5 files changed, 43 insertions, 12 deletions
diff --git a/llvm/lib/CodeGen/AsmPrinter/DbgEntityHistoryCalculator.cpp b/llvm/lib/CodeGen/AsmPrinter/DbgEntityHistoryCalculator.cpp
index 9d05cfe9bdc..7f9d6c618ad 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DbgEntityHistoryCalculator.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DbgEntityHistoryCalculator.cpp
@@ -41,7 +41,7 @@ using EntryIndex = DbgValueHistoryMap::EntryIndex;
 static Register isDescribedByReg(const MachineInstr &MI) {
   assert(MI.isDebugValue());
   assert(MI.getNumOperands() == 4);
-  // If the location of variable is an entry value (DW_OP_entry_value)
+  // If the location of variable is an entry value (DW_OP_LLVM_entry_value)
   // do not consider it as a register location.
   if (MI.getDebugExpression()->isEntryValue())
     return 0;
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
index d284d4ffa44..a61c98ec1c1 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
@@ -1205,7 +1205,7 @@ void DwarfCompileUnit::addComplexAddress(const DbgVariable &DV, DIE &Die,
 
   if (DIExpr->isEntryValue()) {
     DwarfExpr.setEntryValueFlag();
-    DwarfExpr.addEntryValueExpression(Cursor);
+    DwarfExpr.beginEntryValueExpression(Cursor);
   }
 
   const TargetRegisterInfo &TRI = *Asm->MF->getSubtarget().getRegisterInfo();
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 7d7cadcce17..91eb27ca258 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -669,10 +669,9 @@ static void collectCallSiteParameters(const MachineInstr *CallMI,
 
   // Emit the call site parameter's value as an entry value.
   if (ShouldTryEmitEntryVals) {
-    // Create an entry value expression where the expression following
-    // the 'DW_OP_entry_value' will be the size of 1 (a register operation).
-    DIExpression *EntryExpr = DIExpression::get(MF->getFunction().getContext(),
-                                                {dwarf::DW_OP_entry_value, 1});
+    // Create an expression where the register's entry value is used.
+    DIExpression *EntryExpr = DIExpression::get(
+        MF->getFunction().getContext(), {dwarf::DW_OP_LLVM_entry_value, 1});
     for (auto RegEntry : ForwardedRegWorklist) {
       unsigned FwdReg = RegEntry;
       auto EntryValReg = RegsForEntryValues.find(RegEntry);
@@ -2200,7 +2199,7 @@ void DwarfDebug::emitDebugLocValue(const AsmPrinter &AP, const DIBasicType *BT,
 
     if (DIExpr->isEntryValue()) {
       DwarfExpr.setEntryValueFlag();
-      DwarfExpr.addEntryValueExpression(Cursor);
+      DwarfExpr.beginEntryValueExpression(Cursor);
     }
 
     const TargetRegisterInfo &TRI = *AP.MF->getSubtarget().getRegisterInfo();
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
index ea42e60344d..42a7f5607e7 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
@@ -254,6 +254,9 @@ bool DwarfExpression::addMachineRegExpression(const TargetRegisterInfo &TRI,
       addOpPiece(Reg.Size);
     }
 
+    if (isEntryValue())
+      finalizeEntryValue();
+
     if (isEntryValue() && !isParameterValue() && DwarfVersion >= 4)
       emitOp(dwarf::DW_OP_stack_value);
 
@@ -313,14 +316,33 @@ bool DwarfExpression::addMachineRegExpression(const TargetRegisterInfo &TRI,
   return true;
 }
 
-void DwarfExpression::addEntryValueExpression(DIExpressionCursor &ExprCursor) {
+void DwarfExpression::beginEntryValueExpression(
+    DIExpressionCursor &ExprCursor) {
   auto Op = ExprCursor.take();
-  assert(Op && Op->getOp() == dwarf::DW_OP_entry_value);
+  assert(Op && Op->getOp() == dwarf::DW_OP_LLVM_entry_value);
   assert(!isMemoryLocation() &&
          "We don't support entry values of memory locations yet");
+  assert(!IsEmittingEntryValue && "Already emitting entry value?");
+  assert(Op->getArg(0) == 1 &&
+         "Can currently only emit entry values covering a single operation");
 
   emitOp(CU.getDwarf5OrGNULocationAtom(dwarf::DW_OP_entry_value));
-  emitUnsigned(Op->getArg(0));
+  IsEmittingEntryValue = true;
+  enableTemporaryBuffer();
+}
+
+void DwarfExpression::finalizeEntryValue() {
+  assert(IsEmittingEntryValue && "Entry value not open?");
+  disableTemporaryBuffer();
+
+  // Emit the entry value's size operand.
+  unsigned Size = getTemporaryBufferSize();
+  emitUnsigned(Size);
+
+  // Emit the entry value's DWARF block operand.
+  commitTemporaryBuffer();
+
+  IsEmittingEntryValue = false;
 }
 
 /// Assuming a well-formed expression, match "DW_OP_deref* DW_OP_LLVM_fragment?".
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
index a4b566669c2..1ad46669f9b 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
@@ -111,6 +111,9 @@ protected:
     const char *Comment;
   };
 
+  /// Whether we are currently emitting an entry value operation.
+  bool IsEmittingEntryValue = false;
+
   DwarfCompileUnit &CU;
 
   /// The register location, if any.
@@ -260,6 +263,10 @@ protected:
   /// expression.  See PR21176 for more details.
   void addStackValue();
 
+  /// Finalize an entry value by emitting its size operand, and committing the
+  /// DWARF block which has been emitted to the temporary buffer.
+  void finalizeEntryValue();
+
   ~DwarfExpression() = default;
 
 public:
@@ -310,8 +317,11 @@ public:
                                DIExpressionCursor &Expr, unsigned MachineReg,
                                unsigned FragmentOffsetInBits = 0);
 
-  /// Emit entry value dwarf operation.
-  void addEntryValueExpression(DIExpressionCursor &ExprCursor);
+  /// Begin emission of an entry value dwarf operation. The entry value's
+  /// first operand is the size of the DWARF block (its second operand),
+  /// which needs to be calculated at time of emission, so we don't emit
+  /// any operands here.
+  void beginEntryValueExpression(DIExpressionCursor &ExprCursor);
 
   /// Emit all remaining operations in the DIExpressionCursor.
   ///