[Boost-commit] svn:boost r75938 - trunk/tools/build/v2/engine

Subject: [Boost-commit] svn:boost r75938 - trunk/tools/build/v2/engine
From: steven_at_[hidden]
Date: 2011-12-14 13:46:51

Author: steven_watanabe
Date: 2011-12-14 13:46:50 EST (Wed, 14 Dec 2011)
New Revision: 75938
URL: http://svn.boost.org/trac/boost/changeset/75938

Log:
Optimize out the extra PUSH_EMPTY/APPEND when evaluating a list.  Reduces the number of instructions executed by about 25%.  About a 3-5% improvement in overall runtime.
Text files modified: 
   trunk/tools/build/v2/engine/function.c |     7 +++++--                                 
   1 files changed, 5 insertions(+), 2 deletions(-)

Modified: trunk/tools/build/v2/engine/function.c
==============================================================================
--- trunk/tools/build/v2/engine/function.c	(original)
+++ trunk/tools/build/v2/engine/function.c	2011-12-14 13:46:50 EST (Wed, 14 Dec 2011)
@@ -2108,8 +2108,11 @@
             compile_emit( c, INSTR_PUSH_APPEND, 0 );
             parse = parse->left;
         }
-        compile_parse( parse->left, c, RESULT_STACK );
-        compile_emit( c, INSTR_PUSH_APPEND, 0 );
+        if ( parse->left->type != PARSE_NULL )
+        {
+            compile_parse( parse->left, c, RESULT_STACK );
+            compile_emit( c, INSTR_PUSH_APPEND, 0 );
+        }
         adjust_result( c, RESULT_STACK, result_location );
     }
     else if ( parse->type == PARSE_EVAL )