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Review request for Default. Description ------- gcc: Enable Link-Time Optimization for gcc >= 4.6 This patch adds a scons flag to indicate that compilation and linking should be done using LTO. No check is used to guarantee that the linked supports LTO, so the user has to ensure that binutils GNU ld >= 2.21 or the gold linker is available. The same number of jobs is used for the parallel phase of LTO as the jobs specified on the scons command line, using the -flto=n flag that was introduced with gcc 4.6. Currently the LTO option is only useful for gcc >= 4.6, due to the limited support on clang and earlier versions of gcc. The intention is to also add support for clang once the LTO integration matures. The use of LTO is independent of the target, i.e. debug, opt, fast and pro, although opt and fast are the most likely candidates. The compilation and linking (wall) time is increased by almost 50% for the observed cases, and simulation performance improves by roughly 15%, i.e. for long regression runs it really helps. Diffs ----- SConstruct 7f36d4436074 src/SConscript 7f36d4436074 Diff: http://reviews.gem5.org/r/1171/diff/ Testing ------- util/regress all passing (disregarding t1000 and eio) Thanks, Andreas Hansson _______________________________________________ gem5-dev mailing list [email protected] http://m5sim.org/mailman/listinfo/gem5-dev
