Index: docs/SourceLevelDebugging.rst
===================================================================
--- docs/SourceLevelDebugging.rst
+++ docs/SourceLevelDebugging.rst
@@ -570,6 +570,7 @@
     metadata, ;; Reference to the type descriptor
     i32,      ;; flags
     metadata  ;; (optional) Reference to inline location
+    metadata  ;; (optional) Reference to a complex expression (see below)
   }
 
 These descriptors are used to define variables local to a sub program.  The
@@ -588,6 +589,10 @@
 Name the source variable name.  Context and line indicate where the variable
 was defined.  Type descriptor defines the declared type of the variable.
 
+Local variables may point to variable-length complex address, which
+may consist of any combination of ``OpPlus`` and ``OpDeref`` or an
+``OpPiece``. The ``OpPlus`` operator takes one i32 argument that is an
+offset to add to the address and ``OpDeref`` dereferences the address.
 The ``OpPiece`` operator is used for (typically larger aggregate)
 variables that are fragmented across several addresses. It takes two
 i32 arguments, an offset and a size to describe which piece of the
Index: include/llvm/IR/DebugInfo.h
===================================================================
--- include/llvm/IR/DebugInfo.h
+++ include/llvm/IR/DebugInfo.h
@@ -688,12 +688,15 @@
   /// HasComplexAddr - Return true if the variable has a complex address.
   bool hasComplexAddress() const { return getNumAddrElements() > 0; }
 
-  unsigned getNumAddrElements() const;
-
-  uint64_t getAddrElement(unsigned Idx) const {
-    return getUInt64Field(Idx + 8);
+  unsigned getNumAddrElements() const {
+    if (DbgNode->getNumOperands() < 9)
+      return 0;
+    return getDescriptorField(8)->getNumOperands();
   }
 
+  /// \brief return the Idx'th complex address element.
+  uint64_t getAddrElement(unsigned Idx) const;
+
   /// isBlockByrefVariable - Return true if the variable was declared as
   /// a "__block" variable (Apple Blocks).
   bool isBlockByrefVariable(const DITypeIdentifierMap &Map) const {
Index: lib/IR/DIBuilder.cpp
===================================================================
--- lib/IR/DIBuilder.cpp
+++ lib/IR/DIBuilder.cpp
@@ -1035,7 +1035,7 @@
                                             DITypeRef Ty,
                                             ArrayRef<Value *> Addr,
                                             unsigned ArgNo) {
-  SmallVector<Value *, 15> Elts;
+  SmallVector<Value *, 8> Elts;
   Elts.push_back(GetTagConstant(VMContext, Tag));
   Elts.push_back(getNonCompileUnitScope(Scope)),
   Elts.push_back(MDString::get(VMContext, Name));
@@ -1045,7 +1045,10 @@
   Elts.push_back(Ty);
   Elts.push_back(Constant::getNullValue(Type::getInt32Ty(VMContext)));
   Elts.push_back(Constant::getNullValue(Type::getInt32Ty(VMContext)));
-  Elts.append(Addr.begin(), Addr.end());
+  assert(Addr.size() > 0 && "complex address is empty");
+  Elts.push_back(MDNode::get(VMContext, Addr));
+  return DIVariable(MDNode::get(VMContext, Elts));
+}
 
 /// createVariablePiece - Create a descriptor to describe one part
 /// of aggregate variable that is fragmented across multiple Values.
Index: lib/IR/DebugInfo.cpp
===================================================================
--- lib/IR/DebugInfo.cpp
+++ lib/IR/DebugInfo.cpp
@@ -139,8 +139,14 @@
   }
 }
 
-unsigned DIVariable::getNumAddrElements() const {
-  return DbgNode->getNumOperands() - 8;
+uint64_t DIVariable::getAddrElement(unsigned Idx) const {
+  DIDescriptor ComplexExpr = getDescriptorField(8);
+  if (Idx < ComplexExpr->getNumOperands())
+    if (auto *CI = dyn_cast_or_null<ConstantInt>(ComplexExpr->getOperand(Idx)))
+      return CI->getZExtValue();
+
+  assert(false && "non-existing complex address element requested");
+  return 0;
 }
 
 /// getInlinedAt - If this variable is inlined then return inline location.
@@ -598,7 +604,16 @@
   // Make sure that type @ field 5 is a DITypeRef.
   if (!fieldIsTypeRef(DbgNode, 5))
     return false;
-  return DbgNode->getNumOperands() >= 8;
+
+  // Make sure context @ field 1 is an MDNode.
+  if (!fieldIsMDNode(DbgNode, 1))
+    return false;
+
+  if (DbgNode->getNumOperands() == 8)
+    return true;
+
+  // Make sure the complex expression is an MDNode.
+  return (DbgNode->getNumOperands() == 9 && fieldIsMDNode(DbgNode, 8));
 }
 
