On Wed, 4 Mar 2020, Jakub Jelinek wrote:
> Hi!
>
> When a function returns void or the return value is ignored, ass_var
> is NULL_TREE. The tail recursion handling generally assumes DCE has been
> performed and so doesn't expect to encounter useless assignments after the
> call and expects them to be part of the return value adjustment that need
> to be changed into tail recursion additions/multiplications.
> process_assignment does some verification and has a way to tell the caller
> to try to move dead or whatever other stmts that don't participate in the
> return value modifications before it is returned.
> For binary rhs assignments it is just fine, neither op0 nor op1 will be
> NULL_TREE and thus if *ass_var is NULL_TREE, it will not match, but unary
> rhs is handled by only setting op0 to rhs1 and setting op1 to NULL_TREE.
> And at this point, NULL_TREE == NULL_TREE and thus we think e.g. the
> c_2 = -e_3(D);
> dead stmt is actually a return value modification, so we queue it as
> multiplication and then create a void type SSA_NAME accumulator for it
> and ICE shortly after.
>
> Fixed by making sure op1 == *ass_var comparison is done only if *ass_var.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
OK.
Thanks,
Richard.
> 2020-03-04 Jakub Jelinek <ja...@redhat.com>
>
> PR tree-optimization/94001
> * tree-tailcall.c (process_assignment): Before comparing op1 to
> *ass_var, verify *ass_var is non-NULL.
>
> * gcc.dg/pr94001.c: New test.
>
> --- gcc/tree-tailcall.c.jj 2020-01-12 11:54:38.517381665 +0100
> +++ gcc/tree-tailcall.c 2020-03-03 20:38:54.282458700 +0100
> @@ -339,7 +339,8 @@ process_assignment (gassign *stmt,
> && (non_ass_var = independent_of_stmt_p (op1, stmt, call,
> to_move)))
> ;
> - else if (op1 == *ass_var
> + else if (*ass_var
> + && op1 == *ass_var
> && (non_ass_var = independent_of_stmt_p (op0, stmt, call,
> to_move)))
> ;
> --- gcc/testsuite/gcc.dg/pr94001.c.jj 2020-03-03 20:40:20.848184911 +0100
> +++ gcc/testsuite/gcc.dg/pr94001.c 2020-03-03 20:34:13.415591577 +0100
> @@ -0,0 +1,11 @@
> +/* PR tree-optimization/94001 */
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fno-tree-dce" } */
> +
> +void
> +bar (int e)
> +{
> + bar (3);
> + int c;
> + c = -e;
> +}
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Felix Imendörffer; HRB 36809 (AG Nuernberg)
