MIPS: Skip canonicalization check in LStoreKeyedFastDoubleElement when it is not needed

Port r11278 (e5dc7ebd).

Original commit message:

Skip canonicalization check in LStoreKeyedFastDoubleElement when it is not needed:

- if value is a result of integer32 to double conversion (can't be NaN);

- if value was loaded from fast double backing store (already canonicalized).

BUG=
TEST=

Review URL: https://chromiumcodereview.appspot.com/10071004
Patch from Daniel Kalmar <kalmard@homejinni.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@11366 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/mips/lithium-codegen-mips.cc

@@ -3567,14 +3567,16 @@ void LCodeGen::DoStoreKeyedFastDoubleElement(
             Operand(FixedDoubleArray::kHeaderSize - kHeapObjectTag));
   }
 
-  Label is_nan;
-  // Check for NaN. All NaNs must be canonicalized.
-  __ BranchF(NULL, &is_nan, eq, value, value);
-  __ Branch(&not_nan);
-
-  // Only load canonical NaN if the comparison above set the overflow.
-  __ bind(&is_nan);
-  __ Move(value, FixedDoubleArray::canonical_not_the_hole_nan_as_double());
+  if (instr->NeedsCanonicalization()) {
+    Label is_nan;
+    // Check for NaN. All NaNs must be canonicalized.
+    __ BranchF(NULL, &is_nan, eq, value, value);
+    __ Branch(&not_nan);
+
+    // Only load canonical NaN if the comparison above set the overflow.
+    __ bind(&is_nan);
+    __ Move(value, FixedDoubleArray::canonical_not_the_hole_nan_as_double());
+  }
 
   __ bind(&not_nan);
   __ sdc1(value, MemOperand(scratch));

src/mips/lithium-mips.h

@@ -1733,6 +1733,8 @@ class LStoreKeyedFastDoubleElement: public LTemplateInstruction<0, 3, 0> {
   LOperand* elements() { return inputs_[0]; }
   LOperand* key() { return inputs_[1]; }
   LOperand* value() { return inputs_[2]; }
+
+  bool NeedsCanonicalization() { return hydrogen()->NeedsCanonicalization(); }
 };