Jakub Jelinek via Gcc-patches <gcc-patches@gcc.gnu.org> writes:
> Hi!
>
> This is a sequel to the PR85022 changes, inline-asm can (unfortunately)
> introduce VOIDmode MEMs and in PR85022 they have been changed so that
> we don't pretend we know their size (as opposed to assuming they have
> zero size).
>
> This time we ICE in rtx_addr_can_trap_p_1 because it assumes that
> all memory but BLKmode has known size. The patch just treats VOIDmode
> MEMs like BLKmode in that regard. And, the STRICT_ALIGNMENT change
> is needed because VOIDmode has GET_MODE_SIZE of 0 and we don't want to
> check if something is a multiple of 0.
Sorry if this is reopening an old discussion, but could we instead
canonicalise these MEMs to BLKmode when expanding the inline asm?
I think quite a lot of RTL code assumes that MEMs can be VOIDmode,
so I'd be surprised if these two patches are enough.
Thanks,
Richard
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
>
> 2021-04-10 Jakub Jelinek <ja...@redhat.com>
>
> PR rtl-optimization/98601
> * rtlanal.c (rtx_addr_can_trap_p_1): Allow in assert unknown size
> not just for BLKmode, but also for VOIDmode. For STRICT_ALIGNMENT
> unaligned_mems handle VOIDmode like BLKmode.
>
> * gcc.dg/torture/pr98601.c: New test.
>
> --- gcc/rtlanal.c.jj 2021-03-05 21:51:48.689185518 +0100
> +++ gcc/rtlanal.c 2021-04-09 11:15:20.341906331 +0200
> @@ -464,12 +464,17 @@ rtx_addr_can_trap_p_1 (const_rtx x, poly
> machine_mode mode, bool unaligned_mems)
> {
> enum rtx_code code = GET_CODE (x);
> - gcc_checking_assert (mode == BLKmode || known_size_p (size));
> + gcc_checking_assert (mode == BLKmode
> + || mode == VOIDmode
> + || known_size_p (size));
> poly_int64 const_x1;
>
> /* The offset must be a multiple of the mode size if we are considering
> unaligned memory references on strict alignment machines. */
> - if (STRICT_ALIGNMENT && unaligned_mems && mode != BLKmode)
> + if (STRICT_ALIGNMENT
> + && unaligned_mems
> + && mode != BLKmode
> + && mode != VOIDmode)
> {
> poly_int64 actual_offset = offset;
>
> --- gcc/testsuite/gcc.dg/torture/pr98601.c.jj 2021-04-09 11:18:26.964817854
> +0200
> +++ gcc/testsuite/gcc.dg/torture/pr98601.c 2021-04-09 11:18:16.758932053
> +0200
> @@ -0,0 +1,14 @@
> +/* PR rtl-optimization/98601 */
> +/* { dg-do compile } */
> +
> +void
> +foo (void *p)
> +{
> + asm ("" : "=m" (*p)); /* { dg-warning "dereferencing
> 'void \\*' pointer" } */
> +}
> +
> +void
> +bar (void *p)
> +{
> + asm volatile ("" : : "m" (*p)); /* { dg-warning "dereferencing 'void
> \\*' pointer" } */
> +}
>
> Jakub
