Emilio G. Cota
8a6b28c7b5
target/arm: optimize indirect branches
Speed up indirect branches by jumping to the target if it is valid.
Softmmu measurements (see later commit for user-mode results):
Note: baseline (i.e. speedup == 1x) is QEMU v2.9.0.
- Impact on Boot time
| setup | ARM debian jessie boot+shutdown time | stddev |
|--------+--------------------------------------+--------|
| v2.9.0 | 8.84 | 0.07 |
| +cross | 8.85 | 0.03 |
| +jr | 8.83 | 0.06 |
- NBench, arm-softmmu (debian jessie guest). Host: Intel i7-4790K @ 4.00GHz
1.3x +-+-------------------------------------------------------------------------------------------------------------+-+
| |
| cross #### |
1.25x +cross+jr..........................................................#++#.........................................+-+
| #### # # |
| +++# # # # |
| +++ **** # # # |
1.2x +-+...................................####............*..*..#......#..#.........................................+-+
| **** # * * # # # #### |
| * * # * * # # # # # |
1.15x +-+................................*..*..#............*..*..#......#..#.....#..#................................+-+
| * * # * * # # # # # |
| * * # #### * * # # # # # |
| * * # # # * * # # # # # #### |
1.1x +-+................................*..*..#......#..#..*..*..#......#..#.....#..#.........................#..#...+-+
| * * # # # * * # # # # # # # |
| * * # # # * * # # # # # # # |
1.05x +-+..........................####..*..*..#......#..#..*..*..#......#..#.....#..#......+++............*****..#...+-+
| ***** # * * # # # * * # ***** # # # +++ | ****### * * # |
| *+++* # * * # # # * * # *+++* # **** # *****### * * # * * # |
| *****### +++#### * * # * * # ***** # * * # * * # * * # * | *++# * * # * * # |
1x +-++-+*+++*-+#++****++#++*+-+*++#+-*++*++#-+*+++*-+#++*++*++#++*+-+*++#+-*++*++#-+*+++*-+#++*++*++#++*+-+*++#+-++-+
| * * # * * # * * # * * # * * # * * # * * # * * # * * # * * # * * # |
| * * # * * # * * # * * # * * # * * # * * # * * # * * # * * # * * # |
0.95x +-+---*****###--****###--*****###--****###--*****###--****###--*****###--****###--*****###--****###--*****###---+-+
ASSIGNMENT BITFIELD FOURFP EMULATION HUFFMAN LU DECOMPOSITIONEURAL NNUMERIC SOSTRING SORT hmean
png: http://imgur.com/eOLmZNR
NB. 'cross' represents the previous commit.
Signed-off-by: Emilio G. Cota <cota@braap.org>
Message-Id: <1493263764-18657-8-git-send-email-cota@braap.org>
[rth: Replace gen_jr global variable with DISAS_EXIT state.]
Signed-off-by: Richard Henderson <rth@twiddle.net>
2017-06-05 09:25:42 -07:00
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