Re: [PATCH][GCC 13] RISC-V: Fix recursive vsetvli checking [PR114172]

[Kito Cheng <kito.cheng@gmail.com>]

thanks, committed :)

On Wed, Apr 24, 2024 at 6:12 PM juzhe.zhong@rivai.ai
<juzhe.zhong@rivai.ai> wrote:
>
> lgtm.
>
> ________________________________
> juzhe.zhong@rivai.ai
>
>
> From: Kito Cheng
> Date: 2024-04-24 18:09
> To: gcc-patches; kito.cheng; rdapp; juzhe.zhong
> CC: Kito Cheng
> Subject: [PATCH][GCC 13] RISC-V: Fix recursive vsetvli checking [PR114172]
> extract_single_source will recursive checking the sources to
> make sure if it's single source, however it may cause infinite
> recursive when the source is come from itself, so it should just skip
> first source to prevent that.
>
> NOTE: This logic has existing on trunk/GCC 14, but it included in a big
> vsetvli improvement patch, which is not backport to GCC 13.
>
> ```
>
> void saxpy_rvv_m8(float *y, long vl)
> {
>     for (;;)
>     {
>         vl = __riscv_vsetvl_e32m8(vl); //ICE
>         vfloat32m8_t y_vec;
>         __riscv_vse32_v_f32m8(y, y_vec, vl);
>     }
> }
> ```
>
> gcc/ChangeLog:
>
> PR target/114172
> * gcc/config/riscv/riscv-vsetvl.cc (extract_single_source):
> Skip first set.
>
> gcc/testsuite/ChangeLog:
>
> PR target/114172
> * gcc.target/riscv/rvv/vsetvl/pr114172.c: New.
> ---
> gcc/config/riscv/riscv-vsetvl.cc                   |  4 ++++
> .../gcc.target/riscv/rvv/vsetvl/pr114172.c         | 14 ++++++++++++++
> 2 files changed, 18 insertions(+)
> create mode 100644 gcc/testsuite/gcc.target/riscv/rvv/vsetvl/pr114172.c
>
> diff --git a/gcc/config/riscv/riscv-vsetvl.cc b/gcc/config/riscv/riscv-vsetvl.cc
> index 9dca2ce709d..36d2e6e6f20 100644
> --- a/gcc/config/riscv/riscv-vsetvl.cc
> +++ b/gcc/config/riscv/riscv-vsetvl.cc
> @@ -1196,6 +1196,10 @@ extract_single_source (set_info *set)
>      return nullptr;
>    for (const set_info *set : sets)
>      {
> +      /* Skip first set, this can prevent us run into infinite recursive
> + checking if first set is come from itself.  */
> +      if (set == *sets.begin ())
> + continue;
>        /* If there is a head or end insn, we conservative return
> NULL so that VSETVL PASS will insert vsetvl directly.  */
>        if (set->insn ()->is_artificial ())
> diff --git a/gcc/testsuite/gcc.target/riscv/rvv/vsetvl/pr114172.c b/gcc/testsuite/gcc.target/riscv/rvv/vsetvl/pr114172.c
> new file mode 100644
> index 00000000000..ed1494666d6
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/riscv/rvv/vsetvl/pr114172.c
> @@ -0,0 +1,14 @@
> +/* { dg-do compile } */
> +/* { dg-options "-march=rv64gcv -mabi=lp64 -fno-tree-vectorize" } */
> +
> +#include "riscv_vector.h"
> +
> +void e(long, vfloat32m4_t);
> +
> +void b(long c) {
> +  for (;;) {
> +    c = __riscv_vsetvl_e32m4(c);
> +    vfloat32m4_t d;
> +    e(c, d);
> +  }
> +}
> --
> 2.34.1
>
>