MIPS64: Improve and fix nan hole checks and canonicalization.

src/mips64/macro-assembler-mips64.cc

Index: src/mips64/macro-assembler-mips64.cc
diff --git a/src/mips64/macro-assembler-mips64.cc b/src/mips64/macro-assembler-mips64.cc
index bc935326cfe1aac1e816742154a45e0bcc0aeca6..42898c94815b12b1e9bb256ab2918c978f0a8d3b 100644
--- a/src/mips64/macro-assembler-mips64.cc
+++ b/src/mips64/macro-assembler-mips64.cc
@@ -3884,13 +3884,14 @@ void MacroAssembler::StoreNumberToDoubleElements(Register value_reg,
   DoubleRegister double_scratch = f2;
 
   ldc1(double_result, FieldMemOperand(value_reg, HeapNumber::kValueOffset));
+  Branch(USE_DELAY_SLOT, &done);  // Canonicalization is one instruction.
   FPUCanonicalizeNaN(double_result, double_result);
-  Branch(&done);
 
   bind(&smi_value);
   // scratch1 is now effective address of the double element.

[paul.l..., 2015/02/25 16:21:38]

nit: It looks like this comment is now stale - scratch1 is only used in
CheckMap() above, and should have map pointer. Can you correct this as
necessary.

   // Untag and transfer.
-  mthc1(value_reg, double_scratch);
+  dsrl32(at, value_reg, 0);
+  mtc1(at, double_scratch);
   cvt_d_w(double_result, double_scratch);
 
   bind(&done);