Revert r313400 "[DebugInfo] Insert DW_OP_deref when spilling indirect…

… DBG_VALUEs"

This caused asserts in Chromium. See http://crbug.com/766261

> Summary:
> This comes up in optimized debug info for C++ programs that pass and
> return objects indirectly by address. In these programs,
> llvm.dbg.declare survives optimization, which causes us to emit indirect
> DBG_VALUE instructions. The fast register allocator knows to insert
> DW_OP_deref when spilling indirect DBG_VALUE instructions, but the
> LiveDebugVariables did not until this change.
>
> This fixes part of PR34513. I need to look into why this doesn't work at
> -O0 and I'll send follow up patches to handle that.
>
> Reviewers: aprantl, dblaikie, probinson
>
> Subscribers: qcolombet, hiraditya, llvm-commits
>
> Differential Revision: https://reviews.llvm.org/D37911

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@313589 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/LiveDebugVariables.cpp

@@ -108,8 +108,8 @@ class LDVImpl;
 /// held by the same virtual register. The equivalence class is the transitive
 /// closure of that relation.
 class UserValue {
-  const DILocalVariable *Variable; ///< The debug info variable we are part of.
-  const DIExpression *Expression; ///< Any complex address expression.
+  const MDNode *Variable;   ///< The debug info variable we are part of.
+  const MDNode *Expression; ///< Any complex address expression.
   bool IsIndirect;        ///< true if this is a register-indirect+offset value.
   DebugLoc dl;            ///< The debug location for the variable. This is
                           ///< used by dwarf writer to find lexical scope.
@@ -132,9 +132,8 @@ class UserValue {
   void coalesceLocation(unsigned LocNo);
 
   /// insertDebugValue - Insert a DBG_VALUE into MBB at Idx for LocNo.
-  void insertDebugValue(MachineBasicBlock *MBB, SlotIndex Idx,
-                        unsigned LocNo, bool Spilled, LiveIntervals &LIS,
-                        const TargetInstrInfo &TII);
+  void insertDebugValue(MachineBasicBlock *MBB, SlotIndex Idx, unsigned LocNo,
+                        LiveIntervals &LIS, const TargetInstrInfo &TII);
 
   /// splitLocation - Replace OldLocNo ranges with NewRegs ranges where NewRegs
   /// is live. Returns true if any changes were made.
@@ -143,8 +142,8 @@ class UserValue {
 
 public:
   /// UserValue - Create a new UserValue.
-  UserValue(const DILocalVariable *var, const DIExpression *expr, bool i,
-            DebugLoc L, LocMap::Allocator &alloc)
+  UserValue(const MDNode *var, const MDNode *expr, bool i, DebugLoc L,
+            LocMap::Allocator &alloc)
       : Variable(var), Expression(expr), IsIndirect(i), dl(std::move(L)),
         leader(this), locInts(alloc) {}
 
@@ -160,8 +159,8 @@ class UserValue {
   UserValue *getNext() const { return next; }
 
   /// match - Does this UserValue match the parameters?
-  bool match(const DILocalVariable *Var, const DIExpression *Expr,
-             const DILocation *IA, bool indirect) const {
+  bool match(const MDNode *Var, const MDNode *Expr, const DILocation *IA,
+             bool indirect) const {
     return Var == Variable && Expr == Expression && dl->getInlinedAt() == IA &&
            indirect == IsIndirect;
   }
@@ -265,14 +264,12 @@ class UserValue {
                      LiveIntervals &LIS);
 
   /// rewriteLocations - Rewrite virtual register locations according to the
-  /// provided virtual register map. Record which locations were spilled.
-  void rewriteLocations(VirtRegMap &VRM, const TargetRegisterInfo &TRI,
-                        BitVector &SpilledLocations);
+  /// provided virtual register map.
+  void rewriteLocations(VirtRegMap &VRM, const TargetRegisterInfo &TRI);
 
   /// emitDebugValues - Recreate DBG_VALUE instruction from data structures.
-  void emitDebugValues(VirtRegMap *VRM, LiveIntervals &LIS,
-                       const TargetInstrInfo &TRI,
-                       const BitVector &SpilledLocations);
+  void emitDebugValues(VirtRegMap *VRM,
+                       LiveIntervals &LIS, const TargetInstrInfo &TRI);
 
   /// getDebugLoc - Return DebugLoc of this UserValue.
   DebugLoc getDebugLoc() { return dl;}
@@ -302,11 +299,11 @@ class LDVImpl {
   VRMap virtRegToEqClass;
 
