Align definition of DW_OP_plus with DWARF spec [3/3]

[sdesmalen]

Summary

This patch is part of 3 patches that together form a single patch, but must be introduced in stages in order not to break things.

The way that LLVM interprets DW_OP_plus in DIExpression nodes is basically that of the DW_OP_plus_uconst operator since LLVM expects an unsigned constant operand. This unnecessarily restricts the DW_OP_plus operator, preventing it from being used to describe the evaluation of runtime values on the expression stack. These patches try to align the semantics of DW_OP_plus and DW_OP_minus with that of the DWARF definition, which pops two elements off the expression stack, performs the operation and pushes the result back on the stack.

This is done in three stages:
• The first patch (LLVM) adds support for DW_OP_plus_uconst.
• The second patch (Clang) contains changes all its uses from DW_OP_plus to DW_OP_plus_uconst.
• The third patch (LLVM) changes the semantics of DW_OP_plus and DW_OP_minus to be in line with its DWARF meaning. This patch includes the bitcode upgrade from legacy DIExpressions.

Patch by Sander de Smalen.

[aprantl]

This also needs a bitcode upgrade to transform the old use of DW_OP_minus to the new one. See my comment on D33892 for details.

[sdesmalen]

Incremented the expression's Version operand and added backwards compatibility with older bitcode files by constructing a {DW_OP_constu, <opnd>, DW_OP_minus} from a {DW_OP_minus, <opnd>}.

[sdesmalen]

rebased to patch [1/3]

[aprantl]

Ah ok, I see. The cleanest way to do this would be to

1. Implement support for DW_OP_plus_constu in LLVM
2. Switch over Clang to use DW_OP_plus_constu

3a. Retire the old DW_OP_plus and implement the bitcode upgrade in LLVM
3b. Retire the old DW_OP_minus (AFAIK not used by clang) and implement the bitcode upgrade in LLVM
(The last two can be one joined commit so we only need to bump the DIExpression version number once and keep the upgrade code simple).

I understand that this may sound like a lot of busywork at first, but the code is already there and with some git rebase -i and git commit -p reordering the patches this way should go relatively fast. It would have the big advantage that each commit can be committed individually and safely be reverted. (The current patches increment the version number in 1/3 and implement the bitcode upgrade for DW_OP_minus later in 3/3).

Would this work for you?

[sdesmalen]

Patch [1/3], now just adds support for DW_OP_plus_uconst.
Patch [3/3] changes meaning of DW_OP_plus and DW_OP_minus to be in line with its DWARF meaning. This patch includes the bitcode upgrade from legacy DIExpressions.

[sdesmalen]

Hi Adrian, thanks for your thorough review! I agree with reordering the functionality within the patches, it is better to have only a single bitcode upgrade.
I have updated the patches accordingly, hopefully they're getting in the right shape now :)

[aprantl]

This generally LGTM, there is only a bitcode upgrade test for DW_OP_minus missing. I'm marking the review as accepted under the condition that the missing test is added before committing.

test/Bitcode/DIExpression-deref.ll

18

Please also add a test for the old DW_OP_minus. (If you choose to add it to this testcase, you will need to check out a much older version of llvm, rebuild llvm-dis, and re-create the .bc file with it. Otherwise you can add a new upgrade test just for DW_OP_minus and assemble it with today's trunk).

[sdesmalen]

test/Bitcode/DIExpression-deref.ll

18

Good spot, I'll add a test for the DW_OPminus too.

In order for me to do that, what is the preferred way get changes to binary files as a patch file that I can upload to Phabricator?
When I tried this previously (having creating a patch file using 'git diff --binary'), Phabricator was not able to parse the patch file.

[aprantl]

IIRC git diff -U9999 should work just fine. In any case I am not going to review the binary file — I am just going to trust that it is what you say it is in the accompanying testcase :-)

[sdesmalen]

Added test for DW_OP_minus bitcode upgrade:

• test/Bitcode/DIExpression-minus-upgrade.ll
• test/Bitcode/DIExpression-minus-upgrade.ll.bc

[aprantl]

Looks good. Please watch the stage2 and LTO bots carefully after committing.

[sdesmalen]

Somehow I missed unit-test test/DebugInfo/MIR/ARM/split-superreg-complex.mir, so updated it.
It should pass all unit tests now.

docs/LangRef.rst

 ``DIExpression`` nodes represent expressions that are inspired by the DWARF
 expression language. They are used in :ref:`debug intrinsics<dbg_intrinsics>`
 (such as ``llvm.dbg.declare`` and ``llvm.dbg.value``) to describe how the
 referenced LLVM variable relates to the source language variable.
 
 The current supported vocabulary is limited:
 
 - ``DW_OP_deref`` dereferences the top of the expression stack.
-- ``DW_OP_plus, 93`` adds ``93`` to the working expression.
+- ``DW_OP_plus`` pops the last two entries from the expression stack, adds
+  them together and appends the result to the expression stack.
+- ``DW_OP_minus`` pops the last two entries from the expression stack, subtracts
+  the last entry from the second last entry and appends the result to the
+  expression stack.
 - ``DW_OP_plus_uconst, 93`` adds ``93`` to the working expression.
 - ``DW_OP_LLVM_fragment, 16, 8`` specifies the offset and size (``16`` and ``8``
   here, respectively) of the variable fragment from the working expression. Note
   that contrary to DW_OP_bit_piece, the offset is describing the the location
   within the described source variable.
 - ``DW_OP_swap`` swaps top two stack entries.
 - ``DW_OP_xderef`` provides extended dereference mechanism. The entry at the top
   of the stack is treated as an address. The second stack entry is treated as an
   address space identifier.
 - ``DW_OP_stack_value`` marks a constant value.
 
 DWARF specifies three kinds of simple location descriptions: Register, memory,
 and implicit location descriptions. Register and memory location descriptions
 describe the *location* of a source variable (in the sense that a debugger might
 modify its value), whereas implicit locations describe merely the *value* of a
 source variable. DIExpressions also follow this model: A DIExpression that
 doesn't have a trailing ``DW_OP_stack_value`` will describe an *address* when
 combined with a concrete location.
 
 .. code-block:: llvm
 
     !0 = !DIExpression(DW_OP_deref)
-    !1 = !DIExpression(DW_OP_plus, 3)
     !1 = !DIExpression(DW_OP_plus_uconst, 3)
+    !1 = !DIExpression(DW_OP_constu, 3, DW_OP_plus)
     !2 = !DIExpression(DW_OP_bit_piece, 3, 7)
-    !3 = !DIExpression(DW_OP_deref, DW_OP_plus, 3, DW_OP_LLVM_fragment, 3, 7)
+    !3 = !DIExpression(DW_OP_deref, DW_OP_constu, 3, DW_OP_plus, DW_OP_LLVM_fragment, 3, 7)
     !4 = !DIExpression(DW_OP_constu, 2, DW_OP_swap, DW_OP_xderef)
     !5 = !DIExpression(DW_OP_constu, 42, DW_OP_stack_value)
 
 DIObjCProperty
 """"""""""""""
 
 ``DIObjCProperty`` nodes represent Objective-C property nodes.
 

include/llvm/IR/DebugInfoMetadata.h

 };
 
 /// DWARF expression.
 ///
 /// This is (almost) a DWARF expression that modifies the location of a
 /// variable, or the location of a single piece of a variable, or (when using
 /// DW_OP_stack_value) is the constant variable value.
 ///
-/// FIXME: Instead of DW_OP_plus taking an argument, this should use DW_OP_const
-/// and have DW_OP_plus consume the topmost elements on the stack.
-///
 /// TODO: Co-allocate the expression elements.
 /// TODO: Separate from MDNode, or otherwise drop Distinct and Temporary
 /// storage types.
 class DIExpression : public MDNode {
   friend class LLVMContextImpl;
   friend class MDNode;
 
   std::vector<uint64_t> Elements;

lib/Bitcode/Reader/MetadataLoader.cpp

 #endif
     PHs.front().replaceUseWith(MD);
     PHs.pop_front();
   }
 }
 
 } // anonynous namespace
 
+static Error error(const Twine &Message) {
+  return make_error<StringError>(
+      Message, make_error_code(BitcodeError::CorruptedBitcode));
+}
+
 class MetadataLoader::MetadataLoaderImpl {
   BitcodeReaderMetadataList MetadataList;
   BitcodeReaderValueList &ValueList;
   BitstreamCursor &Stream;
   LLVMContext &Context;
   Module &TheModule;
   std::function<Type *(unsigned)> getTypeByID;
 
for (auto &BB : F)
               SmallVector<uint64_t, 8> Ops;
               Ops.append(std::next(DIExpr->elements_begin()),
                          DIExpr->elements_end());
               auto *E = DIExpression::get(Context, Ops);
               DDI->setOperand(2, MetadataAsValue::get(Context, E));
             }
   }
 
