efriedma added a comment. > The expression “llvm.arith.fence(a * b) + c” means that “a * b” must happen > before “+ c” and FMA guarantees that, but to prevent later optimizations from > unpacking the FMA the correct transformation needs to be: > > llvm.arith.fence(a * b) + c → llvm.arith.fence(FMA(a, b, c))
Does this actually block later transforms from unpacking the FMA? Maybe if the FMA isn't marked "fast"... ---- How is llvm.arith.fence() different from using "freeze" on a floating-point value? The goal isn't really the same, sure, but the effects seem similar at first glance. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D99675/new/ https://reviews.llvm.org/D99675 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