 /// Verify - Verify that a location descriptor is well formed.
Index: test/CodeGen/ARM/debug-info-blocks.ll
===================================================================
--- test/CodeGen/ARM/debug-info-blocks.ll
+++ test/CodeGen/ARM/debug-info-blocks.ll
@@ -231,10 +231,10 @@
 !133 = metadata !{i32 609, i32 175, metadata !23, null}
 !134 = metadata !{i32 786689, metadata !23, metadata !"data", metadata !24, i32 67109473, metadata !108, i32 0, null} ; [ DW_TAG_arg_variable ]
 !135 = metadata !{i32 609, i32 190, metadata !23, null}
-!136 = metadata !{i32 786688, metadata !23, metadata !"mydata", metadata !24, i32 604, metadata !50, i32 0, null, i64 1, i64 20, i64 2, i64 1, i64 4, i64 2, i64 1, i64 24} ; [ DW_TAG_auto_variable ]
+!136 = metadata !{i32 786688, metadata !23, metadata !"mydata", metadata !24, i32 604, metadata !50, i32 0, null, metadata !163} ; [ DW_TAG_auto_variable ]
 !137 = metadata !{i32 604, i32 49, metadata !23, null}
-!138 = metadata !{i32 786688, metadata !23, metadata !"self", metadata !40, i32 604, metadata !90, i32 0, null, i64 1, i64 24} ; [ DW_TAG_auto_variable ]
-!139 = metadata !{i32 786688, metadata !23, metadata !"semi", metadata !24, i32 607, metadata !125, i32 0, null, i64 1, i64 28} ; [ DW_TAG_auto_variable ]
+!138 = metadata !{i32 786688, metadata !23, metadata !"self", metadata !40, i32 604, metadata !90, i32 0, null, metadata !164} ; [ DW_TAG_auto_variable ]
+!139 = metadata !{i32 786688, metadata !23, metadata !"semi", metadata !24, i32 607, metadata !125, i32 0, null, metadata !165} ; [ DW_TAG_auto_variable ]
 !140 = metadata !{i32 607, i32 30, metadata !23, null}
 !141 = metadata !{i32 610, i32 17, metadata !142, null}
 !142 = metadata !{i32 786443, metadata !152, metadata !23, i32 609, i32 200, i32 94} ; [ DW_TAG_lexical_block ]
@@ -258,3 +258,6 @@
 !160 = metadata !{metadata !"header.h", metadata !"/Volumes/Sandbox/llvm"}
 !161 = metadata !{metadata !"header2.h", metadata !"/Volumes/Sandbox/llvm"}
 !162 = metadata !{i32 1, metadata !"Debug Info Version", i32 1}
+!163 = metadata !{i64 1, i64 20, i64 2, i64 1, i64 4, i64 2, i64 1, i64 24}
+!164 = metadata !{i64 1, i64 24}
+!165 = metadata !{i64 1, i64 28}
Index: test/DebugInfo/X86/block-capture.ll
===================================================================
--- test/DebugInfo/X86/block-capture.ll
+++ test/DebugInfo/X86/block-capture.ll
@@ -120,7 +120,7 @@
 !50 = metadata !{i32 786445, metadata !63, metadata !6, metadata !"block", i32 7, i64 64, i64 64, i64 256, i32 0, metadata !9} ; [ DW_TAG_member ]
 !51 = metadata !{i32 7, i32 18, metadata !28, null}
 !52 = metadata !{i32 7, i32 19, metadata !28, null}
-!53 = metadata !{i32 786688, metadata !28, metadata !"block", metadata !6, i32 5, metadata !9, i32 0, i32 0, i64 1, i64 32} ; [ DW_TAG_auto_variable ]
+!53 = metadata !{i32 786688, metadata !28, metadata !"block", metadata !6, i32 5, metadata !9, i32 0, i32 0, metadata !65} ; [ DW_TAG_auto_variable ]
 !54 = metadata !{i32 5, i32 27, metadata !28, null}
 !55 = metadata !{i32 8, i32 22, metadata !56, null}
 !56 = metadata !{i32 786443, metadata !57, i32 7, i32 26, metadata !6, i32 2} ; [ DW_TAG_lexical_block ]
@@ -132,3 +132,4 @@
 !62 = metadata !{i32 9, i32 20, metadata !56, null}
 !63 = metadata !{metadata !"foo.m", metadata !"/Users/echristo"}
 !64 = metadata !{i32 1, metadata !"Debug Info Version", i32 1}
+!65 = metadata !{i64 1, i64 32}
Index: test/DebugInfo/X86/dbg_value_direct.ll
===================================================================
