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//===- Layout.h -----------------------------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
// Convenience macros for obtaining offsets of members in structs.
//
// Usage:
//
// #define FOR_EACH_FOO_FIELD(DO) \
// DO(Ptr, bar) \
// DO(uint32_t, baz) \
// CREATE_LAYOUT_CLASS(Foo, FOR_EACH_FOO_FIELD)
// #undef FOR_EACH_FOO_FIELD
//
// This will generate
//
// struct FooLayout {
// uint32_t barOffset;
// uint32_t bazOffset;
// uint32_t totalSize;
//
// FooLayout(size_t wordSize) {
// if (wordSize == 8)
// init<uint64_t>();
// else {
// assert(wordSize == 4);
// init<uint32_t>();
// }
// }
//
// private:
// template <class Ptr> void init() {
// FOR_EACH_FIELD(_INIT_OFFSET);
// barOffset = offsetof(Layout<Ptr>, bar);
// bazOffset = offsetof(Layout<Ptr>, baz);
// totalSize = sizeof(Layout<Ptr>);
// }
// template <class Ptr> struct Layout {
// Ptr bar;
// uint32_t baz;
// };
// };
#define _OFFSET_FOR_FIELD(_, name) uint32_t name##Offset;
#define _INIT_OFFSET(type, name) name##Offset = offsetof(Layout<Ptr>, name);
#define _LAYOUT_ENTRY(type, name) type name;
#define CREATE_LAYOUT_CLASS(className, FOR_EACH_FIELD) \
struct className##Layout { \
FOR_EACH_FIELD(_OFFSET_FOR_FIELD) \
uint32_t totalSize; \
\
className##Layout(size_t wordSize) { \
if (wordSize == 8) \
init<uint64_t>(); \
else { \
assert(wordSize == 4); \
init<uint32_t>(); \
} \
} \
\
private: \
template <class Ptr> void init() { \
FOR_EACH_FIELD(_INIT_OFFSET); \
totalSize = sizeof(Layout<Ptr>); \
} \
template <class Ptr> struct Layout { \
FOR_EACH_FIELD(_LAYOUT_ENTRY) \
}; \
}
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