[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.

This reapplies r289902 with additional testcase upgrades.

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

llvm-svn: 289920

1 files changed, 20 insertions, 5 deletions

diff --git a/llvm/lib/IR/Verifier.cpp b/llvm/lib/IR/Verifier.cpp
index 3609628561b..a7c3db184a8 100644
--- a/llvm/lib/IR/Verifier.cpp
+++ b/llvm/lib/IR/Verifier.cpp
@@ -594,7 +594,6 @@ void Verifier::visitGlobalVariable(const GlobalVariable &GV) {
            "Global variable initializer type does not match global "
            "variable type!",
            &GV);
-
     // If the global has common linkage, it must have a zero initializer and
     // cannot be constant.
     if (GV.hasCommonLinkage()) {
@@ -660,6 +659,15 @@ void Verifier::visitGlobalVariable(const GlobalVariable &GV) {
              GV.hasAvailableExternallyLinkage(),
          "Global is marked as dllimport, but not external", &GV);
 
+  // Visit any debug info attachments.
+  SmallVector<MDNode *, 1> MDs;
+  GV.getMetadata(LLVMContext::MD_dbg, MDs);
+  for (auto *MD : MDs)
+    if (auto *GVE = dyn_cast<DIGlobalVariableExpression>(MD))
+      visitDIGlobalVariableExpression(*GVE);
+    else
+      AssertDI(false, "!dbg attachment of global variable must be a DIGlobalVariableExpression");
+
   if (!GV.hasInitializer()) {
     visitGlobalValue(GV);
     return;
@@ -1002,8 +1010,8 @@ void Verifier::visitDICompileUnit(const DICompileUnit &N) {
   if (auto *Array = N.getRawGlobalVariables()) {
     AssertDI(isa<MDTuple>(Array), "invalid global variable list", &N, Array);
     for (Metadata *Op : N.getGlobalVariables()->operands()) {
-      AssertDI(Op && isa<DIGlobalVariable>(Op), "invalid global variable ref",
-               &N, Op);
+      AssertDI(Op && (isa<DIGlobalVariableExpression>(Op)),
+               "invalid global variable ref", &N, Op);
     }
   }
   if (auto *Array = N.getRawImportedEntities()) {
@@ -1146,8 +1154,6 @@ void Verifier::visitDIGlobalVariable(const DIGlobalVariable &N) {
 
   AssertDI(N.getTag() == dwarf::DW_TAG_variable, "invalid tag", &N);
   AssertDI(!N.getName().empty(), "missing global variable name", &N);
-  if (auto *V = N.getRawExpr())
-    AssertDI(isa<DIExpression>(V), "invalid expression location", &N, V);
   if (auto *Member = N.getRawStaticDataMemberDeclaration()) {
     AssertDI(isa<DIDerivedType>(Member),
              "invalid static data member declaration", &N, Member);
@@ -1167,6 +1173,15 @@ void Verifier::visitDIExpression(const DIExpression &N) {
   AssertDI(N.isValid(), "invalid expression", &N);
 }
 
+void Verifier::visitDIGlobalVariableExpression(
+    const DIGlobalVariableExpression &GVE) {
+  AssertDI(GVE.getVariable(), "missing variable");
+  if (auto *Var = GVE.getVariable())
+    visitDIGlobalVariable(*Var);
+  if (auto *Expr = GVE.getExpression())
+    visitDIExpression(*Expr);
+}
+
 void Verifier::visitDIObjCProperty(const DIObjCProperty &N) {
   AssertDI(N.getTag() == dwarf::DW_TAG_APPLE_property, "invalid tag", &N);
   if (auto *T = N.getRawType())