On 01/16/2014 02:18 PM, Clinton Stimpson wrote: > On Thursday, January 16, 2014 11:49:58 AM Ben Boeckel wrote: >> On Thu, Jan 16, 2014 at 08:41:58 -0700, Clinton Stimpson wrote: >>> I'm surprised how this small change added a 20% slowdown. >>> -set_property(DIRECTORY APPEND PROPERTY COMPILE_DEFINITIONS_DEBUG >>> QT_DEBUG) >>> +set_property(DIRECTORY APPEND PROPERTY COMPILE_DEFINITIONS $<$<NOT: >>> $<CONFIG:Debug>>:QT_NO_DEBUG>) [snip] > However, the profile of my test case showed that the time increase is in the > parser (yylex). Perhaps someone else can look further into this.
The addition of '$' to the value to causes the fast-path in cmMakefile::ExpandVariablesInString to be skipped: http://cmake.org/gitweb?p=cmake.git;a=blob;f=Source/cmMakefile.cxx;hb=v2.8.12.1#l2535 if ( source.empty() || source.find_first_of("$@\\") == source.npos) { return source.c_str(); } Instead full expansion using cmCommandArgumentParserHelper occurs which is much slower. The latter code path is ripe for optimization by re-implementing it without flex/bison generators. Unfortunately the current logic has so many idiosyncrasies that a re-implementation will almost certainly introduce subtle behavior changes. -Brad -- Powered by www.kitware.com Visit other Kitware open-source projects at http://www.kitware.com/opensource/opensource.html Please keep messages on-topic and check the CMake FAQ at: http://www.cmake.org/Wiki/CMake_FAQ Follow this link to subscribe/unsubscribe: http://public.kitware.com/cgi-bin/mailman/listinfo/cmake-developers
