On 10/4/23 08:53, Jeff Law wrote:
On 10/3/23 16:26, Patrick O'Neill wrote:
I vaugely recall some discussion about backporting the Ztso mappings
along with the RVWMO mappings. Now that the RVWMO mappings have been
backported for 13.3, is there interest in also backporting the Ztso
mappings?
Tested using for regressions using rv32gc/rv64gc glibc.
Jeff Law (1):
[RISCV][committed] Remove spurious newline in ztso sequence
Patrick O'Neill (2):
RISC-V: Add Ztso atomic mappings
RISC-V: Specify -mabi for ztso testcases
I recall discussing Ztso mappings, but not the final conclusion. I
think the final decision comes down to the motivation behind the changes.
If they're primarily optimized sequences utilizing the stronger
ordering guarantees from Ztso, then it's probably not a good candidate
for gcc-13. If the primary motivation is to make it easier to port
code from targets with stronger memory models (ie x86), then the Ztso
work is a reasonable candidate for backporting.
Jeff
Discussed during the GCC patchworks meeting.
The Ztso mappings are a subset of RVWMO fences/ordering constraints
(it's an optimization change) [1].
This backport also makes tip-of-tree sync.md files match gcc 13.3+ which
simplifies future atomic-related backports.
If in the future someone needs Ztso/there is a need to backport we can
re-evaluate this backport then.
Thanks
Patrick
[1] https://github.com/riscv-non-isa/riscv-elf-psabi-doc/pull/391
