[DebugInfo] Remove some users of DBG_VALUEs IsIndirect field

This patch kills off a significant user of the "IsIndirect" field of
DBG_VALUE machine insts. Brought up in in PR41675, IsIndirect is
techncally redundant as it can be expressed by the DIExpression of a
DBG_VALUE inst, and it isn't helpful to have two ways of expressing
things.

Rather than setting IsIndirect, have DBG_VALUE creators add an extra deref
to the insts DIExpression. There should now be no appearences of
IsIndirect=True from isel down to LiveDebugVariables / VirtRegRewriter,
which is ensured by an assertion in LDVImpl::handleDebugValue. This means
we also get to delete the IsIndirect handling in LiveDebugVariables. Tests
can be upgraded by for example swapping the following IsIndirect=True
DBG_VALUE:

  DBG_VALUE $somereg, 0, !123, !DIExpression(DW_OP_foo)

With one where the indirection is in the DIExpression, by _appending_
a deref:

  DBG_VALUE $somereg, $noreg, !123, !DIExpression(DW_OP_foo, DW_OP_deref)

Which both mean the same thing. 

Most of the test changes in this patch are updates of that form; also some
changes in how the textual assembly printer handles these insts.

Differential Revision: https://reviews.llvm.org/D68945

llvm-svn: 374877

Author: jmorse

llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp

@@ -1378,7 +1378,7 @@ bool IRTranslator::translateKnownIntrinsic(const CallInst &CI, Intrinsic::ID ID,
     if (!V) {
       // Currently the optimizer can produce this; insert an undef to
       // help debugging.  Probably the optimizer should not do this.
-      MIRBuilder.buildIndirectDbgValue(0, DI.getVariable(), DI.getExpression());
+      MIRBuilder.buildDirectDbgValue(0, DI.getVariable(), DI.getExpression());
     } else if (const auto *CI = dyn_cast<Constant>(V)) {
       MIRBuilder.buildConstDbgValue(*CI, DI.getVariable(), DI.getExpression());
     } else {

llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp

@@ -107,9 +107,13 @@ MachineIRBuilder::buildIndirectDbgValue(Register Reg, const MDNode *Variable,
   assert(
       cast<DILocalVariable>(Variable)->isValidLocationForIntrinsic(getDL()) &&
       "Expected inlined-at fields to agree");
+  // DBG_VALUE insts now carry IR-level indirection in their DIExpression
+  // rather than encoding it in the instruction itself.
+  const DIExpression *DIExpr = cast<DIExpression>(Expr);
+  DIExpr = DIExpression::append(DIExpr, {dwarf::DW_OP_deref});
   return insertInstr(BuildMI(getMF(), getDL(),
                              getTII().get(TargetOpcode::DBG_VALUE),
-                             /*IsIndirect*/ true, Reg, Variable, Expr));
+                             /*IsIndirect*/ false, Reg, Variable, DIExpr));
 }
 
 MachineInstrBuilder MachineIRBuilder::buildFIDbgValue(int FI,
@@ -120,11 +124,15 @@ MachineInstrBuilder MachineIRBuilder::buildFIDbgValue(int FI,
   assert(
       cast<DILocalVariable>(Variable)->isValidLocationForIntrinsic(getDL()) &&
       "Expected inlined-at fields to agree");
+  // DBG_VALUE insts now carry IR-level indirection in their DIExpression
+  // rather than encoding it in the instruction itself.
+  const DIExpression *DIExpr = cast<DIExpression>(Expr);
+  DIExpr = DIExpression::append(DIExpr, {dwarf::DW_OP_deref});
   return buildInstr(TargetOpcode::DBG_VALUE)
       .addFrameIndex(FI)
-      .addImm(0)
+      .addReg(0)
       .addMetadata(Variable)
-      .addMetadata(Expr);
+      .addMetadata(DIExpr);
 }
 
 MachineInstrBuilder MachineIRBuilder::buildConstDbgValue(const Constant &C,
@@ -148,7 +156,7 @@ MachineInstrBuilder MachineIRBuilder::buildConstDbgValue(const Constant &C,
     MIB.addReg(0U);
   }
 
-  return MIB.addImm(0).addMetadata(Variable).addMetadata(Expr);
+  return MIB.addReg(0).addMetadata(Variable).addMetadata(Expr);
 }
 
