[x64] Recognize MOVSXWL.

Also add some debug code to verify correct zero extension of 32-bit
moves.

TEST=mjsunit/asm
R=svenpanne@chromium.org

Review URL: https://codereview.chromium.org/736623002

Cr-Commit-Position: refs/heads/master@{#25385}

src/compiler/x64/code-generator-x64.cc

@@ -484,6 +484,7 @@ void CodeGenerator::AssembleArchInstruction(Instruction* instr) {
       break;
     case kX64Movsxbl:
       __ movsxbl(i.OutputRegister(), i.MemoryOperand());
+      __ AssertZeroExtended(i.OutputRegister());
       break;
     case kX64Movzxbl:
       __ movzxbl(i.OutputRegister(), i.MemoryOperand());
@@ -499,10 +500,18 @@ void CodeGenerator::AssembleArchInstruction(Instruction* instr) {
       break;
     }
     case kX64Movsxwl:
+      if (instr->addressing_mode() != kMode_None) {
         __ movsxwl(i.OutputRegister(), i.MemoryOperand());
+      } else if (instr->InputAt(0)->IsRegister()) {
+        __ movsxwl(i.OutputRegister(), i.InputRegister(0));
+      } else {
+        __ movsxwl(i.OutputRegister(), i.InputOperand(0));
+      }
+      __ AssertZeroExtended(i.OutputRegister());
       break;
     case kX64Movzxwl:
       __ movzxwl(i.OutputRegister(), i.MemoryOperand());
+      __ AssertZeroExtended(i.OutputRegister());
       break;
     case kX64Movw: {
       int index = 0;
@@ -525,6 +534,7 @@ void CodeGenerator::AssembleArchInstruction(Instruction* instr) {
         } else {
           __ movl(i.OutputRegister(), i.MemoryOperand());
         }
+        __ AssertZeroExtended(i.OutputRegister());
       } else {
         int index = 0;
         Operand operand = i.MemoryOperand(&index);
@@ -576,6 +586,7 @@ void CodeGenerator::AssembleArchInstruction(Instruction* instr) {
       break;
     case kX64Lea32:
       __ leal(i.OutputRegister(), i.MemoryOperand());
+      __ AssertZeroExtended(i.OutputRegister());
       break;
     case kX64Lea:
       __ leaq(i.OutputRegister(), i.MemoryOperand());

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

@@ -346,6 +346,15 @@ void InstructionSelector::VisitWord64Shr(Node* node) {
 
 
 void InstructionSelector::VisitWord32Sar(Node* node) {
+  X64OperandGenerator g(this);
+  Int32BinopMatcher m(node);
+  if (CanCover(m.node(), m.left().node()) && m.left().IsWord32Shl()) {
+    Int32BinopMatcher mleft(m.left().node());
+    if (mleft.right().Is(16) && m.right().Is(16)) {
+      Emit(kX64Movsxwl, g.DefineAsRegister(node), g.Use(mleft.left().node()));
+      return;
+    }
+  }
   VisitWord32Shift(this, node, kX64Sar32);
 }
 
@@ -364,6 +373,7 @@ void InstructionSelector::VisitWord64Ror(Node* node) {
   VisitWord64Shift(this, node, kX64Ror);
 }
 
+
 namespace {
 
 AddressingMode GenerateMemoryOperandInputs(X64OperandGenerator* g, Node* scaled,
@@ -1161,6 +1171,7 @@ InstructionSelector::SupportedMachineOperatorFlags() {
   }
   return MachineOperatorBuilder::kNoFlags;
 }
+
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8

src/x64/assembler-x64.cc

@@ -1401,6 +1401,15 @@ void Assembler::movsxbq(Register dst, const Operand& src) {
 }
 
 
+void Assembler::movsxwl(Register dst, Register src) {
+  EnsureSpace ensure_space(this);
+  emit_optional_rex_32(dst, src);
+  emit(0x0F);
+  emit(0xBF);
+  emit_modrm(dst, src);
+}
+
+
 void Assembler::movsxwl(Register dst, const Operand& src) {
   EnsureSpace ensure_space(this);
   emit_optional_rex_32(dst, src);

src/x64/assembler-x64.h

@@ -733,6 +733,7 @@ class Assembler : public AssemblerBase {
 
   void movsxbl(Register dst, const Operand& src);
   void movsxbq(Register dst, const Operand& src);
+  void movsxwl(Register dst, Register src);
   void movsxwl(Register dst, const Operand& src);
   void movsxwq(Register dst, const Operand& src);
   void movsxlq(Register dst, Register src);