Re: [Qemu-devel] [PATCH v2] qemu/compiler: Wrap __attribute__((flatten)) in a macro

[Alex Bennée]

Thomas Huth <address@hidden> writes:

> Older versions of Clang (before 3.5) and GCC (before 4.1) do not
> support the "__attribute__((flatten))" yet. We don't care about
> such old versions of GCC anymore, but since Clang 3.4 is still
> used in EPEL for RHEL7 / CentOS 7, we should not use this attribute
> directly but with a wrapper macro instead.
>
> Signed-off-by: Thomas Huth <address@hidden>
> ---
>  v2: Ignore older versions of GCC since we do not support them anymore
>
>  fpu/softfloat.c         | 39 +++++++++++++++------------------------
>  include/qemu/compiler.h | 16 ++++++++++++++++
>  2 files changed, 31 insertions(+), 24 deletions(-)
>
> diff --git a/fpu/softfloat.c b/fpu/softfloat.c
> index 59ca356..8b91cd6 100644
> --- a/fpu/softfloat.c
> +++ b/fpu/softfloat.c
> @@ -726,8 +726,7 @@ static FloatParts addsub_floats(FloatParts a, FloatParts 
> b, bool subtract,
>   * IEC/IEEE Standard for Binary Floating-Point Arithmetic.
>   */
>
> -float16  __attribute__((flatten)) float16_add(float16 a, float16 b,
> -                                              float_status *status)
> +float16 QEMU_FLATTEN float16_add(float16 a, float16 b, float_status *status)
>  {
>      FloatParts pa = float16_unpack_canonical(a, status);
>      FloatParts pb = float16_unpack_canonical(b, status);
> @@ -736,8 +735,7 @@ float16  __attribute__((flatten)) float16_add(float16 a, 
> float16 b,
>      return float16_round_pack_canonical(pr, status);
>  }
>
> -float32 __attribute__((flatten)) float32_add(float32 a, float32 b,
> -                                             float_status *status)
> +float32 QEMU_FLATTEN float32_add(float32 a, float32 b, float_status *status)
>  {
>      FloatParts pa = float32_unpack_canonical(a, status);
>      FloatParts pb = float32_unpack_canonical(b, status);
> @@ -746,8 +744,7 @@ float32 __attribute__((flatten)) float32_add(float32 a, 
> float32 b,
>      return float32_round_pack_canonical(pr, status);
>  }
>
> -float64 __attribute__((flatten)) float64_add(float64 a, float64 b,
> -                                             float_status *status)
> +float64 QEMU_FLATTEN float64_add(float64 a, float64 b, float_status *status)
>  {
>      FloatParts pa = float64_unpack_canonical(a, status);
>      FloatParts pb = float64_unpack_canonical(b, status);
> @@ -756,8 +753,7 @@ float64 __attribute__((flatten)) float64_add(float64 a, 
> float64 b,
>      return float64_round_pack_canonical(pr, status);
>  }
>
> -float16 __attribute__((flatten)) float16_sub(float16 a, float16 b,
> -                                             float_status *status)
> +float16 QEMU_FLATTEN float16_sub(float16 a, float16 b, float_status *status)
>  {
>      FloatParts pa = float16_unpack_canonical(a, status);
>      FloatParts pb = float16_unpack_canonical(b, status);
> @@ -766,8 +762,7 @@ float16 __attribute__((flatten)) float16_sub(float16 a, 
> float16 b,
>      return float16_round_pack_canonical(pr, status);
>  }
>
> -float32 __attribute__((flatten)) float32_sub(float32 a, float32 b,
> -                                             float_status *status)
> +float32 QEMU_FLATTEN float32_sub(float32 a, float32 b, float_status *status)
>  {
>      FloatParts pa = float32_unpack_canonical(a, status);
>      FloatParts pb = float32_unpack_canonical(b, status);
> @@ -776,8 +771,7 @@ float32 __attribute__((flatten)) float32_sub(float32 a, 
> float32 b,
>      return float32_round_pack_canonical(pr, status);
>  }
>
> -float64 __attribute__((flatten)) float64_sub(float64 a, float64 b,
> -                                             float_status *status)
> +float64 QEMU_FLATTEN float64_sub(float64 a, float64 b, float_status *status)
>  {
>      FloatParts pa = float64_unpack_canonical(a, status);
>      FloatParts pb = float64_unpack_canonical(b, status);
> @@ -835,8 +829,7 @@ static FloatParts mul_floats(FloatParts a, FloatParts b, 
> float_status *s)
>      g_assert_not_reached();
>  }
>
> -float16 __attribute__((flatten)) float16_mul(float16 a, float16 b,
> -                                             float_status *status)
> +float16 QEMU_FLATTEN float16_mul(float16 a, float16 b, float_status *status)
>  {
>      FloatParts pa = float16_unpack_canonical(a, status);
>      FloatParts pb = float16_unpack_canonical(b, status);
> @@ -845,8 +838,7 @@ float16 __attribute__((flatten)) float16_mul(float16 a, 
