binary-operator-reducer: reduce mul+div(shift)

src/compiler/binary-operator-reducer.cc

+// Copyright 2015 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/binary-operator-reducer.h"
+
+#include <algorithm>
+
+#include "src/compiler/common-operator.h"
+#include "src/compiler/graph.h"
+#include "src/compiler/machine-operator.h"
+#include "src/compiler/node.h"
+#include "src/compiler/node-matchers.h"
+#include "src/compiler/node-properties.h"
+#include "src/types-inl.h"
+
+namespace v8 {
+namespace internal {
+namespace compiler {
+
+BinaryOperatorReducer::BinaryOperatorReducer(Editor* editor, Graph* graph,
+                                             CommonOperatorBuilder* common,
+                                             MachineOperatorBuilder* machine)
+    : AdvancedReducer(editor),
+      graph_(graph),
+      common_(common),
+      machine_(machine),
+      dead_(graph->NewNode(common->Dead())) {}
+
+
+Reduction BinaryOperatorReducer::Reduce(Node* node) {
+  switch (node->opcode()) {
+    case IrOpcode::kFloat64Mul:
+      return ReduceFloat52Mul(node);
+    case IrOpcode::kFloat64Div:
+      return ReduceFloat52Div(node);
+    default:
+      break;
+  }
+  return NoChange();
+}
+
+
+Reduction BinaryOperatorReducer::ReduceFloat52Mul(Node* node) {
+  if (!machine()->Is64()) return NoChange();
+
+  Float64BinopMatcher m(node);
+  if (!m.left().IsChangeInt32ToFloat64() ||
+      !m.right().IsChangeInt32ToFloat64()) {
+    return NoChange();
+  }
+
+  Type* type = NodeProperties::GetType(node);
+  Type::RangeType* range = type->GetRange();
+
+  // JavaScript has 52 bit precision in multiplication
+  if (range == nullptr || range->Min() < 0.0 ||
+      range->Max() > 0xFFFFFFFFFFFFFULL) {
+    return NoChange();
+  }
+
+  Node* mul = graph()->NewNode(machine()->Int64Mul(), m.left().InputAt(0),
+                               m.right().InputAt(0));
+  Revisit(mul);
+
+  Type* range_type = Type::Range(range->Min(), range->Max(), graph()->zone());
+
+  // TODO(indutny): Is Type::Number() a proper thing here? It looks like
+  // every other place is using Type:Internal() for int64 values.
+  // Should we off-load range propagation to Typer?
+  NodeProperties::SetType(
+      mul, Type::Intersect(range_type, Type::Number(), graph()->zone()));
+
+  Node* out = graph()->NewNode(machine()->RoundInt64ToFloat64(), mul);
+  return Replace(out);
+}
+
+
+Reduction BinaryOperatorReducer::ReduceFloat52Div(Node* node) {
+  if (!machine()->Is64()) return NoChange();
+
+  Float64BinopMatcher m(node);
+  if (!m.left().IsRoundInt64ToFloat64()) return NoChange();
+
+  // Right value should be positive...
+  if (!m.right().HasValue() || m.right().Value() <= 0) return NoChange();
+
+  // ...integer...
+  int64_t value = static_cast<int64_t>(m.right().Value());
+  if (value != static_cast<int64_t>(m.right().Value())) return NoChange();
+
+  // ...and should be a power of two.
+  if (!base::bits::IsPowerOfTwo64(value)) return NoChange();
+
+  Node* left = m.left().InputAt(0);
+  Type::RangeType* range = NodeProperties::GetType(left)->GetRange();
+
+  // The result should fit into 32bit word
+  int64_t min = static_cast<int64_t>(range->Min()) / value;
+  int64_t max = static_cast<int64_t>(range->Max()) / value;
+  if (min < 0 || max > 0xFFFFFFFLL) {
+    return NoChange();
+  }
+
+  int64_t shift = WhichPowerOf2_64(static_cast<int64_t>(m.right().Value()));
+
+  // Replace division with 64bit right shift
+  Node* shr =
+      graph()->NewNode(machine()->Word64Shr(), left,
+                       graph()->NewNode(common()->Int64Constant(shift)));
+  Revisit(shr);
+
+  Node* out = graph()->NewNode(machine()->RoundInt64ToFloat64(), shr);
+  return Replace(out);
+}
+
+
+Reduction BinaryOperatorReducer::Change(Node* node, Operator const* op,
+                                        Node* a) {
+  node->ReplaceInput(0, a);
+  node->TrimInputCount(1);
+  NodeProperties::ChangeOp(node, op);
+  return Changed(node);
+}
+
+}  // namespace compiler
+}  // namespace internal
+}  // namespace v8