[Bug c/111594] New: RISC-V: Failed to fold VEC_COND_EXPR and COND_LEN_ADD

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111594

            Bug ID: 111594
           Summary: RISC-V: Failed to fold VEC_COND_EXPR and COND_LEN_ADD
           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: ---

Consider this following case:


#include <stdint.h>

void single_loop_with_if_condition(uint64_t * restrict a, 
uint64_t * restrict b,
int loop_size) {
  uint64_t result = 0;

  for (int i = 0; i < loop_size; i++) {
    if (b[i] <= a[i]) {
      result += a[i];
    }
  }

  a[0] = result;
}

In ARM SVE:

vect__ifc__33.15_48 = VEC_COND_EXPR <mask__18.14_46, vect__7.13_45, { 0, ...
}>;
vect__34.16_49 = .COND_ADD (loop_mask_41, vect_result_19.7_38,
vect__ifc__33.15_48, vect_result_19.7_38);

will be folded into:

vect__34.16_49 = .COND_ADD (_50, vect_result_19.7_38, vect__7.13_45,
vect_result_19.7_38);

However, for RVV, if failed to fold VEC_COND_EXPR + COND_LEN_ADD.

vect__ifc__44.30_96 = VEC_COND_EXPR <mask__43.29_94, vect__42.28_93, { 0, ...
}>;
  vect__45.31_97 = .COND_LEN_ADD ({ -1, ... }, vect_result_35.22_78,
vect__ifc__44.30_96, vect_result_35.22_78, _104, 0);

I am not sure where to do this optimization?