[turbofan] Use cbz/cbnz when possible on arm64.

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

Index: test/unittests/compiler/arm64/instruction-selector-arm64-unittest.cc
diff --git a/test/unittests/compiler/arm64/instruction-selector-arm64-unittest.cc b/test/unittests/compiler/arm64/instruction-selector-arm64-unittest.cc
index eee9c58b127ddac04e6439708f3af73c6d0c910d..2d127c448fbf223ce6eca98f3ee8be25e31d2438 100644
--- a/test/unittests/compiler/arm64/instruction-selector-arm64-unittest.cc
+++ b/test/unittests/compiler/arm64/instruction-selector-arm64-unittest.cc
@@ -952,6 +952,41 @@ TEST_F(InstructionSelectorTest, Word64AndBranchWithOneBitMaskOnLeft) {
 }
 
 
+TEST_F(InstructionSelectorTest, CompareAgainstZeroAndBranch) {
+  {
+    StreamBuilder m(this, kMachInt32, kMachInt32);
+    MLabel a, b;
+    Node* p0 = m.Parameter(0);
+    m.Branch(p0, &a, &b);
+    m.Bind(&a);
+    m.Return(m.Int32Constant(1));
+    m.Bind(&b);
+    m.Return(m.Int32Constant(0));
+    Stream s = m.Build();
+    ASSERT_EQ(1U, s.size());
+    EXPECT_EQ(kArm64Cbnz32, s[0]->arch_opcode());
+    EXPECT_EQ(3U, s[0]->InputCount());
+    EXPECT_EQ(s.ToVreg(p0), s.ToVreg(s[0]->InputAt(0)));
+  }
+
+  {
+    StreamBuilder m(this, kMachInt32, kMachInt32);
+    MLabel a, b;
+    Node* p0 = m.Parameter(0);
+    m.Branch(m.Word32BinaryNot(p0), &a, &b);
+    m.Bind(&a);
+    m.Return(m.Int32Constant(1));
+    m.Bind(&b);
+    m.Return(m.Int32Constant(0));
+    Stream s = m.Build();
+    ASSERT_EQ(1U, s.size());
+    EXPECT_EQ(kArm64Cbz32, s[0]->arch_opcode());
+    EXPECT_EQ(3U, s[0]->InputCount());
+    EXPECT_EQ(s.ToVreg(p0), s.ToVreg(s[0]->InputAt(0)));
+  }
+}
+
+
 // -----------------------------------------------------------------------------
 // Add and subtract instructions with overflow.