[Bug target/111451] RISC-V: Missed optimization of vrgather.vv into vrgatherei16.vv

[cvs-commit at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111451

--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Li Xu <x...@gcc.gnu.org>:

https://gcc.gnu.org/g:0ed05db7cee8f92604b5d7761713b7a7161e0db0

commit r14-4219-g0ed05db7cee8f92604b5d7761713b7a7161e0db0
Author: xuli <xu...@eswincomputing.com>
Date:   Fri Sep 22 01:25:39 2023 +0000

    RISC-V: Optimization of vrgather.vv into vrgatherei16.vv[PR111451]

    Consider this following case:

    typedef int32_t vnx32si __attribute__ ((vector_size (128)));

      __attribute__ ((noipa)) void permute_##TYPE (TYPE values1, TYPE values2, 
   \
                                                   TYPE *out)                  
   \
      {                                                                        
   \
        TYPE v                                                                 
   \
          = __builtin_shufflevector (values1, values2, MASK_##NUNITS (0,
NUNITS)); \
        *(TYPE *) out = v;                                                     
   \
      }

      T (vnx32si, 32)                                                          
   \

    TEST_ALL (PERMUTE)

    Before this patch:
      li    a4,31
      vsetvli       a5,zero,e32,m8,ta,ma
      vl8re32.v     v24,0(a0)
      vid.v v8
      vrsub.vx      v8,v8,a4
      vrgather.vv   v16,v24,v8
      vs8r.v        v16,0(a2)
      ret

    The index vector register "v8" occupies 8 registers.
    We should optimize it into vrgatherei16.vv which is
    using int16 as the index elements.

    After this patch:
      vsetvli       a5,zero,e16,m4,ta,ma
      li    a4,31
      vid.v v4
      vl8re32.v     v16,0(a0)
      vrsub.vx      v4,v4,a4
      vsetvli       zero,zero,e32,m8,ta,ma
      vrgatherei16.vv       v8,v16,v4
      vs8r.v        v8,0(a2)
      ret
    With vrgatherei16.vv, the v8 will occupy 4 registers instead
    of 8. Lower the register consuming and register pressure.

            PR target/111451

    gcc/ChangeLog:

            * config/riscv/riscv-v.cc (emit_vlmax_gather_insn): Optimization of
vrgather.vv
                                                            into
vrgatherei16.vv.

    gcc/testsuite/ChangeLog:

            * gcc.target/riscv/rvv/autovec/vls-vlmax/perm-4.c: Adjust case.
            * gcc.target/riscv/rvv/autovec/vls/perm-4.c: Ditto.