[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, 1 insertions, 0 deletions

diff --git a/llvm/lib/AsmParser/LLLexer.cpp b/llvm/lib/AsmParser/LLLexer.cpp
index 372c565..f95a763e 100644
--- a/llvm/lib/AsmParser/LLLexer.cpp
+++ b/llvm/lib/AsmParser/LLLexer.cpp
@@ -591,6 +591,7 @@ lltok::Kind LLLexer::LexIdentifier() {
   KEYWORD(ghccc);
   KEYWORD(hhvmcc);
   KEYWORD(hhvm_ccc);
+  KEYWORD(cxx_fast_tlscc);
 
   KEYWORD(cc);
   KEYWORD(c);