Allow ReadNone and ReadOnly as Function attributes

Author: stanleygambarin

lib/SPIRV/SPIRVInternal.h

@@ -248,6 +248,8 @@ typedef SPIRVMap<Attribute::AttrKind, SPIRVFuncParamAttrKind>
 template <>
 inline void
 SPIRVMap<Attribute::AttrKind, SPIRVFunctionControlMaskKind>::init() {
+  add(Attribute::ReadNone, FunctionControlPureMask);
+  add(Attribute::ReadOnly, FunctionControlConstMask);
   add(Attribute::AlwaysInline, FunctionControlInlineMask);
   add(Attribute::NoInline, FunctionControlDontInlineMask);
   add(Attribute::OptimizeNone, internal::FunctionControlOptNoneINTELMask);