Fix a bug that prevents global variables from having a DW_OP_deref.

For local variables the first DW_OP_deref is consumed by turning the
location kind into a memeory location, but that only makes sense for
values that are in a register to begin with, which cannot happen for
global variables that are attached to a symbol.

rdar://problem/39741860

This reapplies r330970 after fixing an uncovered bug in r331086 and
working around the situation caused by it.

llvm-svn: 331090

3 files changed, 10 insertions, 3 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
index 2eb0157f1e0..4a5c7b324d6 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
@@ -230,8 +230,13 @@ DIE *DwarfCompileUnit::getOrCreateGlobalVariableDIE(
         addOpAddress(*Loc, Sym);
       }
     }
-    if (Expr)
-      DwarfExpr->addExpression(Expr);
+    // Global variables attached to symbols are memory locations.
+    // It would be better if this were unconditional, but malformed input that
+    // mixes non-fragments and fragments for the same variable is too expensive
+    // to detect in the verifier.
+    if (!DwarfExpr->isMemoryLocation())
+      DwarfExpr->setMemoryLocationKind();
+    DwarfExpr->addExpression(Expr);
   }
   if (Loc)
     addBlock(*VariableDIE, dwarf::DW_AT_location, DwarfExpr->finalize());
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
index 379e9b14569..043d02e3ce4 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
@@ -361,7 +361,7 @@ void DwarfExpression::addExpression(DIExpressionCursor &&ExprCursor,
       break;
     case dwarf::DW_OP_deref:
       assert(LocationKind != Register);
-      if (LocationKind != Memory && isMemoryLocation(ExprCursor))
+      if (LocationKind != Memory && ::isMemoryLocation(ExprCursor))
         // Turning this into a memory location description makes the deref
         // implicit.
         LocationKind = Memory;
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
index ea5cbc40ba3..7d6d45e64d6 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
@@ -211,6 +211,8 @@ public:
   /// Emit an unsigned constant.
   void addUnsignedConstant(const APInt &Value);
 
+  bool isMemoryLocation() const { return LocationKind == Memory; }
+
   /// Lock this down to become a memory location description.
   void setMemoryLocationKind() {
     assert(LocationKind == Unknown);