+  /// Upgrade the expression from previous versions.
+  Error upgradeDIExpression(uint64_t FromVersion,
+                            MutableArrayRef<uint64_t> &Expr,
+                            SmallVectorImpl<uint64_t> &Buffer) {
+    auto N = Expr.size();
+    switch (FromVersion) {
+    default:
+      return error("Invalid record");
+    case 0:
+      if (N >= 3 && Expr[N - 3] == dwarf::DW_OP_bit_piece)
+        Expr[N - 3] = dwarf::DW_OP_LLVM_fragment;
+      LLVM_FALLTHROUGH;
+    case 1:
+      // Move DW_OP_deref to the end.
+      if (N && Expr[0] == dwarf::DW_OP_deref) {
+        auto End = Expr.end();
+        if (Expr.size() >= 3 &&
+            *std::prev(End, 3) == dwarf::DW_OP_LLVM_fragment)
+          End = std::prev(End, 3);
+        std::move(std::next(Expr.begin()), End, Expr.begin());
+        *std::prev(End) = dwarf::DW_OP_deref;
+      }
+      NeedDeclareExpressionUpgrade = true;
+      LLVM_FALLTHROUGH;
+    case 2: {
+      // Change DW_OP_plus to DW_OP_plus_uconst.
+      // Change DW_OP_minus to DW_OP_uconst, DW_OP_minus
+      auto SubExpr = ArrayRef<uint64_t>(Expr);
+      while (!SubExpr.empty()) {
+        // Skip past other operators with their operands
+        // for this version of the IR, obtained from
+        // from historic DIExpression::ExprOperand::getSize().
+        size_t HistoricSize;
+        switch (SubExpr.front()) {
+        default:
+          HistoricSize = 1;
+          break;
+        case dwarf::DW_OP_constu:
+        case dwarf::DW_OP_minus:
+        case dwarf::DW_OP_plus:
+          HistoricSize = 2;
+          break;
+        case dwarf::DW_OP_LLVM_fragment:
+          HistoricSize = 3;
+          break;
+        }
+
+        // If the expression is malformed, make sure we don't
+        // copy more elements than we should.
+        HistoricSize = std::min(SubExpr.size(), HistoricSize);
+        ArrayRef<uint64_t> Args = SubExpr.slice(1, HistoricSize-1);
+
+        switch (SubExpr.front()) {
+        case dwarf::DW_OP_plus:
+          Buffer.push_back(dwarf::DW_OP_plus_uconst);
+          Buffer.append(Args.begin(), Args.end());
+          break;
+        case dwarf::DW_OP_minus:
+          Buffer.push_back(dwarf::DW_OP_constu);
+          Buffer.append(Args.begin(), Args.end());
+          Buffer.push_back(dwarf::DW_OP_minus);
+          break;
+        default:
+          Buffer.push_back(*SubExpr.begin());
+          Buffer.append(Args.begin(), Args.end());
+          break;
+        }
+
+        // Continue with remaining elements.
+        SubExpr = SubExpr.slice(HistoricSize);
+      }
+      Expr = MutableArrayRef<uint64_t>(Buffer);
+      LLVM_FALLTHROUGH;
+    }
+    case 3:
+      // Up-to-date!
+      break;
+    }
+
+    return Error::success();
+  }
+
   void upgradeDebugInfo() {
     upgradeCUSubprograms();
     upgradeCUVariables();
   }
 
 public:
   MetadataLoaderImpl(BitstreamCursor &Stream, Module &TheModule,
                      BitcodeReaderValueList &ValueList,
public:
   void setStripTBAA(bool Value) { StripTBAA = Value; }
   bool isStrippingTBAA() { return StripTBAA; }
 
   unsigned size() const { return MetadataList.size(); }
   void shrinkTo(unsigned N) { MetadataList.shrinkTo(N); }
   void upgradeDebugIntrinsics(Function &F) { upgradeDeclareExpressions(F); }
 };
 
-static Error error(const Twine &Message) {
-  return make_error<StringError>(
-      Message, make_error_code(BitcodeError::CorruptedBitcode));
-}
-
 Expected<bool>
 MetadataLoader::MetadataLoaderImpl::lazyLoadModuleMetadataBlock() {
   IndexCursor = Stream;
   SmallVector<uint64_t, 64> Record;
   // Get the abbrevs, and preload record positions to make them lazy-loadable.
   while (true) {
     BitstreamEntry Entry = IndexCursor.advanceSkippingSubblocks(
         BitstreamCursor::AF_DontPopBlockAtEnd);
#define GET_OR_DISTINCT(CLASS, ARGS)                                           \
   }
   case bitc::METADATA_EXPRESSION: {
     if (Record.size() < 1)
       return error("Invalid record");
 
     IsDistinct = Record[0] & 1;
     uint64_t Version = Record[0] >> 1;
     auto Elts = MutableArrayRef<uint64_t>(Record).slice(1);
-    unsigned N = Elts.size();
-    // Perform various upgrades.
-    switch (Version) {
-    case 0:
-      if (N >= 3 && Elts[N - 3] == dwarf::DW_OP_bit_piece)
-        Elts[N - 3] = dwarf::DW_OP_LLVM_fragment;
-      LLVM_FALLTHROUGH;
-    case 1:
-      // Move DW_OP_deref to the end.
-      if (N && Elts[0] == dwarf::DW_OP_deref) {
-        auto End = Elts.end();
-        if (Elts.size() >= 3 && *std::prev(End, 3) == dwarf::DW_OP_LLVM_fragment)
-          End = std::prev(End, 3);
-        std::move(std::next(Elts.begin()), End, Elts.begin());
-        *std::prev(End) = dwarf::DW_OP_deref;
-      }
-      NeedDeclareExpressionUpgrade = true;
-      LLVM_FALLTHROUGH;
-    case 2:
-      // Up-to-date!
-      break;
-    default:
-      return error("Invalid record");
-    }
+
+    SmallVector<uint64_t, 6> Buffer;
+    if (Error Err = upgradeDIExpression(Version, Elts, Buffer))
+      return Err;
 
     MetadataList.assignValue(
-        GET_OR_DISTINCT(DIExpression, (Context, makeArrayRef(Record).slice(1))),
-        NextMetadataNo);
+        GET_OR_DISTINCT(DIExpression, (Context, Elts)), NextMetadataNo);
     NextMetadataNo++;
     break;
   }
   case bitc::METADATA_GLOBAL_VAR_EXPR: {
     if (Record.size() != 3)
       return error("Invalid record");
 
     IsDistinct = Record[0];

lib/Bitcode/Writer/BitcodeWriter.cpp

void ModuleBitcodeWriter::writeDILocalVariable(
   Stream.EmitRecord(bitc::METADATA_LOCAL_VAR, Record, Abbrev);
   Record.clear();
 }
 
 void ModuleBitcodeWriter::writeDIExpression(const DIExpression *N,
                                             SmallVectorImpl<uint64_t> &Record,
                                             unsigned Abbrev) {
   Record.reserve(N->getElements().size() + 1);
-  const uint64_t Version = 2 << 1;
+  const uint64_t Version = 3 << 1;
   Record.push_back((uint64_t)N->isDistinct() | Version);
   Record.append(N->elements_begin(), N->elements_end());
 
