On Mon, 5 Feb 2024, Jakub Jelinek wrote:
> Hi!
>
> The following testcase ICEs, because group_case_labels_stmt optimizes
> switch (a.0_7) <default: <L6> [50.00%], case 0: <L7> [50.00%], case 2: <L7>
> [50.00%]>
> where L7 block starts with __builtin_unreachable (); to
> switch (a.0_7) <default: <L6> [50.00%]>
> and single label GIMPLE_SWITCH is something the switch expansion refuses to
> lower:
> if (gimple_switch_num_labels (m_switch) == 1
> || range_check_type (index_type) == NULL_TREE)
> return false;
> (range_check_type never returns NULL for BITINT_TYPE), but the gimple
> lowering pass relies on all large/huge _BitInt switches to be lowered
> by that pass.
>
> The following patch just removes those after making the single successor
> edge EDGE_FALLTHRU. I've done it even if !optimize just in case in case
> we'd end up with single case label from earlier passes.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
OK.
Richard.
> 2024-02-05 Jakub Jelinek <ja...@redhat.com>
>
> PR tree-optimization/113737
> * gimple-lower-bitint.cc (gimple_lower_bitint): If GIMPLE_SWITCH
> has just a single label, remove it and make single successor edge
> EDGE_FALLTHRU.
>
> * gcc.dg/bitint-84.c: New test.
>
> --- gcc/gimple-lower-bitint.cc.jj 2024-02-02 11:30:05.801776658 +0100
> +++ gcc/gimple-lower-bitint.cc 2024-02-03 12:49:52.997777574 +0100
> @@ -5832,7 +5832,14 @@ gimple_lower_bitint (void)
>
> if (optimize)
> group_case_labels_stmt (swtch);
> - switch_statements.safe_push (swtch);
> + if (gimple_switch_num_labels (swtch) == 1)
> + {
> + single_succ_edge (bb)->flags |= EDGE_FALLTHRU;
> + gimple_stmt_iterator gsi = gsi_for_stmt (swtch);
> + gsi_remove (&gsi, true);
> + }
> + else
> + switch_statements.safe_push (swtch);
> }
> }
>
> --- gcc/testsuite/gcc.dg/bitint-84.c.jj 2024-02-03 12:56:08.153622744
> +0100
> +++ gcc/testsuite/gcc.dg/bitint-84.c 2024-02-03 12:57:05.425835789 +0100
> @@ -0,0 +1,32 @@
> +/* PR tree-optimization/113737 */
> +/* { dg-do compile { target bitint } } */
> +/* { dg-options "-O2 -std=c23" } */
> +
> +#if __BITINT_MAXWIDTH__ >= 129
> +_BitInt(129) a;
> +#else
> +_BitInt(63) a;
> +#endif
> +
> +int b[1], c;
> +
> +int
> +foo (void)
> +{
> + switch (a)
> + case 0:
> + case 2:
> + return 1;
> + return 0;
> +}
> +
> +void
> +bar (int i)
> +{
> + for (;; ++i)
> + {
> + c = b[i];
> + if (!foo ())
> + __asm__ ("");
> + }
> +}
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)
