DebugInfo: Lazily attach definition attributes to definitions.

This is a precursor to fixing inlined debug info where the concrete,
out-of-line definition may preceed any inlined usage. To cope with this,
the attributes that may appear on the concrete definition or the
abstract definition are delayed until the end of the module. Then, if an
abstract definition was created, it is referenced (and no other
attributes are added to the out-of-line definition), otherwise the
attributes are added directly to the out-of-line definition.

In a couple of cases this causes not just reordering of attributes, but
reordering of types. When the creation of the attribute is delayed, if
that creation would create a type (such as for a DW_AT_type attribute)
then other top level DIEs may've been constructed during the delay,
causing the referenced type to be created and added after those
intervening DIEs. In the extreme case, in cross-cu-inlining.ll, this
actually causes the DW_TAG_basic_type for "int" to move from one CU to
another.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209674 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 30 insertions, 1 deletions

diff --git a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 5c802f7a2c..6234f12dd2 100644
--- a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -806,6 +806,25 @@ void DwarfDebug::beginModule() {
   SectionMap[Asm->getObjFileLowering().getTextSection()];
 }
 
+void DwarfDebug::finishSubprogramDefinitions() {
+  const Module *M = MMI->getModule();
+
+  NamedMDNode *CU_Nodes = M->getNamedMetadata("llvm.dbg.cu");
+  for (MDNode *N : CU_Nodes->operands()) {
+    DICompileUnit TheCU(N);
+    // Construct subprogram DIE and add variables DIEs.
+    DwarfCompileUnit *SPCU =
+        static_cast<DwarfCompileUnit *>(CUMap.lookup(TheCU));
+    DIArray Subprograms = TheCU.getSubprograms();
+    for (unsigned i = 0, e = Subprograms.getNumElements(); i != e; ++i) {
+      DISubprogram SP(Subprograms.getElement(i));
+      if (DIE *D = SPCU->getDIE(SP))
+        SPCU->applySubprogramAttributes(SP, *D);
+    }
+  }
+}
+
+
 // Collect info for variables that were optimized out.
 void DwarfDebug::collectDeadVariables() {
   const Module *M = MMI->getModule();
@@ -847,6 +866,8 @@ void DwarfDebug::finalizeModuleInfo() {
   // Collect info for variables that were optimized out.
   collectDeadVariables();
 
+  finishSubprogramDefinitions();
+
   // Handle anything that needs to be done on a per-unit basis after
   // all other generation.
   for (const auto &TheU : getUnits()) {
diff --git a/lib/CodeGen/AsmPrinter/DwarfDebug.h b/lib/CodeGen/AsmPrinter/DwarfDebug.h
index 1b0b1ebafd..4a4d01246c 100644
--- a/lib/CodeGen/AsmPrinter/DwarfDebug.h
+++ b/lib/CodeGen/AsmPrinter/DwarfDebug.h
@@ -389,6 +389,8 @@ class DwarfDebug : public AsmPrinterHandler {
   /// \brief Collect info for variables that were optimized out.
   void collectDeadVariables();
 
+  void finishSubprogramDefinitions();
+
   /// \brief Finish off debug information after all functions have been
   /// processed.
   void finalizeModuleInfo();
diff --git a/lib/CodeGen/AsmPrinter/DwarfUnit.cpp b/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
index c6e47ec072..2707f8b73d 100644
--- a/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
+++ b/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
@@ -1389,6 +1389,11 @@ DIE *DwarfUnit::getOrCreateSubprogramDIE(DISubprogram SP) {
   // DW_TAG_inlined_subroutine may refer to this DIE.
   DIE &SPDie = createAndAddDIE(dwarf::DW_TAG_subprogram, *ContextDIE, SP);
 
+  // Abort here and fill this in later, depending on whether or not this
+  // subprogram turns out to have inlined instances or not.
+  if (SP.isDefinition())
+    return &SPDie;
+
   applySubprogramAttributes(SP, SPDie);
   return &SPDie;
 }
@@ -1397,7 +1402,8 @@ void DwarfUnit::applySubprogramAttributes(DISubprogram SP, DIE &SPDie) {
   DIE *DeclDie = nullptr;
   StringRef DeclLinkageName;
   if (DISubprogram SPDecl = SP.getFunctionDeclaration()) {
-    DeclDie = getOrCreateSubprogramDIE(SPDecl);
+    DeclDie = getDIE(SPDecl);
+    assert(DeclDie);
     DeclLinkageName = SPDecl.getLinkageName();
   }