[x64] Recognize zero extension of 8-bit and 16-bit values.

src/compiler/x64/instruction-selector-x64.cc

Index: src/compiler/x64/instruction-selector-x64.cc
diff --git a/src/compiler/x64/instruction-selector-x64.cc b/src/compiler/x64/instruction-selector-x64.cc
index d3becdbc9dd2ec4ebb682b0be52de5dcd918fa2a..db2d8cb08c7813f944a31f5ac7c8fc98ec7fb244 100644
--- a/src/compiler/x64/instruction-selector-x64.cc
+++ b/src/compiler/x64/instruction-selector-x64.cc
@@ -366,7 +366,15 @@ static void VisitBinop(InstructionSelector* selector, Node* node,
 
 
 void InstructionSelector::VisitWord32And(Node* node) {
-  VisitBinop(this, node, kX64And32);
+  X64OperandGenerator g(this);
+  Uint32BinopMatcher m(node);
+  if (m.right().Is(0xff)) {
+    Emit(kX64Movzxbl, g.DefineAsRegister(node), g.Use(m.left().node()));
+  } else if (m.right().Is(0xffff)) {
+    Emit(kX64Movzxwl, g.DefineAsRegister(node), g.Use(m.left().node()));
+  } else {
+    VisitBinop(this, node, kX64And32);
+  }
 }