target/i386: optimize indirect branches
Speed up indirect branches by jumping to the target if it is valid. Softmmu measurements (see later commit for user-mode numbers): Note: baseline (i.e. speedup == 1x) is QEMU v2.9.0. - SPECint06 (test set), x86_64-softmmu (Ubuntu 16.04 guest). Host: Intel i7-4790K @ 4.00GHz 2.4x +-+--------------------------------------------------------------------------------------------------------------+-+ | | | cross | 2.2x +cross+jr..........................................................................+++...........................+-+ | | | | +++ | | 2x +-+..............................................................................|..|............................+-+ | | | | | | | | 1.8x +-+..............................................................................|####...........................+-+ | |# |# | | **** |# | 1.6x +-+............................................................................*.|*.|#...........................+-+ | * |* |# | | * |* |# | 1.4x +-+.......................................................................+++..*.|*.|#...........................+-+ | ++++++ #### * |*++# +++ | | +++ | | #++# *++* # +++ | | 1.2x +-+......................###.....####....+++............|..|...........****..#.*..*..#....####...|.###.....####..+-+ | +++ **** # **** # #### ***### *++* # * * # #++# ****|# +++#++# | | ****### +++ *++* # *++* # ++# # #### *|* |# +++ * * # * * # *** # *| *|# **** # | 1x +-++-*++*++#++***###++*++*+#++*+-*++#+****++#++***++#+-*+*++#-+****##++*++*-+#+*++*-+#++*+*++#++*-+*+#++*++*++#-++-+ | * * # * * # * * # * * # * * # * * # *|* |# *++* # * * # * * # * * # * * # * * # | | * * # * * # * * # * * # * * # * * # *+*++# * * # * * # * * # * * # * * # * * # | 0.8x +-+--****###--***###--****##--****###-****###--***###--***###--****##--****###-****###--***###--****##--****###--+-+ astar bzip2 gcc gobmk h264ref hmmlibquantum mcf omnetpperlbench sjengxalancbmk hmean png: http://imgur.com/DU36YFU NB. 'cross' represents the previous commit. Reviewed-by: NAlex Bennée <alex.bennee@linaro.org> Reviewed-by: NRichard Henderson <rth@twiddle.net> Signed-off-by: NEmilio G. Cota <cota@braap.org> Message-Id: <1493263764-18657-11-git-send-email-cota@braap.org> Signed-off-by: NRichard Henderson <rth@twiddle.net>
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