Add an c++ itanium demangler to llvm.

This adds a copy of the demangler in libcxxabi.

The code also has no dependencies on anything else in LLVM. To enforce
that I added it as another library. That way a BUILD_SHARED_LIBS will
fail if anyone adds an use of StringRef for example.

The no llvm dependency combined with the fact that this has to build
on linux, OS X and Windows required a few changes to the code. In
particular:

    No constexpr.
    No alignas

On OS X at least this library has only one global symbol:
__ZN4llvm16itanium_demangleEPKcPcPmPi

My current plan is:

    Commit something like this
    Change lld to use it
    Change lldb to use it as the fallback

    Add a few #ifdefs so that exactly the same file can be used in
    libcxxabi to export abi::__cxa_demangle.

Once the fast demangler in lldb can handle any names this
implementation can be replaced with it and we will have the one true
demangler.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@280732 91177308-0d34-0410-b5e6-96231b3b80d8

cmake/config-ix.cmake

@@ -82,13 +82,6 @@ check_include_file(mach/mach.h HAVE_MACH_MACH_H)
 check_include_file(mach-o/dyld.h HAVE_MACH_O_DYLD_H)
 check_include_file(histedit.h HAVE_HISTEDIT_H)
 
-# size_t must be defined before including cxxabi.h on FreeBSD 10.0.
-check_cxx_source_compiles("
-#include <stddef.h>
-#include <cxxabi.h>
-int main() { return 0; }
-" HAVE_CXXABI_H)
-
 # library checks
 if( NOT PURE_WINDOWS )
   check_library_exists(pthread pthread_create "" HAVE_LIBPTHREAD)

include/llvm/Config/config.h.cmake

@@ -28,9 +28,6 @@
 /* Define to 1 if you have the `closedir' function. */
 #cmakedefine HAVE_CLOSEDIR ${HAVE_CLOSEDIR}
 
-/* Define to 1 if you have the <cxxabi.h> header file. */
-#cmakedefine HAVE_CXXABI_H ${HAVE_CXXABI_H}
-
 /* Define to 1 if you have the <CrashReporterClient.h> header file. */
 #undef HAVE_CRASHREPORTERCLIENT_H
 

include/llvm/Demangle/Demangle.h

@@ -0,0 +1,28 @@
+//===--- Demangle.h ---------------------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include <cstddef>
+
+namespace llvm {
+/// This is a llvm local version of __cxa_demangle. Other than the name and
+/// being in the llvm namespace it is identical.
+///
+/// The mangled_name is demangled into buf and returned. If the buffer is not
+/// large enough, realloc is used to expand it.
+///
+/// The *status will be set to
+///   unknown_error: -4
+///   invalid_args:  -3
+///   invalid_mangled_name: -2
+///   memory_alloc_failure: -1
+///   success: 0
+
+char *itaniumDemangle(const char *mangled_name, char *buf, size_t *n,
+                      int *status);
+}

lib/CMakeLists.txt

@@ -1,5 +1,6 @@
 # `Support' and `TableGen' libraries are added on the top-level CMakeLists.txt
 
+add_subdirectory(Demangle)
 add_subdirectory(IR)
 add_subdirectory(IRReader)
 add_subdirectory(CodeGen)

lib/Demangle/CMakeLists.txt

@@ -0,0 +1,3 @@
+add_llvm_library(LLVMDemangle
+  ItaniumDemangle.cpp
+)