On Thu, 27 Mar 2025, Jakub Jelinek wrote:
> Hi!
>
> The following testcase is rejected, because IPA-SRA decides to
> turn bar.constprop call into bar.constprop.isra which returns void.
> While there is no explicit lhs on the call, as it is a musttail call
> the tailc pass checks if IPA-VRP returns singleton from that function
> and the function returns the same value and in that case it still turns
> it into a tail call. This can't work with IPA-SRA changing it into
> void returning function though.
>
> The following patch fixes this by forcing returning the original type
> if there are musttail calls.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
LGTM.
Richard.
> 2025-03-27 Jakub Jelinek <ja...@redhat.com>
>
> PR ipa/119484
> * ipa-sra.cc (isra_analyze_call): Don't set m_return_ignored if
> gimple_call_must_tail_p even if it doesn't have lhs.
>
> * c-c++-common/pr119484.c: New test.
>
> --- gcc/ipa-sra.cc.jj 2025-03-01 09:13:17.736075042 +0100
> +++ gcc/ipa-sra.cc 2025-03-27 14:23:43.884552767 +0100
> @@ -2242,7 +2242,11 @@ isra_analyze_call (cgraph_edge *cs)
> BITMAP_FREE (analyzed);
> }
> }
> - else
> + /* Don't set m_return_ignored for musttail calls. The tailc/musttail
> passes
> + compare the returned value against the IPA-VRP return value range if
> + it is a singleton, but if the call is changed to something which doesn't
> + return anything, it will always fail. */
> + else if (!gimple_call_must_tail_p (call_stmt))
> csum->m_return_ignored = true;
> }
>
> --- gcc/testsuite/c-c++-common/pr119484.c.jj 2025-03-27 14:30:32.988976396
> +0100
> +++ gcc/testsuite/c-c++-common/pr119484.c 2025-03-27 14:31:17.074375485
> +0100
> @@ -0,0 +1,21 @@
> +/* PR ipa/119484 */
> +/* { dg-do compile { target musttail } } */
> +/* { dg-options "-O2 -fdump-tree-optimized" } */
> +/* { dg-final { scan-tree-dump-times "bar\[.a-z0-9]* \\\(\[^\n\r]*\\\);
> \\\[tail call\\\] \\\[must tail call\\\]" 1 "optimized" } } */
> +
> +void foo (int);
> +
> +[[gnu::noinline]] static int
> +bar (int x)
> +{
> + foo (x);
> + return 0;
> +}
> +
> +int
> +baz (int x)
> +{
> + if (x == 1)
> + [[gnu::musttail]] return bar (x);
> + return 0;
> +}
>
> 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)