   /// Map user variable to eq class leader.
-  using UVMap = DenseMap<const DILocalVariable *, UserValue *>;
+  using UVMap = DenseMap<const MDNode *, UserValue *>;
   UVMap userVarMap;
 
   /// getUserValue - Find or create a UserValue.
-  UserValue *getUserValue(const DILocalVariable *Var, const DIExpression *Expr,
+  UserValue *getUserValue(const MDNode *Var, const MDNode *Expr,
                           bool IsIndirect, const DebugLoc &DL);
 
   /// lookupVirtReg - Find the EC leader for VirtReg or null.
@@ -459,9 +456,8 @@ void UserValue::mapVirtRegs(LDVImpl *LDV) {
       LDV->mapVirtReg(locations[i].getReg(), this);
 }
 
-UserValue *LDVImpl::getUserValue(const DILocalVariable *Var,
-                                 const DIExpression *Expr, bool IsIndirect,
-                                 const DebugLoc &DL) {
+UserValue *LDVImpl::getUserValue(const MDNode *Var, const MDNode *Expr,
+                                 bool IsIndirect, const DebugLoc &DL) {
   UserValue *&Leader = userVarMap[Var];
   if (Leader) {
     UserValue *UV = Leader->getLeader();
@@ -500,11 +496,11 @@ bool LDVImpl::handleDebugValue(MachineInstr &MI, SlotIndex Idx) {
   }
 
   // Get or create the UserValue for (variable,offset).
-  bool IsIndirect = MI.getOperand(1).isImm();
+  bool IsIndirect = MI.isIndirectDebugValue();
   if (IsIndirect)
     assert(MI.getOperand(1).getImm() == 0 && "DBG_VALUE with nonzero offset");
-  const DILocalVariable *Var = MI.getDebugVariable();
-  const DIExpression *Expr = MI.getDebugExpression();
+  const MDNode *Var = MI.getDebugVariable();
+  const MDNode *Expr = MI.getDebugExpression();
   //here.
   UserValue *UV = getUserValue(Var, Expr, IsIndirect, MI.getDebugLoc());
   UV->addDef(Idx, MI.getOperand(0));
@@ -977,10 +973,8 @@ splitRegister(unsigned OldReg, ArrayRef<unsigned> NewRegs, LiveIntervals &LIS) {
     static_cast<LDVImpl*>(pImpl)->splitRegister(OldReg, NewRegs);
 }
 
-void UserValue::rewriteLocations(VirtRegMap &VRM, const TargetRegisterInfo &TRI,
-                                 BitVector &SpilledLocations) {
-  SpilledLocations.resize(locations.size());
-
+void
+UserValue::rewriteLocations(VirtRegMap &VRM, const TargetRegisterInfo &TRI) {
   // Iterate over locations in reverse makes it easier to handle coalescing.
   for (unsigned i = locations.size(); i ; --i) {
     unsigned LocNo = i-1;
@@ -999,7 +993,6 @@ void UserValue::rewriteLocations(VirtRegMap &VRM, const TargetRegisterInfo &TRI,
     } else if (VRM.getStackSlot(VirtReg) != VirtRegMap::NO_STACK_SLOT) {
       // FIXME: Translate SubIdx to a stackslot offset.
       Loc = MachineOperand::CreateFI(VRM.getStackSlot(VirtReg));
-      SpilledLocations.set(LocNo);
     } else {
       Loc.setReg(0);
       Loc.setSubReg(0);
@@ -1033,7 +1026,7 @@ findInsertLocation(MachineBasicBlock *MBB, SlotIndex Idx,
 }
 
 void UserValue::insertDebugValue(MachineBasicBlock *MBB, SlotIndex Idx,
-                                 unsigned LocNo, bool Spilled,
+                                 unsigned LocNo,
                                  LiveIntervals &LIS,
                                  const TargetInstrInfo &TII) {
   MachineBasicBlock::iterator I = findInsertLocation(MBB, Idx, LIS);
@@ -1043,35 +1036,25 @@ void UserValue::insertDebugValue(MachineBasicBlock *MBB, SlotIndex Idx,
   assert(cast<DILocalVariable>(Variable)
              ->isValidLocationForIntrinsic(getDebugLoc()) &&
          "Expected inlined-at fields to agree");
-
-  // If the location was spilled, the new DBG_VALUE will be indirect. If the
-  // original DBG_VALUE was indirect, we need to add DW_OP_deref to indicate
-  // that the original virtual register was a pointer.
-  bool NewIndirect = IsIndirect || Spilled;
-  const DIExpression *Expr = Expression;
-  if (Spilled && IsIndirect)
-    Expr = DIExpression::prepend(Expr, DIExpression::WithDeref);
-
-  MachineInstrBuilder MIB =
-      BuildMI(*MBB, I, getDebugLoc(), TII.get(TargetOpcode::DBG_VALUE))
-          .add(Loc);
-  if (NewIndirect)
-    MIB.addImm(0U);
+  if (Loc.isReg())
+    BuildMI(*MBB, I, getDebugLoc(), TII.get(TargetOpcode::DBG_VALUE),
+            IsIndirect, Loc.getReg(), Variable, Expression);
   else
-    MIB.addReg(0U, RegState::Debug);
-  MIB.addMetadata(Variable).addMetadata(Expr);
+    BuildMI(*MBB, I, getDebugLoc(), TII.get(TargetOpcode::DBG_VALUE))
+        .add(Loc)
+        .addImm(0U)
+        .addMetadata(Variable)
+        .addMetadata(Expression);
 }
 
