[wasm] Initial commit for the Int64Reducer.

src/compiler/int64-reducer.cc

+// 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/int64-reducer.h"
+#include "src/compiler/common-operator.h"
+#include "src/compiler/graph.h"
+#include "src/compiler/machine-operator.h"
+#include "src/compiler/node.h"
+#include "src/zone.h"
+
+namespace v8 {
+namespace internal {
+namespace compiler {
+
+Int64Reducer::Int64Reducer(Graph* graph, MachineOperatorBuilder* machine,
+                           CommonOperatorBuilder* common, Zone* zone)
+    : graph_(graph),
+      machine_(machine),
+      common_(common),
+      state_(graph, 4),
+      stack_(zone),
+      replacements_(zone->NewArray<Replacement>(graph->NodeCount())) {}
+
+void Int64Reducer::ReduceGraph() {
+  stack_.push(graph()->end());
+  state_.Set(graph()->end(), State::kOnStack);
+
+  for (;;) {

[titzer, 2016/02/02 10:14:35]

while (!stack.empty()) 

[ahaas, 2016/02/02 13:32:48]

Done.

+    if (stack_.empty()) {
+      break;
+    }
+    Node* top = stack_.top();
+    if (state_.Get(top) == State::kInputsPushed) {
+      stack_.pop();
+      state_.Set(top, State::kVisited);
+      // All inputs of top have already been reduced, now reduce top.
+      ReduceNode(top);
+    } else {
+      // Push all children onto the stack.
+      for (Node* input : top->inputs()) {
+        if (state_.Get(input) == State::kUnvisited) {
+          stack_.push(input);
+          state_.Set(input, State::kOnStack);
+          replacements_[input->id()].low = nullptr;
+        }
+      }
+      state_.Set(top, State::kInputsPushed);
+    }
+  }
+}
+
+void Int64Reducer::ReduceNode(Node* node) {
+  if (node->opcode() == IrOpcode::kInt64Constant) {

[titzer, 2016/02/02 10:14:35]

Make me a switch.

[ahaas, 2016/02/02 13:32:48]

Done.

+    int64_t value = OpParameter<int64_t>(node);
+    Node* low_node =
+        graph()->NewNode(common()->Int32Constant(static_cast<int32_t>(value)));

[titzer, 2016/02/02 10:14:35]

I think you need to do a static_cast<uint32_t>(value & 0xFFFFFFFF) to be
absolutely sure to avoid C++ undefined behavior.

[ahaas, 2016/02/02 13:32:48]

Done.

+    Node* high_node = graph()->NewNode(
+        common()->Int32Constant(static_cast<int32_t>(value >> 32)));
+    replacements_[node->id()].low = low_node;
+    replacements_[node->id()].high = high_node;
+  } else if (node->opcode() == IrOpcode::kWord64And) {
+    Node* left = node->InputAt(0);
+    DCHECK(replacements_[left->id()].low);
+    Node* left_low = replacements_[left->id()].low;
+    Node* left_high = replacements_[left->id()].high;
+
+    Node* right = node->InputAt(1);
+    DCHECK(replacements_[right->id()].low);
+    Node* right_low = replacements_[right->id()].low;
+    Node* right_high = replacements_[right->id()].high;
+
+    replacements_[node->id()].low =
+        graph()->NewNode(machine()->Word32And(), left_low, right_low);
+    replacements_[node->id()].high =
+        graph()->NewNode(machine()->Word32And(), left_high, right_high);
+  } else if (node->opcode() == IrOpcode::kTruncateInt64ToInt32) {
+    Node* input = node->InputAt(0);
+    DCHECK(replacements_[input->id()].low);
+    replacements_[node->id()].low = replacements_[input->id()].low;
+  } else {
+    // Also the inputs of nodes can change which do not expect int64 inputs.
+    for (int i = 0; i < node->InputCount(); i++) {
+      Node* input = node->InputAt(i);
+      // The input has changed altough it was not an int64 input. This can
+      // happen e.g. if the input node is IrOpcode::kTruncateInt64ToInt32. We
+      // use the low word replacement as the new input.
+      if (replacements_[input->id()].low) {
+        node->ReplaceInput(i, replacements_[input->id()].low);
+      }
+    }
+  }
+}
+
+}  // namespace compiler
+}  // namespace internal
+}  // namespace v8