https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82692
--- Comment #14 from Uroš Bizjak <ubizjak at gmail dot com> --- (In reply to Uroš Bizjak from comment #13) > (In reply to Segher Boessenkool from comment #12) > > But why only do this for FLOAT_MODE_P? Either the logic here isn't > > correct, or cc_modes_compatible isn't the correct hook (we'll need > > a new hook then?), or determining ordered/unordered by CC mode does > > not work (does not fit into how RTL works). > > Non-FP compares can select different mode depending on their operands (e.g. > CCmode to CCZmode when one operand is zero) without secondary effects. But > when reversing the condition from UNGE -> LT, SELECT_CC_MODE will return > trapping mode (LT), whereas original, non-reversed mode (UNGE) was > non-trapping. Please see how targets depend mode of their FP compares on the > condition code. > > The solution here is to keep the original comparison mode for FP compares > (as was proposed in the first version of the patch): when qNaN is > encountered at this point, an exception has to be generated, no matter how > the condition was changed. ... an exception should not be generated ... in the above case, when UNGE is reversed to LT.
