Eliminate the IS_PHI_DEF flag and VNInfo::setIsPHIDef().

A value number is a PHI def if and only if it begins at a block
boundary. This can be derived from the def slot, a separate flag is not
necessary.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@160893 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/LiveIntervalAnalysis.cpp

@@ -290,7 +290,6 @@ void LiveIntervals::handleVirtualRegisterDef(MachineBasicBlock *mbb,
         assert(getInstructionFromIndex(Start) == 0 &&
                "PHI def index points at actual instruction.");
         ValNo = interval.getNextValue(Start, VNInfoAllocator);
-        ValNo->setIsPHIDef(true);
       }
       LiveRange LR(Start, killIdx, ValNo);
       interval.addRange(LR);