[turbofan] Recognize sign extension of 8-bit and 16-bit values on arm64.

R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/730183005

Cr-Commit-Position: refs/heads/master@{#25475}

src/compiler/arm64/code-generator-arm64.cc

@@ -416,6 +416,12 @@ void CodeGenerator::AssembleArchInstruction(Instruction* instr) {
     case kArm64Mov32:
       __ Mov(i.OutputRegister32(), i.InputRegister32(0));
       break;
+    case kArm64Sxtb32:
+      __ Sxtb(i.OutputRegister32(), i.InputRegister32(0));
+      break;
+    case kArm64Sxth32:
+      __ Sxth(i.OutputRegister32(), i.InputRegister32(0));
+      break;
     case kArm64Sxtw:
       __ Sxtw(i.OutputRegister(), i.InputRegister32(0));
       break;

src/compiler/arm64/instruction-codes-arm64.h

@@ -65,6 +65,8 @@ namespace compiler {
   V(Arm64Ror)                      \
   V(Arm64Ror32)                    \
   V(Arm64Mov32)                    \
+  V(Arm64Sxtb32)                   \
+  V(Arm64Sxth32)                   \
   V(Arm64Sxtw)                     \
   V(Arm64Ubfx)                     \
   V(Arm64Ubfx32)                   \

src/compiler/arm64/instruction-selector-arm64.cc

@@ -608,6 +608,21 @@ void InstructionSelector::VisitWord64Shr(Node* node) {
 
 
 void InstructionSelector::VisitWord32Sar(Node* node) {
+  Arm64OperandGenerator g(this);
+  Int32BinopMatcher m(node);
+  // Select Sxth/Sxtb for (x << K) >> K where K is 16 or 24.
+  if (CanCover(node, m.left().node()) && m.left().IsWord32Shl()) {
+    Int32BinopMatcher mleft(m.left().node());
+    if (mleft.right().Is(16) && m.right().Is(16)) {
+      Emit(kArm64Sxth32, g.DefineAsRegister(node),
+           g.UseRegister(mleft.left().node()));
+      return;
+    } else if (mleft.right().Is(24) && m.right().Is(24)) {
+      Emit(kArm64Sxtb32, g.DefineAsRegister(node),
+           g.UseRegister(mleft.left().node()));
+      return;
+    }
+  }
   VisitRRO(this, kArm64Asr32, node, kShift32Imm);
 }
 

test/unittests/compiler/arm64/instruction-selector-arm64-unittest.cc

@@ -2129,6 +2129,38 @@ TEST_F(InstructionSelectorTest, Int32MulHighWithParameters) {
   EXPECT_EQ(s.ToVreg(n), s.ToVreg(s[1]->Output()));
 }
 
+
+TEST_F(InstructionSelectorTest, Word32SarWithWord32Shl) {
+  {
+    StreamBuilder m(this, kMachInt32, kMachInt32);
+    Node* const p0 = m.Parameter(0);
+    Node* const r =
+        m.Word32Sar(m.Word32Shl(p0, m.Int32Constant(24)), m.Int32Constant(24));
+    m.Return(r);
+    Stream s = m.Build();
+    ASSERT_EQ(1U, s.size());
+    EXPECT_EQ(kArm64Sxtb32, s[0]->arch_opcode());
+    ASSERT_EQ(1U, s[0]->InputCount());
+    EXPECT_EQ(s.ToVreg(p0), s.ToVreg(s[0]->InputAt(0)));
+    ASSERT_EQ(1U, s[0]->OutputCount());
+    EXPECT_EQ(s.ToVreg(r), s.ToVreg(s[0]->Output()));
+  }
+  {
+    StreamBuilder m(this, kMachInt32, kMachInt32);
+    Node* const p0 = m.Parameter(0);
+    Node* const r =
+        m.Word32Sar(m.Word32Shl(p0, m.Int32Constant(16)), m.Int32Constant(16));
+    m.Return(r);
+    Stream s = m.Build();
+    ASSERT_EQ(1U, s.size());
+    EXPECT_EQ(kArm64Sxth32, s[0]->arch_opcode());
+    ASSERT_EQ(1U, s[0]->InputCount());
+    EXPECT_EQ(s.ToVreg(p0), s.ToVreg(s[0]->InputAt(0)));
+    ASSERT_EQ(1U, s[0]->OutputCount());
+    EXPECT_EQ(s.ToVreg(r), s.ToVreg(s[0]->Output()));
+  }
+}
+
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8