Merge (x & y) == 0 pattern to emit a single test instruction.

runtime/vm/intermediate_language_arm.cc

Index: runtime/vm/intermediate_language_arm.cc
diff --git a/runtime/vm/intermediate_language_arm.cc b/runtime/vm/intermediate_language_arm.cc
index 5ae8494bc9020b3a23ab190dc77f75b6dcb4e9ed..0a6e74b64513d6bac361d729e98f66f4209ab32c 100644
--- a/runtime/vm/intermediate_language_arm.cc
+++ b/runtime/vm/intermediate_language_arm.cc
@@ -609,6 +609,49 @@ void EqualityCompareInstr::EmitBranchCode(FlowGraphCompiler* compiler,
 }
 
 
+LocationSummary* TestSmiInstr::MakeLocationSummary() const {
+  const intptr_t kNumInputs = 2;
+  const intptr_t kNumTemps = 0;
+  LocationSummary* locs =
+      new LocationSummary(kNumInputs, kNumTemps, LocationSummary::kNoCall);
+  locs->set_in(0, Location::RequiresRegister());
+  // Only one input can be a constant operand. The case of two constant
+  // operands should be handled by constant propagation.
+  locs->set_in(1, Location::RegisterOrConstant(right()));
+  return locs;
+}
+
+
+void TestSmiInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
+  // Never emitted outside of the BranchInstr.
+  UNREACHABLE();
+}
+
+
+void TestSmiInstr::EmitBranchCode(FlowGraphCompiler* compiler,
+                                  BranchInstr* branch) {
+  Condition branch_condition = (kind() == Token::kNE) ? NE : EQ;
+  Register left = locs()->in(0).reg();
+  Location right = locs()->in(1);
+  if (right.IsConstant()) {
+    ASSERT(right.constant().IsSmi());
+    const int32_t imm =
+        reinterpret_cast<int32_t>(right.constant().raw());
+    ShifterOperand shifter_op;
+    if (ShifterOperand::CanHold(imm, &shifter_op)) {
+      __ tst(left, shifter_op);
+    } else {
+      // TODO(regis): Try to use bic.
+      __ LoadImmediate(IP, imm);
+      __ tst(left, ShifterOperand(IP));
+    }
+  } else {
+    __ tst(left, ShifterOperand(right.reg()));
+  }
+  branch->EmitBranchOnCondition(compiler, branch_condition);
+}
+
+
 LocationSummary* RelationalOpInstr::MakeLocationSummary() const {
   const intptr_t kNumInputs = 2;
   const intptr_t kNumTemps = 0;