[x64] Recognize MOVSXBL.

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

Review URL: https://codereview.chromium.org/728103007

Cr-Commit-Position: refs/heads/master@{#25386}

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

@@ -483,7 +483,13 @@ void CodeGenerator::AssembleArchInstruction(Instruction* instr) {
       __ cvtqsi2sd(i.OutputDoubleRegister(), kScratchRegister);
       break;
     case kX64Movsxbl:
-      __ movsxbl(i.OutputRegister(), i.MemoryOperand());
+      if (instr->addressing_mode() != kMode_None) {
+        __ movsxbl(i.OutputRegister(), i.MemoryOperand());
+      } else if (instr->InputAt(0)->IsRegister()) {
+        __ movsxbl(i.OutputRegister(), i.InputRegister(0));
+      } else {
+        __ movsxbl(i.OutputRegister(), i.InputOperand(0));
+      }
       __ AssertZeroExtended(i.OutputRegister());
       break;
     case kX64Movzxbl:

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

@@ -353,6 +353,9 @@ void InstructionSelector::VisitWord32Sar(Node* node) {
     if (mleft.right().Is(16) && m.right().Is(16)) {
       Emit(kX64Movsxwl, g.DefineAsRegister(node), g.Use(mleft.left().node()));
       return;
+    } else if (mleft.right().Is(24) && m.right().Is(24)) {
+      Emit(kX64Movsxbl, g.DefineAsRegister(node), g.Use(mleft.left().node()));
+      return;
     }
   }
   VisitWord32Shift(this, node, kX64Sar32);

src/x64/assembler-x64.cc

@@ -1383,6 +1383,20 @@ void Assembler::movl(const Operand& dst, Label* src) {
 }
 
 
+void Assembler::movsxbl(Register dst, Register src) {
+  EnsureSpace ensure_space(this);
+  if (!src.is_byte_register()) {
+    // Register is not one of al, bl, cl, dl.  Its encoding needs REX.
+    emit_rex_32(dst, src);
+  } else {
+    emit_optional_rex_32(dst, src);
+  }
+  emit(0x0F);
+  emit(0xBE);
+  emit_modrm(dst, src);
+}
+
+
 void Assembler::movsxbl(Register dst, const Operand& src) {
   EnsureSpace ensure_space(this);
   emit_optional_rex_32(dst, src);

src/x64/assembler-x64.h

@@ -731,6 +731,7 @@ class Assembler : public AssemblerBase {
   void movq(Register dst, int64_t value);
   void movq(Register dst, uint64_t value);
 
+  void movsxbl(Register dst, Register src);
   void movsxbl(Register dst, const Operand& src);
   void movsxbq(Register dst, const Operand& src);
   void movsxwl(Register dst, Register src);