   Stream.EmitRecord(bitc::METADATA_EXPRESSION, Record, Abbrev);
   Record.clear();
 }
 
 void ModuleBitcodeWriter::writeDIGlobalVariableExpression(

lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp

DIE *DwarfCompileUnit::constructVariableDIEImpl(const DbgVariable &DV,
   DIEDwarfExpression DwarfExpr(*Asm, *this, *Loc);
   for (auto &Fragment : DV.getFrameIndexExprs()) {
     unsigned FrameReg = 0;
     const DIExpression *Expr = Fragment.Expr;
     const TargetFrameLowering *TFI = Asm->MF->getSubtarget().getFrameLowering();
     int Offset = TFI->getFrameIndexReference(*Asm->MF, Fragment.FI, FrameReg);
     DwarfExpr.addFragmentOffset(Expr);
     SmallVector<uint64_t, 8> Ops;
-    Ops.push_back(dwarf::DW_OP_plus);
+    Ops.push_back(dwarf::DW_OP_plus_uconst);
     Ops.push_back(Offset);
     Ops.append(Expr->elements_begin(), Expr->elements_end());
     DIExpressionCursor Cursor(Ops);
     DwarfExpr.setMemoryLocationKind();
     DwarfExpr.addMachineRegExpression(
         *Asm->MF->getSubtarget().getRegisterInfo(), Cursor, FrameReg);
     DwarfExpr.addExpression(std::move(Cursor));
   }
void DwarfCompileUnit::addAddress(DIE &Die, dwarf::Attribute Attribute,
                                   const MachineLocation &Location) {
   DIELoc *Loc = new (DIEValueAllocator) DIELoc;
   DIEDwarfExpression DwarfExpr(*Asm, *this, *Loc);
   if (Location.isIndirect())
     DwarfExpr.setMemoryLocationKind();
 
   SmallVector<uint64_t, 8> Ops;
   if (Location.isIndirect() && Location.getOffset()) {
-    Ops.push_back(dwarf::DW_OP_plus);
+    Ops.push_back(dwarf::DW_OP_plus_uconst);
     Ops.push_back(Location.getOffset());
   }
   DIExpressionCursor Cursor(Ops);
   const TargetRegisterInfo &TRI = *Asm->MF->getSubtarget().getRegisterInfo();
   if (!DwarfExpr.addMachineRegExpression(TRI, Cursor, Location.getReg()))
     return;
   DwarfExpr.addExpression(std::move(Cursor));
 
void DwarfCompileUnit::addComplexAddress(const DbgVariable &DV, DIE &Die,
   DIEDwarfExpression DwarfExpr(*Asm, *this, *Loc);
   const DIExpression *DIExpr = DV.getSingleExpression();
   DwarfExpr.addFragmentOffset(DIExpr);
   if (Location.isIndirect())
     DwarfExpr.setMemoryLocationKind();
 
   SmallVector<uint64_t, 8> Ops;
   if (Location.isIndirect() && Location.getOffset()) {
-    Ops.push_back(dwarf::DW_OP_plus);
+    Ops.push_back(dwarf::DW_OP_plus_uconst);
     Ops.push_back(Location.getOffset());
   }
   Ops.append(DIExpr->elements_begin(), DIExpr->elements_end());
   DIExpressionCursor Cursor(Ops);
   const TargetRegisterInfo &TRI = *Asm->MF->getSubtarget().getRegisterInfo();
   if (!DwarfExpr.addMachineRegExpression(TRI, Cursor, Location.getReg()))
     return;
   DwarfExpr.addExpression(std::move(Cursor));

lib/CodeGen/AsmPrinter/DwarfDebug.cpp

if (Value.isInt()) {
     else
       DwarfExpr.addUnsignedConstant(Value.getInt());
   } else if (Value.isLocation()) {
     MachineLocation Location = Value.getLoc();
     if (Location.isIndirect())
       DwarfExpr.setMemoryLocationKind();
     SmallVector<uint64_t, 8> Ops;
     if (Location.isIndirect() && Location.getOffset()) {
-      Ops.push_back(dwarf::DW_OP_plus);
+      Ops.push_back(dwarf::DW_OP_plus_uconst);
       Ops.push_back(Location.getOffset());
     }
     Ops.append(DIExpr->elements_begin(), DIExpr->elements_end());
     DIExpressionCursor Cursor(Ops);
     const TargetRegisterInfo &TRI = *AP.MF->getSubtarget().getRegisterInfo();
     if (!DwarfExpr.addMachineRegExpression(TRI, Cursor, Location.getReg()))
       return;
     return DwarfExpr.addExpression(std::move(Cursor));

lib/CodeGen/AsmPrinter/DwarfExpression.h

DIExpressionCursor(const DIExpression *Expr) {
     }
     Start = Expr->expr_op_begin();
     End = Expr->expr_op_end();
   }
 
   DIExpressionCursor(ArrayRef<uint64_t> Expr)
       : Start(Expr.begin()), End(Expr.end()) {}
 
+  DIExpressionCursor(const DIExpressionCursor &C)
+      : Start(C.Start), End(C.End) {}
+
   /// Consume one operation.
   Optional<DIExpression::ExprOperand> take() {
     if (Start == End)
       return None;
     return *(Start++);
   }
 
   /// Consume N operations.

lib/CodeGen/AsmPrinter/DwarfExpression.cpp

bool DwarfExpression::addMachineRegExpression(const TargetRegisterInfo &TRI,
 
   // Pattern-match combinations for which more efficient representations exist.
   // [Reg, DW_OP_plus_uconst, Offset] --> [DW_OP_breg, Offset].
   if (Op && (Op->getOp() == dwarf::DW_OP_plus_uconst)) {
     SignedOffset = Op->getArg(0);
     ExprCursor.take();
   }
 
-  // [Reg, Offset, DW_OP_plus] --> [DW_OP_breg, Offset].
-  // [Reg, Offset, DW_OP_minus] --> [DW_OP_breg, -Offset].
+  // [Reg, DW_OP_constu, Offset, DW_OP_plus]  --> [DW_OP_breg, Offset]
+  // [Reg, DW_OP_constu, Offset, DW_OP_minus] --> [DW_OP_breg,-Offset]
   // If Reg is a subregister we need to mask it out before subtracting.
-  if (Op && ((Op->getOp() == dwarf::DW_OP_plus) ||
-             (Op->getOp() == dwarf::DW_OP_minus && !SubRegisterSizeInBits))) {
+  if (Op && Op->getOp() == dwarf::DW_OP_constu) {
+    auto N = ExprCursor.peekNext();
+    if (N && (N->getOp() == dwarf::DW_OP_plus ||
+             (N->getOp() == dwarf::DW_OP_minus && !SubRegisterSizeInBits))) {
       int Offset = Op->getArg(0);
-    SignedOffset = (Op->getOp() == dwarf::DW_OP_plus) ? Offset : -Offset;
-    ExprCursor.take();
+      SignedOffset = (N->getOp() == dwarf::DW_OP_minus) ? -Offset : Offset;
+      ExprCursor.consume(2);
+    }
   }
+
   if (FBReg)
     addFBReg(SignedOffset);
   else
     addBReg(Reg.DwarfRegNo, SignedOffset);
   DwarfRegs.clear();
   return true;
 }
 
case dwarf::DW_OP_LLVM_fragment: {
 
       // Emit the DW_OP_piece.
       addOpPiece(SizeInBits, SubRegisterOffsetInBits);
       setSubRegisterPiece(0, 0);
       // Reset the location description kind.
       LocationKind = Unknown;
       return;
     }
-    case dwarf::DW_OP_plus:
     case dwarf::DW_OP_plus_uconst:
       assert(LocationKind != Register);
       emitOp(dwarf::DW_OP_plus_uconst);
       emitUnsigned(Op->getArg(0));
       break;
+    case dwarf::DW_OP_plus:
     case dwarf::DW_OP_minus:
-      assert(LocationKind != Register);
-      // There is no DW_OP_minus_uconst.
-      emitOp(dwarf::DW_OP_constu);
-      emitUnsigned(Op->getArg(0));
-      emitOp(dwarf::DW_OP_minus);
+      emitOp(Op->getOp());
       break;
     case dwarf::DW_OP_deref: {
       assert(LocationKind != Register);
       if (LocationKind != Memory && isMemoryLocation(ExprCursor))
         // Turning this into a memory location description makes the deref
         // implicit.
         LocationKind = Memory;
       else

lib/CodeGen/AsmPrinter/DwarfUnit.cpp

void DwarfUnit::addBlockByrefAddress(const DbgVariable &DV, DIE &Die,
   // variable's location.
   DIELoc *Loc = new (DIEValueAllocator) DIELoc;
   DIEDwarfExpression DwarfExpr(*Asm, *this, *Loc);
   if (Location.isIndirect())
     DwarfExpr.setMemoryLocationKind();
 
   SmallVector<uint64_t, 9> Ops;
   if (Location.isIndirect() && Location.getOffset()) {
-    Ops.push_back(dwarf::DW_OP_plus);
+    Ops.push_back(dwarf::DW_OP_plus_uconst);
     Ops.push_back(Location.getOffset());
   }
   // If we started with a pointer to the __Block_byref... struct, then
   // the first thing we need to do is dereference the pointer (DW_OP_deref).
   if (isPointer)
     Ops.push_back(dwarf::DW_OP_deref);
 
