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

runtime/vm/intermediate_language.cc

Index: runtime/vm/intermediate_language.cc
diff --git a/runtime/vm/intermediate_language.cc b/runtime/vm/intermediate_language.cc
index 0c64c347fe51721707a272bef7e638cfb00ed102..702cbc8624e600d33733b027e613f5a6ff01abe0 100644
--- a/runtime/vm/intermediate_language.cc
+++ b/runtime/vm/intermediate_language.cc
@@ -607,6 +607,7 @@ BranchInstr::BranchInstr(ComparisonInstr* comparison, bool is_checked)
       is_checked_(is_checked),
       constrained_type_(NULL),
       constant_target_(NULL) {
+  ASSERT(comparison->env() == NULL);
   for (intptr_t i = comparison->InputCount() - 1; i >= 0; --i) {
     comparison->InputAt(i)->set_instruction(this);
   }
@@ -636,6 +637,7 @@ void BranchInstr::SetComparison(ComparisonInstr* comp) {
   }
   // There should be no need to copy or unuse an environment.
   ASSERT(comparison()->env() == NULL);
+  ASSERT(comp->env() == NULL);
   // Remove the current comparison's input uses.

[srdjan, 2013/04/15 20:27:27]

Would be probable more readable if CompareInstr* would be called instr instead
of comp?

[Vyacheslav Egorov (Google), 2013/04/16 11:51:16]

I think instr is somewhat confusing as well. I renamed it to new_comparison.

   comparison()->UnuseAllInputs();
   ASSERT(!comp->HasUses());
@@ -1233,6 +1235,23 @@ Definition* AssertAssignableInstr::Canonicalize(FlowGraphOptimizer* optimizer) {
 }
 
 
+static bool RecognizeTestPattern(Value* left, Value* right) {

[srdjan, 2013/04/15 20:27:27]

Add comment what pattern is being recognized.

[Vyacheslav Egorov (Google), 2013/04/16 11:51:16]

Done.

+  if (!right->BindsToConstant()) {
+    return false;
+  }
+
+  const Object& value = right->BoundConstant();
+  if (!value.IsSmi() || (Smi::Cast(value).Value() != 0)) {
+    return false;
+  }
+
+  Definition* left_defn = left->definition();
+  return left_defn->IsBinarySmiOp() &&
+      (left_defn->AsBinarySmiOp()->op_kind() == Token::kBIT_AND) &&
+      left_defn->HasOnlyUse(left);
+}
+
+
 Instruction* BranchInstr::Canonicalize(FlowGraphOptimizer* optimizer) {
   // Only handle strict-compares.
   if (comparison()->IsStrictCompare()) {
@@ -1261,6 +1280,7 @@ Instruction* BranchInstr::Canonicalize(FlowGraphOptimizer* optimizer) {
       RemoveEnvironment();
       InheritDeoptTarget(comp);
 
+      comp->RemoveEnvironment();
       comp->RemoveFromGraph();
       SetComparison(comp);
       if (FLAG_trace_optimization) {
@@ -1272,6 +1292,25 @@ Instruction* BranchInstr::Canonicalize(FlowGraphOptimizer* optimizer) {
       comp->ClearSSATempIndex();
       comp->ClearTempIndex();
     }
+  } else if (comparison()->IsSmiEquality()) {
+    BinarySmiOpInstr* bit_and = NULL;
+    if (RecognizeTestPattern(comparison()->left(), comparison()->right())) {
+      bit_and = comparison()->left()->definition()->AsBinarySmiOp();
+    } else if (RecognizeTestPattern(comparison()->right(),
+                                    comparison()->left())) {
+      bit_and = comparison()->right()->definition()->AsBinarySmiOp();
+    }
+
+    if (bit_and != NULL) {
+      TestSmiInstr* test = new TestSmiInstr(comparison()->kind(),
+                                            bit_and->left()->Copy(),
+                                            bit_and->right()->Copy());
+      ASSERT(!CanDeoptimize());
+      InheritDeoptTarget(bit_and);
+      RemoveEnvironment();
+      SetComparison(test);
+      bit_and->RemoveFromGraph();
+    }
   }
   return this;
 }