Summary:
If an MIMG instruction has managed to get through to adjustWritemask in isel but
has no uses (and doesn't enable TFC) then prevent an assertion by not attempting
to adjust the writemask.
The instruction will be removed anyway.
Change-Id: I9a5dba6bafe1f35ac99c1b73df390936e2ac27a7
Subscribers: arsenm, kzhuravl, jvesely, wdng, nhaehnle, yaxunl, tpr, t-tye, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D58964
llvm-svn: 356540
David Stuttard