   // Next add the offset for the '__forwarding' field:
   // DW_OP_plus_uconst ForwardingFieldOffset.  Note there's no point in
   // adding the offset if it's 0.
   if (forwardingFieldOffset > 0) {
-    Ops.push_back(dwarf::DW_OP_plus);
+    Ops.push_back(dwarf::DW_OP_plus_uconst);
     Ops.push_back(forwardingFieldOffset);
   }
 
   // Now dereference the __forwarding field to get to the real __Block_byref
   // struct:  DW_OP_deref.
   Ops.push_back(dwarf::DW_OP_deref);
 
   // Now that we've got the real __Block_byref... struct, add the offset
   // for the variable's field to get to the location of the actual variable:
   // DW_OP_plus_uconst varFieldOffset.  Again, don't add if it's 0.
   if (varFieldOffset > 0) {
-    Ops.push_back(dwarf::DW_OP_plus);
+    Ops.push_back(dwarf::DW_OP_plus_uconst);
     Ops.push_back(varFieldOffset);
   }
 
   DIExpressionCursor Cursor(Ops);
   const TargetRegisterInfo &TRI = *Asm->MF->getSubtarget().getRegisterInfo();
   if (!DwarfExpr.addMachineRegExpression(TRI, Cursor, Location.getReg()))
     return;
   DwarfExpr.addExpression(std::move(Cursor));

lib/IR/DebugInfoMetadata.cpp

DIExpression *DIExpression::getImpl(LLVMContext &Context,
   DEFINE_GETIMPL_STORE_NO_OPS(DIExpression, (Elements));
 }
 
 unsigned DIExpression::ExprOperand::getSize() const {
   switch (getOp()) {
   case dwarf::DW_OP_LLVM_fragment:
     return 3;
   case dwarf::DW_OP_constu:
-  case dwarf::DW_OP_plus:
   case dwarf::DW_OP_plus_uconst:
-  case dwarf::DW_OP_minus:
     return 2;
   default:
     return 1;
   }
 }
 
 bool DIExpression::isValid() const {
   for (auto I = expr_op_begin(), E = expr_op_end(); I != E; ++I) {
if (I->getOp() == dwarf::DW_OP_LLVM_fragment) {
       return Info;
     }
   return None;
 }
 
 void DIExpression::appendOffset(SmallVectorImpl<uint64_t> &Ops,
                                 int64_t Offset) {
   if (Offset > 0) {
-    Ops.push_back(dwarf::DW_OP_plus);
+    Ops.push_back(dwarf::DW_OP_plus_uconst);
     Ops.push_back(Offset);
   } else if (Offset < 0) {
-    Ops.push_back(dwarf::DW_OP_minus);
+    Ops.push_back(dwarf::DW_OP_constu);
     Ops.push_back(-Offset);
+    Ops.push_back(dwarf::DW_OP_minus);
   }
 }
 
 bool DIExpression::extractIfOffset(int64_t &Offset) const {
   if (getNumElements() == 0) {
     Offset = 0;
     return true;
   }
-  if (getNumElements() != 2)
-    return false;
-  if (Elements[0] == dwarf::DW_OP_plus ||
-      Elements[0] == dwarf::DW_OP_plus_uconst) {
+
+  if (getNumElements() == 2 && Elements[0] == dwarf::DW_OP_plus_uconst) {
     Offset = Elements[1];
     return true;
   }
-  if (Elements[0] == dwarf::DW_OP_minus) {
+
+  if (getNumElements() == 3 && Elements[0] == dwarf::DW_OP_constu) {
+    if (Elements[2] == dwarf::DW_OP_plus) {
+      Offset = Elements[1];
+      return true;
+    }
+    if (Elements[2] == dwarf::DW_OP_minus) {
       Offset = -Elements[1];
       return true;
     }
+  }
+
   return false;
 }
 
 DIExpression *DIExpression::prepend(const DIExpression *Expr, bool Deref,
                                     int64_t Offset, bool StackValue) {
   SmallVector<uint64_t, 8> Ops;
   appendOffset(Ops, Offset);
   if (Deref)

lib/IR/Metadata.cpp

if (Offset != 0 && MD.first == LLVMContext::MD_dbg) {
         auto *GVE = cast<DIGlobalVariableExpression>(Attachment);
         GV = GVE->getVariable();
         E = GVE->getExpression();
       }
       ArrayRef<uint64_t> OrigElements;
       if (E)
         OrigElements = E->getElements();
       std::vector<uint64_t> Elements(OrigElements.size() + 2);
-      Elements[0] = dwarf::DW_OP_plus;
+      Elements[0] = dwarf::DW_OP_plus_uconst;
       Elements[1] = Offset;
       std::copy(OrigElements.begin(), OrigElements.end(), Elements.begin() + 2);
       E = DIExpression::get(getContext(), Elements);
       Attachment = DIGlobalVariableExpression::get(getContext(), GV, E);
     }
     addMetadata(MD.first, *Attachment);
   }
 }

test/Assembler/diexpression.ll

 ; RUN: llvm-as < %s | llvm-dis | llvm-as | llvm-dis | FileCheck %s
 ; RUN: verify-uselistorder %s
 
 ; CHECK: !named = !{!0, !1, !2, !3, !4, !5, !6}
 !named = !{!0, !1, !2, !3, !4, !5, !6}
 
 ; CHECK:      !0 = !DIExpression()
 ; CHECK-NEXT: !1 = !DIExpression(DW_OP_deref)
-; CHECK-NEXT: !2 = !DIExpression(DW_OP_plus, 3)
+; CHECK-NEXT: !2 = !DIExpression(DW_OP_constu, 3, DW_OP_plus)
 ; CHECK-NEXT: !3 = !DIExpression(DW_OP_LLVM_fragment, 3, 7)
-; CHECK-NEXT: !4 = !DIExpression(DW_OP_deref, DW_OP_plus, 3, DW_OP_LLVM_fragment, 3, 7)
+; CHECK-NEXT: !4 = !DIExpression(DW_OP_deref, DW_OP_plus_uconst, 3, DW_OP_LLVM_fragment, 3, 7)
 ; CHECK-NEXT: !5 = !DIExpression(DW_OP_constu, 2, DW_OP_swap, DW_OP_xderef)
 ; CHECK-NEXT: !6 = !DIExpression(DW_OP_plus_uconst, 3)
 !0 = !DIExpression()
 !1 = !DIExpression(DW_OP_deref)
-!2 = !DIExpression(DW_OP_plus, 3)
+!2 = !DIExpression(DW_OP_constu, 3, DW_OP_plus)
 !3 = !DIExpression(DW_OP_LLVM_fragment, 3, 7)
-!4 = !DIExpression(DW_OP_deref, DW_OP_plus, 3, DW_OP_LLVM_fragment, 3, 7)
+!4 = !DIExpression(DW_OP_deref, DW_OP_plus_uconst, 3, DW_OP_LLVM_fragment, 3, 7)
 !5 = !DIExpression(DW_OP_constu, 2, DW_OP_swap, DW_OP_xderef)
 !6 = !DIExpression(DW_OP_plus_uconst, 3)

