MIPS64: Improve and fix nan hole checks and canonicalization.

src/mips64/lithium-codegen-mips64.cc

Index: src/mips64/lithium-codegen-mips64.cc
diff --git a/src/mips64/lithium-codegen-mips64.cc b/src/mips64/lithium-codegen-mips64.cc
index bb256bff3cf89cb0bdfa30fc6583438eb2a60ec8..6447dced3fb28af800d36b609c43a2ac287b92c8 100644
--- a/src/mips64/lithium-codegen-mips64.cc
+++ b/src/mips64/lithium-codegen-mips64.cc
@@ -2363,9 +2363,8 @@ void LCodeGen::DoCmpHoleAndBranch(LCmpHoleAndBranch* instr) {
 
   Register scratch = scratch0();
   __ FmoveHigh(scratch, input_reg);
-  __ dsll32(scratch, scratch, 0);  // FmoveHigh (mfhc1) sign-extends.
-  __ dsrl32(scratch, scratch, 0);  // Use only low 32-bits.
-  EmitBranch(instr, eq, scratch, Operand(kHoleNanUpper32));
+  EmitBranch(instr, eq, scratch,
+             Operand(static_cast<int32_t>(kHoleNanUpper32)));

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

this looks like nice solution to remove some instructions! Curious if this
changes the number of instructions emitted by the li() in the branch, though. Is
our li() clever enough to sign-extend without needing to explicitly load all 4
16-bit chunks?

 }
 
 
@@ -3280,9 +3279,9 @@ void LCodeGen::DoLoadKeyedFixedDoubleArray(LLoadKeyed* instr) {
   __ ldc1(result, MemOperand(scratch));
 
   if (instr->hydrogen()->RequiresHoleCheck()) {
-    __ lwu(scratch, MemOperand(scratch, sizeof(kHoleNanLower32)));
+    __ FmoveHigh(scratch, result);
     DeoptimizeIf(eq, instr, Deoptimizer::kHole, scratch,
-                 Operand(kHoleNanUpper32));
+                 Operand(static_cast<int32_t>(kHoleNanUpper32)));
   }
 }