From d4135bbc30de3d3dbd44d64d718fb2169f41bae0 Mon Sep 17 00:00:00 2001
From: Peter Collingbourne <peter@pcc.me.uk>
Date: Tue, 13 Sep 2016 01:12:59 +0000
Subject: DebugInfo: New metadata representation for global variables.

This patch reverses the edge from DIGlobalVariable to GlobalVariable.
This will allow us to more easily preserve debug info metadata when
manipulating global variables.

Fixes PR30362. A program for upgrading test cases is attached to that
bug.

Differential Revision: http://reviews.llvm.org/D20147

llvm-svn: 281284
---
 llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

(limited to 'llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp')

diff --git a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
index 017fc20..91a480e 100644
--- a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
@@ -2001,6 +2001,14 @@ void CodeViewDebug::emitDebugInfoForUDTs(
 }
 
 void CodeViewDebug::emitDebugInfoForGlobals() {
+  DenseMap<const DIGlobalVariable *, const GlobalVariable *> GlobalMap;
+  for (const GlobalVariable &GV : MMI->getModule()->globals()) {
+    SmallVector<MDNode *, 1> MDs;
+    GV.getMetadata(LLVMContext::MD_dbg, MDs);
+    for (MDNode *MD : MDs)
+      GlobalMap[cast<DIGlobalVariable>(MD)] = &GV;
+  }
+
   NamedMDNode *CUs = MMI->getModule()->getNamedMetadata("llvm.dbg.cu");
   for (const MDNode *Node : CUs->operands()) {
     const auto *CU = cast<DICompileUnit>(Node);
@@ -2011,15 +2019,14 @@ void CodeViewDebug::emitDebugInfoForGlobals() {
     switchToDebugSectionForSymbol(nullptr);
     MCSymbol *EndLabel = nullptr;
     for (const DIGlobalVariable *G : CU->getGlobalVariables()) {
-      if (const auto *GV = dyn_cast_or_null<GlobalVariable>(G->getVariable())) {
+      if (const auto *GV = GlobalMap.lookup(G))
         if (!GV->hasComdat() && !GV->isDeclarationForLinker()) {
           if (!EndLabel) {
             OS.AddComment("Symbol subsection for globals");
             EndLabel = beginCVSubsection(ModuleSubstreamKind::Symbols);
           }
-          emitDebugInfoForGlobal(G, Asm->getSymbol(GV));
+          emitDebugInfoForGlobal(G, GV, Asm->getSymbol(GV));
         }
-      }
     }
     if (EndLabel)
       endCVSubsection(EndLabel);
@@ -2027,14 +2034,14 @@ void CodeViewDebug::emitDebugInfoForGlobals() {
     // Second, emit each global that is in a comdat into its own .debug$S
     // section along with its own symbol substream.
     for (const DIGlobalVariable *G : CU->getGlobalVariables()) {
-      if (const auto *GV = dyn_cast_or_null<GlobalVariable>(G->getVariable())) {
+      if (const auto *GV = GlobalMap.lookup(G)) {
         if (GV->hasComdat()) {
           MCSymbol *GVSym = Asm->getSymbol(GV);
           OS.AddComment("Symbol subsection for " +
                         Twine(GlobalValue::getRealLinkageName(GV->getName())));
           switchToDebugSectionForSymbol(GVSym);
           EndLabel = beginCVSubsection(ModuleSubstreamKind::Symbols);
-          emitDebugInfoForGlobal(G, GVSym);
+          emitDebugInfoForGlobal(G, GV, GVSym);
           endCVSubsection(EndLabel);
         }
       }
@@ -2055,6 +2062,7 @@ void CodeViewDebug::emitDebugInfoForRetainedTypes() {
 }
 
 void CodeViewDebug::emitDebugInfoForGlobal(const DIGlobalVariable *DIGV,
+                                           const GlobalVariable *GV,
                                            MCSymbol *GVSym) {
   // DataSym record, see SymbolRecord.h for more info.
   // FIXME: Thread local data, etc
@@ -2063,7 +2071,6 @@ void CodeViewDebug::emitDebugInfoForGlobal(const DIGlobalVariable *DIGV,
   OS.AddComment("Record length");
   OS.emitAbsoluteSymbolDiff(DataEnd, DataBegin, 2);
   OS.EmitLabel(DataBegin);
-  const auto *GV = cast<GlobalVariable>(DIGV->getVariable());
   if (DIGV->isLocalToUnit()) {
     if (GV->isThreadLocal()) {
       OS.AddComment("Record kind: S_LTHREAD32");
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