ahueck / irprinter

Explore the generated LLVM IR of a translation unit

irprinter

irprinter is a small commandline-based tool developed to explore LLVM IR code. The tool can print IR code of only specific functions, when dumping of the whole translation unit would produce too much output.

Main features

Print LLVM IR code of a translation unit (C/C++) to a console.

• Ability to modify and add compiler flags (e.g., replace -g with -O2) and re-generate the (modified) IR
• Regex matching of (demangled) function names, with the ability to print
  1. Function signatures only, and,
  2. Functions including body
• Dump whole IR code of the TU

Usage

See main.cpp for all possible commandline arguments.

Example of using irprinter

Assume test.c contains the code:

int foo () {
    return 2; 
}
int main() {
    int val;
    val = foo();    
    return 0;
}

Using irprinter on test.c

In this example we

1. load test.c with standard Clang flags,
2. list all functions in test.c,
3. print the body of main,
4. optimize the code with -O3, and finally,
5. print the body of main again.

ahueck@sys:~/irprint/install$ ./bin/irprinter ../test.c --
ir-printer> l
Match 1 [foo]:
; Function Attrs: noinline nounwind optnone uwtable
define i32 @foo() #0 

Match 2 [main]:
; Function Attrs: noinline nounwind optnone uwtable
define i32 @main() #0 

ir-printer> p main
Match 1 [main]:
; Function Attrs: noinline nounwind optnone uwtable
define i32 @main() #0 {
  %1 = alloca i32, align 4
  %2 = alloca i32, align 4
  store i32 0, i32* %1, align 4
  %3 = call i32 @foo()
  store i32 %3, i32* %2, align 4
  ret i32 0
}

ir-printer> f -O3
Set flag to -O3. Re-generating module...
ir-printer> p main
Match 1 [main]:
; Function Attrs: norecurse nounwind readnone uwtable
define i32 @main() local_unnamed_addr #1 {
  ret i32 0
}

How to build

Requirements

• cmake >= 3.14
• Clang/LLVM 10.0 (cmake needs to find the installation, see the LLVM cmake documentation)
• C++ compiler with support for the C++17 standard, e.g., Clang 10

Build steps

In the root project folder, execute the following commands

cmake -B build -DCMAKE_INSTALL_PREFIX=*your path*
cmake --build build --target install --parallel