On Sun, Jul 18, 2021 at 6:47 PM H.J. Lu <hjl.to...@gmail.com> wrote:
>
> Don't issue vzeroupper before function call if callee returns AVX
> register since callee must be compiled with AVX.
>
> gcc/
>
> PR target/101495
> * config/i386/i386.c (ix86_check_avx_upper_stores): Moved before
> ix86_avx_u128_mode_needed.
> (ix86_avx_u128_mode_needed): Return AVX_U128_DIRTY if callee
> returns AVX register.
>
> gcc/testsuite/
>
> PR target/101495
> * gcc.target/i386/avx-vzeroupper-28.c: New test.
OK.
Thanks,
Uros.
> ---
> gcc/config/i386/i386.c | 32 ++++++++++++-------
> .../gcc.target/i386/avx-vzeroupper-28.c | 17 ++++++++++
> 2 files changed, 37 insertions(+), 12 deletions(-)
> create mode 100644 gcc/testsuite/gcc.target/i386/avx-vzeroupper-28.c
>
> diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
> index 9d74b7a191b..e6c82624272 100644
> --- a/gcc/config/i386/i386.c
> +++ b/gcc/config/i386/i386.c
> @@ -14093,6 +14093,18 @@ ix86_check_avx_upper_register (const_rtx exp)
> && GET_MODE_BITSIZE (GET_MODE (exp)) > 128);
> }
>
> +/* Check if a 256bit or 512bit AVX register is referenced in stores. */
> +
> +static void
> +ix86_check_avx_upper_stores (rtx dest, const_rtx, void *data)
> + {
> + if (ix86_check_avx_upper_register (dest))
> + {
> + bool *used = (bool *) data;
> + *used = true;
> + }
> + }
> +
> /* Return needed mode for entity in optimize_mode_switching pass. */
>
> static int
> @@ -14117,6 +14129,14 @@ ix86_avx_u128_mode_needed (rtx_insn *insn)
> }
> }
>
> + /* Needed mode is set to AVX_U128_CLEAN if there are no 256bit
> + nor 512bit registers used in the function return register. */
> + bool avx_upper_reg_found = false;
> + note_stores (insn, ix86_check_avx_upper_stores,
> + &avx_upper_reg_found);
> + if (avx_upper_reg_found)
> + return AVX_U128_DIRTY;
> +
> /* If the function is known to preserve some SSE registers,
> RA and previous passes can legitimately rely on that for
> modes wider than 256 bits. It's only safe to issue a
> @@ -14217,18 +14237,6 @@ ix86_mode_needed (int entity, rtx_insn *insn)
> return 0;
> }
>
> -/* Check if a 256bit or 512bit AVX register is referenced in stores. */
> -
> -static void
> -ix86_check_avx_upper_stores (rtx dest, const_rtx, void *data)
> - {
> - if (ix86_check_avx_upper_register (dest))
> - {
> - bool *used = (bool *) data;
> - *used = true;
> - }
> - }
> -
> /* Calculate mode of upper 128bit AVX registers after the insn. */
>
> static int
> diff --git a/gcc/testsuite/gcc.target/i386/avx-vzeroupper-28.c
> b/gcc/testsuite/gcc.target/i386/avx-vzeroupper-28.c
> new file mode 100644
> index 00000000000..381ee9a7f96
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/avx-vzeroupper-28.c
> @@ -0,0 +1,17 @@
> +/* PR target/101495 */
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -mavx2 -mtune=generic -dp" } */
> +
> +#include <immintrin.h>
> +
> +extern __m256 x, y;
> +extern __m256 bar (void);
> +
> +__m256
> +foo ()
> +{
> + x = y;
> + return bar ();
> +}
> +
> +/* { dg-final { scan-assembler-not "avx_vzeroupper" } } */
> --
> 2.31.1
>
