On Sun, Nov 01, 2015 at 06:51:19PM -0500, Ganesh Ajjanagadde wrote: > On Sun, Nov 1, 2015 at 6:25 PM, Nicolas George <geo...@nsup.org> wrote: > > Le primidi 11 brumaire, an CCXXIV, Ronald S. Bultje a écrit : > >> So, is this a bug in llrint, or is this a failure to use llrint, or is this > >> different from llrint? It sounds to me that llrint should be used, not our > >> own alternative. > > > > Is there a sized version of the function? int64rint? Otherwise, these > > functions for the native types are as useless as the native types > > themselves. > > No, not in ISO C, or even libc AFAIK. ISO C tends to favor the > "non-sized" types in their signatures. The reason (I believe) stems > from the fact that an implementation is free to not even define the > sized types: > 7.20.1.1, point 3 - "These types are optional. However, if an > implementation provides integer types with widths of 8, 16, 32, or 64 > bits, no padding bits, and (for the signed types) that have a two’s > complement representation [all platforms supported by the project], it > shall define the corresponding typedef names." - > Thus they want to limit their scope to mostly (or perharps only?) stdint.h. > > Even otherwise, these functions are somewhat useless due to the > undefined behavior outside the range. All they really do is get > rounding done correctly according to the current FPU environment and > associated rounding modes, which can be manipulated in C99/C11.
quite some of the undefined behavior also makes more optimizations
possible for advanced compilers
random silly example
min = 0;
for(i=0; i<N; i++) {
float c = whatever()
min = fmin(min, c);
out[i] = llrint(c);
}
here the compiler can remove any and all handling of NaN and +-Inf
from fmin() because llrint(c) implies c is within the range
represetable of the integer types
with a llrint() equivalent that is defined for all cases this is not
possible anymore
[...]
--
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
During times of universal deceit, telling the truth becomes a
revolutionary act. -- George Orwell
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