[PATCH] D124060: [PowerPC] Enable CR bits support for Power8 and above.
Nemanja Ivanovic via Phabricator via cfe-commits
cfe-commits at lists.llvm.org
Wed Apr 27 02:42:56 PDT 2022
nemanjai added inline comments.
Comment at: clang/lib/Basic/Targets/PPC.cpp:519
+ Features["crbits"] = llvm::StringSwitch<bool>(CPU)
+ .Case("ppc64le", true)
> amyk wrote:
> > shchenz wrote:
> > > If we set the `+crbits` by the arch name, do we still need the customization (Turn on crbits for O2 and above) in `computeFSAdditions()`?
> > Yeah, that's a good point. I looked into this previously, and it appears that addition of `-mcrbits` inside `computeFSAdditions()` may still be necessary.
> > In particular, we have test cases that test pre-POWER8 with optimizations on (or, if no optimization level is provided, then -O2 is assumed the default). In these cases, much of the code changes if the customization inside `computeFSAdditions()` is removed because we would no longer be using crbits pre-P8.
> hmm, OK, then we still have the same issue that this patch fixes for pre-POWER8. I'm ok with leaving it for now as IMO Power7/Power6 should not be major versions for PowerPC.
Up until Power8, the only instructions we had that require `crbits` were CR-logicals (which existed since the POWER architecture - i.e. before PowerPC). In Power8, we added BCD instructions that also require `crbits`. So that's why we turn it on for Power8 and up.
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
More information about the cfe-commits