Re: [PATCH] riscv: relax splitter restrictions for creating pseudos

[Jeff Law <jeffreyalaw@gmail.com>]

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.  It also looks 
like you don't have write permissions in the repository (not listed in 
the MAINTAINERS file).  We might as well fix the latter. You can then 
add a ChangeLog and push this yourself.

Start with this form:

https://sourceware.org/cgi-bin/pdw/ps_form.cgi

Go ahead and list me as approving your request.

Thanks,
jeff