On Tue, Nov 08, 2022 at 01:53:48PM +0100, Richard Biener wrote:
> The following makes sure to set alignment information on the LHS
> of __builtin_assume_alignment calls even when not optimizing so
> uses as arguments to builtin functions like memcpy or __atomic_load_n
> can be reflected at RTL expansion time.
>
> Bootstrap and regtest running on x86_64-unknown-linux-gnu, OK?
>
> Thanks,
> Richard.
>
> PR tree-optimization/107389
> * gimple-low.cc (lower_builtin_assume_aligned): New.
> (lower_stmt): Call it.
>
> * gcc.dg/pr107389.c: New testcase.
> ---
> gcc/gimple-low.cc | 41 +++++++++++++++++++++++++++++++++
> gcc/testsuite/gcc.dg/pr107389.c | 13 +++++++++++
> 2 files changed, 54 insertions(+)
> create mode 100644 gcc/testsuite/gcc.dg/pr107389.c
>
> diff --git a/gcc/gimple-low.cc b/gcc/gimple-low.cc
> index 512aa9feada..f9bcb772163 100644
> --- a/gcc/gimple-low.cc
> +++ b/gcc/gimple-low.cc
> @@ -84,6 +84,7 @@ static void lower_try_catch (gimple_stmt_iterator *, struct
> lower_data *);
> static void lower_gimple_return (gimple_stmt_iterator *, struct lower_data
> *);
> static void lower_builtin_setjmp (gimple_stmt_iterator *);
> static void lower_builtin_posix_memalign (gimple_stmt_iterator *);
> +static void lower_builtin_assume_aligned (gimple_stmt_iterator *);
>
>
> /* Lower the body of current_function_decl from High GIMPLE into Low
> @@ -768,6 +769,13 @@ lower_stmt (gimple_stmt_iterator *gsi, struct lower_data
> *data)
> lower_builtin_posix_memalign (gsi);
> return;
> }
> + else if (DECL_FUNCTION_CODE (decl) == BUILT_IN_ASSUME_ALIGNED
> + && !optimize)
> + {
> + lower_builtin_assume_aligned (gsi);
> + data->cannot_fallthru = false;
> + return;
> + }
> }
>
> if (decl && (flags_from_decl_or_type (decl) & ECF_NORETURN))
> @@ -1310,6 +1318,39 @@ lower_builtin_posix_memalign (gimple_stmt_iterator
> *gsi)
> gsi_insert_after (gsi, stmt, GSI_NEW_STMT);
> gsi_insert_after (gsi, gimple_build_label (noalign_label), GSI_NEW_STMT);
> }
> +
> +/* Lower calls to __builtin_assume_aligned when not optimizing. */
> +
> +static void
> +lower_builtin_assume_aligned (gimple_stmt_iterator *gsi)
> +{
> + gcall *call = as_a <gcall *> (gsi_stmt (*gsi));
> +
> + tree lhs = gimple_call_lhs (call);
> + if (!lhs || !POINTER_TYPE_P (TREE_TYPE (lhs)))
> + return;
I think nothing checks that TREE_CODE (lhs) == SSA_NAME,
that isn't guaranteed before ssa pass.
Otherwise LGTM.
Jakub