--- test/DebugInfo/X86/dbg_value_direct.ll
+++ test/DebugInfo/X86/dbg_value_direct.ll
@@ -170,8 +170,9 @@
 !20 = metadata !{i32 786468}
 !21 = metadata !{i32 786468, null, null, metadata !"int", i32 0, i64 32, i64 32, i64 0, i32 0, i32 5} ; [ DW_TAG_base_type ] [int] [line 0, size 32, align 32, offset 0, enc DW_ATE_signed]
 !22 = metadata !{i32 2, metadata !"Dwarf Version", i32 3}
-!23 = metadata !{i32 786689, metadata !4, metadata !"", metadata !5, i32 16777222, metadata !21, i32 0, i32 0, i64 2} ; [ DW_TAG_arg_variable ] [line 6]
+!23 = metadata !{i32 786689, metadata !4, metadata !"", metadata !5, i32 16777222, metadata !21, i32 0, i32 0, metadata !28} ; [ DW_TAG_arg_variable ] [line 6]
 !24 = metadata !{i32 786688, metadata !4, metadata !"a", metadata !5, i32 7, metadata !8, i32 8192, i32 0} ; [ DW_TAG_auto_variable ] [a] [line 7]
 !25 = metadata !{i32 7, i32 0, metadata !4, null}
 !26 = metadata !{i32 8, i32 0, metadata !4, null} ; [ DW_TAG_imported_declaration ]
 !27 = metadata !{i32 1, metadata !"Debug Info Version", i32 1}
+!28 = metadata !{i64 2}
Index: test/DebugInfo/X86/debug-info-block-captured-self.ll
===================================================================
--- test/DebugInfo/X86/debug-info-block-captured-self.ll
+++ test/DebugInfo/X86/debug-info-block-captured-self.ll
@@ -99,10 +99,12 @@
 !41 = metadata !{i32 786447, null, null, metadata !"", i32 0, i64 64, i64 64, i64 0, i32 0, null} ; [ DW_TAG_pointer_type ] [line 0, size 64, align 64, offset 0] [from ]
 !42 = metadata !{i32 786478, metadata !1, metadata !1, metadata !"__24-[Main initWithContext:]_block_invoke_2", metadata !"__24-[Main initWithContext:]_block_invoke_2", metadata !"", i32 35, metadata !39, i1 true, i1 true, i32 0, i32 0, null, i32 256, i1 false, void (i8*, i8*)* @"__24-[Main initWithContext:]_block_invoke_2", null, null, metadata !15, i32 35} ; [ DW_TAG_subprogram ] [line 35] [local] [def] [__24-[Main initWithContext:]_block_invoke_2]
 !84 = metadata !{i32 33, i32 0, metadata !38, null}
-!86 = metadata !{i32 786688, metadata !38, metadata !"self", metadata !1, i32 41, metadata !34, i32 0, i32 0, i64 1, i64 32} ; [ DW_TAG_auto_variable ] [self] [line 41]
+!86 = metadata !{i32 786688, metadata !38, metadata !"self", metadata !1, i32 41, metadata !34, i32 0, i32 0, metadata !110} ; [ DW_TAG_auto_variable ] [self] [line 41]
 !87 = metadata !{i32 41, i32 0, metadata !38, null}
 !103 = metadata !{i32 35, i32 0, metadata !42, null}
-!105 = metadata !{i32 786688, metadata !42, metadata !"self", metadata !1, i32 40, metadata !34, i32 0, i32 0, i64 1, i64 32} ; [ DW_TAG_auto_variable ] [self] [line 40]
+!105 = metadata !{i32 786688, metadata !42, metadata !"self", metadata !1, i32 40, metadata !34, i32 0, i32 0, metadata !109} ; [ DW_TAG_auto_variable ] [self] [line 40]
 !106 = metadata !{i32 40, i32 0, metadata !42, null}
 !107 = metadata !{metadata !"llvm/tools/clang/test/CodeGenObjC/debug-info-block-captured-self.m", metadata !""}
 !108 = metadata !{i32 1, metadata !"Debug Info Version", i32 1}
+!109 = metadata !{i64 1, i64 32}
+!110 = metadata !{i64 1, i64 32}
Index: test/DebugInfo/X86/debug-info-blocks.ll
===================================================================
--- test/DebugInfo/X86/debug-info-blocks.ll
+++ test/DebugInfo/X86/debug-info-blocks.ll
@@ -352,7 +352,7 @@
 !86 = metadata !{i32 786451, metadata !1, null, metadata !"__block_descriptor_withcopydispose", i32 49, i64 0, i64 0, i32 0, i32 4, null, null, i32 0, null, null, null} ; [ DW_TAG_structure_type ] [__block_descriptor_withcopydispose] [line 49, size 0, align 0, offset 0] [decl] [from ]
