DebugInfo: Remove MDString-based type references

Eliminate DITypeIdentifierMap and make DITypeRef a thin wrapper around
DIType*.  It is no longer legal to refer to a DICompositeType by its
'identifier:', and DIBuilder no longer retains all types with an
'identifier:' automatically.

Aside from the bitcode upgrade, this is mainly removing logic to resolve
an MDString-based reference to an actualy DIType.  The commits leading
up to this have made the implicit type map in DICompileUnit's
'retainedTypes:' field superfluous.

This does not remove DITypeRef, DIScopeRef, DINodeRef, and
DITypeRefArray, or stop using them in DI-related metadata.  Although as
of this commit they aren't serving a useful purpose, there are patchces
under review to reuse them for CodeView support.

The tests in LLVM were updated with deref-typerefs.sh, which is attached
to the thread "[RFC] Lazy-loading of debug info metadata":

  http://lists.llvm.org/pipermail/llvm-dev/2016-April/098318.html

llvm-svn: 267296

1 files changed, 4 insertions, 2 deletions

diff --git a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
index 71905364c1d..3be4fe03d51 100644
--- a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -1273,7 +1273,8 @@ void ModuleBitcodeWriter::writeDIDerivedType(const DIDerivedType *N,
 void ModuleBitcodeWriter::writeDICompositeType(
     const DICompositeType *N, SmallVectorImpl<uint64_t> &Record,
     unsigned Abbrev) {
-  Record.push_back(N->isDistinct());
+  const unsigned IsNotUsedInOldTypeRef = 0x2;
+  Record.push_back(IsNotUsedInOldTypeRef | N->isDistinct());
   Record.push_back(N->getTag());
   Record.push_back(VE.getMetadataOrNullID(N->getRawName()));
   Record.push_back(VE.getMetadataOrNullID(N->getFile()));
@@ -1297,7 +1298,8 @@ void ModuleBitcodeWriter::writeDICompositeType(
 void ModuleBitcodeWriter::writeDISubroutineType(
     const DISubroutineType *N, SmallVectorImpl<uint64_t> &Record,
     unsigned Abbrev) {
-  Record.push_back(N->isDistinct());
+  const unsigned HasNoOldTypeRefs = 0x2;
+  Record.push_back(HasNoOldTypeRefs | N->isDistinct());
   Record.push_back(N->getFlags());
   Record.push_back(VE.getMetadataOrNullID(N->getTypeArray().get()));