[Bug target/118137] New: riscv64: sub-word atomic OR with -1 affects surrounding bytes

[zsojka at seznam dot cz via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118137

            Bug ID: 118137
           Summary: riscv64: sub-word atomic OR with -1 affects
                    surrounding bytes
           Product: gcc
           Version: 15.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zsojka at seznam dot cz
  Target Milestone: ---
              Host: x86_64-pc-linux-gnu
            Target: riscv64-unknown-linux-gnu

Created attachment 59929
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=59929&action=edit
reduced testcase

$ riscv64-unknown-linux-gnu-gcc testcase.c -static -O[0123sg]
$ qemu-riscv64 -- ./a.out 
Aborted

When the functions are inlined at-O3:

# testcase.c:4:   __sync_fetch_and_or (x, 0xff);
        li      a3,-256         # tmp147,
        li      a4,-1           # tmp150,
        1:
        lr.w.aqrl       a2, 0(sp)       #, tmp143,
        and     a1, a2, a3      # tmp178, tmp143, tmp147
        or      a1, a1, a4      # tmp178, tmp150
        sc.w.rl a1, a1, 0(sp)   #, tmp178,

'a4' is not masked by 0xff

This might have been introduced by the patch mentioned in PR86005#c11

$ riscv64-unknown-linux-gnu-gcc -v
Using built-in specs.
COLLECT_GCC=/repo/gcc-trunk/binary-latest-riscv64/bin/riscv64-unknown-linux-gnu-gcc
COLLECT_LTO_WRAPPER=/repo/gcc-trunk/binary-trunk-20241218221935-r15-6361-g87f97ffba93a2d-checking-yes-rtl-df-extra-riscv64/bin/../libexec/gcc/riscv64-unknown-linux-gnu/15.0.0/lto-wrapper
Target: riscv64-unknown-linux-gnu
Configured with: /repo/gcc-trunk//configure --enable-languages=c,c++
--enable-valgrind-annotations --disable-nls --enable-checking=yes,rtl,df,extra
--with-cloog --with-ppl --with-isl --with-isa-spec=2.2
--with-sysroot=/usr/riscv64-unknown-linux-gnu --build=x86_64-pc-linux-gnu
--host=x86_64-pc-linux-gnu --target=riscv64-unknown-linux-gnu
--with-ld=/usr/bin/riscv64-unknown-linux-gnu-ld
--with-as=/usr/bin/riscv64-unknown-linux-gnu-as --disable-multilib
--enable-libsanitizer --disable-libstdcxx-pch
--prefix=/repo/gcc-trunk//binary-trunk-20241218221935-r15-6361-g87f97ffba93a2d-checking-yes-rtl-df-extra-riscv64
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 15.0.0 20241219 (experimental) (GCC)