 !87 = metadata !{i32 786445, metadata !5, metadata !6, metadata !"self", i32 49, i64 64, i64 64, i64 256, i32 0, metadata !61} ; [ DW_TAG_member ] [self] [line 49, size 64, align 64, offset 256] [from ]
 !88 = metadata !{i32 49, i32 0, metadata !27, null}
-!89 = metadata !{i32 786688, metadata !27, metadata !"self", metadata !32, i32 52, metadata !23, i32 0, i32 0, i64 2, i64 1, i64 32} ; [ DW_TAG_auto_variable ] [self] [line 52]
+!89 = metadata !{i32 786688, metadata !27, metadata !"self", metadata !32, i32 52, metadata !23, i32 0, i32 0, metadata !111} ; [ DW_TAG_auto_variable ] [self] [line 52]
 !90 = metadata !{i32 52, i32 0, metadata !27, null}
 !91 = metadata !{i32 786688, metadata !92, metadata !"d", metadata !6, i32 50, metadata !93, i32 0, i32 0} ; [ DW_TAG_auto_variable ] [d] [line 50]
 !92 = metadata !{i32 786443, metadata !5, metadata !27, i32 49, i32 0, i32 2} ; [ DW_TAG_lexical_block ] [llvm/tools/clang/test/CodeGenObjC/debug-info-blocks.m]
@@ -374,3 +374,4 @@
 !108 = metadata !{i32 61, i32 0, metadata !36, null}
 !109 = metadata !{i32 62, i32 0, metadata !36, null}
 !110 = metadata !{i32 1, metadata !"Debug Info Version", i32 1}
+!111 = metadata !{i64 2, i64 1, i64 32}
Index: test/DebugInfo/X86/op_deref.ll
===================================================================
--- test/DebugInfo/X86/op_deref.ll
+++ test/DebugInfo/X86/op_deref.ll
@@ -86,7 +86,7 @@
 !11 = metadata !{i32 1, i32 26, metadata !5, null}
 !12 = metadata !{i32 3, i32 13, metadata !13, null}
 !13 = metadata !{i32 786443, metadata !28, metadata !5, i32 2, i32 1, i32 0} ; [ DW_TAG_lexical_block ]
-!14 = metadata !{i32 786688, metadata !13, metadata !"vla", metadata !6, i32 3, metadata !15, i32 8192, i32 0, i64 2} ; [ DW_TAG_auto_variable ]
+!14 = metadata !{i32 786688, metadata !13, metadata !"vla", metadata !6, i32 3, metadata !15, i32 8192, i32 0, metadata !30} ; [ DW_TAG_auto_variable ]
 !15 = metadata !{i32 786433, null, null, metadata !"", i32 0, i64 0, i64 32, i32 0, i32 0, metadata !9, metadata !16, i32 0, null, null, null} ; [ DW_TAG_array_type ] [line 0, size 0, align 32, offset 0] [from int]
 !16 = metadata !{metadata !17}
 !17 = metadata !{i32 786465, i64 0, i64 -1}        ; [ DW_TAG_subrange_type ]
@@ -102,3 +102,4 @@
 !27 = metadata !{i32 8, i32 1, metadata !13, null}
 !28 = metadata !{metadata !"bar.c", metadata !"/Users/echristo/tmp"}
 !29 = metadata !{i32 1, metadata !"Debug Info Version", i32 1}
+!30 = metadata !{i64 2}
Index: test/Instrumentation/AddressSanitizer/debug_info.ll
===================================================================
--- test/Instrumentation/AddressSanitizer/debug_info.ll
+++ test/Instrumentation/AddressSanitizer/debug_info.ll
@@ -47,8 +47,9 @@
 
 ; Verify that debug descriptors for argument and local variable will be replaced
 ; with descriptors that end with OpDeref (encoded as 2).
-;   CHECK: ![[ARG_ID]] = metadata {{.*}} i64 2} ; [ DW_TAG_arg_variable ] [p] [line 1]
-;   CHECK: ![[VAR_ID]] = metadata {{.*}} i64 2} ; [ DW_TAG_auto_variable ] [r] [line 2]
+;   CHECK: ![[ARG_ID]] = {{.*}}metadata ![[OPDEREF:[0-9]+]]} ; [ DW_TAG_arg_variable ] [p] [line 1]
+;   CHECK: ![[OPDEREF]] = metadata !{i64 2}
+;   CHECK: ![[VAR_ID]] = {{.*}}metadata ![[OPDEREF]]} ; [ DW_TAG_auto_variable ] [r] [line 2]
 ; Verify that there are no more variable descriptors.
 ;   CHECK-NOT: DW_TAG_arg_variable
 ;   CHECK-NOT: DW_TAG_auto_variable