Daniel Thornburgh 074af0f30f
[lld][ELF] Add --why-live flag (inspired by Mach-O) (#127112)
This prints a stack of reasons that symbols that match the given glob(s)
survived GC. It has no effect unless section GC occurs.

This implementation does not require -ffunction-sections or
-fdata-sections to produce readable results, althought it does tend to
work better (as does GC).

Details about the semantics:
- Some chain of liveness reasons is reported; it isn't specified which
chain.
 - A symbol or section may be live:
   - Intrisically (e.g., entry point)
   - Because needed by a live symbol or section
   - (Symbols only) Because part of a section live for another reason
   - (Sections only) Because they contain a live symbol
 - Both global and local symbols (`STB_LOCAL`) are supported.
 - References to symbol + offset are considered to point to:
   - If the referenced symbol is a section (`STT_SECTION`):
- If a sized symbol encloses the referenced offset, the enclosing
symbol.
     - Otherwise, the section itself, generically.
   - Otherwise, the referenced symbol.
2025-03-26 09:56:33 -07:00
2025-01-28 19:48:43 -08:00
2025-02-13 17:49:48 +00:00

The LLVM Compiler Infrastructure

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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.

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The LLVM Project is a collection of modular and reusable compiler and toolchain technologies.
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