[Committed] riscv: relax splitter restrictions for creating pseudos

[Vineet Gupta <vineetg@rivosinc.com>]

On 4/18/23 11:36, Jeff Law via Gcc-patches wrote:
>
>
> On 4/18/23 08:36, Vineet Gupta wrote:
>> [partial addressing of PR/109279]
>>
>> RISCV splitters have restrictions to not create pesudos due to a combine
>> limitatation. And despite this being a split-during-combine limitation,
>> all split passes take the hit due to way define*_split are used in gcc.
>>
>> With the original combine issue being fixed 61bee6aed2 ("combine: Don't
>> record for UNDO_MODE pointers into regno_reg_rtx array [PR104985]")
>> the RV splitters can now be relaxed.
>>
>> This improves the codegen in general. e.g.
>>
>>     long long f(void) { return 0x0101010101010101ull; }
>>
>> Before
>>
>>     li    a0,0x01010000
>>     addi    a0,0x0101
>>     slli    a0,a0,16
>>     addi    a0,a0,0x0101
>>     slli    a0,a0,16
>>     addi    a0,a0,0x0101
>>     ret
>>
>> With patch
>>
>>     li    a5,0x01010000
>>     addi    a5,a5,0x0101
>>     mv    a0,a5
>>     slli    a5,a5,32
>>     add    a0,a5,a0
>>     ret
>>
>> This is testsuite clean, no regression w/ patch.
>>
>>                 ========= Summary of gcc testsuite =========
>>                              | # of unexpected case / # of unique 
>> unexpected case
>>                              |          gcc |          g++ | gfortran |
>>   rv64imafdc/  lp64d/ medlow |    2 /     2 |    1 /     1 | 6 /     1 |
>>     rv64imac/   lp64/ medlow |    3 /     3 |    1 /     1 | 43 /     
>> 8 |
>>   rv32imafdc/ ilp32d/ medlow |    1 /     1 |    3 /     2 | 6 /     1 |
>>     rv32imac/  ilp32/ medlow |    1 /     1 |    3 /     2 | 43 /     
>> 8 |
>>
>> This came up as part of IRC chat on PR/109279 and was suggested by
>> Andrew Pinski.
>>
>> Signed-off-by: Vineet Gupta <vineetg@rivosinc.com>
>> ---
>>   gcc/config/riscv/riscv-protos.h |  4 +--
>>   gcc/config/riscv/riscv.cc       | 46 +++++++++++++--------------------
>>   gcc/config/riscv/riscv.md       |  8 +++---
>>   3 files changed, 24 insertions(+), 34 deletions(-)
> This looks fine, except that you don't have a ChangeLog.

Pushed with Changelog and some additional info about qemu icount 
reductions with this patch

     500.perlbench_r 0       1235310737733   1231742384460   0.29%
                     1       744489708820    743515759958
                     2       714072106766    712875768625    0.17%
     502.gcc_r       0       197365353269    197178223030
                     1       235614445254    235465240341
                     2       226769189971    226604663947
                     3       188315686133    188123584015
                     4       289372107644    289187945424
     503.bwaves_r    0       326291538768    326291539697
                     1       515809487294    515809488863
                     2       401647004144    401647005463
                     3       488750661035    488750662484
     505.mcf_r       0       681926695281    681925418147
     507.cactuBSSN_r 0       3832240965352   3832226068734
     508.namd_r      0       1919838790866   1919832527292
     510.parest_r    0       3515999635520   3515878553435
     511.povray_r    0       3073889223775   3074758622749
     519.lbm_r       0       1194077464296   1194077464041
     520.omnetpp_r   0       1014144252460   1011530791131   0.26%
     521.wrf_r       0       3966715533120   3966265425092
     523.xalancbmk_r 0       1064914296949   1064506711802
     525.x264_r      0       509290028335    509258131632
                     1       2001424246635   2001677767181
                     2       1914660798226   1914869407575
     526.blender_r   0       1726083839515   1725974286174
     527.cam4_r      0       2336526136415   2333656336419
     531.deepsjeng_r 0       1689007489539   1686541299243   0.15%
     538.imagick_r   0       3247960667520   3247942048723
     541.leela_r     0       2072315300365   2070248271250
     544.nab_r       0       1527909091282   1527906483039
     548.exchange2_r 0       2086120304280   2086314757502
     549.fotonik3d_r 0       2261694058444   2261670330720
     554.roms_r      0       2640547903140   2640512733483
     557.xz_r        0       388736881767    386880875636    0.48%
                     1       959356981818    959993132842
                     2       547643353034    546374038310    0.23%
     997.specrand_fr 0       512881578       512599641
     999.specrand_ir 0       512881578       512599641