uweigand added a comment. > What are the semantics of vfnmadb with respect to when it rounds vs the > negation?
Hmm, interesting. The z/Architecture Principles of Operation states: > The results for each element of VECTOR FP NEGA- > TIVE MULTIPLY AND ADD and VECTOR FP NEGA- > TIVE MULTIPLY AND SUBTRACT are the same as > for VECTOR FP MULTIPLY AND ADD and VECTOR > FP MULTIPLY AND SUBTRACT, respectively, except > the sign bit of numeric results are inverted. When the > result is a NaN it’s sign bit is unchanged. So as far as rounding is concerned, the vfnmadb should have the exact same result as a vfmadb ; vflcdb sequence we'd get from a fma/fneg. I hadn't realized the NaN special treatment before. This makes the result actually different in that case. OTOH I guess IEEE only says the result has to some NaN, not particularly **which** NaN, so that's probably also OK. (In any case it's unrelated to strict FP.) Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D72722/new/ https://reviews.llvm.org/D72722 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
