[RegisterCoalescer] Add wrapper for Erasing Instructions

Summary:
      To delete an instruction the coalescer needs to call eraseFromParent()
      on the MachineInstr, insert it in the ErasedInstrs list and update the
      Live Ranges structure. This patch re-factors the code to do all that in
      one function. This will also fix cases where previous code wasn't
      inserting deleted instructions in the ErasedList.

Reviewers: qcolombet, kparzysz

Reviewed By: qcolombet

Subscribers: MatzeB, llvm-commits, qcolombet

Differential Revision: https://reviews.llvm.org/D36204

llvm-svn: 309915

llvm/lib/CodeGen/RegisterCoalescer.cpp

@@ -248,6 +248,16 @@ namespace {
       }
     }
 
+    /// Wrapper Method to do all the necessary work when an Instruction is
+    /// deleted.
+    /// Optimizations should use this to make sure that deleted instructions
+    /// are always accounted for.
+    void deleteInstr(MachineInstr* MI) {
+      ErasedInstrs.insert(MI);
+      LIS->RemoveMachineInstrFromMaps(*MI);
+      MI->eraseFromParent();
+    }
+
   public:
     static char ID; ///< Class identification, replacement for typeinfo
     RegisterCoalescer() : MachineFunctionPass(ID) {
@@ -797,9 +807,7 @@ bool RegisterCoalescer::removeCopyByCommutingDef(const CoalescerPair &CP,
       S.MergeValueNumberInto(SubDVNI, SubBValNo);
     }
 
-    ErasedInstrs.insert(UseMI);
-    LIS->RemoveMachineInstrFromMaps(*UseMI);
-    UseMI->eraseFromParent();
+    deleteInstr(UseMI);
   }
 
   // Extend BValNo by merging in IntA live segments of AValNo. Val# definition
@@ -993,10 +1001,8 @@ bool RegisterCoalescer::removePartialRedundancy(const CoalescerPair &CP,
   // Note: This is fine to remove the copy before updating the live-ranges.
   // 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();
+  deleteInstr(&CopyMI);
 
   // Update the liveness.
   SmallVector<SlotIndex, 8> EndPoints;
@@ -1578,8 +1584,7 @@ bool RegisterCoalescer::joinCopy(MachineInstr *CopyMI, bool &Again) {
 
   // Eliminate undefs.
   if (!CP.isPhys() && eliminateUndefCopy(CopyMI)) {
-    LIS->RemoveMachineInstrFromMaps(*CopyMI);
-    CopyMI->eraseFromParent();
+    deleteInstr(CopyMI);
     return false;  // Not coalescable.
   }
 
@@ -1607,8 +1612,7 @@ bool RegisterCoalescer::joinCopy(MachineInstr *CopyMI, bool &Again) {
       }
       DEBUG(dbgs() << "\tMerged values:          " << LI << '\n');
     }
-    LIS->RemoveMachineInstrFromMaps(*CopyMI);
-    CopyMI->eraseFromParent();
+    deleteInstr(CopyMI);
     return true;
   }
 
@@ -1668,8 +1672,7 @@ bool RegisterCoalescer::joinCopy(MachineInstr *CopyMI, bool &Again) {
     if (!CP.isPartial() && !CP.isPhys()) {
       if (adjustCopiesBackFrom(CP, CopyMI) ||
           removeCopyByCommutingDef(CP, CopyMI)) {
-        LIS->RemoveMachineInstrFromMaps(*CopyMI);
-        CopyMI->eraseFromParent();
+        deleteInstr(CopyMI);
         DEBUG(dbgs() << "\tTrivial!\n");
         return true;
       }
@@ -1855,8 +1858,7 @@ bool RegisterCoalescer::joinReservedPhysReg(CoalescerPair &CP) {
     }
   }
 
-  LIS->RemoveMachineInstrFromMaps(*CopyMI);
-  CopyMI->eraseFromParent();
+  deleteInstr(CopyMI);
 
   // We don't track kills for reserved registers.
   MRI->clearKillFlags(CP.getSrcReg());