toyc is a toy compiler for C subset, translating C-like source code into the x86_64 assembly (other architectures are not supported).

C Subset

Only a subset of C grammar is supported currently.

• only int type is supported
• only 1-D array and pointer is supported
• only a number of arithmetic and relational operators are supported
• only decimal integers can be treated as constant values
• global variables and function calls are supported
• DO NOT support do-while, switch, goto, header , macros, typedefs, struct, qualifiers, library functions, bitwise operators, strings, etc.

Please refer to the Lexer and Parser part for more details of our grammar.

Optimizations

After lexer and parser, we can obtain the AST. Then several passes would be conducted upon it.

• CFG and callgraph would be built, therefore unreachable code can be removed
• data flow analysis can be performed
• constant propagation
• common subexpression elimination
• peephole and register selection for backend

Usage

toyc is implemented in Python3. Given a source code src.c, simply run python3 toyc.py -i src.c and you would get:

• the corresponding assembly file src.c.S and
• the log file src.c.LOG where a lot of useful information along every phase (e.g., tokenization, AST generation, the symbol table/CFG/call graph, optimization passes, instruction selection) are recorded.

Note that option --opt should be add if you want to enable optimization passes.

Another assembler is needed if we want to run our compiled/generated assembly code (firstly turning the assembly into object file). Besides as built-in library functions are not supported in our grammar, we may want to use another test driver to print out the computation results of our generated code.

Take test/fib.c as an example. Function fib() computes the Fibonacci number and we need another file to call this function and dump the result.

python3 toyc.py -i fib.c
gcc -c fib.c.S -o fib.o
gcc -c drive.c -o drive.o
gcc fib.o drive.o -o a.out
./a.out

Docs

In the following, each phase is demonstrated in details.

Lexer, Parser

TBA

Test

A simple test framework is provided to check the correctness of every stage of toyc. See Test

python3 test/test.py --src $PATH_TO_TOYC

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Please feel free to raise issues if you have any question. Thanks :)