MIPS: Fix kraken 1.1 benchmark failure.

This makes sure that the DoubleToIStub::Generate method
does not overwrite the value of the f12 register.

TEST=bencnhmarks/kraken/stanford-crypto-pbkdf2
BUG=
R=plind44@gmail.com

Review URL: https://codereview.chromium.org/33463002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@17306 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/mips/code-stubs-mips.cc

@@ -547,23 +547,27 @@ void DoubleToIStub::Generate(MacroAssembler* masm) {
       GetRegisterThatIsNotOneOf(input_reg, result_reg, scratch);
   Register scratch3 =
       GetRegisterThatIsNotOneOf(input_reg, result_reg, scratch, scratch2);
-  DoubleRegister double_scratch = kLithiumScratchDouble.low();
-  DoubleRegister double_input = f12;
+  DoubleRegister double_scratch = kLithiumScratchDouble;
 
   __ Push(scratch, scratch2, scratch3);
 
-  __ ldc1(double_input, MemOperand(input_reg, double_offset));
-
   if (!skip_fastpath()) {
+    // Load double input.
+    __ ldc1(double_scratch, MemOperand(input_reg, double_offset));
+
     // Clear cumulative exception flags and save the FCSR.
     __ cfc1(scratch2, FCSR);
     __ ctc1(zero_reg, FCSR);
+
     // Try a conversion to a signed integer.
-    __ trunc_w_d(double_scratch, double_input);
+    __ Trunc_w_d(double_scratch, double_scratch);
+    // Move the converted value into the result register.
     __ mfc1(result_reg, double_scratch);
+
     // Retrieve and restore the FCSR.
     __ cfc1(scratch, FCSR);
     __ ctc1(scratch2, FCSR);
+
     // Check for overflow and NaNs.
     __ And(
         scratch, scratch,
@@ -576,7 +580,9 @@ void DoubleToIStub::Generate(MacroAssembler* masm) {
   // Load the double value and perform a manual truncation.
   Register input_high = scratch2;
   Register input_low = scratch3;
-  __ Move(input_low, input_high, double_input);
+
+  __ lw(input_low, MemOperand(input_reg, double_offset));
+  __ lw(input_high, MemOperand(input_reg, double_offset + kIntSize));
 
   Label normal_exponent, restore_sign;
   // Extract the biased exponent in result.