[turbofan] Single entry into deferred regions

src/compiler/register-allocator.cc

Index: src/compiler/register-allocator.cc
diff --git a/src/compiler/register-allocator.cc b/src/compiler/register-allocator.cc
index 0368380b8cdf93fb4ea8976ad35e6ea07247559e..81775679968ac6fe584f2a9ee75c130bee089cec 100644
--- a/src/compiler/register-allocator.cc
+++ b/src/compiler/register-allocator.cc
@@ -3411,6 +3411,8 @@ void LiveRangeConnector::ResolveControlFlow(Zone* local_zone) {
     BitVector* live = live_in_sets[block->rpo_number().ToInt()];
     BitVector::Iterator iterator(live);
     while (!iterator.Done()) {
+      int vreg = iterator.Current();

[Benedikt Meurer, 2016/04/23 12:04:49]

Stale change?

[Mircea Trofin, 2016/04/23 16:27:07]

Ya, I meant to use vreg in the finder.ArrayFor call below. For some reason, the
debugger (or at least lldb) 
won't show the value of iterator.Current() (or its underlying field). Small
change, and helps with debuggability.

+      USE(vreg);
       LiveRangeBoundArray* array = finder.ArrayFor(iterator.Current());
       for (const RpoNumber& pred : block->predecessors()) {
         FindResult result;
@@ -3628,6 +3630,7 @@ void LiveRangeConnector::CommitSpillsInDeferredBlocks(
     worklist.push(iterator.Current());
   }
 
+  ZoneSet<std::pair<RpoNumber, int>> done_moves(temp_zone);
   // Seek the deferred blocks that dominate locations requiring spill operands,
   // and spill there. We only need to spill at the start of such blocks.
   BitVector done_blocks(
@@ -3654,10 +3657,15 @@ void LiveRangeConnector::CommitSpillsInDeferredBlocks(
 
         InstructionOperand pred_op = bound->range_->GetAssignedOperand();
 
-        data()->AddGapMove(spill_block->first_instruction_index(),
-                           Instruction::GapPosition::START, pred_op,
-                           spill_operand);
-        spill_block->mark_needs_frame();
+        RpoNumber spill_block_number = spill_block->rpo_number();
+        if (done_moves.find(std::make_pair(
+                spill_block_number, range->vreg())) == done_moves.end()) {
+          data()->AddGapMove(spill_block->first_instruction_index(),
+                             Instruction::GapPosition::START, pred_op,
+                             spill_operand);
+          done_moves.insert(std::make_pair(spill_block_number, range->vreg()));
+          spill_block->mark_needs_frame();
+        }
       }
     }
   }