> float16 b,
>      return float16_round_pack_canonical(pr, status);
>  }
>
> -float32 __attribute__((flatten)) float32_mul(float32 a, float32 b,
> -                                             float_status *status)
> +float32 QEMU_FLATTEN float32_mul(float32 a, float32 b, float_status *status)
>  {
>      FloatParts pa = float32_unpack_canonical(a, status);
>      FloatParts pb = float32_unpack_canonical(b, status);
> @@ -855,8 +847,7 @@ float32 __attribute__((flatten)) float32_mul(float32 a, 
> float32 b,
>      return float32_round_pack_canonical(pr, status);
>  }
>
> -float64 __attribute__((flatten)) float64_mul(float64 a, float64 b,
> -                                             float_status *status)
> +float64 QEMU_FLATTEN float64_mul(float64 a, float64 b, float_status *status)
>  {
>      FloatParts pa = float64_unpack_canonical(a, status);
>      FloatParts pb = float64_unpack_canonical(b, status);
> @@ -1068,7 +1059,7 @@ static FloatParts muladd_floats(FloatParts a, 
> FloatParts b, FloatParts c,
>      return a;
>  }
>
> -float16 __attribute__((flatten)) float16_muladd(float16 a, float16 b, 
> float16 c,
> +float16 QEMU_FLATTEN float16_muladd(float16 a, float16 b, float16 c,
>                                                  int flags, float_status 
> *status)
>  {
>      FloatParts pa = float16_unpack_canonical(a, status);
> @@ -1079,7 +1070,7 @@ float16 __attribute__((flatten)) float16_muladd(float16 
> a, float16 b, float16 c,
>      return float16_round_pack_canonical(pr, status);
>  }
>
> -float32 __attribute__((flatten)) float32_muladd(float32 a, float32 b, 
> float32 c,
> +float32 QEMU_FLATTEN float32_muladd(float32 a, float32 b, float32 c,
>                                                  int flags, float_status 
> *status)
>  {
>      FloatParts pa = float32_unpack_canonical(a, status);
> @@ -1090,7 +1081,7 @@ float32 __attribute__((flatten)) float32_muladd(float32 
> a, float32 b, float32 c,
>      return float32_round_pack_canonical(pr, status);
>  }
>
> -float64 __attribute__((flatten)) float64_muladd(float64 a, float64 b, 
> float64 c,
> +float64 QEMU_FLATTEN float64_muladd(float64 a, float64 b, float64 c,
>                                                  int flags, float_status 
> *status)
>  {
>      FloatParts pa = float64_unpack_canonical(a, status);
> @@ -2402,21 +2393,21 @@ static FloatParts sqrt_float(FloatParts a, 
> float_status *s, const FloatFmt *p)
>      return a;
>  }
>
> -float16 __attribute__((flatten)) float16_sqrt(float16 a, float_status 
> *status)
> +float16 QEMU_FLATTEN float16_sqrt(float16 a, float_status *status)
>  {
>      FloatParts pa = float16_unpack_canonical(a, status);
>      FloatParts pr = sqrt_float(pa, status, &float16_params);
>      return float16_round_pack_canonical(pr, status);
>  }
>
> -float32 __attribute__((flatten)) float32_sqrt(float32 a, float_status 
> *status)
> +float32 QEMU_FLATTEN float32_sqrt(float32 a, float_status *status)
>  {
>      FloatParts pa = float32_unpack_canonical(a, status);
>      FloatParts pr = sqrt_float(pa, status, &float32_params);
>      return float32_round_pack_canonical(pr, status);
>  }
>
> -float64 __attribute__((flatten)) float64_sqrt(float64 a, float_status 
> *status)
> +float64 QEMU_FLATTEN float64_sqrt(float64 a, float_status *status)
>  {
>      FloatParts pa = float64_unpack_canonical(a, status);
>      FloatParts pr = sqrt_float(pa, status, &float64_params);
> diff --git a/include/qemu/compiler.h b/include/qemu/compiler.h
> index 5843812..a4aafa1 100644
> --- a/include/qemu/compiler.h
> +++ b/include/qemu/compiler.h
> @@ -122,6 +122,22 @@
>  #ifndef __has_feature
>  #define __has_feature(x) 0 /* compatibility with non-clang compilers */
>  #endif
> +
> +#ifndef __has_attribute
> +#define __has_attribute(x) 0 /* compatibility with older GCC */
> +#endif
> +
> +/*
> + * GCC doesn't provide __has_attribute() until GCC 5, but we know all the GCC
> + * versions we support have the "flatten" attribute. Clang may not have the
> + * "flatten" attribute but always has __has_attribute() to check for it.
> + */
> +#if __has_attribute(flatten) || !defined(__clang__)
> +# define QEMU_FLATTEN __attribute__((flatten))
> +#else
> +# define QEMU_FLATTEN
> +#endif
> +
>  /* Implement C11 _Generic via GCC builtins.  Example:
>   *
>   *    QEMU_GENERIC(x, (float, sinf), (long double, sinl), sin) (x)

Reviewed-by: Alex Bennée <address@hidden>

--
Alex Bennée