Add a Transform to SSA phase to the optimizing compiler.
Change-Id: Ia9700756a0396d797a00b529896487d52c989329
diff --git a/compiler/optimizing/ssa_builder.cc b/compiler/optimizing/ssa_builder.cc
new file mode 100644
index 0000000..bfb4f38
--- /dev/null
+++ b/compiler/optimizing/ssa_builder.cc
@@ -0,0 +1,134 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "ssa_builder.h"
+#include "nodes.h"
+
+namespace art {
+
+void SsaBuilder::BuildSsa() {
+ // 1) Visit in dominator order. We need to have all predecessors of a block visited
+ // (with the exception of loops) in order to create the right environment for that
+ // block. For loops, we create phis whose inputs will be set in 2).
+ for (size_t i = 0; i < GetGraph()->GetDominatorOrder()->Size(); i++) {
+ VisitBasicBlock(GetGraph()->GetDominatorOrder()->Get(i));
+ }
+
+ // 2) Set inputs of loop phis.
+ for (size_t i = 0; i < loop_headers_.Size(); i++) {
+ HBasicBlock* block = loop_headers_.Get(i);
+ for (HInstructionIterator it(*block->GetPhis()); !it.Done(); it.Advance()) {
+ HPhi* phi = it.Current()->AsPhi();
+ for (size_t pred = 0; pred < block->GetPredecessors()->Size(); pred++) {
+ phi->AddInput(ValueOfLocal(block->GetPredecessors()->Get(pred), phi->GetRegNumber()));
+ }
+ }
+ }
+
+ // 3) Clear locals.
+ // TODO: Move this to a dead code eliminator phase.
+ for (HInstructionIterator it(*GetGraph()->GetEntryBlock()->GetInstructions());
+ !it.Done();
+ it.Advance()) {
+ HInstruction* current = it.Current();
+ if (current->AsLocal() != nullptr) {
+ current->GetBlock()->RemoveInstruction(current);
+ }
+ }
+}
+
+HInstruction* SsaBuilder::ValueOfLocal(HBasicBlock* block, size_t local) {
+ return GetLocalsFor(block)->Get(local);
+}
+
+void SsaBuilder::VisitBasicBlock(HBasicBlock* block) {
+ current_locals_ = GetLocalsFor(block);
+
+ if (block->IsLoopHeader()) {
+ // If the block is a loop header, we know we only have visited the pre header
+ // because we are visiting in dominator order. We create phis for all initialized
+ // locals from the pre header. Their inputs will be populated at the end of
+ // the analysis.
+ for (size_t local = 0; local < current_locals_->Size(); local++) {
+ HInstruction* incoming = ValueOfLocal(block->GetLoopInformation()->GetPreHeader(), local);
+ if (incoming != nullptr) {
+ // TODO: Compute union type.
+ HPhi* phi = new (GetGraph()->GetArena()) HPhi(
+ GetGraph()->GetArena(), local, 0, Primitive::kPrimVoid);
+ block->AddPhi(phi);
+ current_locals_->Put(local, phi);
+ }
+ }
+ // Save the loop header so that the last phase of the analysis knows which
+ // blocks need to be updated.
+ loop_headers_.Add(block);
+ } else if (block->GetPredecessors()->Size() > 0) {
+ // All predecessors have already been visited because we are visiting in dominator order.
+ // We merge the values of all locals, creating phis if those values differ.
+ for (size_t local = 0; local < current_locals_->Size(); local++) {
+ bool is_different = false;
+ HInstruction* value = ValueOfLocal(block->GetPredecessors()->Get(0), local);
+ for (size_t i = 1; i < block->GetPredecessors()->Size(); i++) {
+ if (ValueOfLocal(block->GetPredecessors()->Get(i), local) != value) {
+ is_different = true;
+ break;
+ }
+ }
+ if (is_different) {
+ // TODO: Compute union type.
+ HPhi* phi = new (GetGraph()->GetArena()) HPhi(
+ GetGraph()->GetArena(), local, block->GetPredecessors()->Size(), Primitive::kPrimVoid);
+ for (size_t i = 0; i < block->GetPredecessors()->Size(); i++) {
+ phi->SetRawInputAt(i, ValueOfLocal(block->GetPredecessors()->Get(i), local));
+ }
+ block->AddPhi(phi);
+ value = phi;
+ }
+ current_locals_->Put(local, value);
+ }
+ }
+
+ // Visit all instructions. The instructions of interest are:
+ // - HLoadLocal: replace them with the current value of the local.
+ // - HStoreLocal: update current value of the local and remove the instruction.
+ // - Instructions that require an environment: populate their environment
+ // with the current values of the locals.
+ for (HInstructionIterator it(*block->GetInstructions()); !it.Done(); it.Advance()) {
+ it.Current()->Accept(this);
+ }
+}
+
+void SsaBuilder::VisitLoadLocal(HLoadLocal* load) {
+ load->ReplaceWith(current_locals_->Get(load->GetLocal()->GetRegNumber()));
+ load->GetBlock()->RemoveInstruction(load);
+}
+
+void SsaBuilder::VisitStoreLocal(HStoreLocal* store) {
+ current_locals_->Put(store->GetLocal()->GetRegNumber(), store->InputAt(1));
+ store->GetBlock()->RemoveInstruction(store);
+}
+
+void SsaBuilder::VisitInstruction(HInstruction* instruction) {
+ if (!instruction->NeedsEnvironment()) {
+ return;
+ }
+ HEnvironment* environment = new (GetGraph()->GetArena()) HEnvironment(
+ GetGraph()->GetArena(), current_locals_->Size());
+ environment->Populate(*current_locals_);
+ instruction->SetEnvironment(environment);
+}
+
+} // namespace art