[Mlir-commits] [mlir] [mlir][Arith] Add FTZ (Flush-to-Zero) fast-math flag (PR #112700)

[Diego Caballero]

dcaballe wrote:

I talked to Jakub during the LLVM Dev and I still have reservations about this. I don't see FTZ as significantly different from other flags in FMF that lead to approximate results. If we are concerned about the specific approximation to zero that FTZ enforces, we should consider a more open-ended “approxDenormals” FMF. Honestly, I would be surprised if functions used for “approxFunc” FMF are handling denormals properly. In my opinion, “approxDenormals” should allow for the approximation of denormals, and omitting this flag should result in more accurate results without necessarily changing the semantics. I wouldn’t walk the FMF vs rounding mode path. One could argue that “allowContract” is actually a “rounding mode” as, beyond contracting operations, what this flag states is that it’s ok to not round the intermediate results of the operations being contracted. 

https://github.com/llvm/llvm-project/pull/112700