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/Transforms/IPO/StripSymbols.cpp | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

(limited to 'llvm/lib/Transforms/IPO/StripSymbols.cpp')

diff --git a/llvm/lib/Transforms/IPO/StripSymbols.cpp b/llvm/lib/Transforms/IPO/StripSymbols.cpp
index fd250366cef..51c2103e0e5 100644
--- a/llvm/lib/Transforms/IPO/StripSymbols.cpp
+++ b/llvm/lib/Transforms/IPO/StripSymbols.cpp
@@ -312,13 +312,14 @@ bool StripDeadDebugInfo::runOnModule(Module &M) {
   // replace the current list of potentially dead global variables/functions
   // with the live list.
   SmallVector<Metadata *, 64> LiveGlobalVariables;
-  SmallVector<Metadata *, 64> LiveSubprograms;
   DenseSet<const MDNode *> VisitedSet;
 
-  std::set<DISubprogram *> LiveSPs;
-  for (Function &F : M) {
-    if (DISubprogram *SP = F.getSubprogram())
-      LiveSPs.insert(SP);
+  std::set<DIGlobalVariable *> LiveGVs;
+  for (GlobalVariable &GV : M.globals()) {
+    SmallVector<DIGlobalVariable *, 1> DIs;
+    GV.getDebugInfo(DIs);
+    for (DIGlobalVariable *DI : DIs)
+      LiveGVs.insert(DI);
   }
 
   for (DICompileUnit *DIC : F.compile_units()) {
@@ -329,9 +330,8 @@ bool StripDeadDebugInfo::runOnModule(Module &M) {
       if (!VisitedSet.insert(DIG).second)
         continue;
 
-      // If the global variable referenced by DIG is not null, the global
-      // variable is live.
-      if (DIG->getVariable())
+      // If a global variable references DIG, the global variable is live.
+      if (LiveGVs.count(DIG))
         LiveGlobalVariables.push_back(DIG);
       else
         GlobalVariableChange = true;
@@ -345,7 +345,6 @@ bool StripDeadDebugInfo::runOnModule(Module &M) {
     }
 
     // Reset lists for the next iteration.
-    LiveSubprograms.clear();
     LiveGlobalVariables.clear();
   }
 
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