commit 7a01dc2107d4255b445c32867d15d45fcebb3acd
author Vladimir Marko <vmarko@google.com> Fri Jan 02 17:00:44 2015 +0000
committer Vladimir Marko <vmarko@google.com> Tue Feb 17 21:06:27 2015 +0000
tree 5f25d4a2889e6fbcb5119484f2b0b6a4253f9b00
parent bce889940f10319bf67bdc5630c84dd7f6e5c246

Dead code elimination based on GVN results.

Change-Id: I5b77411a8f088f0b561da14b123cf6b0501c9db5

compiler/dex/mir_optimization.cc

diff --git a/compiler/dex/mir_optimization.cc b/compiler/dex/mir_optimization.cc
index dac0210..2f547ea 100644
--- a/compiler/dex/mir_optimization.cc
+++ b/compiler/dex/mir_optimization.cc
@@ -21,6 +21,7 @@
 #include "driver/compiler_driver.h"
 #include "driver/dex_compilation_unit.h"
 #include "global_value_numbering.h"
+#include "gvn_dead_code_elimination.h"
 #include "local_value_numbering.h"
 #include "mir_field_info.h"
 #include "quick/dex_file_method_inliner.h"
@@ -1333,9 +1334,9 @@
 
   DCHECK(temp_scoped_alloc_ == nullptr);
   temp_scoped_alloc_.reset(ScopedArenaAllocator::Create(&cu_->arena_stack));
-  temp_.gvn.ifield_ids_ =
+  temp_.gvn.ifield_ids =
       GlobalValueNumbering::PrepareGvnFieldIds(temp_scoped_alloc_.get(), ifield_lowering_infos_);
-  temp_.gvn.sfield_ids_ =
+  temp_.gvn.sfield_ids =
       GlobalValueNumbering::PrepareGvnFieldIds(temp_scoped_alloc_.get(), sfield_lowering_infos_);
   DCHECK(temp_.gvn.gvn == nullptr);
   temp_.gvn.gvn = new (temp_scoped_alloc_.get()) GlobalValueNumbering(
@@ -1359,8 +1360,8 @@
   // Perform modifications.
   DCHECK(temp_.gvn.gvn != nullptr);
   if (temp_.gvn.gvn->Good()) {
+    temp_.gvn.gvn->StartPostProcessing();
     if (max_nested_loops_ != 0u) {
-      temp_.gvn.gvn->StartPostProcessing();
       TopologicalSortIterator iter(this);
       for (BasicBlock* bb = iter.Next(); bb != nullptr; bb = iter.Next()) {
         ScopedArenaAllocator allocator(&cu_->arena_stack);  // Reclaim memory after each LVN.
@@ -1378,12 +1379,45 @@
     cu_->disable_opt |= (1u << kLocalValueNumbering);
   } else {
     LOG(WARNING) << "GVN failed for " << PrettyMethod(cu_->method_idx, *cu_->dex_file);
+    cu_->disable_opt |= (1u << kGvnDeadCodeElimination);
   }
 
+  if ((cu_->disable_opt & (1 << kGvnDeadCodeElimination)) != 0) {
+    EliminateDeadCodeEnd();
+  }  // else preserve GVN data for CSE.
+}
+
+bool MIRGraph::EliminateDeadCodeGate() {
+  if ((cu_->disable_opt & (1 << kGvnDeadCodeElimination)) != 0) {
+    return false;
+  }
+  DCHECK(temp_scoped_alloc_ != nullptr);
+  temp_.gvn.dce = new (temp_scoped_alloc_.get()) GvnDeadCodeElimination(temp_.gvn.gvn,
+                                                                        temp_scoped_alloc_.get());
+  return true;
+}
+
+bool MIRGraph::EliminateDeadCode(BasicBlock* bb) {
+  DCHECK(temp_scoped_alloc_ != nullptr);
+  DCHECK(temp_.gvn.gvn != nullptr);
+  if (bb->block_type != kDalvikByteCode) {
+    return false;
+  }
+  DCHECK(temp_.gvn.dce != nullptr);
+  temp_.gvn.dce->Apply(bb);
+  return false;  // No need to repeat.
+}
+
+void MIRGraph::EliminateDeadCodeEnd() {
+  DCHECK_EQ(temp_.gvn.dce != nullptr, (cu_->disable_opt & (1 << kGvnDeadCodeElimination)) == 0);
+  if (temp_.gvn.dce != nullptr) {
+    delete temp_.gvn.dce;
+    temp_.gvn.dce = nullptr;
+  }
   delete temp_.gvn.gvn;
   temp_.gvn.gvn = nullptr;
-  temp_.gvn.ifield_ids_ = nullptr;
-  temp_.gvn.sfield_ids_ = nullptr;
+  temp_.gvn.ifield_ids = nullptr;
+  temp_.gvn.sfield_ids = nullptr;
   DCHECK(temp_scoped_alloc_ != nullptr);
   temp_scoped_alloc_.reset();
 }
@@ -1553,9 +1587,9 @@
 void MIRGraph::BasicBlockOptimizationStart() {
   if ((cu_->disable_opt & (1 << kLocalValueNumbering)) == 0) {
     temp_scoped_alloc_.reset(ScopedArenaAllocator::Create(&cu_->arena_stack));
-    temp_.gvn.ifield_ids_ =
+    temp_.gvn.ifield_ids =
         GlobalValueNumbering::PrepareGvnFieldIds(temp_scoped_alloc_.get(), ifield_lowering_infos_);
-    temp_.gvn.sfield_ids_ =
+    temp_.gvn.sfield_ids =
         GlobalValueNumbering::PrepareGvnFieldIds(temp_scoped_alloc_.get(), sfield_lowering_infos_);
   }
 }
@@ -1581,8 +1615,8 @@
 
 void MIRGraph::BasicBlockOptimizationEnd() {
   // Clean up after LVN.
-  temp_.gvn.ifield_ids_ = nullptr;
-  temp_.gvn.sfield_ids_ = nullptr;
+  temp_.gvn.ifield_ids = nullptr;
+  temp_.gvn.sfield_ids = nullptr;
   temp_scoped_alloc_.reset();
 }
 
@@ -1684,7 +1718,7 @@
   temp_.sce.inliner = nullptr;
 }
 
-bool MIRGraph::CanThrow(MIR* mir) {
+bool MIRGraph::CanThrow(MIR* mir) const {
   if ((mir->dalvikInsn.FlagsOf() & Instruction::kThrow) == 0) {
     return false;
   }
@@ -1718,7 +1752,6 @@
     // Non-throwing only if range check has been eliminated.
     return ((opt_flags & MIR_IGNORE_RANGE_CHECK) == 0);
   } else if (mir->dalvikInsn.opcode == Instruction::ARRAY_LENGTH ||
-      mir->dalvikInsn.opcode == Instruction::FILL_ARRAY_DATA ||
       static_cast<int>(mir->dalvikInsn.opcode) == kMirOpNullCheck) {
     // No more checks for these (null check was processed above).
     return false;