Rewrite BitVector index iterator.

The BitVector::Iterator was not iterating over the bits but
rather over indexes of the set bits. Therefore, we rename it
to IndexIterator and provide a BitVector::Indexes() to get
a container-style interface with begin() and end() for range
based for loops.

Also, simplify InsertPhiNodes where the tmp_blocks isn't
needed since the phi_nodes and input_blocks cannot lose any
blocks in subsequent iterations, so we can do the Union()
directly in those bit vectors and we need to repeat the loop
only if we have new input_blocks, rather than on phi_nodes
change. And move the temporary bit vectors to scoped arena.

Change-Id: I6cb87a2f60724eeef67c6aaa34b36ed5acde6d43

1 files changed, 7 insertions, 31 deletions

diff --git a/compiler/optimizing/ssa_liveness_analysis.cc b/compiler/optimizing/ssa_liveness_analysis.cc
index 0f16ad2..938c5ec 100644
--- a/compiler/optimizing/ssa_liveness_analysis.cc
+++ b/compiler/optimizing/ssa_liveness_analysis.cc
@@ -174,28 +174,6 @@ void SsaLivenessAnalysis::ComputeLiveness() {
   ComputeLiveInAndLiveOutSets();
 }
 
-class InstructionBitVectorIterator : public ValueObject {
- public:
-  InstructionBitVectorIterator(const BitVector& vector,
-                               const GrowableArray<HInstruction*>& instructions)
-        : instructions_(instructions),
-          iterator_(BitVector::Iterator(&vector)),
-          current_bit_index_(iterator_.Next()) {}
-
-  bool Done() const { return current_bit_index_ == -1; }
-  HInstruction* Current() const { return instructions_.Get(current_bit_index_); }
-  void Advance() {
-    current_bit_index_ = iterator_.Next();
-  }
-
- private:
-  const GrowableArray<HInstruction*> instructions_;
-  BitVector::Iterator iterator_;
-  int32_t current_bit_index_;
-
-  DISALLOW_COPY_AND_ASSIGN(InstructionBitVectorIterator);
-};
-
 void SsaLivenessAnalysis::ComputeLiveRanges() {
   // Do a post order visit, adding inputs of instructions live in the block where
   // that instruction is defined, and killing instructions that are being visited.
@@ -218,10 +196,9 @@ void SsaLivenessAnalysis::ComputeLiveRanges() {
     }
 
     // Add a range that covers this block to all instructions live_in because of successors.
-    for (InstructionBitVectorIterator it(*live_in, instructions_from_ssa_index_);
-         !it.Done();
-         it.Advance()) {
-      it.Current()->GetLiveInterval()->AddRange(block->GetLifetimeStart(), block->GetLifetimeEnd());
+    for (uint32_t idx : live_in->Indexes()) {
+      HInstruction* current = instructions_from_ssa_index_.Get(idx);
+      current->GetLiveInterval()->AddRange(block->GetLifetimeStart(), block->GetLifetimeEnd());
     }
 
     for (HBackwardInstructionIterator it(block->GetInstructions()); !it.Done(); it.Advance()) {
@@ -268,11 +245,10 @@ void SsaLivenessAnalysis::ComputeLiveRanges() {
       HBasicBlock* back_edge = block->GetLoopInformation()->GetBackEdges().Get(0);
       // For all live_in instructions at the loop header, we need to create a range
       // that covers the full loop.
-      for (InstructionBitVectorIterator it(*live_in, instructions_from_ssa_index_);
-           !it.Done();
-           it.Advance()) {
-        it.Current()->GetLiveInterval()->AddLoopRange(block->GetLifetimeStart(),
-                                                      back_edge->GetLifetimeEnd());
+      for (uint32_t idx : live_in->Indexes()) {
+        HInstruction* current = instructions_from_ssa_index_.Get(idx);
+        current->GetLiveInterval()->AddLoopRange(block->GetLifetimeStart(),
+                                                 back_edge->GetLifetimeEnd());
       }
     }
   }