Avoid PhiPlaceholder pointers

The LSE pass passed around const PhiPlaceholder* in many places. This
meant it was difficult to extend the PhiPlaceholder system in some
ways. Change to have the list of PhiPlaceholders be implicit and pass
them around by value when needed.

Test: 67037140
Bug: ./test.py --host

Change-Id: I57ef0b0d39893340a14055c3f78ae4abc14721e1
1 file changed