Compiler Final Project - Fall 2023

Running Instructions

mkdir build
cd build
cmake ..
make
cd src
./ap "<the input code you want to be compiled>"

Introduction

• A simple compiler with integer data type based on llvm Compiler Infrastructure.
• In the designed language, the variables have values specified at compile time.
• In the given input codes, the result variable is defined with the default value first. $${\color{red} Dead \space Variable}$$
• A variable that is not related to the result and the value of the result is not dependent on it, is a dead variable.
  • For example in the below code, a is a Dead Variable:

  • int result;
    int a = (2 + 5) * 8;
    

$${\color{lightgreen} Live \space Variable}$$

• A variable that is related to the result and the value of the result depends on it, is a live variable.
  • For example in the below code, a and b are Live Variables:

  • int result;
    int a = (2 + 5) * 8;
    int b = 2 * a;
    result = b / 2;
    

• In this project, we remove all dead variables related to result from the given code.

Sample Input Codes With Their Outputs

Input Code 1

int a;
int b;
int result;
result = a + b;
a = 2;"

Output IR 1 With Implementing Dead Code Elimination

; ModuleID = 'calc.expr'
source_filename = "calc.expr"

define i32 @main(i32 %0, i8** %1) {
entry:
  %2 = alloca i32, align 4
  store i32 0, i32* %2, align 4
  %3 = alloca i32, align 4
  store i32 0, i32* %3, align 4
  %4 = alloca i32, align 4
  store i32 0, i32* %4, align 4
  %5 = load i32, i32* %2, align 4
  %6 = load i32, i32* %3, align 4
  %7 = add nsw i32 %5, %6
  %8 = load i32, i32* %4, align 4
  store i32 %7, i32* %4, align 4
  call void @ap_write(i32 %7)
  %9 = load i32, i32* %2, align 4
  store i32 2, i32* %2, align 4
  call void @ap_write.1(i32 2)
  ret i32 0
}

declare void @ap_write(i32)

declare void @ap_write.1(i32)

<Note that in the above code, there is no dead variable to eliminate>

Input Code 2

int result;
int a = 4;
int b = 2;
b += a;
int c = 12;
int d;
d = c;
result *= ((a * b) - 34 * 5 + 12);

Output IR 2 With Implementing Dead Code Elimination

variable 'c' is dead.
variable 'd' is dead.
; ModuleID = 'calc.expr'
source_filename = "calc.expr"

define i32 @main(i32 %0, i8** %1) {
entry:
  %2 = alloca i32, align 4
  store i32 0, i32* %2, align 4
  %3 = alloca i32, align 4
  store i32 4, i32* %3, align 4
  %4 = alloca i32, align 4
  store i32 2, i32* %4, align 4
  %5 = load i32, i32* %3, align 4
  %6 = load i32, i32* %4, align 4
  %7 = add nsw i32 %6, %5
  store i32 %7, i32* %4, align 4
  call void @ap_write(i32 %7)
  %8 = load i32, i32* %3, align 4
  %9 = load i32, i32* %4, align 4
  %10 = mul nsw i32 %8, %9
  %11 = sub nsw i32 %10, 170
  %12 = add nsw i32 %11, 12
  %13 = load i32, i32* %2, align 4
  %14 = mul nsw i32 %13, %12
  store i32 %14, i32* %2, align 4
  call void @ap_write.1(i32 %14)
  ret i32 0
}

declare void @ap_write(i32)

declare void @ap_write.1(i32)

<Two variables c and d are dead as it is printed in the output, and the corresponding IR is optimized due to eliminating them>