[ObjC][CodeGen] CodeGen support for @available.

CodeGens uses of @available into calls to the compiler-rt function
__isOSVersionAtLeast.

This commit is part of a feature that I proposed here:
http://lists.llvm.org/pipermail/cfe-dev/2016-July/049851.html

Differential revision: https://reviews.llvm.org/D27827

llvm-svn: 296015

1 files changed, 16 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CGObjC.cpp b/clang/lib/CodeGen/CGObjC.cpp
index 913a2ea72e7..adeb6d1839b 100644
--- a/clang/lib/CodeGen/CGObjC.cpp
+++ b/clang/lib/CodeGen/CGObjC.cpp
@@ -3399,5 +3399,21 @@ CodeGenFunction::EmitBlockCopyAndAutorelease(llvm::Value *Block, QualType Ty) {
   return Val;
 }
 
+llvm::Value *
+CodeGenFunction::EmitBuiltinAvailable(ArrayRef<llvm::Value *> Args) {
+  assert(Args.size() == 3 && "Expected 3 argument here!");
+
+  if (!CGM.IsOSVersionAtLeastFn) {
+    llvm::FunctionType *FTy =
+        llvm::FunctionType::get(Int32Ty, {Int32Ty, Int32Ty, Int32Ty}, false);
+    CGM.IsOSVersionAtLeastFn =
+        CGM.CreateRuntimeFunction(FTy, "__isOSVersionAtLeast");
+  }
+
+  llvm::Value *CallRes =
+      EmitNounwindRuntimeCall(CGM.IsOSVersionAtLeastFn, Args);
+
+  return Builder.CreateICmpNE(CallRes, llvm::Constant::getNullValue(Int32Ty));
+}
 
 CGObjCRuntime::~CGObjCRuntime() {}