| Issue |
172651
|
| Summary |
[clang] [x86_64] __builtin_isinf_sign raises FE_INVALID for denormal numbers
|
| Labels |
clang
|
| Assignees |
|
| Reporter |
zatrazz
|
On x86_64/Linux:
```
$ cat t.c
#include <stdint.h>
#include <fenv.h>
#include <math.h>
typedef union
{
long double value;
struct
{
uint32_t lsw;
uint32_t msw;
int sign_exponent:16;
unsigned int empty1:16;
unsigned int empty0:32;
} parts;
} ieee_long_double_shape_type;
static const ieee_long_double_shape_type pseudo_zero = { .parts = { 0x00000000, 0x00000000, 0x0100 } };
int main (int argc, char *argv[])
{
feenableexcept (FE_INVALID);
return __builtin_isinf_sign (pseudo_zero.value);
}
$ clang -target x86_64-linux-gnu t.c -o t -D_GNU_SOURCE -lm
$ ./t
Floating point exception
```
The glibc math.h adds a isinf optimization to use the __builtin_isinf_sign, but it is disabled when -fsignaling-nan is used (GCC [bug 66462](https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66462)). It is always enabled on clang/x86_64 because it does define __SUPPORT_SNAN__.
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