 MachineInstrBuilder MachineIRBuilder::buildDbgLabel(const MDNode *Label) {

llvm/lib/CodeGen/LiveDebugVariables.cpp

@@ -99,28 +99,27 @@ enum : unsigned { UndefLocNo = ~0U };
 /// usage of the location.
 class DbgValueLocation {
 public:
-  DbgValueLocation(unsigned LocNo, bool WasIndirect)
-      : LocNo(LocNo), WasIndirect(WasIndirect) {
+  DbgValueLocation(unsigned LocNo)
+      : LocNo(LocNo) {
     static_assert(sizeof(*this) == sizeof(unsigned), "bad bitfield packing");
     assert(locNo() == LocNo && "location truncation");
   }
 
-  DbgValueLocation() : LocNo(0), WasIndirect(0) {}
+  DbgValueLocation() : LocNo(0) {}
 
   unsigned locNo() const {
     // Fix up the undef location number, which gets truncated.
     return LocNo == INT_MAX ? UndefLocNo : LocNo;
   }
-  bool wasIndirect() const { return WasIndirect; }
   bool isUndef() const { return locNo() == UndefLocNo; }
 
   DbgValueLocation changeLocNo(unsigned NewLocNo) const {
-    return DbgValueLocation(NewLocNo, WasIndirect);
+    return DbgValueLocation(NewLocNo);
   }
 
   friend inline bool operator==(const DbgValueLocation &LHS,
                                 const DbgValueLocation &RHS) {
-    return LHS.LocNo == RHS.LocNo && LHS.WasIndirect == RHS.WasIndirect;
+    return LHS.LocNo == RHS.LocNo;
   }
 
   friend inline bool operator!=(const DbgValueLocation &LHS,
@@ -129,8 +128,7 @@ class DbgValueLocation {
   }
 
 private:
-  unsigned LocNo : 31;
-  unsigned WasIndirect : 1;
+  unsigned LocNo;
 };
 
 /// Map of where a user value is live, and its location.
@@ -261,8 +259,8 @@ class UserValue {
   void mapVirtRegs(LDVImpl *LDV);
 
   /// Add a definition point to this value.
-  void addDef(SlotIndex Idx, const MachineOperand &LocMO, bool IsIndirect) {
-    DbgValueLocation Loc(getLocationNo(LocMO), IsIndirect);
+  void addDef(SlotIndex Idx, const MachineOperand &LocMO) {
+    DbgValueLocation Loc(getLocationNo(LocMO));
     // Add a singular (Idx,Idx) -> Loc mapping.
     LocMap::iterator I = locInts.find(Idx);
     if (!I.valid() || I.start() != Idx)
@@ -297,11 +295,10 @@ class UserValue {
   ///
   /// \param LI Scan for copies of the value in LI->reg.
   /// \param LocNo Location number of LI->reg.
-  /// \param WasIndirect Indicates if the original use of LI->reg was indirect
   /// \param Kills Points where the range of LocNo could be extended.
   /// \param [in,out] NewDefs Append (Idx, LocNo) of inserted defs here.
   void addDefsFromCopies(
-      LiveInterval *LI, unsigned LocNo, bool WasIndirect,
+      LiveInterval *LI, unsigned LocNo,
       const SmallVectorImpl<SlotIndex> &Kills,
       SmallVectorImpl<std::pair<SlotIndex, DbgValueLocation>> &NewDefs,
       MachineRegisterInfo &MRI, LiveIntervals &LIS);
@@ -521,8 +518,6 @@ void UserValue::print(raw_ostream &OS, const TargetRegisterInfo *TRI) {
       OS << "undef";
     else {
       OS << I.value().locNo();
-      if (I.value().wasIndirect())
-        OS << " ind";
     }
   }
   for (unsigned i = 0, e = locations.size(); i != e; ++i) {
@@ -631,19 +626,18 @@ bool LDVImpl::handleDebugValue(MachineInstr &MI, SlotIndex Idx) {
   }
 
   // Get or create the UserValue for (variable,offset) here.
-  bool IsIndirect = MI.getOperand(1).isImm();
-  if (IsIndirect)
-    assert(MI.getOperand(1).getImm() == 0 && "DBG_VALUE with nonzero offset");
+  assert(!MI.getOperand(1).isImm() && "DBG_VALUE with indirect flag before "
+                                      "LiveDebugVariables");
   const DILocalVariable *Var = MI.getDebugVariable();
   const DIExpression *Expr = MI.getDebugExpression();
   UserValue *UV =
       getUserValue(Var, Expr, MI.getDebugLoc());
   if (!Discard)
-    UV->addDef(Idx, MI.getOperand(0), IsIndirect);
+    UV->addDef(Idx, MI.getOperand(0));
   else {
     MachineOperand MO = MachineOperand::CreateReg(0U, false);
     MO.setIsDebug();
-    UV->addDef(Idx, MO, false);
+    UV->addDef(Idx, MO);
   }
   return true;
 }
@@ -751,7 +745,7 @@ void UserValue::extendDef(SlotIndex Idx, DbgValueLocation Loc, LiveRange *LR,
 }
 
