IR: Add COMDATs to the IR

This new IR facility allows us to represent the object-file semantic of
a COMDAT group.

COMDATs allow us to tie together sections and make the inclusion of one
dependent on another. This is required to implement features like MS
ABI VFTables and optimizing away certain kinds of initialization in C++.

This functionality is only representable in COFF and ELF, Mach-O has no
similar mechanism.

Differential Revision: http://reviews.llvm.org/D4178

llvm-svn: 211920

1 files changed, 8 insertions, 0 deletions

diff --git a/llvm/lib/IR/Module.cpp b/llvm/lib/IR/Module.cpp
index 9889f00..d853bf4 100644
--- a/llvm/lib/IR/Module.cpp
+++ b/llvm/lib/IR/Module.cpp
@@ -453,3 +453,11 @@ unsigned Module::getDwarfVersion() const {
     return dwarf::DWARF_VERSION;
   return cast<ConstantInt>(Val)->getZExtValue();
 }
+
+Comdat *Module::getOrInsertComdat(StringRef Name) {
+  Comdat C;
+  StringMapEntry<Comdat> &Entry =
+      ComdatSymTab.GetOrCreateValue(Name, std::move(C));
+  Entry.second.Name = &Entry;
+  return &Entry.second;
+}