[RegisterCoalescer] Account for instructions deleted by removePartialredunduncy and in WorkList

Summary:
 removePartialRedundency optimization introduces a state in the
 RegisterCoalescer where an instruction pointed to in the WorkList
 is deleted from the MBB and then removed from the ErasedList.
 This patch updates the ErasedList to be used globally by not erasing
 erased Instructions from  it to solve the problem.

 The patch also accounts for the case where an Instruction was previously
 deleted and the same memory was reused by BuildMI to create a new instruction.

Reviewers: kparzysz, qcolombet

Reviewed By: qcolombet

Subscribers: MatzeB, qcolombet, llvm-commits

Differential Revision: https://reviews.llvm.org/D34902

llvm-svn: 306915

Author: Sameer AbuAsal

llvm/lib/CodeGen/RegisterCoalescer.cpp

@@ -979,6 +979,11 @@ bool RegisterCoalescer::removePartialRedundancy(const CoalescerPair &CP,
     IntB.createDeadDef(NewCopyIdx, LIS->getVNInfoAllocator());
     for (LiveInterval::SubRange &SR : IntB.subranges())
       SR.createDeadDef(NewCopyIdx, LIS->getVNInfoAllocator());
+
+    // If the newly created Instruction has an address of an instruction that was
+    // deleted before (object recycled by the allocator) it needs to be removed from
+    // the deleted list.
+    ErasedInstrs.erase(NewCopyMI);
   } else {
     DEBUG(dbgs() << "\tremovePartialRedundancy: Remove the copy from BB#"
                  << MBB.getNumber() << '\t' << CopyMI);
@@ -989,6 +994,8 @@ bool RegisterCoalescer::removePartialRedundancy(const CoalescerPair &CP,
   // While updating the live-ranges, we only look at slot indices and
   // never go back to the instruction.
   LIS->RemoveMachineInstrFromMaps(CopyMI);
+  // Mark instructions as deleted.
+  ErasedInstrs.insert(&CopyMI);
   CopyMI.eraseFromParent();
 
   // Update the liveness.
@@ -3095,7 +3102,7 @@ copyCoalesceWorkList(MutableArrayRef<MachineInstr*> CurrList) {
       continue;
     // Skip instruction pointers that have already been erased, for example by
     // dead code elimination.
-    if (ErasedInstrs.erase(CurrList[i])) {
+    if (ErasedInstrs.count(CurrList[i])) {
       CurrList[i] = nullptr;
       continue;
     }