https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61219
Bug ID: 61219
Summary: float to double conversion do not silence sNaN on
soft-float ARM
Product: gcc
Version: 4.10.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: aurelien at aurel32 dot net
Host: armv5tejl-unknown-linux-gnueabi
Target: armv5tejl-unknown-linux-gnueabi
Build: armv5tejl-unknown-linux-gnueabi
Consider the following code:
#define _GNU_SOURCE
#include <stdio.h>
#include <math.h>
int main (void)
{
float sNaN = __builtin_nansf ("");
double x = (double) sNaN;
return issignaling(x);
}
It returns 1 on soft-float ARM, but 0 on hard-float ARM or other architecture.
Quoting the IEEE Std 754 standard:
"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. This
case is not handled in extendsfdf2.
This bug is basically present since the ARM EABI support has been added to GCC.
Patch will follow on the gcc-patches mailing list.
