[clang] [Clang] Add BuiltinTemplates.td to generate code for builtin templates (PR #123736)

[via cfe-commits]

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@@ -0,0 +1,184 @@
+//=- ClangBuiltinsEmitter.cpp - Generate Clang builtin templates-*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This tablegen backend emits Clang's builtin templates.
+//
+//===----------------------------------------------------------------------===//
+
+#include "TableGenBackends.h"
+#include "llvm/TableGen/Error.h"
+#include "llvm/TableGen/TableGenBackend.h"
+
+using namespace llvm;
+
+std::string TemplateNameList;
+std::string CreateBuiltinTemplateParameterList;
+
+namespace {
+struct ParserState {
+  size_t UniqueCounter = 0;
+  size_t CurrentDepth = 0;
+  bool EmittedSizeTInfo = false;
+};
+
+std::pair<std::string, std::string>
+ParseTemplateParameterList(ParserState &PS, StringRef &TemplateParmList) {
+  auto Alphabetic = [](char c) { return std::isalpha(c); };
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Sirraide wrote:

I’m not familiar w/ every last thing that would go into that, but can we maybe literally just use the actual parser for this?

As in, this might be a stupid idea, but would it be feasible to just throw this as source text at the start of the translation unit and then parse it, maybe w/ something like a `[[clang::__builtin_template__]]` attribute?

https://github.com/llvm/llvm-project/pull/123736