Re: [PATCH][Middle-end][Backport to GCC11][PR100775]Updating the reg use in exit block for -fzero-call-used-regs

[Richard Biener <richard.guenther@gmail.com>]

On Fri, Mar 11, 2022 at 5:31 PM Qing Zhao via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
>
> Hi,
>
> I plan to backport the patch to fix PR100775:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100775
>
> To gcc11 since this is a general bug to -fzero-call-used-regs. And should be fixed in gcc11 as well.
>
> I have tested the patch with gcc11 release branch on both x86 and aarch64, no regression.
>
> Okay for commit?

OK

> thanks.
>
> Qing.
>
> ==================================================
>
>
> From 737a0ccccb0824111f46da44c5578b9769070c52 Mon Sep 17 00:00:00 2001
> From: Qing Zhao <qing.zhao@oracle.com>
> Date: Thu, 10 Mar 2022 23:22:29 +0000
> Subject: [PATCH] middle-end: updating the reg use in exit block for
>  -fzero-call-used-regs [PR100775] GCC11 backport.
>
> In the pass_zero_call_used_regs, when updating dataflow info after adding
> the register zeroing sequence in the epilogue of the function, we should
> call "df_update_exit_block_uses" to update the register use information in
> the exit block to include all the registers that have been zeroed.
>
> gcc/ChangeLog:
>
>         PR middle-end/100775
>         * function.c (gen_call_used_regs_seq): Call
>         df_update_exit_block_uses when updating df.
>
> gcc/testsuite/ChangeLog:
>
>         PR middle-end/100775
>         * gcc.target/arm/pr100775.c: New test.
> ---
>  gcc/function.c                          | 2 +-
>  gcc/testsuite/gcc.target/arm/pr100775.c | 9 +++++++++
>  2 files changed, 10 insertions(+), 1 deletion(-)
>  create mode 100644 gcc/testsuite/gcc.target/arm/pr100775.c
>
> diff --git a/gcc/function.c b/gcc/function.c
> index fc7b147b5f1..0495e9f1b81 100644
> --- a/gcc/function.c
> +++ b/gcc/function.c
> @@ -5922,7 +5922,7 @@ gen_call_used_regs_seq (rtx_insn *ret, unsigned int zero_regs_type)
>
>        /* Update the data flow information.  */
>        crtl->must_be_zero_on_return |= zeroed_hardregs;
> -      df_set_bb_dirty (EXIT_BLOCK_PTR_FOR_FN (cfun));
> +      df_update_exit_block_uses ();
>      }
>  }
>
> diff --git a/gcc/testsuite/gcc.target/arm/pr100775.c b/gcc/testsuite/gcc.target/arm/pr100775.c
> new file mode 100644
> index 00000000000..c648cd5e8f7
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/arm/pr100775.c
> @@ -0,0 +1,9 @@
> +/* { dg-do compile } */
> +/* { dg-skip-if "" { ! { arm_thumb1_ok || arm_thumb2_ok } } } */
> +/* { dg-options "-mthumb -fzero-call-used-regs=used" } */
> +
> +int
> +foo (int x)
> +{
> +  return x;
> +}
> --
> 2.27.0
>
>