Add an error when calling a builtin that requires features that don't

match the feature set of the function that they're being called from.

This ensures that we can effectively diagnose some[1] code that would
instead ICE in the backend with a failure to select message.

Example:

__m128d foo(__m128d a, __m128d b) {
  return __builtin_ia32_addsubps(b, a);
}

compiled for normal x86_64 via:

clang -target x86_64-linux-gnu -c

would fail to compile in the back end because the normal subtarget
features for x86_64 only include sse2 and the builtin requires sse3.

[1] We're still not erroring on:

__m128i bar(__m128i const *p) { return _mm_lddqu_si128(p); }

where we should fail and error on an always_inline function being
inlined into a function that doesn't support the subtarget features
required.

llvm-svn: 250473

clang/lib/CodeGen/CodeGenFunction.h

@@ -2633,6 +2633,8 @@ public:
   RValue EmitCallExpr(const CallExpr *E,
                       ReturnValueSlot ReturnValue = ReturnValueSlot());
 
+  bool checkBuiltinTargetFeatures(const FunctionDecl *TargetDecl);
+
   llvm::CallInst *EmitRuntimeCall(llvm::Value *callee,
                                   const Twine &name = "");
   llvm::CallInst *EmitRuntimeCall(llvm::Value *callee,