On Tue, 22 Oct 2024, Martin Jambor wrote:
> Hi,
>
> PR 117142 shows that the current SRA probably never worked reliably
> with arguments passed to a function returning twice, because it then
> creates statements before the call which however needs to be at the
> beginning of a basic block.
>
> While it should be possible to make at least the case of passing
> arguments by value work with SRA (the statements would need to be put
> just on the non-abnormal edges leading to the BB), this would mean
> large surgery of function sra_modify_expr and I guess the time would
> better be spent re-organizing the whole pass.
>
> Bootstrapped and tested on x86_64-linux. OK for master and all active
> release branches (though for gcc 13 and 12 the condition will probable
> be elsewhere, IIRC)?
OK.
Richard.
> Thanks,
>
> Martin
>
>
> gcc/ChangeLog:
>
> 2024-10-21 Martin Jambor <mjam...@suse.cz>
>
> PR tree-optimization/117142
> * tree-sra.cc (build_access_from_call_arg): Disqualify any
> candidate passed to a function returning twice.
>
> gcc/testsuite/ChangeLog:
>
> 2024-10-21 Martin Jambor <mjam...@suse.cz>
>
> PR tree-optimization/117142
> * gcc.dg/tree-ssa/pr117142.c: New test.
> ---
> gcc/testsuite/gcc.dg/tree-ssa/pr117142.c | 14 ++++++++++++++
> gcc/tree-sra.cc | 9 +++++++++
> 2 files changed, 23 insertions(+)
> create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr117142.c
>
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr117142.c
> b/gcc/testsuite/gcc.dg/tree-ssa/pr117142.c
> new file mode 100644
> index 00000000000..fc62c1e58f2
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/pr117142.c
> @@ -0,0 +1,14 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O1" } */
> +
> +struct a {
> + int b;
> +};
> +void c(int, int);
> +void __attribute__((returns_twice))
> +bar1(struct a);
> +void bar(struct a) {
> + struct a d;
> + bar1(d);
> + c(d.b, d.b);
> +}
> diff --git a/gcc/tree-sra.cc b/gcc/tree-sra.cc
> index 64e2f007d68..c0915dce5c4 100644
> --- a/gcc/tree-sra.cc
> +++ b/gcc/tree-sra.cc
> @@ -1397,6 +1397,15 @@ static bool
> build_access_from_call_arg (tree expr, gimple *stmt, bool can_be_returned,
> enum out_edge_check *oe_check)
> {
> + if (gimple_call_flags (stmt) & ECF_RETURNS_TWICE)
> + {
> + tree base = expr;
> + if (TREE_CODE (expr) == ADDR_EXPR)
> + base = get_base_address (TREE_OPERAND (expr, 0));
> + disqualify_base_of_expr (base, "Passed to a returns_twice call.");
> + return false;
> + }
> +
> if (TREE_CODE (expr) == ADDR_EXPR)
> {
> tree base = get_base_address (TREE_OPERAND (expr, 0));
>
--
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)
