On Mon, Jun 26, 2023 at 3:31 AM liuhongt via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> > > Hmm, good question. GENERIC has a direct truncation to unsigned char
> > > for example, the C standard generally says if the integral part cannot
> > > be represented then the behavior is undefined. So I think we should be
> > > safe here (0x1.0p32 doesn't fit an int).
> >
> > We should be following Annex F (unspecified value plus "invalid" exception
> > for out-of-range floating-to-integer conversions rather than undefined
> > behavior). But we don't achieve that very well at present (see bug 93806
> > comments 27-29 for examples of how such conversions produce wobbly
> > values).
>
> That would mean guarding this with !flag_trapping_math would be the
> appropriate
> thing to do.
>
> Bootstrapped and regtested on x86_64-pc-linux-gnu{-m32,} and
> aarch64-linux-gnu.
> Ok for trunk?
OK.
Thanks,
Richard.
> gcc/ChangeLog:
>
> PR tree-optimization/110371
> PR tree-optimization/110018
> * tree-vect-stmts.cc (vectorizable_conversion): Don't use
> intermiediate type for FIX_TRUNC_EXPR when ftrapping-math.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.target/i386/pr110018-1.c: Add -fno-trapping-math to dg-options.
> * gcc.target/i386/pr110018-2.c: Ditto.
> ---
> gcc/testsuite/gcc.target/i386/pr110018-1.c | 2 +-
> gcc/testsuite/gcc.target/i386/pr110018-2.c | 2 +-
> gcc/tree-vect-stmts.cc | 3 ++-
> 3 files changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/gcc/testsuite/gcc.target/i386/pr110018-1.c
> b/gcc/testsuite/gcc.target/i386/pr110018-1.c
> index b6a3be7b7a2..24eeca60f6f 100644
> --- a/gcc/testsuite/gcc.target/i386/pr110018-1.c
> +++ b/gcc/testsuite/gcc.target/i386/pr110018-1.c
> @@ -1,5 +1,5 @@
> /* { dg-do compile } */
> -/* { dg-options "-mavx512fp16 -mavx512vl -O2 -mavx512dq" } */
> +/* { dg-options "-mavx512fp16 -mavx512vl -O2 -mavx512dq -fno-trapping-math"
> } */
> /* { dg-final { scan-assembler-times {(?n)vcvttp[dsh]2[dqw]} 5 } } */
> /* { dg-final { scan-assembler-times {(?n)vcvt[dqw]*2p[dsh]} 5 } } */
>
> diff --git a/gcc/testsuite/gcc.target/i386/pr110018-2.c
> b/gcc/testsuite/gcc.target/i386/pr110018-2.c
> index a663e074698..9a2d9e17894 100644
> --- a/gcc/testsuite/gcc.target/i386/pr110018-2.c
> +++ b/gcc/testsuite/gcc.target/i386/pr110018-2.c
> @@ -1,5 +1,5 @@
> /* { dg-do compile } */
> -/* { dg-options "-mavx512fp16 -mavx512vl -O2 -mavx512dq" } */
> +/* { dg-options "-mavx512fp16 -mavx512vl -O2 -mavx512dq -fno-trapping-math"
> } */
> /* { dg-final { scan-assembler-times {(?n)vcvttp[dsh]2[dqw]} 5 } } */
> /* { dg-final { scan-assembler-times {(?n)vcvt[dqw]*2p[dsh]} 5 } } */
>
> diff --git a/gcc/tree-vect-stmts.cc b/gcc/tree-vect-stmts.cc
> index 1748555a625..bf61461939b 100644
> --- a/gcc/tree-vect-stmts.cc
> +++ b/gcc/tree-vect-stmts.cc
> @@ -5263,7 +5263,8 @@ vectorizable_conversion (vec_info *vinfo,
> if ((code == FLOAT_EXPR
> && GET_MODE_SIZE (lhs_mode) > GET_MODE_SIZE (rhs_mode))
> || (code == FIX_TRUNC_EXPR
> - && GET_MODE_SIZE (rhs_mode) > GET_MODE_SIZE (lhs_mode)))
> + && GET_MODE_SIZE (rhs_mode) > GET_MODE_SIZE (lhs_mode)
> + && !flag_trapping_math))
> {
> bool float_expr_p = code == FLOAT_EXPR;
> scalar_mode imode = float_expr_p ? rhs_mode : lhs_mode;
> --
> 2.39.1.388.g2fc9e9ca3c
>
