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

src/ia32/codegen-ia32.cc

Index: src/ia32/codegen-ia32.cc
===================================================================
--- src/ia32/codegen-ia32.cc	(revision 2836)
+++ src/ia32/codegen-ia32.cc	(working copy)
@@ -6509,11 +6509,7 @@
   __ 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|.
 
@@ -6766,18 +6762,14 @@
         // 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);
       }