ARM64: avoid duplicate load of double constants

R=bmeurer@chromium.org, ulan@chromium.org

BUG=

Review URL: https://codereview.chromium.org/357973002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22051 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/arm64/lithium-arm64.cc

@@ -1274,15 +1274,13 @@ LInstruction* LChunkBuilder::DoCompareNumericAndBranch(
     ASSERT(r.IsDouble());
     ASSERT(instr->left()->representation().IsDouble());
     ASSERT(instr->right()->representation().IsDouble());
-    // TODO(all): In fact the only case that we can handle more efficiently is
-    // when one of the operand is the constant 0. Currently the MacroAssembler
-    // will be able to cope with any constant by loading it into an internal
-    // scratch register. This means that if the constant is used more that once,
-    // it will be loaded multiple times. Unfortunatly crankshaft already
-    // duplicates constant loads, but we should modify the code below once this
-    // issue has been addressed in crankshaft.
-    LOperand* left = UseRegisterOrConstantAtStart(instr->left());
-    LOperand* right = UseRegisterOrConstantAtStart(instr->right());
+    if (instr->left()->IsConstant() && instr->right()->IsConstant()) {
+      LOperand* left = UseConstant(instr->left());
+      LOperand* right = UseConstant(instr->right());
+      return new(zone()) LCompareNumericAndBranch(left, right);
+    }
+    LOperand* left = UseRegisterAtStart(instr->left());
+    LOperand* right = UseRegisterAtStart(instr->right());
     return new(zone()) LCompareNumericAndBranch(left, right);
   }
 }

src/arm64/lithium-codegen-arm64.cc

@@ -2484,17 +2484,7 @@ void LCodeGen::DoCompareNumericAndBranch(LCompareNumericAndBranch* instr) {
     EmitGoto(next_block);
   } else {
     if (instr->is_double()) {
-      if (right->IsConstantOperand()) {
-        __ Fcmp(ToDoubleRegister(left),
-                ToDouble(LConstantOperand::cast(right)));
-      } else if (left->IsConstantOperand()) {
-        // Commute the operands and the condition.
-        __ Fcmp(ToDoubleRegister(right),
-                ToDouble(LConstantOperand::cast(left)));
-        cond = CommuteCondition(cond);
-      } else {
-        __ Fcmp(ToDoubleRegister(left), ToDoubleRegister(right));
-      }
+      __ Fcmp(ToDoubleRegister(left), ToDoubleRegister(right));
 
       // If a NaN is involved, i.e. the result is unordered (V set),
       // jump to false block label.