Re: [gcc13 backport] RISCV: Inline subword atomic ops

[Patrick O'Neill <patrick@rivosinc.com>]

Ping.

On 5/3/23 10:19, Patrick O'Neill wrote:

> RISC-V has no support for subword atomic operations; code currently
> generates libatomic library calls.
>
> This patch changes the default behavior to inline subword atomic calls
> (using the same logic as the existing library call).
> Behavior can be specified using the -minline-atomics and
> -mno-inline-atomics command line flags.
>
> gcc/libgcc/config/riscv/atomic.c has the same logic implemented in asm.
> This will need to stay for backwards compatibility and the
> -mno-inline-atomics flag.
>
> 2023-05-03 Patrick O'Neill <patrick@rivosinc.com>
>
> gcc/ChangeLog:
> 	PR target/104338
> 	* config/riscv/riscv-protos.h: Add helper function stubs.
> 	* config/riscv/riscv.cc: Add helper functions for subword masking.
> 	* config/riscv/riscv.opt: Add command-line flags
> 	-minline-atomics and -mno-inline-atomics.
> 	* config/riscv/sync.md: Add masking logic and inline asm for
> 	fetch_and_op, fetch_and_nand, CAS, and exchange ops.
> 	* doc/invoke.texi: Add blurb regarding new command-line flags
> 	-minline-atomics and -mno-inline-atomics.
>
> libgcc/ChangeLog:
> 	PR target/104338
> 	* config/riscv/atomic.c: Add reference to duplicate logic.
>
> gcc/testsuite/ChangeLog:
> 	PR target/104338
> 	* gcc.target/riscv/inline-atomics-1.c: New test.
> 	* gcc.target/riscv/inline-atomics-2.c: New test.
> 	* gcc.target/riscv/inline-atomics-3.c: New test.
> 	* gcc.target/riscv/inline-atomics-4.c: New test.
> 	* gcc.target/riscv/inline-atomics-5.c: New test.
> 	* gcc.target/riscv/inline-atomics-6.c: New test.
> 	* gcc.target/riscv/inline-atomics-7.c: New test.
> 	* gcc.target/riscv/inline-atomics-8.c: New test.
>
> Signed-off-by: Patrick O'Neill <patrick@rivosinc.com>
> Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
> ---
> This backport includes all the subsequent fixes.
> Squashed GCC-14 commits:
>    https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=f797260adaf52bee0ec0e16190bbefbe1bfc3692
>    https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=2a26872984c109a98d0ad733b0c68c3e1648ec86
>
> Fixed ChangeLog:
>    https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=9cfdd5af3efd4a7e52ae7f97f55effc436c0cf45
> ---
> The GCC-14 build error[1] was caused by the subsequent A.6 mappings
> change[2], not the inline atomics change (this backport).
> [1] https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=4bd434fbfc7865961a8e10d7e9601b28765ce7be
> [2] https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=bff7c77386447936dd614ebc7086b826c99c6642
> ---
> There is a related follow-on GCC-14 patch to config/riscv/linux:
>    https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=203f3060dd363361b172f7295f42bb6bf5ac0b3b
>
> The changes from that patch are not included in this backport.
> ---