[PATCH] D50616: [Fixed Point Arithmetic] FixedPointCast

[John McCall via Phabricator via cfe-commits]

rjmccall added a comment.

>> Has anyone actually asked LLVM whether they would accept fixed-point types into IR?  I'm just a frontend guy, but it seems to me that there are advantages to directly representing these operations in a portable way even if there are no in-tree targets providing special support for them.  And there are certainly in-tree targets that could provide such support if someone was motivated to do it.
> 
> I haven't brought this up to llvm-dev, but the main reason for why we decided to only implement this in clang was because we thought it would be a lot harder pushing a new type into upstream llvm, especially since a lot of the features can be supported on the frontend using clang's existing infrastructure. We are open to adding fixed point types to LLVM IR in the future though once all the frontend stuff is laid out and if the community is willing to accept it.

Mostly I'm reluctant to add a ton of customization points to get more optimizable IR patterns from the frontend when I think it's really clear that the right thing to do is to represent these operations semantically through LLVM IR.

If LLVM people don't want to add an `llvm::FixedPointType` then we should at least add portable intrinsics for them instead of target intrinsics, in which case there's still no point in customizing this in the frontend.


Repository:
  rC Clang

https://reviews.llvm.org/D50616