[X86] Support of no_caller_saved_registers attribute
This patch implements the LLVM part for no_caller_saved_registers attribute as appears here: https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=5ed3cc7b66af4758f7849ed6f65f4365be8223be.
In order to implement the attribute, we use the dynamic CSR mechanism to remove returned/passed arguments from the function regmask/CSR list.
Differential Revision: https://reviews.llvm.org/D31876
llvm-svn: 302020
diff --git a/llvm/lib/Target/X86/X86FastISel.cpp b/llvm/lib/Target/X86/X86FastISel.cpp
index fd11b67..ebd179e 100644
--- a/llvm/lib/Target/X86/X86FastISel.cpp
+++ b/llvm/lib/Target/X86/X86FastISel.cpp
@@ -3181,6 +3181,15 @@
bool Is64Bit = Subtarget->is64Bit();
bool IsWin64 = Subtarget->isCallingConvWin64(CC);
+ const CallInst *CI =
+ CLI.CS ? dyn_cast<CallInst>(CLI.CS->getInstruction()) : nullptr;
+ const Function *CalledFn = CI ? CI->getCalledFunction() : nullptr;
+
+ // Functions with no_caller_saved_registers that need special handling.
+ if ((CI && CI->hasFnAttr("no_caller_saved_registers")) ||
+ (CalledFn && CalledFn->hasFnAttribute("no_caller_saved_registers")))
+ return false;
+
// Handle only C, fastcc, and webkit_js calling conventions for now.
switch (CC) {
default: return false;