IPRA: Run RegUsageInfoPropagate much later
IPRA: Run RegUsageInfoPropagate much later

This was running immediately after isel, before
isel pseudos were even expanded which is really
unreasonable. Move this to before pre-reglloc
passes in case some other pre-regalloc pass wants to
use the updated regmask info.

Fixes one of the reasons IPRA doesn't do anything on
AMDGPU currently. Tests will be included with future
patch after a few more are fixed.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@310875 91177308-0d34-0410-b5e6-96231b3b80d8

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