test/Bitcode/DIExpression-deref.ll

 ; RUN: llvm-dis -o - %s.bc | FileCheck %s
 
 !llvm.dbg.cu = !{!1}
 !llvm.module.flags = !{!20, !21}
 
 !0 = distinct !DIGlobalVariable(name: "g", scope: !1, file: !2, line: 1, type: !5, isLocal: false, isDefinition: true)
 !1 = distinct !DICompileUnit(language: DW_LANG_C99, file: !2, producer: "clang (llvm/trunk 288154)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !3, globals: !4)
 !2 = !DIFile(filename: "a.c", directory: "/")
 !3 = !{}
 !4 = !{!10, !11, !12, !13}
 !5 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
 ; DW_OP_deref should be moved to the back of the expression.
 ;
-; CHECK: !DIExpression(DW_OP_plus, 0, DW_OP_deref, DW_OP_LLVM_fragment, 8, 32)
+; CHECK: !DIExpression(DW_OP_plus_uconst, 0, DW_OP_deref, DW_OP_LLVM_fragment, 8, 32)
 !6 = !DIExpression(DW_OP_deref, DW_OP_plus, 0, DW_OP_LLVM_fragment, 8, 32)
-; CHECK: !DIExpression(DW_OP_plus, 0, DW_OP_deref)
+; CHECK: !DIExpression(DW_OP_plus_uconst, 0, DW_OP_deref)
 !7 = !DIExpression(DW_OP_deref, DW_OP_plus, 0)
-; CHECK: !DIExpression(DW_OP_plus, 1, DW_OP_deref)
+; CHECK: !DIExpression(DW_OP_plus_uconst, 1, DW_OP_deref)
 !8 = !DIExpression(DW_OP_plus, 1, DW_OP_deref)
 ; CHECK: !DIExpression(DW_OP_deref)
 !9 = !DIExpression(DW_OP_deref)
 !10 = !DIGlobalVariableExpression(var: !0, expr: !6)
 !11 = !DIGlobalVariableExpression(var: !0, expr: !7)
 !12 = !DIGlobalVariableExpression(var: !0, expr: !8)
 !13 = !DIGlobalVariableExpression(var: !0, expr: !9)
 !20 = !{i32 2, !"Dwarf Version", i32 4}
 !21 = !{i32 2, !"Debug Info Version", i32 3}

test/Bitcode/DIGlobalVariableExpression.ll

 ; RUN: llvm-dis -o - %s.bc | FileCheck %s
 ; RUN: llvm-dis -o - %s.bc | llvm-as - | llvm-bcanalyzer -dump - | FileCheck %s --check-prefix=BC
 
 ; BC: GLOBAL_VAR_EXPR
 ; BC: GLOBAL_DECL_ATTACHMENT
 ; CHECK: @g = common global i32 0, align 4, !dbg ![[G:[0-9]+]]
 ; CHECK: @h = common global i32 0, align 4, !dbg ![[H:[0-9]+]]
 ; CHECK: ![[G]] = {{.*}}!DIGlobalVariableExpression(var: ![[GVAR:[0-9]+]], expr: ![[GEXPR:[0-9]+]])
 ; CHECK: ![[GVAR]] = distinct !DIGlobalVariable(name: "g",
 ; CHECK: DICompileUnit({{.*}}, imports: ![[IMPORTS:[0-9]+]]
 ; CHECK: !DIGlobalVariableExpression(var: ![[CVAR:[0-9]+]], expr: ![[CEXPR:[0-9]+]])
 ; CHECK: ![[CVAR]] = distinct !DIGlobalVariable(name: "c",
 ; CHECK: ![[CEXPR]] = !DIExpression(DW_OP_constu, 23, DW_OP_stack_value)
 ; CHECK: ![[HVAR:[0-9]+]] = distinct !DIGlobalVariable(name: "h",
 ; CHECK: ![[IMPORTS]] = !{![[CIMPORT:[0-9]+]]}
 ; CHECK: ![[CIMPORT]] = !DIImportedEntity({{.*}}entity: ![[HVAR]]
-; CHECK: ![[GEXPR]] = !DIExpression(DW_OP_plus, 1)
+; CHECK: ![[GEXPR]] = !DIExpression(DW_OP_plus_uconst, 1)
 ; CHECK: ![[H]] = {{.*}}!DIGlobalVariableExpression(var: ![[HVAR]])
 
 @g = common global i32 0, align 4, !dbg !0
 @h = common global i32 0, align 4, !dbg !11
 
 !llvm.dbg.cu = !{!1}
 !llvm.module.flags = !{!6, !7, !8}
 !llvm.ident = !{!9}

test/CodeGen/ARM/debug-info-blocks.ll

 !155 = !DIFile(filename: "NSO.h", directory: "/Volumes/Sandbox/llvm")
 !156 = !DIFile(filename: "header12.h", directory: "/Volumes/Sandbox/llvm")
 !157 = !DIFile(filename: "header13.h", directory: "/Volumes/Sandbox/llvm")
 !158 = !DIFile(filename: "header14.h", directory: "/Volumes/Sandbox/llvm")
 !159 = !DIFile(filename: "header15.h", directory: "/Volumes/Sandbox/llvm")
 !160 = !DIFile(filename: "header.h", directory: "/Volumes/Sandbox/llvm")
 !161 = !{!"header2.h", !"/Volumes/Sandbox/llvm"}
 !162 = !{i32 1, !"Debug Info Version", i32 3}
-!163 = !DIExpression(DW_OP_plus, 20, DW_OP_deref, DW_OP_plus, 4, DW_OP_deref, DW_OP_plus, 24)
-!164 = !DIExpression(DW_OP_deref, DW_OP_plus, 24)
-!165 = !DIExpression(DW_OP_deref, DW_OP_plus, 28)
+!163 = !DIExpression(DW_OP_plus_uconst, 20, DW_OP_deref, DW_OP_plus_uconst, 4, DW_OP_deref, DW_OP_plus_uconst, 24)
+!164 = !DIExpression(DW_OP_deref, DW_OP_plus_uconst, 24)
+!165 = !DIExpression(DW_OP_deref, DW_OP_plus_uconst, 28)

test/CodeGen/X86/lea-opt-with-debug.mir

--- |
   !0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, retainedTypes: !3, globals: !2)
   !1 = !DIFile(filename: "test.c", directory: "")
   !2 = !{}
   !3 = !{!4}
   !4 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
   !5 = !{i32 2, !"Dwarf Version", i32 4}
   !6 = !{i32 2, !"Debug Info Version", i32 3}
   !7 = !{i32 1, !"PIC Level", i32 2}
-  !8 = !DIExpression(DW_OP_plus, 8, DW_OP_stack_value)
+  !8 = !DIExpression(DW_OP_plus_uconst, 8, DW_OP_stack_value)
   !9 = distinct !DISubprogram(name: "fn1", scope: !1, file: !1, line: 7, type: !10, isLocal: false, isDefinition: true, scopeLine: 7, isOptimized: true, unit: !0, variables: !11)
   !10 = !DISubroutineType(types: !3)
   !11 = !{!12}
   !12 = !DILocalVariable(name: "e", scope: !9, file: !1, line: 8, type: !13)
   !13 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !4, size: 64)
   !14 = !DILocation(line: 9, scope: !9)
   !15 = !DILocation(line: 10, scope: !9)
   !16 = !DIExpression()

test/DebugInfo/Generic/block-asan.ll

 ; RUN: opt -S -asan %s | FileCheck %s
 
 ; The IR of this testcase is generated from the following C code:
 ; void bar (int);
 ;
 ; void foo() {
 ;   __block int x;
 ;   bar(x);
 ; }
 ; by compiling it with 'clang -emit-llvm -g -S' and then by manually
 ; adding the sanitize_address attribute to the @foo() function (so
 ; that ASAN accepts to instrument the function in the above opt run).
 
 ; Check that the location of the ASAN instrumented __block variable is
 ; correct.
-; CHECK: !DIExpression(DW_OP_plus, 8, DW_OP_deref, DW_OP_plus, 24)
+; CHECK: !DIExpression(DW_OP_plus_uconst, 8, DW_OP_deref, DW_OP_plus_uconst, 24)
 
 target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
 
 %struct.__block_byref_x = type { i8*, %struct.__block_byref_x*, i32, i32, i32 }
 
 ; Function Attrs: nounwind ssp uwtable
 define void @foo() #0 !dbg !4 {
 entry:

 !14 = !{!15, !17, !18, !20, !21}
 !15 = !DIDerivedType(tag: DW_TAG_member, name: "__isa", size: 64, align: 64, file: !1, scope: !5, baseType: !16)
 !16 = !DIDerivedType(tag: DW_TAG_pointer_type, size: 64, align: 64, baseType: null)
 !17 = !DIDerivedType(tag: DW_TAG_member, name: "__forwarding", size: 64, align: 64, offset: 64, file: !1, scope: !5, baseType: !16)
 !18 = !DIDerivedType(tag: DW_TAG_member, name: "__flags", size: 32, align: 32, offset: 128, file: !1, scope: !5, baseType: !19)
 !19 = !DIBasicType(tag: DW_TAG_base_type, name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
 !20 = !DIDerivedType(tag: DW_TAG_member, name: "__size", size: 32, align: 32, offset: 160, file: !1, scope: !5, baseType: !19)
 !21 = !DIDerivedType(tag: DW_TAG_member, name: "x", size: 32, align: 32, offset: 192, file: !1, scope: !5, baseType: !19)
-!22 = !DIExpression(DW_OP_plus, 8, DW_OP_deref, DW_OP_plus, 24)
+!22 = !DIExpression(DW_OP_plus_uconst, 8, DW_OP_deref, DW_OP_plus_uconst, 24)
 !23 = !DILocation(line: 4, column: 15, scope: !4)
 !24 = !DILocation(line: 4, column: 3, scope: !4)
 !25 = !DILocation(line: 5, column: 3, scope: !4)
 !26 = !DILocation(line: 6, column: 1, scope: !4)

test/DebugInfo/X86/block-capture.ll

 !61 = !DIDerivedType(tag: DW_TAG_member, name: "Size", line: 2, size: 64, align: 64, offset: 64, file: !1, scope: !58, baseType: !41)
 !62 = !DIDerivedType(tag: DW_TAG_member, name: "CopyFuncPtr", line: 2, size: 64, align: 64, offset: 128, file: !1, scope: !58, baseType: !63)
 !63 = !DIDerivedType(tag: DW_TAG_pointer_type, size: 64, align: 64, baseType: !11)
 !64 = !DIDerivedType(tag: DW_TAG_member, name: "DestroyFuncPtr", line: 2, size: 64, align: 64, offset: 192, file: !1, scope: !58, baseType: !63)
 !65 = !DIDerivedType(tag: DW_TAG_member, name: "block", line: 2, size: 64, align: 64, offset: 256, flags: DIFlagPublic, file: !1, scope: !5, baseType: !25)
 !66 = !DILocation(line: 2, column: 20, scope: !8)
 !67 = !DILocation(line: 2, column: 21, scope: !8)
 !68 = !DILocalVariable(name: "block", line: 2, scope: !8, file: !5, type: !25)
-!69 = !DIExpression(DW_OP_deref, DW_OP_plus, 32)
+!69 = !DIExpression(DW_OP_deref, DW_OP_plus_uconst, 32)
 !70 = !DILocation(line: 2, column: 9, scope: !8)
 !71 = !DILocation(line: 2, column: 23, scope: !72)
 !72 = distinct !DILexicalBlock(line: 2, column: 21, file: !1, scope: !8)
 !73 = !DILocation(line: 2, column: 32, scope: !8)

test/DebugInfo/X86/debug-info-block-captured-self.ll

 !84 = !DILocation(line: 33, scope: !38)
 !86 = !DILocalVariable(name: "self", line: 41, scope: !38, file: !1, type: !34)
 !87 = !DILocation(line: 41, scope: !38)
 !103 = !DILocation(line: 35, scope: !42)
 !105 = !DILocalVariable(name: "self", line: 40, scope: !42, file: !1, type: !34)
 !106 = !DILocation(line: 40, scope: !42)
 !107 = !DIFile(filename: "llvm/tools/clang/test/CodeGenObjC/debug-info-block-captured-self.m", directory: "")
 !108 = !{i32 1, !"Debug Info Version", i32 3}
-!109 = !DIExpression(DW_OP_plus, 32, DW_OP_deref)
-!110 = !DIExpression(DW_OP_plus, 32, DW_OP_deref)
+!109 = !DIExpression(DW_OP_plus_uconst, 32, DW_OP_deref)
+!110 = !DIExpression(DW_OP_plus_uconst, 32, DW_OP_deref)

test/DebugInfo/X86/debug-info-blocks.ll

 !103 = !DILocation(line: 52, scope: !31)
 !104 = !DILocalVariable(name: "", line: 52, arg: 2, flags: DIFlagArtificial, scope: !31, file: !32, type: !30)
 !105 = !DILocalVariable(name: "", line: 52, arg: 1, flags: DIFlagArtificial | DIFlagObjectPointer, scope: !35, file: !32, type: !30)
 !106 = !DILocation(line: 52, scope: !35)
 !107 = !DILocalVariable(name: "a", line: 61, scope: !36, file: !6, type: !61)
 !108 = !DILocation(line: 61, scope: !36)
 !109 = !DILocation(line: 62, scope: !36)
 !110 = !{i32 1, !"Debug Info Version", i32 3}
-!111 = !DIExpression(DW_OP_deref, DW_OP_plus, 32)
+!111 = !DIExpression(DW_OP_deref, DW_OP_plus_uconst, 32)

test/DebugInfo/X86/dw_op_minus.ll

 ; Test dwarf codegen of DW_OP_minus.
 ; RUN: llc -O0 -mtriple=x86_64-unknown-linux-gnu < %s | FileCheck %s
 
 ; This was built by compiling the following source with SafeStack and
 ; simplifying the result a little.
 ; extern "C" {
 ; void Capture(int *);
 ; void f() {
 ;   int buf[100];
 ;   Capture(buf);
 ; }
 ; }
-; The interesting part is !DIExpression(DW_OP_minus, 400)
+; The interesting part is !DIExpression(DW_OP_constu, 400, DW_OP_minus)
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
 @__safestack_unsafe_stack_ptr = external thread_local(initialexec) global i8*
 
 define void @f() !dbg !4 {
 entry:

 !9 = !DICompositeType(tag: DW_TAG_array_type, baseType: !10, size: 3200, align: 32, elements: !11)
 !10 = !DIBasicType(name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
 !11 = !{!12}
 !12 = !DISubrange(count: 100)
 !13 = !{i32 2, !"Dwarf Version", i32 4}
 !14 = !{i32 2, !"Debug Info Version", i32 3}
 !15 = !{!"clang version 3.8.0 (trunk 248518) (llvm/trunk 248512)"}
 !16 = !DILocation(line: 5, column: 3, scope: !4)
-!17 = !DIExpression(DW_OP_minus, 400)
+!17 = !DIExpression(DW_OP_constu, 400, DW_OP_minus)
 !18 = !DILocation(line: 5, column: 7, scope: !4)
 !19 = !DILocation(line: 6, column: 11, scope: !4)
 !20 = !DILocation(line: 6, column: 3, scope: !4)
 !21 = !DILocation(line: 7, column: 1, scope: !4)
 
 ; RCX - 400
 ; CHECK:      .short  3                       # Loc expr size
 ; CHECK-NEXT: .byte 114                     # DW_OP_breg2

test/DebugInfo/X86/dw_op_minus_direct.ll

 !5 = !{i32 1, !"PIC Level", i32 2}
 !6 = !{!"clang version 4.0.0 (trunk 286322) (llvm/trunk 286305)"}
 !7 = distinct !DISubprogram(name: "inc", scope: !1, file: !1, line: 1, type: !8, isLocal: false, isDefinition: true, scopeLine: 1, flags: DIFlagPrototyped, isOptimized: true, unit: !0, variables: !11)
 !8 = !DISubroutineType(types: !9)
 !9 = !{!10, !10}
 !10 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
 !11 = !{!12}
 !12 = !DILocalVariable(name: "i", arg: 1, scope: !7, file: !1, line: 1, type: !10)
-!13 = !DIExpression(DW_OP_minus, 1, DW_OP_stack_value)
+!13 = !DIExpression(DW_OP_constu, 1, DW_OP_minus, DW_OP_stack_value)
 !14 = !DILocation(line: 1, column: 13, scope: !7)
 !15 = !DILocation(line: 2, column: 11, scope: !7)
 !16 = !DILocation(line: 2, column: 3, scope: !7)

test/DebugInfo/X86/safestack-byval.ll

 ; Test dwarf codegen for DILocalVariable of a byval function argument that
 ; points to neither an argument nor an alloca. This kind of IR is generated by
 ; SafeStack for unsafe byval arguments.
 ; RUN: llc -mtriple=x86_64-unknown-unknown -stop-after expand-isel-pseudos %s -o - | FileCheck %s
 
 ; This was built by compiling the following source with SafeStack and
 ; simplifying the result a little.
 ; struct S {
 ;   int a[100];
 ; };
 ;
 ; int f(S zzz, unsigned long len) {
 ;   return zzz.a[len];
 ; }
 
 ; CHECK: ![[ZZZ:.*]] = !DILocalVariable(name: "zzz",
-; CHECK: ![[ZZZ_EXPR:.*]] = !DIExpression(DW_OP_deref, DW_OP_minus, 400)
+; CHECK: ![[ZZZ_EXPR:.*]] = !DIExpression(DW_OP_deref, DW_OP_constu, 400, DW_OP_minus)
 ; CHECK: DBG_VALUE {{.*}} ![[ZZZ]], ![[ZZZ_EXPR]]
 