 void UserValue::addDefsFromCopies(
-    LiveInterval *LI, unsigned LocNo, bool WasIndirect,
+    LiveInterval *LI, unsigned LocNo,
     const SmallVectorImpl<SlotIndex> &Kills,
     SmallVectorImpl<std::pair<SlotIndex, DbgValueLocation>> &NewDefs,
     MachineRegisterInfo &MRI, LiveIntervals &LIS) {
@@ -815,7 +809,7 @@ void UserValue::addDefsFromCopies(
       MachineInstr *CopyMI = LIS.getInstructionFromIndex(DstVNI->def);
       assert(CopyMI && CopyMI->isCopy() && "Bad copy value");
       unsigned LocNo = getLocationNo(CopyMI->getOperand(0));
-      DbgValueLocation NewLoc(LocNo, WasIndirect);
+      DbgValueLocation NewLoc(LocNo);
       I.insert(Idx, Idx.getNextSlot(), NewLoc);
       NewDefs.push_back(std::make_pair(Idx, NewLoc));
       break;
@@ -863,8 +857,7 @@ void UserValue::computeIntervals(MachineRegisterInfo &MRI,
       // sub-register in that regclass). For now, simply skip handling copies if
       // a sub-register is involved.
       if (LI && !LocMO.getSubReg())
-        addDefsFromCopies(LI, Loc.locNo(), Loc.wasIndirect(), Kills, Defs, MRI,
-                          LIS);
+        addDefsFromCopies(LI, Loc.locNo(), Kills, Defs, MRI, LIS);
       continue;
     }
 
@@ -1302,21 +1295,14 @@ void UserValue::insertDebugValue(MachineBasicBlock *MBB, SlotIndex StartIdx,
   // that the original virtual register was a pointer. Also, add the stack slot
   // offset for the spilled register to the expression.
   const DIExpression *Expr = Expression;
-  uint8_t DIExprFlags = DIExpression::ApplyOffset;
-  bool IsIndirect = Loc.wasIndirect();
-  if (Spilled) {
-    if (IsIndirect)
-      DIExprFlags |= DIExpression::DerefAfter;
-    Expr =
-        DIExpression::prepend(Expr, DIExprFlags, SpillOffset);
-    IsIndirect = true;
-  }
+  if (Spilled)
+    Expr = DIExpression::prepend(Expr, DIExpression::ApplyOffset, SpillOffset);
 
   assert((!Spilled || MO.isFI()) && "a spilled location must be a frame index");
 
   do {
     BuildMI(*MBB, I, getDebugLoc(), TII.get(TargetOpcode::DBG_VALUE),
-            IsIndirect, MO, Variable, Expr);
+            Spilled, MO, Variable, Expr);
 
     // Continue and insert DBG_VALUES after every redefinition of register
     // associated with the debug value within the range

llvm/lib/CodeGen/SelectionDAG/FastISel.cpp

@@ -1389,9 +1389,11 @@ bool FastISel::selectIntrinsicCall(const IntrinsicInst *II) {
              "Expected inlined-at fields to agree");
       // A dbg.declare describes the address of a source variable, so lower it
       // into an indirect DBG_VALUE.
+      auto *Expr = DI->getExpression();
+      Expr = DIExpression::append(Expr, {dwarf::DW_OP_deref});
       BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc,
-              TII.get(TargetOpcode::DBG_VALUE), /*IsIndirect*/ true,
-              *Op, DI->getVariable(), DI->getExpression());
+              TII.get(TargetOpcode::DBG_VALUE), /*IsIndirect*/ false,
+              *Op, DI->getVariable(), Expr);
     } else {
       // We can't yet handle anything else here because it would require
       // generating code, thus altering codegen because of debug info.
@@ -1415,19 +1417,19 @@ bool FastISel::selectIntrinsicCall(const IntrinsicInst *II) {
       if (CI->getBitWidth() > 64)
         BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc, II)
             .addCImm(CI)
-            .addImm(0U)
+            .addReg(0U)
             .addMetadata(DI->getVariable())
             .addMetadata(DI->getExpression());
       else
         BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc, II)
             .addImm(CI->getZExtValue())
-            .addImm(0U)
+            .addReg(0U)
             .addMetadata(DI->getVariable())
             .addMetadata(DI->getExpression());
     } else if (const auto *CF = dyn_cast<ConstantFP>(V)) {
       BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc, II)
           .addFPImm(CF)
-          .addImm(0U)
+          .addReg(0U)
           .addMetadata(DI->getVariable())
           .addMetadata(DI->getExpression());
     } else if (unsigned Reg = lookUpRegForValue(V)) {

