3 files changed, 41 insertions, 18 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 1043d0a1435..296a799d33c 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -1438,10 +1438,10 @@ static void emitDebugLocValue(const AsmPrinter &AP, const DIBasicType *BT,
         DwarfExpr.AddMachineRegExpression(Expr, Loc.getReg(),
                                           PieceOffsetInBits);
     }
+  } else if (Value.isConstantFP()) {
+    APInt RawBytes = Value.getConstantFP()->getValueAPF().bitcastToAPInt();
+    DwarfExpr.AddUnsignedConstant(RawBytes);
   }
-  // else ... ignore constant fp. There is not any good way to
-  // to represent them here in dwarf.
-  // FIXME: ^
 }
 
 void DebugLocEntry::finalize(const AsmPrinter &AP,
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
index 7b5b831da16..0608e05edd5 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
@@ -159,29 +159,37 @@ bool DwarfExpression::AddMachineRegPiece(unsigned MachineReg,
   return CurPos > PieceOffsetInBits;
 }
 
+void DwarfExpression::AddStackValue() {
+  if (DwarfVersion >= 4)
+    EmitOp(dwarf::DW_OP_stack_value);
+}
+
 void DwarfExpression::AddSignedConstant(int Value) {
   EmitOp(dwarf::DW_OP_consts);
   EmitSigned(Value);
-  // The proper way to describe a constant value is
-  // DW_OP_constu <const>, DW_OP_stack_value.
-  // Unfortunately, DW_OP_stack_value was not available until DWARF-4,
-  // so we will continue to generate DW_OP_constu <const> for DWARF-2
-  // and DWARF-3. Technically, this is incorrect since DW_OP_const <const>
-  // actually describes a value at a constant addess, not a constant value.
-  // However, in the past there was no better way  to describe a constant
-  // value, so the producers and consumers started to rely on heuristics
-  // to disambiguate the value vs. location status of the expression.
-  // See PR21176 for more details.
-  if (DwarfVersion >= 4)
-    EmitOp(dwarf::DW_OP_stack_value);
+  AddStackValue();
 }
 
 void DwarfExpression::AddUnsignedConstant(unsigned Value) {
   EmitOp(dwarf::DW_OP_constu);
   EmitUnsigned(Value);
-  // cf. comment in DwarfExpression::AddSignedConstant().
-  if (DwarfVersion >= 4)
-    EmitOp(dwarf::DW_OP_stack_value);
+  AddStackValue();
+}
+
+void DwarfExpression::AddUnsignedConstant(APInt Value) {
+  unsigned Size = Value.getBitWidth();
+  const uint64_t *Data = Value.getRawData();
+
+  // Chop it up into 64-bit pieces, because that's the maximum that
+  // AddUnsignedConstant takes.
+  unsigned Offset = 0;
+  while (Offset < Size) {
+    AddUnsignedConstant(*Data++);
+    if (Offset == 0 && Size <= 64)
+      break;
+    AddOpPiece(std::min(Size-Offset, 64u), Offset);
+    Offset += 64;
+  }
 }
 
 static unsigned getOffsetOrZero(unsigned OffsetInBits,
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
index 78ec937a6b6..5de9131d5c4 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
@@ -61,6 +61,19 @@ public:
   void AddOpPiece(unsigned SizeInBits, unsigned OffsetInBits = 0);
   /// Emit a shift-right dwarf expression.
   void AddShr(unsigned ShiftBy);
+  /// Emit a DW_OP_stack_value, if supported.
+  ///
+  /// The proper way to describe a constant value is
+  /// DW_OP_constu <const>, DW_OP_stack_value.
+  /// Unfortunately, DW_OP_stack_value was not available until DWARF-4,
+  /// so we will continue to generate DW_OP_constu <const> for DWARF-2
+  /// and DWARF-3. Technically, this is incorrect since DW_OP_const <const>
+  /// actually describes a value at a constant addess, not a constant value.
+  /// However, in the past there was no better way  to describe a constant
+  /// value, so the producers and consumers started to rely on heuristics
+  /// to disambiguate the value vs. location status of the expression.
+  /// See PR21176 for more details.
+  void AddStackValue();
 
   /// Emit an indirect dwarf register operation for the given machine register.
   /// \return false if no DWARF register exists for MachineReg.
@@ -87,6 +100,8 @@ public:
   void AddSignedConstant(int Value);
   /// Emit an unsigned constant.
   void AddUnsignedConstant(unsigned Value);
+  /// Emit an unsigned constant.
+  void AddUnsignedConstant(APInt Value);
 
   /// \brief Emit an entire expression on top of a machine register location.
   ///