[turbofan] decouple register allocation from schedule and graph

src/compiler/instruction-selector.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/instruction-selector.h"
 
 #include "src/compiler/instruction-selector-impl.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/node-properties-inl.h"
 #include "src/compiler/pipeline.h"
@@ skipping 834 matching lines @@
 void InstructionSelector::VisitParameter(Node* node) {
   OperandGenerator g(this);
   int index = OpParameter<int>(node);
   Emit(kArchNop,
        g.DefineAsLocation(node, linkage()->GetParameterLocation(index),
                           linkage()->GetParameterType(index)));
 }
 
 
 void InstructionSelector::VisitPhi(Node* node) {
   // TODO(bmeurer): Emit a PhiInstruction here.

[Benedikt Meurer, 2014/10/19 18:13:03]

Remove this TODO.

-  for (InputIter i = node->inputs().begin(); i != node->inputs().end(); ++i) {
-    MarkAsUsed(*i);
+  PhiInstruction* phi = new (instruction_zone())
+      PhiInstruction(instruction_zone(), sequence()->GetVirtualRegister(node));
+  sequence()->InstructionBlockAt(current_block_->GetRpoNumber())->AddPhi(phi);
+  Node::Inputs inputs = node->inputs();
+  size_t j = 0;
+  for (Node::Inputs::iterator iter(inputs.begin()); iter != inputs.end();

[Benedikt Meurer, 2014/10/19 18:13:03]

How about this instead?

const int input_count = node->op()->InputCount();
phi->operands().reserve(static_cast<size_t>(input_count));
for (int i = 0; i < node->op()->InputCount(); ++i) {
  Node* const input = node->InputAt(i);
  MarkAsUsed(input);
  phi->operands().push_back(sequence()->GetVirtualRegister(input));
}

+       ++iter, ++j) {
+    MarkAsUsed(*iter);
+    // TODO(mstarzinger): Use a ValueInputIterator instead.
+    if (j >= current_block_->PredecessorCount()) continue;
+    phi->operands().push_back(sequence()->GetVirtualRegister(*iter));
   }
 }
 
 
 void InstructionSelector::VisitProjection(Node* node) {
   OperandGenerator g(this);
   Node* value = node->InputAt(0);
   switch (value->opcode()) {
     case IrOpcode::kInt32AddWithOverflow:
     case IrOpcode::kInt32SubWithOverflow:
@@ skipping 156 matching lines @@
 void InstructionSelector::VisitBranch(Node* branch, BasicBlock* tbranch,
                                       BasicBlock* fbranch) {
   UNIMPLEMENTED();
 }
 
 #endif  // !V8_TURBOFAN_BACKEND
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8