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

2 files changed, 5 insertions, 0 deletions

diff --git a/test/Demangle/lit.local.cfg b/test/Demangle/lit.local.cfg
new file mode 100644
index 00000000000..df9b335dd13
--- /dev/null
+++ b/test/Demangle/lit.local.cfg
@@ -0,0 +1 @@
+config.suffixes = ['.test']
diff --git a/test/Demangle/simple.test b/test/Demangle/simple.test
new file mode 100644
index 00000000000..76e70dbba30
--- /dev/null
+++ b/test/Demangle/simple.test
@@ -0,0 +1,4 @@
+RUN: llvm-cxxfilt _Z1fi abc | FileCheck %s
+
+CHECK: f(int)
+CHECK-NEXT: abc