> Am 13.02.2026 um 17:45 schrieb Andrew Pinski <[email protected]>:
>
> I didn't implement this before today as I had not see any code
> where this would make a difference. I noticed while looking into
> regressions an uninitialized warning that shows up only with
> -fsanitize=address. This because SRA causes some extra total
> scalaization when using -fsanitize=address. Which in turn exposes
> an uninitialized warning. This fixes the uninitialized warning
> by doing a simple copy prop into the return statement.
>
> That is if we have:
> ```
> D.3407 = D.3418;
> return D.3407;
> ```
>
> turn it into:
> ```
> D.3407 = D.3418;
> return D.3418;
> ```
>
> This forces SRA not to do total scalarization on D.3418 and allows for better
> code
> too.
>
> Bootstrapped and tested on x86_64-linux-gnu.
Ok.
Thanks,
Richard
>
> PR tree-optimization/95825
>
> gcc/ChangeLog:
>
> * tree-ssa-forwprop.cc (optimize_agr_copyprop_return): New function.
> (optimize_agr_copyprop): Call optimize_agr_copyprop_return
> for return statements.
>
> gcc/testsuite/ChangeLog:
>
> * g++.dg/warn/uninit-pr95825-1.C: New test.
> * gcc.dg/tree-ssa/copy-prop-aggregate-return-1.c: New test.
>
> Signed-off-by: Andrew Pinski <[email protected]>
> ---
> gcc/testsuite/g++.dg/warn/uninit-pr95825-1.C | 22 +++++++++++
> .../tree-ssa/copy-prop-aggregate-return-1.c | 22 +++++++++++
> gcc/tree-ssa-forwprop.cc | 37 +++++++++++++++++++
> 3 files changed, 81 insertions(+)
> create mode 100644 gcc/testsuite/g++.dg/warn/uninit-pr95825-1.C
> create mode 100644
> gcc/testsuite/gcc.dg/tree-ssa/copy-prop-aggregate-return-1.c
>
> diff --git a/gcc/testsuite/g++.dg/warn/uninit-pr95825-1.C
> b/gcc/testsuite/g++.dg/warn/uninit-pr95825-1.C
> new file mode 100644
> index 00000000000..01a9b26a1f2
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/warn/uninit-pr95825-1.C
> @@ -0,0 +1,22 @@
> +// { dg-do compile }
> +// { dg-options "-O1 -fsanitize=address" }
> +
> +// PR tree-optimization/95825
> +
> +struct s1
> +{
> + char init;
> + int value;
> +};
> +
> +static struct s1 f()
> +{
> + struct s1 t;
> + t.init = 0;
> + return t; /* { dg-bogus "is used uninitialized" } */
> +}
> +
> +struct s1 g()
> +{
> + return f();
> +}
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/copy-prop-aggregate-return-1.c
> b/gcc/testsuite/gcc.dg/tree-ssa/copy-prop-aggregate-return-1.c
> new file mode 100644
> index 00000000000..f402931a0ee
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/copy-prop-aggregate-return-1.c
> @@ -0,0 +1,22 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O1 -fdump-tree-forwprop1-details" } */
> +
> +struct s1
> +{
> + char init;
> + int value;
> +};
> +
> +static inline struct s1 f()
> +{
> + struct s1 t;
> + t.init = 0;
> + return t;
> +}
> +
> +struct s1 g()
> +{
> + return f();
> +}
> +
> +/* { dg-final { scan-tree-dump-times "after previous" 1 "forwprop1"} } */
> diff --git a/gcc/tree-ssa-forwprop.cc b/gcc/tree-ssa-forwprop.cc
> index b1d63e189bd..c4fde7b4aae 100644
> --- a/gcc/tree-ssa-forwprop.cc
> +++ b/gcc/tree-ssa-forwprop.cc
> @@ -1721,6 +1721,41 @@ optimize_agr_copyprop_arg (gimple *defstmt, gcall
> *call,
> update_stmt (call);
> }
>
> +/* Helper function for optimize_agr_copyprop, propagate aggregates
> + into the return stmt USE if the operand of the return matches DEST;
> + replacing it with SRC. */
> +static void
> +optimize_agr_copyprop_return (gimple *defstmt, greturn *use,
> + tree dest, tree src)
> +{
> + tree rvalue = gimple_return_retval (use);
> + if (!rvalue
> + || TREE_CODE (rvalue) == SSA_NAME
> + || is_gimple_min_invariant (rvalue)
> + || TYPE_VOLATILE (TREE_TYPE (rvalue)))
> + return;
> + tree newsrc = new_src_based_on_copy (rvalue, dest, src);
> + if (!newsrc)
> + return;
> + /* Currently only support decls, could support VCEs too? */
> + if (!DECL_P (newsrc))
> + return;
> + if (dump_file && (dump_flags & TDF_DETAILS))
> + {
> + fprintf (dump_file, "Simplified\n ");
> + print_gimple_stmt (dump_file, use, 0, dump_flags);
> + fprintf (dump_file, "after previous\n ");
> + print_gimple_stmt (dump_file, defstmt, 0, dump_flags);
> + }
> + gimple_return_set_retval (use, newsrc);
> + if (dump_file && (dump_flags & TDF_DETAILS))
> + {
> + fprintf (dump_file, "into\n ");
> + print_gimple_stmt (dump_file, use, 0, dump_flags);
> + }
> + update_stmt (use);
> +}
> +
> /* Optimizes
> DEST = SRC;
> DEST2 = DEST; # DEST2 = SRC2;
> @@ -1764,6 +1799,8 @@ optimize_agr_copyprop (gimple *stmt)
> optimize_agr_copyprop_1 (stmt, use_stmt, dest, src);
> else if (is_gimple_call (use_stmt))
> optimize_agr_copyprop_arg (stmt, as_a<gcall*>(use_stmt), dest, src);
> + else if (is_a<greturn*> (use_stmt))
> + optimize_agr_copyprop_return (stmt, as_a<greturn*>(use_stmt), dest, src);
> }
> }
>
> --
> 2.43.0
>
