Fix 12892.

Dead code elimination during coalescing could cause a virtual register
to be split into connected components. The following rewriting would be
confused about the already joined copies present in the code, but
without a corresponding value number in the live range.

Erase all joined copies instantly when joining intervals such that the
MI and LiveInterval representations are always in sync.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@157135 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/LiveRangeEdit.cpp

@@ -308,6 +308,10 @@ void LiveRangeEdit::eliminateDeadDefs(SmallVectorImpl<MachineInstr*> &Dead,
         TheDelegate->LRE_DidCloneVirtReg(Dups.back()->reg, LI->reg);
     }
     ConEQ.Distribute(&Dups[0], MRI);
+    DEBUG({
+      for (unsigned i = 0; i != NumComp; ++i)
+        dbgs() << '\t' << *Dups[i] << '\n';
+    });
   }
 }
 

lib/CodeGen/RegisterCoalescer.cpp

@@ -1081,9 +1081,10 @@ bool RegisterCoalescer::joinCopy(MachineInstr *CopyMI, bool &Again) {
   if (!CP.isPhys() && RegClassInfo.isProperSubClass(CP.getNewRC()))
     InflateRegs.push_back(CP.getDstReg());
 
-  // Remember to delete the copy instruction.
+  // CopyMI has been erased by joinIntervals at this point. Remove it from
-  LIS->RemoveMachineInstrFromMaps(CopyMI);
+  // ErasedInstrs since copyCoalesceWorkList() won't add a successful join back
-  CopyMI->eraseFromParent();
+  // to the work list. This keeps ErasedInstrs from growing needlessly.
+  ErasedInstrs.erase(CopyMI);
 
   // Rewrite all SrcReg operands to DstReg.
   // Also update DstReg operands to include DstIdx if it is set.
@@ -1285,6 +1286,7 @@ bool RegisterCoalescer::joinIntervals(CoalescerPair &CP) {
   SmallVector<VNInfo*, 16> NewVNInfo;
 
   SmallVector<MachineInstr*, 8> DupCopies;
+  SmallVector<MachineInstr*, 8> DeadCopies;
 
   LiveInterval &LHS = LIS->getOrCreateInterval(CP.getDstReg());
   DEBUG({ dbgs() << "\t\tLHS = "; LHS.print(dbgs(), TRI); dbgs() << "\n"; });
@@ -1313,6 +1315,7 @@ bool RegisterCoalescer::joinIntervals(CoalescerPair &CP) {
       continue;
 
     LHSValsDefinedFromRHS[VNI] = lr->valno;
+    DeadCopies.push_back(MI);
   }
 
   // Loop over the value numbers of the RHS, seeing if any are defined from
@@ -1339,6 +1342,7 @@ bool RegisterCoalescer::joinIntervals(CoalescerPair &CP) {
         continue;
 
     RHSValsDefinedFromLHS[VNI] = lr->valno;
+    DeadCopies.push_back(MI);
   }
 
   LHSValNoAssignments.resize(LHS.getNumValNums(), -1);
@@ -1438,6 +1442,17 @@ bool RegisterCoalescer::joinIntervals(CoalescerPair &CP) {
   if (RHSValNoAssignments.empty())
     RHSValNoAssignments.push_back(-1);
 
+  // Now erase all the redundant copies.
+  for (unsigned i = 0, e = DeadCopies.size(); i != e; ++i) {
+    MachineInstr *MI = DeadCopies[i];
+    DEBUG(dbgs() << "\t\terased:\t" << LIS->getInstructionIndex(MI)
+                 << '\t' << *MI);
+    if (!ErasedInstrs.insert(MI))
+      continue;
+    LIS->RemoveMachineInstrFromMaps(MI);
+    MI->eraseFromParent();
+  }
+
   SmallVector<unsigned, 8> SourceRegisters;
   for (SmallVector<MachineInstr*, 8>::iterator I = DupCopies.begin(),
          E = DupCopies.end(); I != E; ++I) {
@@ -1451,7 +1466,8 @@ bool RegisterCoalescer::joinIntervals(CoalescerPair &CP) {
     // A = X
     unsigned Src = MI->getOperand(1).getReg();
     SourceRegisters.push_back(Src);
-    ErasedInstrs.insert(MI);
+    if (!ErasedInstrs.insert(MI))
+      continue;
     LIS->RemoveMachineInstrFromMaps(MI);
     MI->eraseFromParent();
   }