 %struct.S = type { [100 x i32] }
 
 @__safestack_unsafe_stack_ptr = external thread_local(initialexec) global i8*
 
 ; Function Attrs: norecurse nounwind readonly safestack uwtable
 define i32 @_Z1f1Sm(%struct.S* byval nocapture readonly align 8 %zzz, i64 %len) #0 !dbg !12 {

 !15 = !DIBasicType(name: "long unsigned int", size: 64, align: 64, encoding: DW_ATE_unsigned)
 !16 = !{!17, !18}
 !17 = !DILocalVariable(name: "zzz", arg: 1, scope: !12, file: !1, line: 8, type: !4)
 !18 = !DILocalVariable(name: "len", arg: 2, scope: !12, file: !1, line: 8, type: !15)
 !19 = !{i32 2, !"Dwarf Version", i32 4}
 !20 = !{i32 2, !"Debug Info Version", i32 3}
 !21 = !{!"clang version 3.8.0 (trunk 254107) (llvm/trunk 254109)"}
 !22 = !DILocation(line: 8, column: 9, scope: !12)
-!23 = !DIExpression(DW_OP_deref, DW_OP_minus, 400)
+!23 = !DIExpression(DW_OP_deref, DW_OP_constu, 400, DW_OP_minus)
 !24 = !DILocation(line: 8, column: 28, scope: !12)
 !25 = !DIExpression()
 !26 = !DILocation(line: 9, column: 10, scope: !12)
 !27 = !{!28, !28, i64 0}
 !28 = !{!"int", !29, i64 0}
 !29 = !{!"omnipotent char", !30, i64 0}
 !30 = !{!"Simple C/C++ TBAA"}
 !31 = !DILocation(line: 9, column: 3, scope: !12)

test/DebugInfo/X86/stack-value-dwarf2.ll

 !10 = distinct !DICompositeType(tag: DW_TAG_class_type, scope: !0, file: !1, line: 28, size: 96, elements: !2)
 !11 = !DIExpression(DW_OP_stack_value, DW_OP_LLVM_fragment, 0, 32)
 !12 = !DILocation(line: 23, column: 33, scope: !8, inlinedAt: !13)
 !13 = distinct !DILocation(line: 28, column: 5, scope: !14, inlinedAt: !16)
 !14 = distinct !DISubprogram(name: "<(lambda at test.ii:87:58)>", scope: !0, file: !1, line: 27, type: !6, isLocal: false, isDefinition: true, scopeLine: 27, flags: DIFlagPrototyped, isOptimized: true, unit: !0, templateParams: !2, declaration: !15, variables: !2)
 !15 = !DISubprogram(name: "<(lambda at test.ii:87:58)>", scope: !0, file: !1, line: 27, type: !6, isLocal: false, isDefinition: false, scopeLine: 27, flags: DIFlagPublic | DIFlagPrototyped, isOptimized: true, templateParams: !2)
 !16 = distinct !DILocation(line: 99, column: 21, scope: !17)
 !17 = !DILexicalBlockFile(scope: !5, file: !1, discriminator: 2)
-!18 = !DIExpression(DW_OP_plus, 4, DW_OP_stack_value, DW_OP_LLVM_fragment, 64, 32)
+!18 = !DIExpression(DW_OP_plus_uconst, 4, DW_OP_stack_value, DW_OP_LLVM_fragment, 64, 32)

test/DebugInfo/X86/unattached-global.ll

 ; RUN: %llc_dwarf -filetype=obj -o - %s | llvm-dwarfdump - | FileCheck %s
 
 target datalayout = "e-p:64:64"
 target triple = "x86_64-unknown-linux-gnu"
 
 ; CHECK: DW_TAG_variable
 ; CHECK: DW_AT_name {{.*}}"a"
 ; CHECK-NOT: DW_AT_location
 ; CHECK: DW_TAG
 
 !0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, producer: "clang", file: !5, globals: !1, emissionKind: FullDebug)
 !1 = !{!2}
 !2 = !DIGlobalVariableExpression(var: !3, expr: !4)
 !3 = distinct !DIGlobalVariable(name: "a", scope: null, isLocal: false, isDefinition: true, type: !6)
-!4 = !DIExpression(DW_OP_plus, 4)
+!4 = !DIExpression(DW_OP_plus_uconst, 4)
 !5 = !DIFile(filename: "<stdin>", directory: "/")
 !6 = !DIBasicType(name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
 
 !7 = !{i32 2, !"Dwarf Version", i32 2}
 !8 = !{i32 2, !"Debug Info Version", i32 3}
 
 !llvm.dbg.cu = !{!0}
 !llvm.module.flags = !{!7, !8}

test/Transforms/GlobalMerge/debug-info.ll

define void @use1() {
   %x = load i32, i32* @a
   %y = load i32, i32* @b
   ret void
 }
 ; CHECK: [[A]] = !DIGlobalVariableExpression(var: [[AVAR:![0-9]+]])
 ; CHECK: [[AVAR]] = !DIGlobalVariable(name: "a", scope: null, isLocal: false, isDefinition: true)
 ; CHECK: [[B]] = !DIGlobalVariableExpression(var: [[BVAR:![0-9]+]], expr: [[EXPR:![0-9]+]])
 ; CHECK: [[BVAR]] = !DIGlobalVariable(name: "b", scope: null, isLocal: false, isDefinition: true)
-; CHECK: [[EXPR]] = !DIExpression(DW_OP_plus, 4)
+; CHECK: [[EXPR]] = !DIExpression(DW_OP_plus_uconst, 4)
 
 !llvm.module.flags = !{!4, !5}
 
 !0 = !DIGlobalVariableExpression(var: !1)
 !1 = !DIGlobalVariable(name: "a", scope: null, isLocal: false, isDefinition: true)
 !2 = !DIGlobalVariableExpression(var: !3)
 !3 = !DIGlobalVariable(name: "b", scope: null, isLocal: false, isDefinition: true)
 !4 = !{i32 2, !"Debug Info Version", i32 3}
 !5 = !{i32 2, !"Dwarf Version", i32 4}
 

test/Transforms/InstCombine/debuginfo-dce.ll

 ; CHECK: define void @salvage_gep2
 ; CHECK-NEXT: entry:
 ; CHECK-NEXT: call void @llvm.dbg.value(metadata %struct.entry* %queue, i64 0,
 ; CHECK-SAME:                           metadata ![[GEP2_EXPR:[0-9]+]])
   store %struct.entry** %1, %struct.entry*** %im_not_dead, align 8
   ret void, !dbg !32
 }
 
-; CHECK: ![[LOAD_EXPR]] = !DIExpression(DW_OP_deref, DW_OP_plus, 0)
-; CHECK: ![[BITCAST_EXPR]] = !DIExpression(DW_OP_plus, 0)
-; CHECK: ![[GEP0_EXPR]] = !DIExpression(DW_OP_minus, 8, DW_OP_plus, 0, DW_OP_stack_value)
-; CHECK: ![[GEP1_EXPR]] = !DIExpression(DW_OP_minus, 8, DW_OP_stack_value,
+; CHECK: ![[LOAD_EXPR]] = !DIExpression(DW_OP_deref, DW_OP_plus_uconst, 0)
+; CHECK: ![[BITCAST_EXPR]] = !DIExpression(DW_OP_plus_uconst, 0)
+; CHECK: ![[GEP0_EXPR]] = !DIExpression(DW_OP_constu, 8, DW_OP_minus, DW_OP_plus_uconst, 0, DW_OP_stack_value)
+; CHECK: ![[GEP1_EXPR]] = !DIExpression(DW_OP_constu, 8, DW_OP_minus, DW_OP_stack_value,
 ; CHECK-SAME:                           DW_OP_LLVM_fragment, 0, 32)
-; CHECK: ![[GEP2_EXPR]] = !DIExpression(DW_OP_minus, 8, DW_OP_stack_value)
+; CHECK: ![[GEP2_EXPR]] = !DIExpression(DW_OP_constu, 8, DW_OP_minus, DW_OP_stack_value)
 
