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, 25 insertions, 0 deletions

diff --git a/llvm/lib/IR/Comdat.cpp b/llvm/lib/IR/Comdat.cpp
new file mode 100644
index 0000000..80715ff
--- /dev/null
+++ b/llvm/lib/IR/Comdat.cpp
@@ -0,0 +1,25 @@
+//===-- Comdat.cpp - Implement Metadata classes --------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the Comdat class.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/IR/Comdat.h"
+#include "llvm/ADT/StringMap.h"
+using namespace llvm;
+
+Comdat::Comdat(SelectionKind SK, StringMapEntry<Comdat> *Name)
+    : Name(Name), SK(SK) {}
+
+Comdat::Comdat(Comdat &&C) : Name(C.Name), SK(C.SK) {}
+
+Comdat::Comdat() : Name(nullptr), SK(Comdat::Any) {}
+
+StringRef Comdat::getName() const { return Name->first(); }