[IR] Remove the DIExpression field from DIGlobalVariable.

This patch implements PR31013 by introducing a
DIGlobalVariableExpression that holds a pair of DIGlobalVariable and
DIExpression.

Currently, DIGlobalVariables holds a DIExpression. This is not the
best way to model this:

(1) The DIGlobalVariable should describe the source level variable,
    not how to get to its location.

(2) It makes it unsafe/hard to update the expressions when we call
    replaceExpression on the DIGLobalVariable.

(3) It makes it impossible to represent a global variable that is in
    more than one location (e.g., a variable with multiple
    DW_OP_LLVM_fragment-s).  We also moved away from attaching the
    DIExpression to DILocalVariable for the same reasons.

<rdar://problem/29250149>
https://llvm.org/bugs/show_bug.cgi?id=31013
Differential Revision: https://reviews.llvm.org/D26769

llvm-svn: 289902

1 files changed, 12 insertions, 1 deletions

diff --git a/llvm/lib/IR/AsmWriter.cpp b/llvm/lib/IR/AsmWriter.cpp
index d58618f99ff..5c104f6ce0c 100644
--- a/llvm/lib/IR/AsmWriter.cpp
+++ b/llvm/lib/IR/AsmWriter.cpp
@@ -1827,7 +1827,6 @@ static void writeDIGlobalVariable(raw_ostream &Out, const DIGlobalVariable *N,
   Printer.printMetadata("type", N->getRawType());
   Printer.printBool("isLocal", N->isLocalToUnit());
   Printer.printBool("isDefinition", N->isDefinition());
-  Printer.printMetadata("expr", N->getExpr());
   Printer.printMetadata("declaration", N->getRawStaticDataMemberDeclaration());
   Printer.printInt("align", N->getAlignInBits());
   Out << ")";
@@ -1870,6 +1869,18 @@ static void writeDIExpression(raw_ostream &Out, const DIExpression *N,
   Out << ")";
 }
 
+static void writeDIGlobalVariableExpression(raw_ostream &Out,
+                                            const DIGlobalVariableExpression *N,
+                                            TypePrinting *TypePrinter,
+                                            SlotTracker *Machine,
+                                            const Module *Context) {
+  Out << "!DIGlobalVariableExpression(";
+  MDFieldPrinter Printer(Out, TypePrinter, Machine, Context);
+  Printer.printMetadata("var", N->getVariable());
+  Printer.printMetadata("expr", N->getExpression());
+  Out << ")";
+}
+
 static void writeDIObjCProperty(raw_ostream &Out, const DIObjCProperty *N,
                                 TypePrinting *TypePrinter, SlotTracker *Machine,
                                 const Module *Context) {