llvm/lib/CodeGen/SelectionDAG/InstrEmitter.cpp

@@ -677,7 +677,7 @@ MachineInstr *
 InstrEmitter::EmitDbgValue(SDDbgValue *SD,
                            DenseMap<SDValue, unsigned> &VRBaseMap) {
   MDNode *Var = SD->getVariable();
-  MDNode *Expr = SD->getExpression();
+  const DIExpression *Expr = SD->getExpression();
   DebugLoc DL = SD->getDebugLoc();
   assert(cast<DILocalVariable>(Var)->isValidLocationForIntrinsic(DL) &&
          "Expected inlined-at fields to agree");
@@ -701,12 +701,11 @@ InstrEmitter::EmitDbgValue(SDDbgValue *SD,
     // EmitTargetCodeForFrameDebugValue is responsible for allocation.
     auto FrameMI = BuildMI(*MF, DL, TII->get(TargetOpcode::DBG_VALUE))
                        .addFrameIndex(SD->getFrameIx());
+
     if (SD->isIndirect())
-      // Push [fi + 0] onto the DIExpression stack.
-      FrameMI.addImm(0);
-    else
-      // Push fi onto the DIExpression stack.
-      FrameMI.addReg(0);
+      Expr = DIExpression::append(Expr, {dwarf::DW_OP_deref});
+
+    FrameMI.addReg(0);
     return FrameMI.addMetadata(Var).addMetadata(Expr);
   }
   // Otherwise, we're going to create an instruction here.
@@ -752,9 +751,9 @@ InstrEmitter::EmitDbgValue(SDDbgValue *SD,
 
   // Indirect addressing is indicated by an Imm as the second parameter.
   if (SD->isIndirect())
-    MIB.addImm(0U);
-  else
-    MIB.addReg(0U, RegState::Debug);
+    Expr = DIExpression::append(Expr, {dwarf::DW_OP_deref});
+
+  MIB.addReg(0U, RegState::Debug);
 
   MIB.addMetadata(Var);
   MIB.addMetadata(Expr);

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

@@ -5519,8 +5519,9 @@ bool SelectionDAGBuilder::EmitFuncArgumentDbgValue(
           Expr, Offset, RegAndSize.second);
         if (!FragmentExpr)
           continue;
+        assert(!IsDbgDeclare && "DbgDeclare operand is not in memory?");
         FuncInfo.ArgDbgValues.push_back(
-          BuildMI(MF, DL, TII->get(TargetOpcode::DBG_VALUE), IsDbgDeclare,
+          BuildMI(MF, DL, TII->get(TargetOpcode::DBG_VALUE), false,
                   RegAndSize.first, Variable, *FragmentExpr));
         Offset += RegAndSize.second;
       }
@@ -5554,8 +5555,10 @@ bool SelectionDAGBuilder::EmitFuncArgumentDbgValue(
   assert(Variable->isValidLocationForIntrinsic(DL) &&
          "Expected inlined-at fields to agree");
   IsIndirect = (Op->isReg()) ? IsIndirect : true;
+  if (IsIndirect)
+    Expr = DIExpression::append(Expr, {dwarf::DW_OP_deref});
   FuncInfo.ArgDbgValues.push_back(
-      BuildMI(MF, DL, TII->get(TargetOpcode::DBG_VALUE), IsIndirect,
+      BuildMI(MF, DL, TII->get(TargetOpcode::DBG_VALUE), false,
               *Op, Variable, Expr));
 
   return true;

llvm/test/CodeGen/AArch64/GlobalISel/debug-cpp.ll

@@ -18,7 +18,7 @@ target triple = "aarch64-unknown-linux-gnu"
 %struct.NTCopy = type { i32 }
 
