Re: [Patch] OpenMP: Fix var replacement with 'simd' and linear-step vars [PR106548]

[Jakub Jelinek <jakub@redhat.com>]

On Tue, Aug 16, 2022 at 05:28:40PM +0200, Tobias Burnus wrote:
> The testcase is just a copy of linear-1 with 'omp ... for' replaced by 'omp ... for simd',
> matching what the PR report referred to.
> 
> The problem occurs for 'omp ... for simd linear( i : step)' when 'step' is a variable
> when a omp_fn... is generated - as in this case, the original variable is used (in the
> reduced example of the PR, the PARM_DECL of 'f') instead of the replacement.
> 
> OK for mainline? Thoughts on backporting (and for which versions)?
> 
> Tobias
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> OpenMP: Fix var replacement with 'simd' and linear-step vars [PR106548]
> 
> gcc/ChangeLog:
> 
> 	PR middle-end/106548
> 	* omp-low.cc (lower_rec_input_clauses): Use build_outer_var_ref
> 	for 'simd' linear-step values that are variable.
> 
> libgomp/ChangeLog:
> 
> 	PR middle-end/106548
> 	* testsuite/libgomp.c/linear-2.c: New test.
> 
> diff --git a/gcc/omp-low.cc b/gcc/omp-low.cc
> index 3c4b8593c8b..d6d6ff372a1 100644
> --- a/gcc/omp-low.cc
> +++ b/gcc/omp-low.cc
> @@ -6188,6 +6188,10 @@ lower_rec_input_clauses (tree clauses, gimple_seq *ilist, gimple_seq *dlist,
>  		      && gimple_omp_for_combined_into_p (ctx->stmt))
>  		    {
>  		      tree t = OMP_CLAUSE_LINEAR_STEP (c);
> +		      if (VAR_P (t)
> +			  || TREE_CODE (t) == PARM_DECL
> +			  || TREE_CODE (t) == RESULT_DECL)
> +			t = build_outer_var_ref (t, ctx);

I think this should be just
		      if (DECL_P (t))
			t = build_outer_var_ref (t, ctx);

Ok with that change.
With backports I'd wait a week or two (12.2 is frozen anyway), can be
applied to any open release branches you are willing to backport it to.

> --- /dev/null
> +++ b/libgomp/testsuite/libgomp.c/linear-2.c
> @@ -0,0 +1,251 @@
> +/* PR middle-end/106548.  */

Usually simd related runtime tests in libgomp use something like
/* { dg-do run } */
/* { dg-additional-options "-msse2" { target sse2_runtime } } */
/* { dg-additional-options "-mavx" { target avx_runtime } } */
to test some actual vectorization if possible.

	Jakub