[Bug target/122869] New: risc-v loops miscompiled: loop with fault-only-first intrinsics never terminates when `-O0`

[rvismith1115 at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122869

            Bug ID: 122869
           Summary: risc-v loops miscompiled: loop with fault-only-first
                    intrinsics never terminates when `-O0`
           Product: gcc
           Version: 16.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rvismith1115 at gmail dot com
  Target Milestone: ---

Code: https://godbolt.org/z/q45Gh9bW5
```
#include <riscv_vector.h>
uint8_t a[1];
int16_t b[1];
int main() {
  for (size_t c = 0, avl = 1; avl > 0;) {
    size_t d(avl);
    vint16mf2_t g = __riscv_vle16ff_v_i16mf2(&b[c], &d, d);
    avl -= d; 
    // c += d; // Segmentation fault
  }
}
```

Command:
> riscv64-unknown-elf-g++ -O0 -march=rv64gcv_zvfh -mabi=lp64d -o a.out && $QEMU 
> a.out

Version:
> riscv64-unknown-elf-g++ --version
riscv64-unknown-elf-g++ () 16.0.0 20251123 (experimental)
Copyright (C) 2025 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Wrong assembly:
```
        sub     a5,a4,a5
        sd      a5,-24(s0)
.L2:
        ld      a5,-24(s0)
        bne     a5,zero,.L3
```
This means that the loop continues when `d != 0` not `avl != 0`.