[PATCH] Prevent user-supplied libc implementations from premature removal in LTO

[Rafael Espíndola]

> Please have another look!

+                        const llvm::TargetLibraryInfo& TLI,

We normally put the & close to the value. Just running clang-format on
the patch should handle this.

CHECK-NOT: myprintf

unfortunately this only checks that there is no myprintf before
memset. I guess you need to redirect llvm-nm's output to a file and
run FileCheck twice.

I think this patch is OK with those changes. Nick, can you confirm
that TLI.getLibFunc is the right function to use for this for now? We
have to add the compiler-rt functions to the list of functions we
don't drop, but TLI.getLibFunc should not be preventing us from
dropping anything we should be able to, correct?

Cheers,
Rafael