Optimize functions containing try-catch.

runtime/vm/parser.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/parser.h"
 
 #include "lib/invocation_mirror.h"
 #include "vm/bigint_operations.h"
 #include "vm/class_finalizer.h"
 #include "vm/compiler.h"
@@ skipping 6003 matching lines @@
   //                     thrown.
   // :exception_var and :stacktrace_var get set with the exception object
   // and the stacktrace object when an exception is thrown.
   // These three implicit variables can never be captured variables.
   LocalVariable* context_var =
       current_block_->scope->LocalLookupVariable(Symbols::SavedTryContextVar());
   if (context_var == NULL) {
     context_var = new LocalVariable(TokenPos(),
                                     Symbols::SavedTryContextVar(),
                                     Type::ZoneHandle(Type::DynamicType()));
+    context_var->mark_as_always_live();

[Kevin Millikin (Google), 2013/05/08 11:42:00]

Eeek, what a hack (to set a bit here in the parser, so we can have special
handling in the optimizing compiler liveness analysis).

We should probably come up with a way to handle it within the system.  Maybe we
just need to expose the stores to the variables that are implicit in the catch
entry?

[Florian Schneider, 2013/05/08 17:10:55]

Removed. The conservative approximation in the variable liveness analysis makes
this flag obsolete.

     current_block_->scope->AddVariable(context_var);
   }
   LocalVariable* catch_excp_var =
       current_block_->scope->LocalLookupVariable(Symbols::ExceptionVar());
   if (catch_excp_var == NULL) {
     catch_excp_var = new LocalVariable(TokenPos(),
                                        Symbols::ExceptionVar(),
                                        Type::ZoneHandle(Type::DynamicType()));
+    catch_excp_var->mark_as_always_live();
     current_block_->scope->AddVariable(catch_excp_var);
   }
   LocalVariable* catch_trace_var =
       current_block_->scope->LocalLookupVariable(Symbols::StacktraceVar());
   if (catch_trace_var == NULL) {
     catch_trace_var = new LocalVariable(TokenPos(),
                                         Symbols::StacktraceVar(),
                                         Type::ZoneHandle(Type::DynamicType()));
+    catch_trace_var->mark_as_always_live();
     current_block_->scope->AddVariable(catch_trace_var);
   }
 
   const intptr_t try_pos = TokenPos();
   ConsumeToken();  // Consume the 'try'.
 
   SourceLabel* try_label = NULL;
   if (label_name != NULL) {
     try_label = SourceLabel::New(try_pos, label_name, SourceLabel::kStatement);
     OpenBlock();
@@ skipping 3904 matching lines @@
 void Parser::SkipQualIdent() {
   ASSERT(IsIdentifier());
   ConsumeToken();
   if (CurrentToken() == Token::kPERIOD) {
     ConsumeToken();  // Consume the kPERIOD token.
     ExpectIdentifier("identifier expected after '.'");
   }
 }
 
 }  // namespace dart