GlobalsModRef+OptNone: Don't prove readnone/other properties from an optnone function

Seems like at least one reasonable interpretation of optnone is that the
optimizer never "looks inside" a function. This fix is consistent with
that interpretation.

Specifically this came up in the situation:

f3 calls f2 calls f1
f2 is always_inline
f1 is optnone

The application of readnone to f1 (& thus to f2) caused the inliner to
kill the call to f2 as being trivially dead (without even checking the
cost function, as it happens - not sure if that's also a bug).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@304833 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed