(FieldOperand(eax, HeapNumber::kValueOffset));
-  __ fucompp();
-  __ push(eax);
-  __ fnstsw_ax();
-  __ sahf();
-  __ pop(eax);
+  __ FCmp();
   __ j(zero, &false_result);
   // Fall through to |true_result|.
 
   // Return 1/0 for true/false in eax.
   __ bind(&true_result);
   __ mov(eax, 1);
   __ ret(1 * kPointerSize);
   __ bind(&false_result);
   __ mov(eax, 0);
   __ ret(1 * kPointerSize);
@@ skipping 232 matching lines @@
         CpuFeatures::Scope scope(CpuFeatures::SSE3);
         __ fisttp_s(Operand(esp, 0 * kPointerSize));
         __ fisttp_s(Operand(esp, 1 * kPointerSize));
         __ fnstsw_ax();
         __ test(eax, Immediate(1));
         __ j(not_zero, &operand_conversion_failure);
       } else {
         // Check if right operand is int32.
         __ fist_s(Operand(esp, 0 * kPointerSize));
         __ fild_s(Operand(esp, 0 * kPointerSize));
-        __ fucompp();
-        __ fnstsw_ax();
-        __ sahf();
+        __ FCmp();
         __ j(not_zero, &operand_conversion_failure);
         __ j(parity_even, &operand_conversion_failure);
 
         // Check if left operand is int32.
         __ fist_s(Operand(esp, 1 * kPointerSize));
         __ fild_s(Operand(esp, 1 * kPointerSize));
-        __ fucompp();
-        __ fnstsw_ax();
-        __ sahf();
+        __ FCmp();
         __ j(not_zero, &operand_conversion_failure);
         __ j(parity_even, &operand_conversion_failure);
       }
 
       // Get int32 operands and perform bitop.
       __ pop(ecx);
       __ pop(eax);
       switch (op_) {
         case Token::BIT_OR:  __ or_(eax, Operand(ecx)); break;
         case Token::BIT_AND: __ and_(eax, Operand(ecx)); break;
@@ skipping 1078 matching lines @@
 
 int CompareStub::MinorKey() {
   // Encode the two parameters in a unique 16 bit value.
   ASSERT(static_cast<unsigned>(cc_) < (1 << 15));
   return (static_cast<unsigned>(cc_) << 1) | (strict_ ? 1 : 0);
 }
 
 #undef __
 
 } }  // namespace v8::internal