Uniphiler: the compiler you love!

This is a compiler written in Prolog using DCG for the language Latte.

Usage

Compiling

Running

> ./latc path/to/source.lat

for correct programs will produce path/to/source.prelink.ll, path/to/source.ll and path/to/source.bc.

Show LLVM

Running

> ./latc_llvm path/to/source.lat

for correct programs will print the prelink LLVM code.

Just checking for errors

Running

> ./latc_check path/to/source.lat

will return "OK" for accepted programs and "ERROR" with additional errors for all others.

Show Latte AST

> ./latc_ast path/to/source.lat

Show Latte tokens

> ./latc_tokens path/to/source.lat

The executables are just wrappers for swi-prolog running the scripts prolog scripts:

• latc and latc_llvm run src/compile.prolog
• latc_check runs src/check_latte.prolog
• latc_ast runs src/show_parse.prolog
• latc_tokens runs src/show_tokens.prolog

Structure

The main stages of compilation:

1. Tokenization (src/tokenize.prolog)
2. Building Latte AST (src/parse.prolog)
3. Type derivation and error checks (src/typing_and_checks.prolog)
4. Generating LLVM AST (src/llvm.prolog)
5. Optimization of LLVM AST (src/llvm_opts.prolog)
6. Register numbering and printing LLVM (src/llvm_print.prolog)

Additionally, some helper modules:

• uniform error handling for all stages of compilation (src/errors.prolog)
• a Context structure useful for tracking types and register allocations (src/context.prolog)
• simplification of simple boolean expressions (src/simplify.prolog)

Some builtin functions are compiled from C, those can be found in runtime/lib.c, and compiled by running make.

Optimization

Constant / copy propagation

In order to comply with SSA, the compiler keeps track of all constants and copy instructions, automatically avoiding unnecessary assignments and copies.

Examples: examples/opts/const* and examples/opts/copy*

Use of phi for loops and conditionals

Instead of allocating variables, the compiler uses phis to implement if and while statements. It will detect which variables are changing to avoid creating unnecessary phis. It will also try to clean up ones discovered to be redundant during optimization.

Examples: examples/opts/if* and examples/opts/while*

Global common subexpression optimization

The compiler will avoid recalculating instructions that don't have side effects.

Examples: examples/opts/gcse*