On Mon, Sep 11, 2017 at 3:57 AM, H.J. Lu <hjl.to...@gmail.com> wrote:
> preferred_stack_boundary may not be the minimum stack alignment. For
> leaf functions without TLS access, max_used_stack_slot_alignment may be
> smaller. We should update preferred_stack_boundary for leaf functions.
>
> Tested on i686 and x86-64. OK for trunk?
>
> H.J.
> ---
> gcc/
>
> PR target/82166
> * config/i386/i386.c (ix86_finalize_stack_frame_flags): Properly
> compute the minimum stack alignment. Also update preferred stack
> boundary when main () is a leaf function.
>
> gcc/testsuite/
>
> PR target/82166
> * gcc.target/i386/pr82166.c: New test.
LGTM.
Thanks,
Uros.
> ---
> gcc/config/i386/i386.c | 17 ++++++++++++-----
> gcc/testsuite/gcc.target/i386/pr82166.c | 14 ++++++++++++++
> 2 files changed, 26 insertions(+), 5 deletions(-)
> create mode 100644 gcc/testsuite/gcc.target/i386/pr82166.c
>
> diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
> index 4e93cc1043b..03338e422be 100644
> --- a/gcc/config/i386/i386.c
> +++ b/gcc/config/i386/i386.c
> @@ -14257,11 +14257,12 @@ ix86_finalize_stack_frame_flags (void)
> unsigned int incoming_stack_boundary
> = (crtl->parm_stack_boundary > ix86_incoming_stack_boundary
> ? crtl->parm_stack_boundary : ix86_incoming_stack_boundary);
> + unsigned int stack_alignment
> + = (crtl->is_leaf && !ix86_current_function_calls_tls_descriptor
> + ? crtl->max_used_stack_slot_alignment
> + : crtl->stack_alignment_needed);
> unsigned int stack_realign
> - = (incoming_stack_boundary
> - < (crtl->is_leaf && !ix86_current_function_calls_tls_descriptor
> - ? crtl->max_used_stack_slot_alignment
> - : crtl->stack_alignment_needed));
> + = (incoming_stack_boundary < stack_alignment);
> bool recompute_frame_layout_p = false;
>
> if (crtl->stack_realign_finalized)
> @@ -14306,7 +14307,9 @@ ix86_finalize_stack_frame_flags (void)
> HARD_FRAME_POINTER_REGNUM);
>
> /* The preferred stack alignment is the minimum stack alignment. */
> - unsigned int stack_alignment = crtl->preferred_stack_boundary;
> + if (stack_alignment > crtl->preferred_stack_boundary)
> + stack_alignment = crtl->preferred_stack_boundary;
> +
> bool require_stack_frame = false;
>
> FOR_EACH_BB_FN (bb, cfun)
> @@ -14349,6 +14352,10 @@ ix86_finalize_stack_frame_flags (void)
> = incoming_stack_boundary;
> crtl->stack_alignment_needed
> = incoming_stack_boundary;
> + /* Also update preferred_stack_boundary for leaf
> + functions. */
> + crtl->preferred_stack_boundary
> + = incoming_stack_boundary;
> }
> }
> else
> diff --git a/gcc/testsuite/gcc.target/i386/pr82166.c
> b/gcc/testsuite/gcc.target/i386/pr82166.c
> new file mode 100644
> index 00000000000..8bc63e15231
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/pr82166.c
> @@ -0,0 +1,14 @@
> +/* { dg-do compile } */
> +/* { dg-options "-Os" } */
> +
> +void foo (void);
> +int a, b, c;
> +int
> +main (void)
> +{
> + int j;
> + for (; c;)
> + a = b;
> + for (; j;)
> + foo ();
> +}
> --
> 2.13.5
>
