> On 31 Oct 2019, at 00:28, David Blaikie <dblai...@gmail.com> wrote: > > > > On Wed, Oct 30, 2019 at 4:25 PM Hans Åberg <haber...@telia.com> wrote: > >> I believe that GMP is just using integer types, and then uses that to make >> multiprecision integers, rational numbers, and floating point numbers. At >> least MPFR uses only the integer and rational number part of GMP, and builds >> multiprecision floating point numbers on top of that, which is necessary >> because of special requirements of the standards they adhere to. > > Ah, fair enough - that narrows down the points of failure a little.
In addition, they use assembly code, but that can be turned off with configure --disable-assembly, though I did not 'make check' with that. >> GMP has been used in three years in a sequenced operation that must be exact >> and without errors to solve the problem [1], and I would think it used GCC >> with optimizations. So that puts Clang in a tough spot. :-) > > Not as much as it would seem - again, the spec allows for a fair bit of > flexibility in a bunch of ways. (admittedly, within integer arithmetic > without invoking UB (but, again, that's not proven - UBSan isn't guaranteed > to catch everything)) Different compilers optimize code in different ways - > that the code "works"/produces the desired behavior on one compiler/under > some optimizations and not others doesn't give us much idea about whether the > code or the compiler is correct. Different behavior is acceptable in C++ in a > bunch of ways & compilers rely on that flexibility. Yes, but assuming that the GMP adheres to the C standard, there should be no difference in the arithmetical values produced. _______________________________________________ cfe-users mailing list cfe-users@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-users
