On Wed, Jul 20, 2016 at 8:48 AM, Aurelien Jarno <aurel...@aurel32.net> wrote:
> On ARM soft-float, the float to double conversion doesn't convert a sNaN
> to qNaN as the IEEE Std 754 standard mandates:
>
> "Under default exception handling, any operation signaling an invalid
> operation exception and for which a floating-point result is to be
> delivered shall deliver a quiet NaN."
>
> Given the soft float ARM code ignores exceptions and always provides a
> result, a float to double conversion of a signaling NaN should return a
> quiet NaN. Fix this in extendsfdf2.
>
> gcc/ChangeLog:
>
> PR target/59833
> * config/arm/ieee754-df.S (extendsfdf2): Convert sNaN to qNaN.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.dg/pr59833.c: New testcase.
Ok - assuming this was tested appropriately with no regressions.
Thanks for following up.
Ramana
> ---
> gcc/testsuite/gcc.dg/pr59833.c | 18 ++++++++++++++++++
> libgcc/config/arm/ieee754-df.S | 10 +++++++---
> 2 files changed, 25 insertions(+), 3 deletions(-)
> create mode 100644 gcc/testsuite/gcc.dg/pr59833.c
>
> diff --git a/gcc/testsuite/gcc.dg/pr59833.c b/gcc/testsuite/gcc.dg/pr59833.c
> new file mode 100644
> index 0000000..e0e4ed5
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/pr59833.c
> @@ -0,0 +1,18 @@
> +/* { dg-do run { target { *-*-linux* *-*-gnu* } } } */
> +/* { dg-options "-O0 -lm" } */
> +/* { dg-require-effective-target issignaling } */
> +
> +#define _GNU_SOURCE
> +#include <math.h>
> +
> +int main (void)
> +{
> + float sNaN = __builtin_nansf ("");
> + double x = (double) sNaN;
> + if (issignaling(x))
> + {
> + __builtin_abort();
> + }
> +
> + return 0;
> +}
> diff --git a/libgcc/config/arm/ieee754-df.S b/libgcc/config/arm/ieee754-df.S
> index a2aac70..1ecaa9d 100644
> --- a/libgcc/config/arm/ieee754-df.S
> +++ b/libgcc/config/arm/ieee754-df.S
> @@ -507,11 +507,15 @@ ARM_FUNC_ALIAS aeabi_f2d extendsfdf2
> eorne xh, xh, #0x38000000 @ fixup exponent otherwise.
> RETc(ne) @ and return it.
>
> - teq r2, #0 @ if actually 0
> - do_it ne, e
> - teqne r3, #0xff000000 @ or INF or NAN
> + bics r2, r2, #0xff000000 @ isolate mantissa
> + do_it eq @ if 0, that is ZERO or INF,
> RETc(eq) @ we are done already.
>
> + teq r3, #0xff000000 @ check for NAN
> + do_it eq, t
> + orreq xh, xh, #0x00080000 @ change to quiet NAN
> + RETc(eq) @ and return it.
> +
> @ value was denormalized. We can normalize it now.
> do_push {r4, r5, lr}
> .cfi_adjust_cfa_offset 12 @ CFA is now sp + previousOffset + 12
>
> --
> Aurelien Jarno GPG: 4096R/1DDD8C9B
> aurel...@aurel32.net http://www.aurel32.net
