Atomic.S Generator

This V program generates an architecture-independent assembly file (atomic.S) implementing atomic operations by extracting disassembled code from pre-compiled libatomic.a libraries for multiple CPU architectures.

Features

• Supports 5 CPU architectures: i386, x86_64, arm, aarch64, riscv
• Implements 16 size-suffixed atomic operations (__atomic_*_1/2/4/8)
• Includes 6 non-size-suffixed atomic operations (atomic_*)
• Generates both raw machine code (for TinyCC) and assembly mnemonics
• Handles symbol name translation and label formatting

Supported Functions

Size-Suffixed Operations (1/2/4/8 bytes)

__atomic_load
__atomic_store
__atomic_compare_exchange
__atomic_exchange
__atomic_fetch_add
__atomic_add_fetch
__atomic_fetch_sub
__atomic_sub_fetch
__atomic_fetch_and
__atomic_and_fetch
__atomic_fetch_or
__atomic_or_fetch
__atomic_fetch_nand
__atomic_nand_fetch
__atomic_fetch_xor
__atomic_xor_fetch
__atomic_test_and_set

Non-Size-Suffixed Operations

atomic_thread_fence
atomic_signal_fence
atomic_flag_test_and_set
atomic_flag_test_and_set_explicit
atomic_flag_clear
atomic_flag_clear_explicit

Requirements

• V compiler
• objdump supporting all target architectures

tar -zxf binutils-2.44.tar.gz
cd binutils-2.44
mkdir build
cd build
../configure --enable-targets=all
make
sudo make install

• Pre-compiled libatomic.a files for each architecture:
  • libatomic.a.i386
  • libatomic.a.x86_64
  • libatomic.a.arm
  • libatomic.a.aarch64
  • libatomic.a.riscv

Usage

1. Place pre-compiled libatomic.a.[arch] files in the working directory
2. Compile and run the generator:

v run gen_atomic.v

3. Output file atomic.S will be generated containing atomic implementations

File Structure

• output_global_header(): Global header with metadata
• output_arch_header()/footer(): Architecture-specific sections
• gen_objdump_file(): Extracts disassembly via objdump
• fix_objdump_asm(): Formats assembly labels
• output_f_*(): Generates function headers/bodies/footers
• process_arch(): Processes all functions for an architecture

Verification (Optional)

Enable the verify() step in main() to:

1. Assemble atomic.S to object files
2. Compare disassembly with original libatomic
3. Requires architecture-specific GCC toolchains

Special Notes

• ARM architectures require symbol name fixes (libat_ → __atomic_)
• TinyCC compatibility mode uses raw machine code (.int/.short)
• Label format conversion: 44 <.L1^B2> → .L___atomic_fetch_add_8_44