test/CodeGen/X86/2012-05-19-CoalescerCrash.ll

@@ -0,0 +1,122 @@
+; RUN: llc < %s -verify-coalescing
+; PR12892
+;
+; Dead code elimination during coalesing causes a live range to split into two
+; virtual registers. Stale identity copies that had already been joined were
+; interfering with the liveness computations.
+
+target triple = "i386-pc-linux-gnu"
+
+define void @_ZN4llvm17AsmMatcherEmitter3runERNS_11raw_ostreamE() align 2 {
+  invoke void @_ZNK4llvm13CodeGenTarget12getAsmParserEv()
+          to label %1 unwind label %5
+
+; <label>:1                                       ; preds = %0
+  invoke void @_ZNK4llvm6Record16getValueAsStringENS_9StringRefE()
+          to label %4 unwind label %2
+
+; <label>:2                                       ; preds = %1
+  %3 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*)
+          cleanup
+  unreachable
+
+; <label>:4                                       ; preds = %1
+  invoke void @_ZN4llvm18isCurrentDebugTypeEPKc()
+          to label %12 unwind label %7
+
+; <label>:5                                       ; preds = %0
+  %6 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*)
+          cleanup
+  br label %33
+
+; <label>:7                                       ; preds = %4
+  %8 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*)
+          cleanup
+  br label %9
+
+; <label>:9                                       ; preds = %28, %7
+  %10 = phi { i8*, i32 } [ %29, %28 ], [ %8, %7 ]
+  %11 = extractvalue { i8*, i32 } %10, 1
+  invoke fastcc void @_ZN12_GLOBAL__N_114AsmMatcherInfoD2Ev()
+          to label %32 unwind label %35
+
+; <label>:12                                      ; preds = %4
+  invoke void @_ZNK4llvm13CodeGenTarget10getRegBankEv()
+          to label %13 unwind label %16
+
+; <label>:13                                      ; preds = %12
+  br label %14
+
+; <label>:14                                      ; preds = %20, %13
+  %15 = icmp eq i32 undef, 0
+  br i1 %15, label %20, label %18
+
+; <label>:16                                      ; preds = %12
+  %17 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*)
+          cleanup
+  br label %26
+
+; <label>:18                                      ; preds = %14
+  invoke void @_ZNSs4_Rep9_S_createEjjRKSaIcE()
+          to label %19 unwind label %21
+
+; <label>:19                                      ; preds = %18
+  unreachable
+
+; <label>:20                                      ; preds = %14
+  br label %14
+
+; <label>:21                                      ; preds = %18
+  %22 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*)
+          cleanup
+  %23 = extractvalue { i8*, i32 } %22, 1
+  br i1 undef, label %26, label %24
+
+; <label>:24                                      ; preds = %21
+  br i1 undef, label %25, label %26
+
+; <label>:25                                      ; preds = %24
+  unreachable
+
+; <label>:26                                      ; preds = %24, %21, %16
+  %27 = phi i32 [ 0, %16 ], [ %23, %21 ], [ %23, %24 ]
+  invoke void @_ZNSt6vectorISt4pairISsSsESaIS1_EED1Ev()
+          to label %28 unwind label %30
+
+; <label>:28                                      ; preds = %26
+  %29 = insertvalue { i8*, i32 } undef, i32 %27, 1
+  br label %9
+
+; <label>:30                                      ; preds = %26
+  %31 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*)
+          catch i8* null
+  unreachable
+
+; <label>:32                                      ; preds = %9
+  br label %33
+
+; <label>:33                                      ; preds = %32, %5
+  %34 = phi i32 [ undef, %5 ], [ %11, %32 ]
+  unreachable
+
+; <label>:35                                      ; preds = %9
+  %36 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*)
+          catch i8* null
+  unreachable
+}
+
+declare void @_ZNK4llvm13CodeGenTarget12getAsmParserEv()
+
+declare i32 @__gxx_personality_v0(...)
+
+declare void @_ZNK4llvm6Record16getValueAsStringENS_9StringRefE()
+
+declare void @_ZN4llvm18isCurrentDebugTypeEPKc()
+
+declare fastcc void @_ZN12_GLOBAL__N_114AsmMatcherInfoD2Ev() unnamed_addr inlinehint align 2
+
+declare hidden void @_ZNSt6vectorISt4pairISsSsESaIS1_EED1Ev() unnamed_addr align 2
+
+declare void @_ZNSs4_Rep9_S_createEjjRKSaIcE()
+
+declare void @_ZNK4llvm13CodeGenTarget10getRegBankEv()