On Tue, 22 Mar 2022, Jakub Jelinek wrote:
> Hi!
>
> On Mon, Feb 28, 2022 at 07:52:56AM -0000, Roger Sayle wrote:
> > This patch resolves PR c++/84964 which is an ICE in the middle-end after
> > emitting a "sorry, unimplemented" message, and is a regression from
> > earlier releases of GCC. This issue is that after encountering a
> > function call requiring an unreasonable amount of stack space, the
> > code continues and falls foul of an assert checking that stack pointer
> > has been correctly updated. The fix is to (locally) consider aborted
> > function calls as "no return", which skips this downstream sanity check.
>
> As can be seen on PR104989, just setting ECF_NORETURN after sorry is quite
> risky and leads to other ICEs. The problem is that ECF_NORETURN calls
> better should be at the end of basic blocks that don't have any fallthru
> successor edges, otherwise we can ICE later.
>
> This patch instead sets sibcall_failure if in pass == 0 (sibcall_failure
> means that the tail call sequence is not useful/not desirable and throws
> it away) and otherwise sets a new bool variable that will let us pass
> the assertion and also throws away the whole call sequence, I think that is
> best for error recovery.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
OK.
Richard.
> 2022-03-22 Jakub Jelinek <ja...@redhat.com>
>
> PR rtl-optimization/104989
> * calls.cc (expand_call): Don't set ECF_NORETURN in flags after
> sorry for passing too large argument, instead set sibcall_failure
> for pass == 0, or a new normal_failure flag otherwise. If
> normal_failure is set, don't assert all stack has been deallocated
> at the end and throw away the whole insn sequence.
>
> * g++.dg/other/pr104989.C: New test.
>
> --- gcc/calls.cc.jj 2022-03-11 13:11:53.613095003 +0100
> +++ gcc/calls.cc 2022-03-21 11:21:52.997671148 +0100
> @@ -3068,6 +3068,7 @@ expand_call (tree exp, rtx target, int i
> for (pass = try_tail_call ? 0 : 1; pass < 2; pass++)
> {
> int sibcall_failure = 0;
> + bool normal_failure = false;
> /* We want to emit any pending stack adjustments before the tail
> recursion "call". That way we know any adjustment after the tail
> recursion call can be ignored if we indeed use the tail
> @@ -3448,7 +3449,10 @@ expand_call (tree exp, rtx target, int i
> {
> sorry ("passing too large argument on stack");
> /* Don't worry about stack clean-up. */
> - flags |= ECF_NORETURN;
> + if (pass == 0)
> + sibcall_failure = 1;
> + else
> + normal_failure = true;
> continue;
> }
>
> @@ -3905,9 +3909,12 @@ expand_call (tree exp, rtx target, int i
>
> /* Verify that we've deallocated all the stack we used. */
> gcc_assert ((flags & ECF_NORETURN)
> + || normal_failure
> || known_eq (old_stack_allocated,
> stack_pointer_delta
> - pending_stack_adjust));
> + if (normal_failure)
> + normal_call_insns = NULL;
> }
>
> /* If something prevents making this a sibling call,
> --- gcc/testsuite/g++.dg/other/pr104989.C.jj 2022-03-21 11:19:41.633496189
> +0100
> +++ gcc/testsuite/g++.dg/other/pr104989.C 2022-03-21 11:20:08.248126431
> +0100
> @@ -0,0 +1,9 @@
> +// PR rtl-optimization/104989
> +// { dg-do compile }
> +// { dg-options "-fnon-call-exceptions" }
> +
> +struct a {
> + short b : -1ULL;
> +};
> +void c(...) { c(a()); }
> +// { dg-excess-errors "" }
>
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Ivo Totev; HRB 36809 (AG Nuernberg)
