silvas added a comment.
Thanks for splitting this out.
I think the `-fprofile-instrument=llvm` is straightforward and uncontroversial.
Let's focus this review on that and split the others into a separate review.
But a quick preview of my thoughs about `-fprofile-instrument={llvm,clang}-use`:
I think that fully decoupling the cc1 options from the driver options like you
are doing here is a good cleanup, but we need a more refined approach. For
example, the current patch has "use" modes as mutually exclusive with the "gen"
modes, which doesn't make sense. In fact, we have already seen a situation
where we may want to have "use" and "gen" in the same clang invocation: for
profile guided MST instr. And I don't see a reason to artificially prohibit FE
"use" to annotate MD_prof metadata and then use that metadata for profile
guided MST instr (however, it would be a strange workflow for users...).
Perhaps something like `-fprofile-instrument-use={llvm,clang}` which sets a
CodeGenOpt `ProfileUse` which is either {None, Clang, LLVM}. We can use a
common PGOInstrumentor enum for both, since there is a 1:1 mapping between the
instrumentor and its corresponding "use" logic.
In the long run I imagine we will want two mirror options
`-fpgo-gen={none,llvm,clang}` and `-fpgo-use={none,llvm,clang}`, but the
details of renaming to the final state can wait until we clearly see the right
design (this is cc1 so it is easy to refactor as needed later).
http://reviews.llvm.org/D17622
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