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tiger

Implementing a compiler for tiger as described in the book Modern Compiler Implementation in ML by Andrew Appel. This implementation uses OCaml as opposed to SML as I thought that it'd be easier to pull this off in OCaml.

What's implemented so far?

  1. Lexing
  2. Parsing to AST
  3. Semantic analysis
  4. Production of activation records
  5. Translation to intermediate representation (IR)
  6. Producing basic blocks and traces from IR
  7. Instruction selection (RISC-V)
  8. Liveness analysis
  9. Register allocation

Postprocessing

A few steps need to be taken before the code can actually be run (this is only necessary if certain files are edited). All of the below operations are idempotent. A ./run_postprocessing.sh bash file is included to run all of the below steps.

Generate lexer

# Remove extraneous lines (tests dont work otherwise)
ocamllex lib/lexer.mll && sed -i '' "/^#.*$/c\\" lib/lexer.ml

This generates lib/lexer.ml (this file is typically checked into the repository).

Generate parser

ocamlyacc lib/grammar.mly && sed -i '' "/^#.*$/c\\" lib/grammar.ml
# Additional something that we need to add to the mli file
cat lib/grammar.mli_ >> lib/grammar.mli

This generates lib/grammar.ml (this file is also typically checked into the repository).

Run tests

To run unit tests and integration tests

dune runtest

How to run the compiler

This command compiles an input tiger file and produces a RISC-V assembly file.

dune exec bin/main.exe -- input.tig -o output.s

The output file needs to be linked with the runtime library. Here, we use riscv64-unknown-elf-gcc as our RISC-V assembler and linker. We also remap the getchar and strcmp functions using a wrapper, i.e. redirecting calls to these functions to our version of them.

riscv64-unknown-elf-gcc output.s btl/runtime.c -Wl,--wrap=getchar,--wrap=strcmp -o ./a.out

On a machine that does not run on the RISC-V architecture, we may run the executable using spike and pk.

spike pk ./a.out