C+- compiler frontend

This repository contains a frontend for the C+- compiler frontend. The frontend is implemented in C++, using ANTLR4 for parsing and LLVM IR for intermediate representation. The compiler takes in a C+- source code and emits (unoptimized) LLVM IR.

C+- language

C+- is an (almost) subset of C++. In a nutshell, it's C with classes. More in depth feature specification can be found in the thesis/ directory.

We say C+- is an 'almost' subset of C++ because it breaks from C++ in a few places, including:

• break and continue can branch from multiple nested loops,
• class definition doesn't have to be followed by a semicolon.

BI-PJP students

FIT CTU students taking the BI-PJP source might find this project helpful to help them with their LLVM IR generation. For that, please go look into to the src/ll_builder/ directory. Note that since this project is built with LLVM 14, some things will very likely not work if you use a newer LLVM version. For example, we use typed pointers and getPointerElementType method, but this is not supported since LLVM 17.

Installation

You'll need:

• LLVM 14 libraries
• ANTLR 4.13 jar (tested with 4.13.0. and 4.13.1)
• ANTLR4 C++ runtime
• C++20 standard library
• Clang for building tests with cmake
• Boost (>=1.82)

Please see ci/build_antlr.sh to see how you can get all the ANTLR related tools.

##Usage Consider the following example code in file example.cpp:

int main() {
    // our compiler automatically declares printf and some other functions
    printf("Hello, World!");
}

Once the project is build, we can call the cpm executable with the source code to be compiled:

./cpm example.cpp

and get the LLVM IR output:

; ModuleID = 'basic'
source_filename = "basic"

@0 = private unnamed_addr constant [14 x i8] c"Hello, World!\00", align 1

declare i32 @printf(i8*, ...)

define i32 @main() {
entry:
  %ret_val = alloca i32, align 4
  store i32 0, i32* %ret_val, align 4
  %0 = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([14 x i8], [14 x i8]* @0, i32 0, i32 0))
  br label %return

return:                                           ; preds = %entry
  %1 = load i32, i32* %ret_val, align 4
  ret i32 

We can also call the program with the --ast-dump option, which prints the AST:

TranslationUnit <line:1:1> 
|-SimpleDeclar <line:0:0>
|  -InitDeclarator <line:0:0>
|    -FunctionDecl <line:0:0> printf 'int (ptr to const char, ...)'
|      -Param <line:0:0>
|        -Decl <line:0:0> format 'ptr to const char'
| /* other implicit declarations */
 -FuncDef <line:1:1>
  |-FunctionDecl <line:1:5> main 'int ()'
   -FuncBody <line:1:12>
     -CompoundStmt <line:1:12>
       -ExprStmt <line:3:2>
         -CallExpr <line:3:2> 'int (ptr to const char, ...)', function declared on line: 0
          |-IdExpr <line:3:2> printf, declared on line 0
           -ArrToPtrExpr <line:0:0>
             -StringLiteral <line:3:9> "Hello, World!"

You can also run tests by calling ctest in the build directory.

Authors

Daniel Kral

License

MIT license