[CodeView] Don't output S_UDT symbols for forward decls.

S_UDT symbols are the debugger's "index" for all the structs,
typedefs, classes, and enums in a program.  If any of those
structs/classes don't have a complete declaration, or if there
is a typedef to something that doesn't have a complete definition,
then emitting the S_UDT is unhelpful because it doesn't give
the debugger enough information to do anything useful.  On the
other hand, it results in a huge size blow-up in the resulting
PDB, which is exacerbated by an order of magnitude when linking
with /DEBUG:FASTLINK.

With this patch, we drop S_UDT records for types that refer either
directly or indirectly (e.g. through a typedef, pointer, etc) to
a class/struct/union/enum without a complete definition.  This
brings us about 50% of the way towards parity with /DEBUG:FASTLINK
PDBs generated from cl-compiled object files.

Differential Revision: https://reviews.llvm.org/D37162

llvm-svn: 311904

1 files changed, 5 insertions, 5 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.h b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.h
index fd8f60425c2..91f691c635e 100644
--- a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.h
+++ b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.h
@@ -187,8 +187,8 @@ class LLVM_LIBRARY_VISIBILITY CodeViewDebug : public DebugHandlerBase {
 
   // The UDTs we have seen while processing types; each entry is a pair of type
   // index and type name.
-  std::vector<std::pair<std::string, codeview::TypeIndex>> LocalUDTs,
-      GlobalUDTs;
+  std::vector<std::pair<std::string, const DIType *>> LocalUDTs;
+  std::vector<std::pair<std::string, const DIType *>> GlobalUDTs;
 
   using FileToFilepathMapTy = std::map<const DIFile *, std::string>;
   FileToFilepathMapTy FileToFilepathMap;
@@ -222,8 +222,8 @@ class LLVM_LIBRARY_VISIBILITY CodeViewDebug : public DebugHandlerBase {
 
   void emitDebugInfoForRetainedTypes();
 
-  void emitDebugInfoForUDTs(
-      ArrayRef<std::pair<std::string, codeview::TypeIndex>> UDTs);
+  void
+  emitDebugInfoForUDTs(ArrayRef<std::pair<std::string, const DIType *>> UDTs);
 
   void emitDebugInfoForGlobal(const DIGlobalVariable *DIGV,
                               const GlobalVariable *GV, MCSymbol *GVSym);
@@ -266,7 +266,7 @@ class LLVM_LIBRARY_VISIBILITY CodeViewDebug : public DebugHandlerBase {
 
   codeview::TypeIndex getVBPTypeIndex();
 
-  void addToUDTs(const DIType *Ty, codeview::TypeIndex TI);
+  void addToUDTs(const DIType *Ty);
 
   codeview::TypeIndex lowerType(const DIType *Ty, const DIType *ClassTy);
   codeview::TypeIndex lowerTypeAlias(const DIDerivedType *Ty);