[wasm] Initial commit for the Int64Reducer.

src/compiler/int64-lowering.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-lowering.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 {
+
+Int64Lowering::Int64Lowering(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())) {
+  memset(replacements_, 0, sizeof(Replacement) * graph->NodeCount());
+}
+
+void Int64Lowering::ReduceGraph() {
+  stack_.push(graph()->end());
+  state_.Set(graph()->end(), State::kOnStack);
+
+  while (!stack_.empty()) {
+    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);
+        }
+      }
+      state_.Set(top, State::kInputsPushed);
+    }
+  }
+}
+
+void Int64Lowering::ReduceNode(Node* node) {
+  switch (node->opcode()) {
+    case IrOpcode::kInt64Constant: {
+      int64_t value = OpParameter<int64_t>(node);
+      Node* low_node = graph()->NewNode(
+          common()->Int32Constant(static_cast<int32_t>(value & 0xFFFFFFFF)));
+      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;
+      break;
+    }
+    case 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);
+      break;
+    }
+    case IrOpcode::kTruncateInt64ToInt32: {
+      Node* input = node->InputAt(0);
+      DCHECK(replacements_[input->id()].low);
+      replacements_[node->id()].low = replacements_[input->id()].low;
+      break;
+    }
+    default: {
+      // 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