LLVM Cookbook

Converting a C source code to LLVM assembly

Here we will convert a C code to intermediate representation in LLVM using the C frontend Clang.

Getting ready

Clang must be installed in the PATH.

How to do it...

1. Lets create a C code in the multiply.c file, which will look something like the following:

   $ cat multiply.c
   int mult() {
   int a =5;
   int b = 3;
   int c = a * b;
   return c;
   }
   

2. Use the following command to generate LLVM IR from the C code:

   $ clang -emit-llvm -S multiply.c -o multiply.ll
   

3. Have a look at the generated IR:

   $ cat multiply.ll
   ; ModuleID = 'multiply.c'
   target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
   target triple = "x86_64-unknown-linux-gnu"
   
   ; Function Attrs: nounwind uwtable
   define i32 @mult() #0 {
     %a = alloca i32, align 4
    %b ...