From d15717170fbaaa24dacf2afbd8c6e9d8da4e8fa3 Mon Sep 17 00:00:00 2001
From: Chandler Carruth <chandlerc@gmail.com>
Date: Mon, 20 Jan 2014 08:07:07 +0000
Subject: [PATCH] Fix a DenseMap iterator invalidation bug causing lots of
 crashes when type units were enabled. The crux of the issue is that the
 addDwarfTypeUnitType routine can end up being indirectly recursive. In this
 case, the reference into the dense map (TU) became invalid by the time we
 popped all the way back and used it to add the DIE type signature.

Instead, use early return in the case where we can bypass the recursive
step and creating a type unit. Then use the pointer to the new type unit
to set up the DIE type signature in the case where we have to.

I tried really hard to reduce a testcase for this, but it's really
annoying. You have to get this to be mid-recursion when the densemap
grows. Even if we got a test case for this today, it'd be very unlikely
to continue exercising this pattern.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199630 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/AsmPrinter/DwarfDebug.cpp | 62 ++++++++++++++-------------
 1 file changed, 33 insertions(+), 29 deletions(-)

diff --git a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index f76e898cfb5..8e612c3e6eb 100644
--- a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -3027,36 +3027,40 @@ void DwarfDebug::emitDebugStrDWO() {
 void DwarfDebug::addDwarfTypeUnitType(DICompileUnit CUNode,
                                       StringRef Identifier, DIE *RefDie,
                                       DICompositeType CTy) {
+
   const DwarfTypeUnit *&TU = DwarfTypeUnits[CTy];
-  if (!TU) {
-    DIE *UnitDie = new DIE(dwarf::DW_TAG_type_unit);
-    DwarfTypeUnit *NewTU = new DwarfTypeUnit(
-        InfoHolder.getUnits().size(), UnitDie, CUNode, Asm, this, &InfoHolder);
-    TU = NewTU;
-    InfoHolder.addUnit(NewTU);
-
-    NewTU->addUInt(UnitDie, dwarf::DW_AT_language, dwarf::DW_FORM_data2,
-                   CUNode.getLanguage());
-
-    MD5 Hash;
-    Hash.update(Identifier);
-    // ... take the least significant 8 bytes and return those. Our MD5
-    // implementation always returns its results in little endian, swap bytes
-    // appropriately.
-    MD5::MD5Result Result;
-    Hash.final(Result);
-    uint64_t Signature = *reinterpret_cast<support::ulittle64_t *>(Result + 8);
-    NewTU->setTypeSignature(Signature);
-    if (useSplitDwarf())
-      NewTU->setSkeleton(constructSkeletonTU(NewTU));
-
-    NewTU->setType(NewTU->createTypeDIE(CTy));
-
-    NewTU->initSection(
-        useSplitDwarf()
-            ? Asm->getObjFileLowering().getDwarfTypesDWOSection(Signature)
-            : Asm->getObjFileLowering().getDwarfTypesSection(Signature));
+  if (TU) {
+    CUMap.begin()->second->addDIETypeSignature(RefDie, *TU);
+    return;
   }
 
-  CUMap.begin()->second->addDIETypeSignature(RefDie, *TU);
+  DIE *UnitDie = new DIE(dwarf::DW_TAG_type_unit);
+  DwarfTypeUnit *NewTU = new DwarfTypeUnit(
+      InfoHolder.getUnits().size(), UnitDie, CUNode, Asm, this, &InfoHolder);
+  TU = NewTU;
+  InfoHolder.addUnit(NewTU);
+
+  NewTU->addUInt(UnitDie, dwarf::DW_AT_language, dwarf::DW_FORM_data2,
+                 CUNode.getLanguage());
+
+  MD5 Hash;
+  Hash.update(Identifier);
+  // ... take the least significant 8 bytes and return those. Our MD5
+  // implementation always returns its results in little endian, swap bytes
+  // appropriately.
+  MD5::MD5Result Result;
+  Hash.final(Result);
+  uint64_t Signature = *reinterpret_cast<support::ulittle64_t *>(Result + 8);
+  NewTU->setTypeSignature(Signature);
+  if (useSplitDwarf())
+    NewTU->setSkeleton(constructSkeletonTU(NewTU));
+
+  NewTU->setType(NewTU->createTypeDIE(CTy));
+
+  NewTU->initSection(
+      useSplitDwarf()
+          ? Asm->getObjFileLowering().getDwarfTypesDWOSection(Signature)
+          : Asm->getObjFileLowering().getDwarfTypesSection(Signature));
+
+  CUMap.begin()->second->addDIETypeSignature(RefDie, *NewTU);
 }