 ; CHECK-LABEL: name: _Z3foo6NTCopy
-; CHECK: DBG_VALUE %{{[0-9]+}}(p0), 0, !23, !DIExpression(), debug-location !24
+; CHECK: DBG_VALUE %{{[0-9]+}}(p0), $noreg, !23, !DIExpression(DW_OP_deref), debug-location !24
 ; Function Attrs: noinline nounwind optnone
 define dso_local i32 @_Z3foo6NTCopy(%struct.NTCopy* %o) #0 !dbg !7 {
 entry:

llvm/test/CodeGen/AArch64/GlobalISel/debug-insts.ll

@@ -15,7 +15,7 @@ entry:
 }
 
 ; CHECK-LABEL: name: debug_declare_vla
-; CHECK: DBG_VALUE %{{[0-9]+}}(p0), 0, !14, !DIExpression(), debug-location !15
+; CHECK: DBG_VALUE %{{[0-9]+}}(p0), $noreg, !14, !DIExpression(DW_OP_deref), debug-location !15
 define void @debug_declare_vla(i32 %in) #0 !dbg !13 {
 entry:
   %vla.addr = alloca i32, i32 %in
@@ -32,11 +32,11 @@ define void @debug_value(i32 %in) #0 !dbg !16 {
   store i32 %in, i32* %addr
 ; CHECK: DBG_VALUE %1(p0), $noreg, !17, !DIExpression(DW_OP_deref), debug-location !18
   call void @llvm.dbg.value(metadata i32* %addr, i64 0, metadata !17, metadata !DIExpression(DW_OP_deref)), !dbg !18
-; CHECK: DBG_VALUE 123, 0, !17, !DIExpression(), debug-location !18
+; CHECK: DBG_VALUE 123, $noreg, !17, !DIExpression(), debug-location !18
   call void @llvm.dbg.value(metadata i32 123, i64 0, metadata !17, metadata !DIExpression()), !dbg !18
-; CHECK: DBG_VALUE float 1.000000e+00, 0, !17, !DIExpression(), debug-location !18
+; CHECK: DBG_VALUE float 1.000000e+00, $noreg, !17, !DIExpression(), debug-location !18
   call void @llvm.dbg.value(metadata float 1.000000e+00, i64 0, metadata !17, metadata !DIExpression()), !dbg !18
-; CHECK: DBG_VALUE $noreg, 0, !17, !DIExpression(), debug-location !18
+; CHECK: DBG_VALUE $noreg, $noreg, !17, !DIExpression(), debug-location !18
   call void @llvm.dbg.value(metadata i32* null, i64 0, metadata !17, metadata !DIExpression()), !dbg !18
   ret void
 }

llvm/test/CodeGen/ARM/debug-info-arg.ll

@@ -11,7 +11,7 @@ define void @foo(%struct.tag_s* nocapture %this, %struct.tag_s* %c, i64 %x, i64
   tail call void @llvm.dbg.value(metadata %struct.tag_s* %c, metadata !13, metadata !DIExpression()), !dbg !21
   tail call void @llvm.dbg.value(metadata i64 %x, metadata !14, metadata !DIExpression()), !dbg !22
   tail call void @llvm.dbg.value(metadata i64 %y, metadata !17, metadata !DIExpression()), !dbg !23
-;CHECK:	@DEBUG_VALUE: foo:y <- [DW_OP_plus_uconst 8] [$r7+0]
+;CHECK:	@DEBUG_VALUE: foo:y <- [DW_OP_plus_uconst 8, DW_OP_deref] $r7
   tail call void @llvm.dbg.value(metadata %struct.tag_s* %ptr1, metadata !18, metadata !DIExpression()), !dbg !24
   tail call void @llvm.dbg.value(metadata %struct.tag_s* %ptr2, metadata !19, metadata !DIExpression()), !dbg !25
   %1 = icmp eq %struct.tag_s* %c, null, !dbg !26

llvm/test/CodeGen/PowerPC/debuginfo-stackarg.ll

@@ -34,7 +34,7 @@ define i64 @foo(i64 %bar1, i64 %bar2, i64 %bar3, i64 %bar4, i64 %bar5) local_unn
 ; We expect to find a DBG_VALUE refering to the metadata id for bar5, using the lowest
 ; of the two fixed stack offsets found earlier.
 ; CHECK-LABEL: body:
-; CHECK: DBG_VALUE $r1, 0, !17, !DIExpression(DW_OP_plus_uconst, 8)
+; CHECK: DBG_VALUE $r1, $noreg, !17, !DIExpression(DW_OP_plus_uconst, 8, DW_OP_deref)
 entry:
   tail call void @llvm.dbg.value(metadata i64 %bar1, metadata !13, metadata !DIExpression()), !dbg !18
   tail call void @llvm.dbg.value(metadata i64 %bar2, metadata !14, metadata !DIExpression()), !dbg !19