Eliminate unnecessary deoptimization environments.

vm/flow_graph_allocator.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/flow_graph_allocator.h"
 
 #include "vm/bit_vector.h"
 #include "vm/intermediate_language.h"
 #include "vm/il_printer.h"
 #include "vm/flow_graph_builder.h"
@@ skipping 64 matching lines @@
 
   blocked_cpu_regs_[CTX] = true;
   if (TMP != kNoRegister) {
     blocked_cpu_regs_[TMP] = true;
   }
   blocked_cpu_regs_[SPREG] = true;
   blocked_cpu_regs_[FPREG] = true;
 }
 
 
+void FlowGraphAllocator::EliminateEnvironmentUses() {
+  for (intptr_t i = 0; i < block_order_.length(); ++i) {
+    BlockEntryInstr* block = block_order_[i];
+    for (ForwardInstructionIterator it(block); !it.Done(); it.Advance()) {
+      Instruction* current = it.Current();
+      if (!current->CanDeoptimize()) current->set_env(NULL);
+    }
+  }
+}
+
+
 void FlowGraphAllocator::ComputeInitialSets() {
   const intptr_t block_count = postorder_.length();
   for (intptr_t i = 0; i < block_count; i++) {
     BlockEntryInstr* block = postorder_[i];
 
     BitVector* kill = kill_[i];
     BitVector* live_in = live_in_[i];
 
     // Iterate backwards starting at the last instruction.
     for (BackwardInstructionIterator it(block); !it.Done(); it.Advance()) {
@@ skipping 1552 matching lines @@
       LiveRange* range = GetLiveRange(it.Current());
       for (intptr_t j = 0; j < block->PredecessorCount(); j++) {
         ConnectSplitSiblings(range, block->PredecessorAt(j), block);
       }
     }
   }
 }
 
 
 void FlowGraphAllocator::AllocateRegisters() {
+  EliminateEnvironmentUses();
+
   AnalyzeLiveness();
 
   BuildLiveRanges();
 
   if (FLAG_print_ssa_liveness) {
     DumpLiveness();
   }
 
   if (FLAG_trace_ssa_allocator) {
     PrintLiveRanges();
   }
 
   AllocateCPURegisters();
 
   ResolveControlFlow();
 
   GraphEntryInstr* entry = block_order_[0]->AsGraphEntry();
   ASSERT(entry != NULL);
   entry->set_spill_slot_count(spill_slots_.length());
 
   if (FLAG_trace_ssa_allocator) {
     OS::Print("-- ir after allocation -------------------------\n");
     FlowGraphPrinter printer(Function::Handle(), block_order_, true);
     printer.PrintBlocks();
   }
 }
 
 
 }  // namespace dart