 void UserValue::emitDebugValues(VirtRegMap *VRM, LiveIntervals &LIS,
-                                const TargetInstrInfo &TII,
-                                const BitVector &SpilledLocations) {
+                                const TargetInstrInfo &TII) {
   MachineFunction::iterator MFEnd = VRM->getMachineFunction().end();
 
   for (LocMap::const_iterator I = locInts.begin(); I.valid();) {
     SlotIndex Start = I.start();
     SlotIndex Stop = I.stop();
     unsigned LocNo = I.value();
-    bool Spilled = LocNo != UndefLocNo ? SpilledLocations.test(LocNo) : false;
 
     // If the interval start was trimmed to the lexical scope insert the
     // DBG_VALUE at the previous index (otherwise it appears after the
@@ -1084,7 +1067,7 @@ void UserValue::emitDebugValues(VirtRegMap *VRM, LiveIntervals &LIS,
     SlotIndex MBBEnd = LIS.getMBBEndIdx(&*MBB);
 
     DEBUG(dbgs() << " BB#" << MBB->getNumber() << '-' << MBBEnd);
-    insertDebugValue(&*MBB, Start, LocNo, Spilled, LIS, TII);
+    insertDebugValue(&*MBB, Start, LocNo, LIS, TII);
     // This interval may span multiple basic blocks.
     // Insert a DBG_VALUE into each one.
     while(Stop > MBBEnd) {
@@ -1094,7 +1077,7 @@ void UserValue::emitDebugValues(VirtRegMap *VRM, LiveIntervals &LIS,
         break;
       MBBEnd = LIS.getMBBEndIdx(&*MBB);
       DEBUG(dbgs() << " BB#" << MBB->getNumber() << '-' << MBBEnd);
-      insertDebugValue(&*MBB, Start, LocNo, Spilled, LIS, TII);
+      insertDebugValue(&*MBB, Start, LocNo, LIS, TII);
     }
     DEBUG(dbgs() << '\n');
     if (MBB == MFEnd)
@@ -1109,11 +1092,10 @@ void LDVImpl::emitDebugValues(VirtRegMap *VRM) {
   if (!MF)
     return;
   const TargetInstrInfo *TII = MF->getSubtarget().getInstrInfo();
-  BitVector SpilledLocations;
   for (unsigned i = 0, e = userValues.size(); i != e; ++i) {
     DEBUG(userValues[i]->print(dbgs(), TRI));
-    userValues[i]->rewriteLocations(*VRM, *TRI, SpilledLocations);
-    userValues[i]->emitDebugValues(VRM, *LIS, *TII, SpilledLocations);
+    userValues[i]->rewriteLocations(*VRM, *TRI);
+    userValues[i]->emitDebugValues(VRM, *LIS, *TII);
   }
   EmitDone = true;
 }

test/DebugInfo/X86/bbjoin.ll

@@ -11,12 +11,12 @@
 ; }
 ; CHECK: ![[X:.*]] = !DILocalVariable(name: "x",
 ; CHECK: bb.0.entry:
-; CHECK:   DBG_VALUE 23, debug-use _, ![[X]],
+; CHECK:   DBG_VALUE 23, 0, ![[X]],
 ; CHECK:   DBG_VALUE %rsp, 0, ![[X]], !DIExpression(DW_OP_plus_uconst, 4, DW_OP_deref),
 ; CHECK: bb.1.if.then:
-; CHECK:   DBG_VALUE 43, debug-use _, ![[X]],
+; CHECK:   DBG_VALUE 43, 0, ![[X]],
 ; CHECK: bb.2.if.end:
-; CHECK-NOT:  DBG_VALUE 23, debug-use _, ![[X]],
+; CHECK-NOT:  DBG_VALUE 23, 0, ![[X]],
 ; CHECK:   RETQ %eax
 
 target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"