[x64] 64-bit shift left by 32 or more covers sign/zero extend.

src/compiler/x64/instruction-selector-x64.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/generic-node-inl.h"
 #include "src/compiler/instruction-selector-impl.h"
 #include "src/compiler/node-matchers.h"
 
 namespace v8 {
 namespace internal {
@@ skipping 302 matching lines @@
 
 }  // namespace
 
 
 void InstructionSelector::VisitWord32Shl(Node* node) {
   VisitWord32Shift(this, node, kX64Shl32);
 }
 
 
 void InstructionSelector::VisitWord64Shl(Node* node) {
+  X64OperandGenerator g(this);
+  Int64BinopMatcher m(node);
+  if ((m.left().IsChangeInt32ToInt64() || m.left().IsChangeUint32ToUint64()) &&
+      m.right().IsInRange(32, 63)) {
+    // There's no need to sign/zero-extend to 64-bit if we shift out the upper
+    // 32 bits anyway.
+    Emit(kX64Shl, g.DefineSameAsFirst(node),
+         g.UseRegister(m.left().node()->InputAt(0)),
+         g.UseImmediate(m.right().node()));
+    return;
+  }
   VisitWord64Shift(this, node, kX64Shl);
 }
 
 
 void InstructionSelector::VisitWord32Shr(Node* node) {
   VisitWord32Shift(this, node, kX64Shr32);
 }
 
 
 void InstructionSelector::VisitWord64Shr(Node* node) {
@@ skipping 739 matching lines @@
   if (CpuFeatures::IsSupported(SSE4_1)) {
     return MachineOperatorBuilder::kFloat64Floor |
            MachineOperatorBuilder::kFloat64Ceil |
            MachineOperatorBuilder::kFloat64RoundTruncate;
   }
   return MachineOperatorBuilder::kNoFlags;
 }
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8