Add JSBuiltinReducer for inlining well-known builtins.

src/compiler/js-builtin-reducer.cc

Index: src/compiler/js-builtin-reducer.cc
diff --git a/src/compiler/js-builtin-reducer.cc b/src/compiler/js-builtin-reducer.cc
new file mode 100644
index 0000000000000000000000000000000000000000..90027a57adbd80438554b9277a72c29739086cb8
--- /dev/null
+++ b/src/compiler/js-builtin-reducer.cc
@@ -0,0 +1,109 @@
+// Copyright 2014 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "src/compiler/graph-inl.h"
+#include "src/compiler/js-builtin-reducer.h"
+#include "src/compiler/node-matchers.h"
+#include "src/compiler/node-properties-inl.h"
+#include "src/types.h"
+
+namespace v8 {
+namespace internal {
+namespace compiler {
+
+
+// Helper method that assumes replacement nodes are pure values that don't
+// produce an effect. Replaces {node} with {reduction} and relaxes effects.
+static Reduction ReplaceWithPureReduction(Node* node, Reduction reduction) {
+  if (reduction.Changed()) {
+    NodeProperties::ReplaceWithValue(node, reduction.replacement());
+    return reduction;
+  }
+  return Reducer::NoChange();
+}
+
+
+// Helper class to access JSCallFunction nodes that are potential candidates
+// for reduction when they have a BuiltinFunctionId associated with them.
+class JSCallReduction {
+ public:
+  explicit JSCallReduction(Node* node) : node_(node) {}
+
+  // Determines whether the node is a JSCallFunction operation that targets a
+  // constant callee being a well-known builtin with a BuiltinFunctionId.
+  bool HasBuiltinFunctionId() {
+    if (node_->opcode() != IrOpcode::kJSCallFunction) return false;
+    HeapObjectMatcher<JSFunction> m(NodeProperties::GetValueInput(node_, 0));
+    return m.HasValue() && m.Value().handle()->shared()->HasBuiltinFunctionId();
+  }
+
+  // Retrieves the BuiltinFunctionId as described above.
+  BuiltinFunctionId GetBuiltinFunctionId() {
+    DCHECK_EQ(IrOpcode::kJSCallFunction, node_->opcode());
+    HeapObjectMatcher<JSFunction> m(NodeProperties::GetValueInput(node_, 0));
+    return m.Value().handle()->shared()->builtin_function_id();
+  }
+
+  // Determines whether the call takes one input of the given type.
+  bool InputsMatch(Type* t1) {
+    return GetJSCallArity() == 1 &&
+           NodeProperties::GetBounds(GetJSCallInput(0)).upper->Is(t1);
+  }
+
+  // Determines whether the call takes two inputs of the given types.
+  bool InputsMatch(Type* t1, Type* t2) {
+    return GetJSCallArity() == 2 &&
+           NodeProperties::GetBounds(GetJSCallInput(0)).upper->Is(t1) &&
+           NodeProperties::GetBounds(GetJSCallInput(1)).upper->Is(t2);
+  }
+
+  Node* left() { return GetJSCallInput(0); }
+  Node* right() { return GetJSCallInput(1); }
+
+ protected:
+  int GetJSCallArity() {
+    DCHECK_EQ(IrOpcode::kJSCallFunction, node_->opcode());
+    return OperatorProperties::GetValueInputCount(node_->op()) - 2;

[titzer, 2014/09/19 11:06:15]

+/- magic numbers should be documented.

[Michael Starzinger, 2014/09/19 11:18:30]

Done.

+  }
+
+  Node* GetJSCallInput(int index) {
+    DCHECK_EQ(IrOpcode::kJSCallFunction, node_->opcode());
+    DCHECK_LT(index, GetJSCallArity());
+    return NodeProperties::GetValueInput(node_, index + 2);
+  }
+
+ private:
+  Node* node_;
+};
+
+
+// ES6 draft 08-24-14, section 20.2.2.19.
+Reduction JSBuiltinReducer::ReduceMathImul(Node* node) {
+  JSCallReduction r(node);
+  if (r.InputsMatch(Type::Integral32(), Type::Integral32())) {
+    // Math.imul(a:int32, b:int32) -> Int32Mul(a, b)
+    Node* value = graph()->NewNode(machine()->Int32Mul(), r.left(), r.right());
+    return Replace(value);
+  }
+  return NoChange();
+}
+
+
+Reduction JSBuiltinReducer::Reduce(Node* node) {
+  JSCallReduction r(node);
+
+  // Dispatch according to the BuiltinFunctionId if present.
+  if (!r.HasBuiltinFunctionId()) return NoChange();
+  switch (r.GetBuiltinFunctionId()) {
+    case kMathImul:
+      return ReplaceWithPureReduction(node, ReduceMathImul(node));
+    default:
+      break;
+  }
+  return NoChange();
+}
+
+}  // namespace compiler
+}  // namespace internal
+}  // namespace v8