6f53f1c8d2
Without linker relaxation enabled for a particular relocatable file or section (e.g., using .option norelax), the assembler will not generate R_RISCV_ALIGN relocations for alignment directives. This becomes problematic in a two-stage linking process: ``` ld -r a.o b.o -o ab.o // b.o is norelax. Its alignment information is lost in ab.o. ld ab.o -o ab ``` When ab.o is linked into an executable, the preceding relaxed section (a.o's content) might shrink. Since there's no R_RISCV_ALIGN relocation in b.o for the linker to act upon, the `.word 0x3a393837` data in b.o may end up unaligned in the final executable. To address the issue, this patch inserts NOP bytes and synthesizes an R_RISCV_ALIGN relocation at the beginning of a text section when the alignment >= 4. For simplicity, when RVC is disabled, we synthesize an ALIGN relocation (addend: 2) for a 4-byte aligned section, allowing the linker to trim the excess 2 bytes. See also https://sourceware.org/bugzilla/show_bug.cgi?id=33236 Pull Request: https://github.com/llvm/llvm-project/pull/151639
LLVM Linker (lld)
This directory and its subdirectories contain source code for the LLVM Linker, a modular cross platform linker which is built as part of the LLVM compiler infrastructure project.
lld is open source software. You may freely distribute it under the terms of the license agreement found in LICENSE.txt.
Benchmarking
In order to make sure various developers can evaluate patches over the same tests, we create a collection of self contained programs.
It is hosted at https://s3-us-west-2.amazonaws.com/linker-tests/lld-speed-test.tar.xz
The current sha256 is 10eec685463d5a8bbf08d77f4ca96282161d396c65bd97dc99dbde644a31610f.