On Wed, 1 Jul 2015, Zinovy Nis wrote: > Had anyone a chance to compare FP implementation in compiler_rt? I > still wonder why the sizes differ so much, Incomplete implementation > in compiler_rt? > compiler_rt claims it is IEEE-compliant.
If you examine the implementation approaches, you will see that apart from the compiler_rt code not being set up for rounding mode and exceptions support (and in some cases, it can be hard to completely optimize generic code as much as code that never has to consider those issues), it (for addition) does normalization in one place, and swaps the arguments in one place so as to know which has the larger magnitude, whereas soft-fp tries to reduce the amount of processing in each case by only normalizing when and to the extent needed and duplicating code for each choice of which argument has the larger exponent (and having separate code for the case of equal exponents). -- Joseph S. Myers jos...@codesourcery.com
