[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

1 files changed, 2 insertions, 0 deletions

diff --git a/llvm/lib/AsmParser/LLParser.cpp b/llvm/lib/AsmParser/LLParser.cpp
index 307ed397834..145b5eaacec 100644
--- a/llvm/lib/AsmParser/LLParser.cpp
+++ b/llvm/lib/AsmParser/LLParser.cpp
@@ -1544,6 +1544,7 @@ bool LLParser::ParseOptionalDLLStorageClass(unsigned &Res) {
 ///   ::= 'ghccc'
 ///   ::= 'hhvmcc'
 ///   ::= 'hhvm_ccc'
+///   ::= 'cxx_fast_tlscc'
 ///   ::= 'cc' UINT
 ///
 bool LLParser::ParseOptionalCallingConv(unsigned &CC) {
@@ -1574,6 +1575,7 @@ bool LLParser::ParseOptionalCallingConv(unsigned &CC) {
   case lltok::kw_ghccc:          CC = CallingConv::GHC; break;
   case lltok::kw_hhvmcc:         CC = CallingConv::HHVM; break;
   case lltok::kw_hhvm_ccc:       CC = CallingConv::HHVM_C; break;
+  case lltok::kw_cxx_fast_tlscc: CC = CallingConv::CXX_FAST_TLS; break;
   case lltok::kw_cc: {
       Lex.Lex();
       return ParseUInt32(CC);