Whitee

Whitee is a tiny compiler written in C++17, which translates SysY language into ARM-v7a assembly.

Table of Contents

• Background
• Install
• Usage
• Architecture
• Contributing
• License

Background

Whitee is the final work of team Good Morning! Whitegivers with a wild card in 2021 Huawei Bisheng Cup Compilation System Design Competition, which ranked 5th in the final and won the 2nd prize.

• SysY language: a subset of C language, whose source code is usually stored in a file with the extension sy. Only one main function is allowed in SysY, which supports global variable declaration, constant declaration, other function definitions, etc. For more details see SysY-Language-Definition.pdf.
• SysY runtime library: the library provides a series of I/O functions and timing functions. For more details see SysY-Runtime-Library.pdf.
• target platform: Raspberry 4B with Raspberry Pi OS(Raspbian GNU/Linux 10) and ARM Cortex-A72 CPU.

Install

Environment

• Make 4.2+
• CMake 3.13+
• GCC 9.3+ or other compilers supporting C++17

Steps

$ git clone https://github.com/Forever518/Whitee.git
$ mkdir Whitee/build/ && cd Whitee/build/
$ cmake .. && make -j 8

Usage

$ ./whitee [-S] [-o] [-h | --help] [-d | --debug <level>] [-c | --check <level>] [--set-debug-path=<path>] <target-file> <source-file> [-O <level>]

Options

• -S: generate assembly, can be omitted.
• -o: set output file, can be omitted.
• -h, --help: show usage.
• -d <level>, --debug <level>: dump debug messages to certain files.
  • level 1: dump IR and optimized IR.
  • level 2: append AST.
  • level 3: append Lexer, each Optimization Pass and Register Allocation.
• -c <level>, --check <level>: check IR's relation.
  • level 1: check IR and final optimized IR only.
  • level 2: check IR after each optimization pass.
• --set-debug-path=<path>: set debug messages output path, default the same path with target assembly file.
• <target-file>: target assembly file in ARM-v7a.
• <source-file>: source code file matching SysY grammar.
• -O <level>: set optimization level, default non-optimization -O0.

Additional Details

• When the debug-path is not set and the option -d or --debug is used, the compiler will dump debug messages to the same directory with target assembly file as whitee-debug-<target-file>. Each message is dumped to its target file:
  • IR: ir.txt
  • AST: ast.txt
  • FIR: ir_final.txt
  • optimized IR: ir_optimized.txt
  • lexer vector: lexer.txt
  • conflict graph of variables in FIR(taking id in IR as identification): ir_conflict_graph.txt
  • result of global register allocation(taking id in IR as identification): ir_register_alloc.txt
  • IR after each pass: directory optimize under debug-path.
• The option -c or --check can make the compiler check IR's realtion after IR successfully built or each optimized pass, helping developers find more problems and bugs.
• The option -O will set the optimization level.
  • -O0: only constant propagation, copy propagation and temporary register allocation.
  • -O1: append dead code elimination, constant folding, assembly peephole optimization, etc.
  • -O2: append multiplication & division optimization, function inlining, etc.
  • -O3: append local array propagation, constant array globalization, etc.
• The target assembly directory or the debug path will be created when not exists.

Architecture

front-end optimize

• Strength Reduction
• Simple Loop Unrolling

SSA IR building optimize

• Constant Propagation
• Copy Propagation
• Loop Structure Simplification

SSA IR optimize

• Dead Code Elimination
• Constant Folding（including Peephole Optimization）
• Function Inlining Conditionally
• Local Common Subexpression Elimination
• Loop Invariant Code Motion
• Advanced Dead Code Elimination
• Basic Block Merging and Elimination
• Read-only Global Variable or Array to Constant
• Local Array Propagation
• Write-only Global Variable or Array Elimination

FIR optimize

• Global Register Allocation based on Graph Coloring

MIR optimize

• Constant Multiplication & Division Simplification
• Assembly Peephole Optimization

Contributing

All 4 members of team Good Morning! Whitegivers.

• Forever518
• T-Muller
• willipwk
• violet73

License

GPL-3.0 License © Dihao Fan, Zhenwei Liu, Weikun Peng, Kelun Lei