On Fri, Nov 24, 2023 at 6:33 AM Xi Ruoyao <xry...@xry111.site> wrote:
>
> With -fno-fp-int-builtin-inexact, trunc is not allowed to raise
> FE_INEXACT and it should produce an integral result (if the input is not
> NaN or Inf). Thus FE_INEXACT should not be raised.
>
> But (int)x may raise FE_INEXACT when x is a non-integer, non-NaN, and
> non-Inf value. C23 recommends to do so in a footnote.
>
> Thus we should not simplify (int)trunc(x) to (int)x if
> -fno-fp-int-builtin-inexact.
>
> gcc/ChangeLog:
>
> PR middle-end/107723
> * convert.cc (convert_to_integer_1) [case BUILT_IN_TRUNC]: Break
> early if !flag_fp_int_builtin_inexact.
>
> gcc/testsuite/ChangeLog:
>
> PR middle-end/107723
> * gcc.dg/torture/builtin-fp-int-inexact-trunc.c: New test.
> ---
>
> Bootstrapped and regtested on x86_64-linux-gnu. Ok for trunk?
>
> gcc/convert.cc | 3 ++-
> .../gcc.dg/torture/builtin-fp-int-inexact-trunc.c | 12 ++++++++++++
> 2 files changed, 14 insertions(+), 1 deletion(-)
> create mode 100644
> gcc/testsuite/gcc.dg/torture/builtin-fp-int-inexact-trunc.c
>
> diff --git a/gcc/convert.cc b/gcc/convert.cc
> index 46c8bcb31f8..31f63ea783b 100644
> --- a/gcc/convert.cc
> +++ b/gcc/convert.cc
> @@ -591,7 +591,8 @@ convert_to_integer_1 (tree type, tree expr, bool dofold)
> CASE_FLT_FN (BUILT_IN_TRUNC):
> CASE_FLT_FN_FLOATN_NX (BUILT_IN_TRUNC):
> if (call_expr_nargs (s_expr) != 1
> - || !SCALAR_FLOAT_TYPE_P (TREE_TYPE (CALL_EXPR_ARG (s_expr, 0))))
> + || !SCALAR_FLOAT_TYPE_P (TREE_TYPE (CALL_EXPR_ARG (s_expr, 0)))
> + || !flag_fp_int_builtin_inexact)
shouldn't that be (!flag_fp_int_builtn_inexact && flag_trapping_math)?
> break;
> return convert_to_integer_1 (type, CALL_EXPR_ARG (s_expr, 0),
> dofold);
> diff --git a/gcc/testsuite/gcc.dg/torture/builtin-fp-int-inexact-trunc.c
> b/gcc/testsuite/gcc.dg/torture/builtin-fp-int-inexact-trunc.c
> new file mode 100644
> index 00000000000..09731183621
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/torture/builtin-fp-int-inexact-trunc.c
> @@ -0,0 +1,12 @@
> +/* Test -fno-fp-int-builtin-inexact. */
> +/* { dg-do compile } */
> +/* { dg-options "-fno-fp-int-builtin-inexact -fdump-tree-original" } */
> +
> +long
> +x (double y)
> +{
> + return __builtin_trunc (y);
> +}
> +
> +/* Optimization should not discard the __builtin_trunc call. */
> +/* { dg-final { scan-tree-dump "__builtin_trunc" "original" } } */
> --
> 2.43.0
>
