Implement a variation of scalar replacement for non-escaping allocations.

runtime/vm/compiler.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/compiler.h"
 
 #include "vm/assembler.h"
 
 #include "vm/ast_printer.h"
 #include "vm/code_generator.h"
@@ skipping 27 matching lines @@
 DEFINE_FLAG(bool, disassemble_optimized, false, "Disassemble optimized code.");
 DEFINE_FLAG(bool, trace_bailout, false, "Print bailout from ssa compiler.");
 DEFINE_FLAG(bool, trace_compiler, false, "Trace compiler operations.");
 DEFINE_FLAG(bool, constant_propagation, true,
     "Do conditional constant propagation/unreachable code elimination.");
 DEFINE_FLAG(bool, common_subexpression_elimination, true,
     "Do common subexpression elimination.");
 DEFINE_FLAG(bool, loop_invariant_code_motion, true,
     "Do loop invariant code motion.");
 DEFINE_FLAG(bool, propagate_types, true, "Do static type propagation.");
+DEFINE_FLAG(bool, allocation_sinking, true,
+    "attempt to sink temporary allocations to side exits");
 DEFINE_FLAG(int, deoptimization_counter_threshold, 16,
     "How many times we allow deoptimization before we disallow optimization.");
 DEFINE_FLAG(bool, use_inlining, true, "Enable call-site inlining");
 DEFINE_FLAG(bool, range_analysis, true, "Enable range analysis");
 DEFINE_FLAG(bool, verify_compiler, false,
     "Enable compiler verification assertions");
 DECLARE_FLAG(bool, print_flow_graph);
 DECLARE_FLAG(bool, print_flow_graph_optimized);
 DECLARE_FLAG(bool, trace_failed_optimization_attempts);
 
@@ skipping 227 matching lines @@
       }
 
       // The final canonicalization pass before the code generation.
       if (FLAG_propagate_types) {
         // Recompute types after code movement was done to ensure correct
         // reaching types for hoisted values.
         FlowGraphTypePropagator propagator(flow_graph);
         propagator.Propagate();
         DEBUG_ASSERT(flow_graph->VerifyUseLists());
       }
+
+      // Detach environments from the instructions that can't deoptimized.

[srdjan, 2013/05/07 23:11:45]

s/deoptimized/deoptimize/

[Vyacheslav Egorov (Google), 2013/05/07 23:28:21]

Done.

+      // Do it before we attempt to perform allocation sinking to minimize
+      // amount of materializations it has to perform.
+      optimizer.EliminateEnvironments();
+
+      // Attempt to sink allocations of temporary non-escaping objects to
+      // the deoptimization path.
+      AllocationSinking* sinking = NULL;
+      if (FLAG_allocation_sinking) {
+        sinking = new AllocationSinking(flow_graph);
+        sinking->Optimize();
+      }
+
       if (optimizer.Canonicalize()) {
         // To fully remove redundant boxing (e.g. BoxDouble used only in
         // environments and UnboxDouble instructions) instruction we
         // first need to replace all their uses and then fold them away.
         // For now we just repeat Canonicalize twice to do that.
         // TODO(vegorov): implement a separate representation folding pass.
         optimizer.Canonicalize();
       }
       DEBUG_ASSERT(flow_graph->VerifyUseLists());
 
+      if (sinking != NULL) {
+        // Remove all MaterializeObject instructions inserted by allocation
+        // sinking from the flow graph and let them float on the side referenced
+        // only from environments. Register allocator will consider them
+        // as part of a deoptimization environment.
+        sinking->DetachMaterializations();
+      }
+
       // Perform register allocation on the SSA graph.
       FlowGraphAllocator allocator(*flow_graph);
       allocator.AllocateRegisters();
 
       if (FLAG_print_flow_graph || FLAG_print_flow_graph_optimized) {
         FlowGraphPrinter::PrintGraph("After Optimizations", flow_graph);
       }
     }
 
     Assembler assembler;
@@ skipping 394 matching lines @@
       Object::Handle(isolate->object_store()->sticky_error());
     isolate->object_store()->clear_sticky_error();
     isolate->set_long_jump_base(base);
     return result.raw();
   }
   UNREACHABLE();
   return Object::null();
 }
 
 }  // namespace dart