[Bug c/111317] New: RISC-V: Incorrect COST model for RVV conversions

[juzhe.zhong at rivai dot ai via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111317

            Bug ID: 111317
           Summary: RISC-V: Incorrect COST model for RVV conversions
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: juzhe.zhong at rivai dot ai
  Target Milestone: ---

#include <stdint.h>

void foo (int32_t *__restrict a, int64_t * __restrict b, int n)
{
    for (int i = 0; i < n; i++)
      b[i] = (int64_t)a[i];
}

--param=riscv-autovec-preference=scalable -O3 -fopt-info-vec-missed:
Failed to vectorize:

<source>:5:23: missed: couldn't vectorize loop
<source>:6:24: missed: not vectorized: no vectype for stmt: _4 = *_3;

However, try -fno-vect-cost-model.

We must adjust the COST model for RVV corretly.