On Fri, 16 Apr 2021, Jakub Jelinek wrote:
> Hi!
>
> The following testcase ICEs because disabling of DCE means there are dead
> stmts in the loop (though, in theory they could become dead only shortly
> before if-conv through some optimization), ifcvt which goes through all
> stmts in the loop if-converts them into .COND_DIV etc. internal fn calls
> in the copy of the loop meant for vectorization only, the loop is
> successfully vectorized but the particular .COND_* call is not because
> it isn't a live statement and the scalar .COND_* remains in the IL until
> expansion where it ICEs because these ifns only support vectors and not
> scalars.
>
> These ifns are similar to .MASK_{LOAD,STORE} in this behavior.
>
> One possible fix could be to expand scalar versions of them during
> expansion, basically undoing what if-conv did to create them, i.e.
> expand them as the lhs = else; if (mask) { lhs = statement; } or so.
>
> For .MASK_LOAD we have code to replace them in vect_transform_loop already
> though (not needed for .MASK_STORE, as stores should be always live
> and thus always vectorized), so this patch instead replaces .COND_*
> similarly to .MASK_LOAD in that loop, with the small difference
> that lhs = .MASK_LOAD (...); is replaced by lhs = 0; while
> lhs = .COND_* (..., else_arg); is replaced by lhs = else_arg.
> The statement must be dead, otherwise it would be vectorized, so I think
> it is not a big deal we don't turn it back into multiple basic blocks etc.
> (and it might be not possible to do that at that point).
>
> Bootstrapped/regtested on {x86_64,i686,aarch64}-linux, ok for trunk?
OK.
Thanks,
Richard.
> 2021-04-16 Jakub Jelinek <[email protected]>
>
> PR target/99767
> * tree-vect-loop.c (vect_transform_loop): Don't remove just
> dead scalar .MASK_LOAD calls, but also dead .COND_* calls - replace
> them by their last argument.
>
> * gcc.target/aarch64/pr99767.c: New test.
>
> --- gcc/tree-vect-loop.c.jj 2021-04-07 12:35:13.000000000 +0200
> +++ gcc/tree-vect-loop.c 2021-04-15 17:21:58.750101894 +0200
> @@ -9676,7 +9676,10 @@ vect_transform_loop (loop_vec_info loop_
> !gsi_end_p (gsi); gsi_next (&gsi))
> {
> gcall *call = dyn_cast <gcall *> (gsi_stmt (gsi));
> - if (call && gimple_call_internal_p (call, IFN_MASK_LOAD))
> + if (!call || !gimple_call_internal_p (call))
> + continue;
> + internal_fn ifn = gimple_call_internal_fn (call);
> + if (ifn == IFN_MASK_LOAD)
> {
> tree lhs = gimple_get_lhs (call);
> if (!VECTOR_TYPE_P (TREE_TYPE (lhs)))
> @@ -9686,6 +9689,17 @@ vect_transform_loop (loop_vec_info loop_
> gsi_replace (&gsi, new_stmt, true);
> }
> }
> + else if (conditional_internal_fn_code (ifn) != ERROR_MARK)
> + {
> + tree lhs = gimple_get_lhs (call);
> + if (!VECTOR_TYPE_P (TREE_TYPE (lhs)))
> + {
> + tree else_arg
> + = gimple_call_arg (call, gimple_call_num_args (call) - 1);
> + gimple *new_stmt = gimple_build_assign (lhs, else_arg);
> + gsi_replace (&gsi, new_stmt, true);
> + }
> + }
> }
> } /* BBs in loop */
>
> --- gcc/testsuite/gcc.target/aarch64/pr99767.c.jj 2021-04-15
> 17:28:10.466928380 +0200
> +++ gcc/testsuite/gcc.target/aarch64/pr99767.c 2021-04-15
> 17:28:45.653533566 +0200
> @@ -0,0 +1,16 @@
> +/* PR target/99767 */
> +/* { dg-do compile } */
> +/* { dg-options " -O1 -fopenmp-simd -fno-tree-dce -march=armv8-a+sve" } */
> +
> +int a[1024], b[1024];
> +
> +void
> +foo (void)
> +{
> + #pragma omp simd
> + for (int i = 0; i < 1024; i++)
> + if (b[i] > 23) {
> + a[i] = b[i] + 1;
> + int v = 1 / 0; /* { dg-warning "division by zero" } */
> + }
> +}
>
> Jakub
>
>
--
Richard Biener <[email protected]>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Felix Imendörffer; HRB 36809 (AG Nuernberg)
