nemanjai added inline comments.
================
Comment at: clang/lib/Basic/Targets/PPC.cpp:519
.Default(false);
+ Features["crbits"] = llvm::StringSwitch<bool>(CPU)
+ .Case("ppc64le", true)
----------------
shchenz wrote:
> 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.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D124060/new/
https://reviews.llvm.org/D124060
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