[turbofan] Reduce Float64 comparison to Float32.

src/compiler/machine-operator-reducer.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler/machine-operator-reducer.h"
 
 #include "src/base/bits.h"
 #include "src/base/division-by-constant.h"
 #include "src/codegen.h"
 #include "src/compiler/diamond.h"
@@ skipping 421 matching lines @@
       if (m.HasValue()) return ReplaceFloat32(DoubleToFloat32(m.Value()));
       if (m.IsChangeFloat32ToFloat64()) return Replace(m.node()->InputAt(0));
       break;
     }
     case IrOpcode::kFloat64InsertLowWord32:
       return ReduceFloat64InsertLowWord32(node);
     case IrOpcode::kFloat64InsertHighWord32:
       return ReduceFloat64InsertHighWord32(node);
     case IrOpcode::kStore:
       return ReduceStore(node);
+    case IrOpcode::kFloat64Equal:
+    case IrOpcode::kFloat64LessThan:
+    case IrOpcode::kFloat64LessThanOrEqual:
+      return ReduceFloat64Compare(node);
     default:
       break;
   }
   return NoChange();
 }
 
 
 Reduction MachineOperatorReducer::ReduceInt32Add(Node* node) {
   DCHECK_EQ(IrOpcode::kInt32Add, node->opcode());
   Int32BinopMatcher m(node);
@@ skipping 545 matching lines @@
   Uint32Matcher mrhs(node->InputAt(1));
   if (mlhs.HasValue() && mrhs.HasValue()) {
     return ReplaceFloat64(bit_cast<double>(
         (bit_cast<uint64_t>(mlhs.Value()) & V8_UINT64_C(0xFFFFFFFF)) |
         (static_cast<uint64_t>(mrhs.Value()) << 32)));
   }
   return NoChange();
 }
 
 
+Reduction MachineOperatorReducer::ReduceFloat64Compare(Node* node) {
+  DCHECK((IrOpcode::kFloat64Equal == node->opcode()) ||
+         (IrOpcode::kFloat64LessThan == node->opcode()) ||
+         (IrOpcode::kFloat64LessThanOrEqual == node->opcode()));
+  // As all Float32 values have an exact representation in Float64, comparing
+  // two Float64 values both converted from Float32 is equivalent to comparing
+  // the original Float32s, so we can ignore the conversions.
+  Float64BinopMatcher m(node);
+  if (m.left().IsChangeFloat32ToFloat64() &&
+      m.right().IsChangeFloat32ToFloat64()) {
+    switch (node->opcode()) {
+      case IrOpcode::kFloat64Equal:
+        node->set_op(machine()->Float32Equal());
+        break;
+      case IrOpcode::kFloat64LessThan:
+        node->set_op(machine()->Float32LessThan());
+        break;
+      case IrOpcode::kFloat64LessThanOrEqual:
+        node->set_op(machine()->Float32LessThanOrEqual());
+        break;
+      default:
+        return NoChange();
+    }
+    node->ReplaceInput(0, m.left().InputAt(0));
+    node->ReplaceInput(1, m.right().InputAt(0));
+    return Changed(node);
+  }
+  return NoChange();
+}
+
+
 CommonOperatorBuilder* MachineOperatorReducer::common() const {
   return jsgraph()->common();
 }
 
 
 MachineOperatorBuilder* MachineOperatorReducer::machine() const {
   return jsgraph()->machine();
 }
 
 
 Graph* MachineOperatorReducer::graph() const { return jsgraph()->graph(); }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8