[machine-operator-reducer] fix float truncation

src/compiler/opcodes.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/opcodes.h"
 
 #include <algorithm>
 #include <ostream>
 
 #include "src/base/macros.h"
@@ skipping 17 matching lines @@
 char const* IrOpcode::Mnemonic(Value value) {
   size_t const n = std::min<size_t>(value, arraysize(kMnemonics) - 1);
   return kMnemonics[n];
 }
 
 
 std::ostream& operator<<(std::ostream& os, IrOpcode::Value opcode) {
   return os << IrOpcode::Mnemonic(opcode);
 }
 
+
+// static
+bool IrOpcode::Is64(Value value) {

[titzer, 2015/11/13 23:35:17]

What are the semantics of this predicate? It's not quite clear, e.g.
Float64Constants are listed here too.

[fedor.indutny, 2015/11/14 00:15:52]

This method returns true if the opcode output is a 64-bit value.

+  switch (value) {
+    case kInt64Constant:
+    case kFloat64Constant:
+    case kChangeTaggedToFloat64:
+    case kWord64Equal:
+    case kInt64LessThan:
+    case kInt64LessThanOrEqual:
+    case kUint64LessThan:
+    case kUint64LessThanOrEqual:
+    case kFloat64Equal:
+    case kFloat64LessThan:
+    case kFloat64LessThanOrEqual:
+    case kChangeFloat32ToFloat64:
+    case kChangeInt32ToFloat64:
+    case kChangeInt32ToInt64:
+    case kChangeUint32ToFloat64:
+    case kChangeUint32ToUint64:
+    case kRoundInt64ToFloat64:
+    case kRoundUint64ToFloat64:
+    case kBitcastFloat64ToInt64:
+    case kBitcastInt64ToFloat64:
+      return true;
+
+    default:
+      return (value >= kWord64Popcnt && value <= kWord64Ctz) ||
+             (value >= kInt64Add && value <= kUint64Mod) ||
+             (value >= kFloat64Add && value <= kFloat64InsertHighWord32);
+  }
+}
+
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8