 ; Function Attrs: nounwind readnone
 declare void @llvm.dbg.value(metadata, i64, metadata, metadata) #1
 
 attributes #0 = { nounwind ssp uwtable }
 attributes #1 = { nounwind readnone }
 
 !llvm.dbg.cu = !{!0}

 !12 = !{i32 1, !"PIC Level", i32 2}
 !13 = !{!"clang version 5.0.0 (trunk 297628) (llvm/trunk 297643)"}
 !14 = distinct !DISubprogram(name: "scan", scope: !1, file: !1, line: 4, type: !15, isLocal: false, isDefinition: true, scopeLine: 5, flags: DIFlagPrototyped, isOptimized: true, unit: !0, variables: !17)
 !15 = !DISubroutineType(types: !16)
 !16 = !{null, !4, !4}
 !17 = !{!18}
 !18 = !DILocalVariable(name: "entry", scope: !14, file: !1, line: 6, type: !4)
 !19 = !DILocation(line: 6, column: 17, scope: !14)
-!20 = !DIExpression(DW_OP_plus, 0)
+!20 = !DIExpression(DW_OP_plus_uconst, 0)
 !21 = !DILocation(line: 11, column: 1, scope: !14)
 !22 = distinct !DISubprogram(name: "scan", scope: !1, file: !1, line: 4, type: !15, isLocal: false, isDefinition: true, scopeLine: 5, flags: DIFlagPrototyped, isOptimized: true, unit: !0, variables: !17)
 !23 = !DILocation(line: 6, column: 17, scope: !22)
 !24 = !DILocalVariable(name: "entry", scope: !22, file: !1, line: 6, type: !4)
 !25 = distinct !DISubprogram(name: "scan", scope: !1, file: !1, line: 4, type: !15, isLocal: false, isDefinition: true, scopeLine: 5, flags: DIFlagPrototyped, isOptimized: true, unit: !0, variables: !17)
 !26 = !DILocation(line: 6, column: 17, scope: !25)
 !27 = !DILocalVariable(name: "entry", scope: !25, file: !1, line: 6, type: !4)
 !28 = distinct !DISubprogram(name: "scan", scope: !1, file: !1, line: 4, type: !15, isLocal: false, isDefinition: true, scopeLine: 5, flags: DIFlagPrototyped, isOptimized: true, unit: !0, variables: !17)
 !29 = !DILocation(line: 6, column: 17, scope: !28)
 !30 = !DILocalVariable(name: "entry", scope: !28, file: !1, line: 6, type: !4)
 !31 = distinct !DISubprogram(name: "scan", scope: !1, file: !1, line: 4, type: !15, isLocal: false, isDefinition: true, scopeLine: 5, flags: DIFlagPrototyped, isOptimized: true, unit: !0, variables: !17)
 !32 = !DILocation(line: 6, column: 17, scope: !31)
 !33 = !DILocalVariable(name: "entry", scope: !31, file: !1, line: 6, type: !4)

test/Transforms/SafeStack/X86/debug-loc.ll

 ; CHECK:   call void @Capture
 ; CHECK:   call void @Capture
 
   ret void, !dbg !25
 }
 
 ; CHECK-DAG: ![[VAR_ARG]] = !DILocalVariable(name: "zzz"
 ; 100 aligned up to 8
-; CHECK-DAG: ![[EXPR_ARG]] = !DIExpression(DW_OP_minus, 104)
+; CHECK-DAG: ![[EXPR_ARG]] = !DIExpression(DW_OP_constu, 104, DW_OP_minus
 
 ; CHECK-DAG: ![[VAR_LOCAL]] = !DILocalVariable(name: "xxx"
-; CHECK-DAG: ![[EXPR_LOCAL]] = !DIExpression(DW_OP_minus, 208)
+; CHECK-DAG: ![[EXPR_LOCAL]] = !DIExpression(DW_OP_constu, 208, DW_OP_minus
 
 ; Function Attrs: nounwind readnone
 declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
 
 declare void @Capture(%struct.S*) #2
 
 attributes #0 = { safestack uwtable "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2" "unsafe-fp-math"="false" "use-soft-float"="false" }
 attributes #1 = { nounwind readnone }

test/Transforms/SafeStack/X86/debug-loc2.ll

 !10 = !DILocalVariable(name: "x1", scope: !6, file: !1, line: 5, type: !11)
 !11 = !DIBasicType(name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
 
 ; CHECK-DAG: ![[X2]] = !DILocalVariable(name: "x2",
 !12 = !DILocalVariable(name: "x2", scope: !6, file: !1, line: 6, type: !11)
 !13 = !DILocation(line: 5, column: 3, scope: !6)
 !14 = !DILocation(line: 6, column: 3, scope: !6)
 
-; CHECK-DAG: ![[X1_EXPR]] = !DIExpression(DW_OP_deref, DW_OP_minus, 4)
-; CHECK-DAG: ![[X2_EXPR]] = !DIExpression(DW_OP_deref, DW_OP_minus, 8)
+; CHECK-DAG: ![[X1_EXPR]] = !DIExpression(DW_OP_deref, DW_OP_constu, 4, DW_OP_minus)
+; CHECK-DAG: ![[X2_EXPR]] = !DIExpression(DW_OP_deref, DW_OP_constu, 8, DW_OP_minus)
 !15 = !DIExpression(DW_OP_deref)
 !16 = !DILocation(line: 5, column: 7, scope: !6)
 !17 = !DILocation(line: 8, column: 3, scope: !6)
 !18 = !DILocation(line: 6, column: 7, scope: !6)
 !19 = !DILocation(line: 9, column: 3, scope: !6)
 !20 = !DILocation(line: 10, column: 1, scope: !6)
 !21 = !DILocation(line: 10, column: 1, scope: !22)
 !22 = !DILexicalBlockFile(scope: !6, file: !1, discriminator: 1)
 !23 = !DIExpression()
-!24 = !DIExpression(DW_OP_minus, 42)
+!24 = !DIExpression(DW_OP_constu, 42, DW_OP_minus)

unittests/IR/MetadataTest.cpp

do {                                                                         \
     uint64_t Elements[] = {__VA_ARGS__};                                       \
     EXPECT_FALSE(DIExpression::get(Context, Elements)->isValid());             \
   } while (false)
 
   // Empty expression should be valid.
   EXPECT_TRUE(DIExpression::get(Context, None));
 
   // Valid constructions.
-  EXPECT_VALID(dwarf::DW_OP_plus, 6);
   EXPECT_VALID(dwarf::DW_OP_plus_uconst, 6);
+  EXPECT_VALID(dwarf::DW_OP_constu, 6, dwarf::DW_OP_plus);
   EXPECT_VALID(dwarf::DW_OP_deref);
   EXPECT_VALID(dwarf::DW_OP_LLVM_fragment, 3, 7);
-  EXPECT_VALID(dwarf::DW_OP_plus, 6, dwarf::DW_OP_deref);
-  EXPECT_VALID(dwarf::DW_OP_deref, dwarf::DW_OP_plus, 6);
+  EXPECT_VALID(dwarf::DW_OP_plus_uconst, 6, dwarf::DW_OP_deref);
+  EXPECT_VALID(dwarf::DW_OP_deref, dwarf::DW_OP_plus_uconst, 6);
   EXPECT_VALID(dwarf::DW_OP_deref, dwarf::DW_OP_LLVM_fragment, 3, 7);
-  EXPECT_VALID(dwarf::DW_OP_deref, dwarf::DW_OP_plus, 6,
+  EXPECT_VALID(dwarf::DW_OP_deref, dwarf::DW_OP_plus_uconst, 6,
                dwarf::DW_OP_LLVM_fragment, 3, 7);
 
   // Invalid constructions.
   EXPECT_INVALID(~0u);
-  EXPECT_INVALID(dwarf::DW_OP_plus);
+  EXPECT_INVALID(dwarf::DW_OP_plus, 0);
   EXPECT_INVALID(dwarf::DW_OP_plus_uconst);
   EXPECT_INVALID(dwarf::DW_OP_LLVM_fragment);
   EXPECT_INVALID(dwarf::DW_OP_LLVM_fragment, 3);
-  EXPECT_INVALID(dwarf::DW_OP_LLVM_fragment, 3, 7, dwarf::DW_OP_plus, 3);
+  EXPECT_INVALID(dwarf::DW_OP_LLVM_fragment, 3, 7, dwarf::DW_OP_plus_uconst, 3);
   EXPECT_INVALID(dwarf::DW_OP_LLVM_fragment, 3, 7, dwarf::DW_OP_deref);
 
 #undef EXPECT_VALID
 #undef EXPECT_INVALID
 }
 
 typedef MetadataTest DIObjCPropertyTest;