MIPS32R2: Share address computation

For array accesses the element address has the following structure:
Address = CONST_OFFSET + base_addr + index << ELEM_SHIFT

The address part (index << ELEM_SHIFT) can be shared across array
accesses with the same data type and index.

For example, in the following loop 5 accesses can share address
computation:

void foo(int[] a, int[] b, int[] c) {
  for (i...) {
    a[i] = a[i] + 5;
    b[i] = b[i] + c[i];
  }
}

Test: test-art-host, test-art-target
Change-Id: Id09fa782934aad4ee47669275e7e1a4d7d23b0fa

1 files changed, 142 insertions, 0 deletions

diff --git a/compiler/optimizing/instruction_simplifier_mips.cc b/compiler/optimizing/instruction_simplifier_mips.cc
new file mode 100644
index 0000000000..4bf1bfb9f3
--- /dev/null
+++ b/compiler/optimizing/instruction_simplifier_mips.cc
@@ -0,0 +1,142 @@
+/*
+ * Copyright (C) 2017 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 "instruction_simplifier_mips.h"
+
+#include "arch/mips/instruction_set_features_mips.h"
+#include "mirror/array-inl.h"
+
+namespace art {
+namespace mips {
+
+class InstructionSimplifierMipsVisitor : public HGraphVisitor {
+ public:
+  InstructionSimplifierMipsVisitor(HGraph* graph,
+                                   CodeGenerator* codegen,
+                                   OptimizingCompilerStats* stats)
+      : HGraphVisitor(graph),
+        stats_(stats),
+        codegen_(down_cast<CodeGeneratorMIPS*>(codegen)) {}
+
+ private:
+  void RecordSimplification() {
+    if (stats_ != nullptr) {
+      stats_->RecordStat(kInstructionSimplificationsArch);
+    }
+  }
+
+  bool TryExtractArrayAccessIndex(HInstruction* access,
+                                  HInstruction* index,
+                                  DataType::Type packed_type);
+  void VisitArrayGet(HArrayGet* instruction) OVERRIDE;
+  void VisitArraySet(HArraySet* instruction) OVERRIDE;
+
+  OptimizingCompilerStats* stats_;
+  CodeGeneratorMIPS* codegen_;
+};
+
+bool InstructionSimplifierMipsVisitor::TryExtractArrayAccessIndex(HInstruction* access,
+                                                                  HInstruction* index,
+                                                                  DataType::Type packed_type) {
+  if (codegen_->GetInstructionSetFeatures().IsR6() ||
+      codegen_->GetInstructionSetFeatures().HasMsa()) {
+    return false;
+  }
+  if (index->IsConstant() ||
+      (index->IsBoundsCheck() && index->AsBoundsCheck()->GetIndex()->IsConstant())) {
+    // If index is constant the whole address calculation often can be done by load/store
+    // instructions themselves.
+    // TODO: Treat the case with non-embeddable constants.
+    return false;
+  }
+
+  if (packed_type != DataType::Type::kInt16 && packed_type != DataType::Type::kUint16 &&
+      packed_type != DataType::Type::kInt32 && packed_type != DataType::Type::kInt64 &&
+      packed_type != DataType::Type::kFloat32 && packed_type != DataType::Type::kFloat64) {
+    return false;
+  }
+
+  if (access->IsArrayGet() && access->AsArrayGet()->IsStringCharAt()) {
+    return false;
+  }
+
+  HGraph* graph = access->GetBlock()->GetGraph();
+  ArenaAllocator* arena = graph->GetArena();
+  size_t component_shift = DataType::SizeShift(packed_type);
+
+  bool is_extracting_beneficial = false;
+  // It is beneficial to extract index intermediate address only if there are at least 2 users.
+  for (const HUseListNode<HInstruction*>& use : index->GetUses()) {
+    HInstruction* user = use.GetUser();
+    if (user->IsArrayGet() && user != access && !user->AsArrayGet()->IsStringCharAt()) {
+      HArrayGet* another_access = user->AsArrayGet();
+      DataType::Type another_packed_type = another_access->GetType();
+      size_t another_component_shift = DataType::SizeShift(another_packed_type);
+      if (another_component_shift == component_shift) {
+        is_extracting_beneficial = true;
+        break;
+      }
+    } else if (user->IsArraySet() && user != access) {
+      HArraySet* another_access = user->AsArraySet();
+      DataType::Type another_packed_type = another_access->GetType();
+      size_t another_component_shift = DataType::SizeShift(another_packed_type);
+      if (another_component_shift == component_shift) {
+        is_extracting_beneficial = true;
+        break;
+      }
+    } else if (user->IsIntermediateArrayAddressIndex()) {
+      HIntermediateArrayAddressIndex* another_access = user->AsIntermediateArrayAddressIndex();
+      size_t another_component_shift = another_access->GetShift()->AsIntConstant()->GetValue();
+      if (another_component_shift == component_shift) {
+        is_extracting_beneficial = true;
+        break;
+      }
+    }
+  }
+
+  if (!is_extracting_beneficial) {
+    return false;
+  }
+
+  HIntConstant* shift = graph->GetIntConstant(component_shift);
+  HIntermediateArrayAddressIndex* address =
+      new (arena) HIntermediateArrayAddressIndex(index, shift, kNoDexPc);
+  access->GetBlock()->InsertInstructionBefore(address, access);
+  access->ReplaceInput(address, 1);
+  return true;
+}
+
+void InstructionSimplifierMipsVisitor::VisitArrayGet(HArrayGet* instruction) {
+  DataType::Type packed_type = instruction->GetType();
+  if (TryExtractArrayAccessIndex(instruction, instruction->GetIndex(), packed_type)) {
+    RecordSimplification();
+  }
+}
+
+void InstructionSimplifierMipsVisitor::VisitArraySet(HArraySet* instruction) {
+  DataType::Type packed_type = instruction->GetComponentType();
+  if (TryExtractArrayAccessIndex(instruction, instruction->GetIndex(), packed_type)) {
+    RecordSimplification();
+  }
+}
+
+void InstructionSimplifierMips::Run() {
+  InstructionSimplifierMipsVisitor visitor(graph_, codegen_, stats_);
+  visitor.VisitReversePostOrder();
+}
+
+}  // namespace mips
+}  // namespace art