Reapply "Initial implementation of sparse conditional constant propagation."

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"
 #include "vm/code_patcher.h"
@@ skipping 17 matching lines @@
 #include "vm/scanner.h"
 #include "vm/symbols.h"
 #include "vm/timer.h"
 
 namespace dart {
 
 DEFINE_FLAG(bool, disassemble, false, "Disassemble dart code.");
 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, cp, true,

[Ivan Posva, 2012/09/19 22:20:18]

This is a perfect example of a bad flag name. I am changing this to be something
that cannot be mistaken for copy.

+    "Do conditional constant propagation/unreachable code elimination.");
 DEFINE_FLAG(bool, cse, true, "Do common subexpression elimination.");

[Ivan Posva, 2012/09/19 22:20:18]

ditto

 DEFINE_FLAG(bool, licm, true, "Do loop invariant code motion.");

[Ivan Posva, 2012/09/19 22:20:18]

ditto

 DEFINE_FLAG(int, deoptimization_counter_threshold, 5,
     "How many times we allow deoptimization before we disallow"
     " certain optimizations");
 DEFINE_FLAG(bool, use_inlining, true, "Enable call-site inlining");
 DECLARE_FLAG(bool, print_flow_graph);
 
 
 // Compile a function. Should call only if the function has not been compiled.
 //   Arg0: function object.
 DEFINE_RUNTIME_ENTRY(CompileFunction, 1) {
@@ skipping 138 matching lines @@
         // Propagate sminess from CheckSmi to phis.
         optimizer.PropagateSminess();
 
         // Do optimizations that depend on the propagated type information.
         optimizer.OptimizeComputations();
 
         // Unbox doubles.
         flow_graph->ComputeUseLists();
         optimizer.SelectRepresentations();
 
-        if (FLAG_cse) {
-          flow_graph->ComputeUseLists();
-          DominatorBasedCSE::Optimize(flow_graph);
-        }
-        if (FLAG_licm) {
-          LICM::Optimize(flow_graph);
-        }
+        if (FLAG_cp || FLAG_cse) flow_graph->ComputeUseLists();
+        if (FLAG_cp) ConstantPropagator::Optimize(flow_graph);
+        if (FLAG_cse) DominatorBasedCSE::Optimize(flow_graph);
+        if (FLAG_licm) LICM::Optimize(flow_graph);
 
         // Perform register allocation on the SSA graph.
         FlowGraphAllocator allocator(*flow_graph);
         allocator.AllocateRegisters();
 
         if (FLAG_print_flow_graph) {
           OS::Print("After Optimizations:\n");
           FlowGraphPrinter printer(*flow_graph);
           printer.PrintBlocks();
         }
@@ skipping 345 matching lines @@
     result = 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