[CXX TLS calling convention] Add CXX TLS calling convention.
This commit adds a new target-independent calling convention for C++ TLS
access functions. It aims to minimize overhead in the caller by perserving as
many registers as possible.
The target-specific implementation for X86-64 is defined as following:
Arguments are passed as for the default C calling convention
The same applies for the return value(s)
The callee preserves all GPRs - except RAX and RDI
The access function makes C-style TLS function calls in the entry and exit
block, C-style TLS functions save a lot more registers than normal calls.
The added calling convention ties into the existing implementation of the
C-style TLS functions, so we can't simply use existing calling conventions
such as preserve_mostcc.
rdar://9001553
llvm-svn: 254737
diff --git a/llvm/lib/IR/AsmWriter.cpp b/llvm/lib/IR/AsmWriter.cpp
index fae1ebe..f8040a7 100644
--- a/llvm/lib/IR/AsmWriter.cpp
+++ b/llvm/lib/IR/AsmWriter.cpp
@@ -304,6 +304,7 @@
case CallingConv::AnyReg: Out << "anyregcc"; break;
case CallingConv::PreserveMost: Out << "preserve_mostcc"; break;
case CallingConv::PreserveAll: Out << "preserve_allcc"; break;
+ case CallingConv::CXX_FAST_TLS: Out << "cxx_fast_tlscc"; break;
case CallingConv::GHC: Out << "ghccc"; break;
case CallingConv::X86_StdCall: Out << "x86_stdcallcc"; break;
case CallingConv::X86_FastCall: Out << "x86_fastcallcc"; break;