Eliminate excessive PCH deserialization caused by the search for

__cxxabiv1::__fundamental_type_info in every translation
unit. Previously, we would perform name lookup for
__cxxabiv1::__fundamental_type_info at the end of IRGen for a each
translation unit, to determine whether it was present. If so, we we
produce type information for all of the fundamental types. However,
this name lookup causes PCH deserialization of a significant part of the
translation unit, which has a woeful impact on performance.

With this change, we now look at each record type after we've
generated its vtable to see if it is
__cxxabiv1::__fundamental_type_info. If so, we generate type info for
all of the fundamental types. This works because
__cxxabiv1::__fundamental_type_info should always have a key function
(typically the virtual destructor), that will be defined once in the
support library. The fundamental type information will end up there.

Fixes <rdar://problem/7840011>.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@100772 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 12 insertions, 0 deletions

diff --git a/lib/CodeGen/CGVtable.cpp b/lib/CodeGen/CGVtable.cpp
index fc6d1a8e37..e23289a01a 100644
--- a/lib/CodeGen/CGVtable.cpp
+++ b/lib/CodeGen/CGVtable.cpp
@@ -3121,6 +3121,18 @@ CodeGenVTables::GenerateClassData(llvm::GlobalVariable::LinkageTypes Linkage,
   EmitVTableDefinition(VTable, Linkage, RD);
 
   GenerateVTT(Linkage, /*GenerateDefinition=*/true, RD);
+
+  // If this is the magic class __cxxabiv1::__fundamental_type_info,
+  // we will emit the typeinfo for the fundamental types. This is the
+  // same behaviour as GCC.
+  const DeclContext *DC = RD->getDeclContext();
+  if (RD->getIdentifier() &&
+      RD->getIdentifier()->isStr("__fundamental_type_info") &&
+      isa<NamespaceDecl>(DC) &&
+      cast<NamespaceDecl>(DC)->getIdentifier() &&
+      cast<NamespaceDecl>(DC)->getIdentifier()->isStr("__cxxabiv1") &&
+      DC->getParent()->isTranslationUnit())
+    CGM.EmitFundamentalRTTIDescriptors();
 }
 
 void CodeGenVTables::EmitVTableRelatedData(GlobalDecl GD) {