1*700637cbSDimitry Andric //===- TemplateArgumentHasher.h - Hash Template Arguments -------*- C++ -*-===// 2*700637cbSDimitry Andric // 3*700637cbSDimitry Andric // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4*700637cbSDimitry Andric // See https://llvm.org/LICENSE.txt for license information. 5*700637cbSDimitry Andric // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6*700637cbSDimitry Andric // 7*700637cbSDimitry Andric //===----------------------------------------------------------------------===// 8*700637cbSDimitry Andric 9*700637cbSDimitry Andric #include "clang/AST/TemplateBase.h" 10*700637cbSDimitry Andric 11*700637cbSDimitry Andric namespace clang { 12*700637cbSDimitry Andric namespace serialization { 13*700637cbSDimitry Andric 14*700637cbSDimitry Andric /// Calculate a stable hash value for template arguments. We guarantee that 15*700637cbSDimitry Andric /// the same template arguments must have the same hashed values. But we don't 16*700637cbSDimitry Andric /// guarantee that the template arguments with the same hashed value are the 17*700637cbSDimitry Andric /// same template arguments. 18*700637cbSDimitry Andric /// 19*700637cbSDimitry Andric /// ODR hashing may not be the best mechanism to hash the template 20*700637cbSDimitry Andric /// arguments. ODR hashing is (or perhaps, should be) about determining whether 21*700637cbSDimitry Andric /// two things are spelled the same way and have the same meaning (as required 22*700637cbSDimitry Andric /// by the C++ ODR), whereas what we want here is whether they have the same 23*700637cbSDimitry Andric /// meaning regardless of spelling. Maybe we can get away with reusing ODR 24*700637cbSDimitry Andric /// hashing anyway, on the basis that any canonical, non-dependent template 25*700637cbSDimitry Andric /// argument should have the same (invented) spelling in every translation 26*700637cbSDimitry Andric /// unit, but it is not sure that's true in all cases. There may still be cases 27*700637cbSDimitry Andric /// where the canonical type includes some aspect of "whatever we saw first", 28*700637cbSDimitry Andric /// in which case the ODR hash can differ across translation units for 29*700637cbSDimitry Andric /// non-dependent, canonical template arguments that are spelled differently 30*700637cbSDimitry Andric /// but have the same meaning. But it is not easy to raise examples. 31*700637cbSDimitry Andric unsigned StableHashForTemplateArguments(llvm::ArrayRef<TemplateArgument> Args); 32*700637cbSDimitry Andric 33*700637cbSDimitry Andric } // namespace serialization 34*700637cbSDimitry Andric } // namespace clang 35