Richard Smith 4b163e343c Implement mangling rules for C++20 concepts and requires-expressions.
This implements proposals from:

- https://github.com/itanium-cxx-abi/cxx-abi/issues/24: mangling for
  constraints, requires-clauses, requires-expressions.
- https://github.com/itanium-cxx-abi/cxx-abi/issues/31: requires-clauses and
  template parameters in a lambda expression are mangled into the <lambda-sig>.
- https://github.com/itanium-cxx-abi/cxx-abi/issues/47 (STEP 3): mangling for
  template argument is prefixed by mangling of template parameter declaration
  if it's not "obvious", for example because the template parameter is
  constrained (we already implemented STEP 1 and STEP 2).

This changes the manglings for a few cases:

- Functions and function templates with constraints.
- Function templates with template parameters with deduced types:
  `typename<auto N> void f();`
- Function templates with template template parameters where the argument has a
  different template-head:
  `template<template<typename...T>> void f(); f<std::vector>();`

In each case where a mangling changed, the change fixes a mangling collision.

Note that only function templates are affected, not class templates or variable
templates, and only new constructs (template parameters with deduced types,
constrained templates) and esoteric constructs (templates with template
template parameters with non-matching template template arguments, most of
which Clang still does not accept by default due to
`-frelaxed-template-template-args` not being enabled by default), so the risk
to ABI stability from this change is relatively low. Nonetheless,
`-fclang-abi-compat=17` can be used to restore the old manglings for cases
which we could successfully but incorrectly mangle before.

Fixes #48216, #49884, #61273

Reviewed By: erichkeane, #libc_abi

Differential Revision: https://reviews.llvm.org/D147655
2023-09-20 12:38:15 -07:00
2023-09-20 11:53:59 -07:00

The LLVM Compiler Infrastructure

Welcome to the LLVM project!

This repository contains the source code for LLVM, a toolkit for the construction of highly optimized compilers, optimizers, and run-time environments.

The LLVM project has multiple components. The core of the project is itself called "LLVM". This contains all of the tools, libraries, and header files needed to process intermediate representations and convert them into object files. Tools include an assembler, disassembler, bitcode analyzer, and bitcode optimizer.

C-like languages use the Clang frontend. This component compiles C, C++, Objective-C, and Objective-C++ code into LLVM bitcode -- and from there into object files, using LLVM.

Other components include: the libc++ C++ standard library, the LLD linker, and more.

Getting the Source Code and Building LLVM

Consult the Getting Started with LLVM page for information on building and running LLVM.

For information on how to contribute to the LLVM project, please take a look at the Contributing to LLVM guide.

Getting in touch

Join the LLVM Discourse forums, Discord chat, or #llvm IRC channel on OFTC.

The LLVM project has adopted a code of conduct for participants to all modes of communication within the project.

Description
llvm with tablegen backend for capstone disassembler
Readme 2.1 GiB
Languages
LLVM 34.8%
C++ 32.7%
C 19.6%
Assembly 8.6%
MLIR 1.2%
Other 2.7%