Fuse comparisons that are used by branches together.

runtime/vm/flow_graph_optimizer.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/flow_graph_optimizer.h"
 
 #include "vm/flow_graph_builder.h"
 #include "vm/il_printer.h"
 #include "vm/object_store.h"
 
@@ skipping 512 matching lines @@
 
   const intptr_t class_id = ReceiverClassId(comp);
   switch (class_id) {
     case kArray:
     case kGrowableObjectArray:
       comp->set_receiver_type(static_cast<ObjectKind>(class_id));
   }
 }
 
 
+static void TryFuseComparisonWithBranch(ComparisonComp* comp) {
+  Instruction* instr = comp->instr();
+  Instruction* next_instr = instr->StraightLineSuccessor();
+  if (next_instr != NULL && next_instr->IsBranch()) {
+    BranchInstr* branch = next_instr->AsBranch();
+    UseVal* use = branch->value()->AsUse();
+    if (instr == use->definition()) {
+      comp->MarkFusedWithBranch(branch);
+      branch->MarkFusedWithComparison();
+    }
+  }
+}
+
+
 void FlowGraphOptimizer::VisitRelationalOp(RelationalOpComp* comp) {
   if (!comp->HasICData()) return;
 
   const ICData& ic_data = *comp->ic_data();
   if (ic_data.NumberOfChecks() == 0) return;
   // TODO(srdjan): Add multiple receiver type support.
   if (ic_data.NumberOfChecks() != 1) return;
   ASSERT(HasOneTarget(ic_data));
 
   if (HasTwoSmi(ic_data)) {
     comp->set_operands_class_id(kSmi);
   } else if (HasTwoDouble(ic_data)) {
     comp->set_operands_class_id(kDouble);
+  } else {
+    return;
   }
+
+  // For smi and double comparisons if the next instruction is a conditional
+  // branch that uses the value of this comparison mark them as fused together
+  // to avoid materializing a boolean value.
+  // TODO(vegorov): recognize the pattern with BooleanNegate between comparsion
+  // and a branch.
+  TryFuseComparisonWithBranch(comp);
 }
 
 
+void FlowGraphOptimizer::VisitStrictCompareComp(StrictCompareComp* comp) {
+  // TODO(vegorov): recognize the pattern with BooleanNegate between comparsion
+  // and a branch.
+  TryFuseComparisonWithBranch(comp);
+}
+
+
+void FlowGraphOptimizer::VisitEqualityCompare(EqualityCompareComp* comp) {
+  // TODO(vegorov): recognize the pattern with BooleanNegate between comparsion
+  // and a branch.
+  TryFuseComparisonWithBranch(comp);
+}
+
+
 void FlowGraphOptimizer::VisitDo(DoInstr* instr) {
   instr->computation()->Accept(this);
 }
 
 
 void FlowGraphOptimizer::VisitBind(BindInstr* instr) {
   instr->computation()->Accept(this);
 }
 
 
 }  // namespace dart