Re: [PATCH] openmp-simd-clone: Match shift type

[Jakub Jelinek <jakub@redhat.com>]

On Fri, Jul 29, 2022 at 04:53:51PM +0100, Andrew Stubbs wrote:
> This patch adjusts the generation of SIMD "inbranch" clones that use integer
> masks to ensure that it vectorizes on amdgcn.
> 
> The problem was only that an amdgcn mask is DImode and the shift amount was
> SImode, and the difference causes vectorization to fail.
> 
> OK for mainline?
> 
> Andrew

> openmp-simd-clone: Match shift types
> 
> Ensure that both parameters to vector shifts use the same mode.  This is most
> important for amdgcn where the masks are DImode.
> 
> gcc/ChangeLog:
> 
> 	* omp-simd-clone.cc (simd_clone_adjust): Convert shift_cnt to match
> 	the mask type.
> 
> diff --git a/gcc/omp-simd-clone.cc b/gcc/omp-simd-clone.cc
> index 32649bc3f9a..5d3a90730e7 100644
> --- a/gcc/omp-simd-clone.cc
> +++ b/gcc/omp-simd-clone.cc
> @@ -1305,8 +1305,12 @@ simd_clone_adjust (struct cgraph_node *node)
>  				       build_int_cst (TREE_TYPE (iter1), c));
>  	      gsi_insert_after (&gsi, g, GSI_CONTINUE_LINKING);
>  	    }
> +	  tree shift_cnt_conv = make_ssa_name (TREE_TYPE (mask));
> +	  g = gimple_build_assign (shift_cnt_conv,
> +				   fold_convert (TREE_TYPE (mask), shift_cnt));
> +	  gsi_insert_after (&gsi, g, GSI_CONTINUE_LINKING);

Doing the fold_convert seems to be a wasted effort to me.
Can't this be done conditional on whether some change is needed at all
and just using gimple_build_assign with NOP_EXPR, so something like:
	  tree shift_cvt_conv = shift_cnt;
	  if (!useless_type_conversion_p (TREE_TYPE (mask),
					  TREE_TYPE (shift_cnt)))
	    {
	      shift_cnt_conv = make_ssa_name (TREE_TYPE (mask));
	      g = gimple_build_assign (shift_cnt_conv, NOP_EXPR, shift_cnt);
	      gsi_insert_after (&gsi, g, GSI_CONTINUE_LINKING);
	    }

>  	  g = gimple_build_assign (make_ssa_name (TREE_TYPE (mask)),
> -				   RSHIFT_EXPR, mask, shift_cnt);
> +				   RSHIFT_EXPR, mask, shift_cnt_conv);
>  	  gsi_insert_after (&gsi, g, GSI_CONTINUE_LINKING);
>  	  mask = gimple_assign_lhs (g);
>  	  g = gimple_build_assign (make_ssa_name (TREE_TYPE (mask)),

?

	Jakub