[PATCH] D34902: [RegisterCoalescer] Account for instructions deleted by removePartialredunduncy and in WorkList

[Sameer AbuAsal via Phabricator via llvm-commits]

sabuasal created this revision.
Herald added subscribers: qcolombet, MatzeB.

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. Update
 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.

I discovered these problem in an out of tree build.


Repository:
  rL LLVM

https://reviews.llvm.org/D34902

Files:
  lib/CodeGen/RegisterCoalescer.cpp


Index: lib/CodeGen/RegisterCoalescer.cpp
===================================================================
--- lib/CodeGen/RegisterCoalescer.cpp
+++ lib/CodeGen/RegisterCoalescer.cpp
@@ -979,6 +979,11 @@
     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 @@
   // 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 @@
       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;
     }


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