When deciding whether to perform rounding on the significand,
the generated IR was using (width - leading zeros - 1) rather
than (width - leading zeros). This is different from how the
routine in compiler-rt does it:
int sd = srcBits - clzSrcT(a);
int e = sd - 1;
if (sd > dstMantDig) {
This bug means that the following code, when built on -O0:
#include <stdio.h>
_BitInt(233) v_1037 = 0;
int main(void)
{
v_1037 = 18014398509481982wb;
double d = v_1037;
printf("d = %f\n", d);
return 0;
}
prints "d = 9007199254740992.000000", which is incorrect.
The correct result is "d = 18014398509481982.000000".
