[PATCH] vect: Don't update inits for simd_lane_access DRs [PR102789]

[PATCH] vect: Don't update inits for simd_lane_access DRs [PR102789]

[Kewen.Lin]

Hi,

As PR102789 shows, when vectorizer does some peelings for alignment
in prologue, function vect_update_inits_of_drs would update the
inits of some drs.  But as the failed case, we shouldn't update the
dr for simd_lane_access, it has the fixed-length storage mainly for
the main loop, the update can make the access out of bound and access
the unexpected elements.

I tried to test this broadly to ensure it's safe, since I was not
sure if it's reasonable to exclude all kinds of simd_lane_access drs.
The testings didn't catch any failures, I hope this is on the right
track.

It's bootstrapped and regtested on:
  - x86_64-redhat-linux
  - aarch64-linux-gnu
  - powerpc64le-linux-gnu P9
  - powerpc64-linux-gnu P8 and P7.

Is it ok for trunk?

BR,
Kewen
-----
gcc/ChangeLog:

	PR tree-optimization/102789
	* tree-vect-loop-manip.c (vect_update_inits_of_drs): Do not
	update inits of simd_lane_access.

diff --git a/gcc/tree-vect-loop-manip.c b/gcc/tree-vect-loop-manip.c
index 4988c93fdb6..378b1026baa 100644
--- a/gcc/tree-vect-loop-manip.c
+++ b/gcc/tree-vect-loop-manip.c
@@ -1820,7 +1820,8 @@ vect_update_inits_of_drs (loop_vec_info loop_vinfo, tree niters,
   FOR_EACH_VEC_ELT (datarefs, i, dr)
     {
       dr_vec_info *dr_info = loop_vinfo->lookup_dr (dr);
-      if (!STMT_VINFO_GATHER_SCATTER_P (dr_info->stmt))
+      if (!STMT_VINFO_GATHER_SCATTER_P (dr_info->stmt)
+	  && !STMT_VINFO_SIMD_LANE_ACCESS_P (dr_info->stmt))
 	vect_update_init_of_dr (dr_info, niters, code);
     }
 }

Re: [PATCH] vect: Don't update inits for simd_lane_access DRs [PR102789]

[Jakub Jelinek]

On Mon, Oct 25, 2021 at 11:01:35AM +0800, Kewen.Lin wrote:
> gcc/ChangeLog:
> 
> 	PR tree-optimization/102789
> 	* tree-vect-loop-manip.c (vect_update_inits_of_drs): Do not
> 	update inits of simd_lane_access.

Ok, thanks.

> diff --git a/gcc/tree-vect-loop-manip.c b/gcc/tree-vect-loop-manip.c
> index 4988c93fdb6..378b1026baa 100644
> --- a/gcc/tree-vect-loop-manip.c
> +++ b/gcc/tree-vect-loop-manip.c
> @@ -1820,7 +1820,8 @@ vect_update_inits_of_drs (loop_vec_info loop_vinfo, tree niters,
>    FOR_EACH_VEC_ELT (datarefs, i, dr)
>      {
>        dr_vec_info *dr_info = loop_vinfo->lookup_dr (dr);
> -      if (!STMT_VINFO_GATHER_SCATTER_P (dr_info->stmt))
> +      if (!STMT_VINFO_GATHER_SCATTER_P (dr_info->stmt)
> +	  && !STMT_VINFO_SIMD_LANE_ACCESS_P (dr_info->stmt))
>  	vect_update_init_of_dr (dr_info, niters, code);
>      }
>  }

	Jakub