#define NULL ((void *)0)
typedef unsigned long size_t; // Customize by platform.
typedef long intptr_t;
typedef unsigned long uintptr_t;
typedef long scalar_t__; // Either arithmetic or pointer type.
/* By default, we understand bool (as a convenience). */
typedef int bool;
#define false 0
#define true 1

/* Forward declarations */

/* Type definitions */

/* Variables and functions */
int strlen(char *);
int count_difference(char *student, char *instructor) {
  int count, i = 0;
  for (i = 0; i < strlen(student); i++) {
    if (student[i] != instructor[i]) {
      count++;
    }
  }
  return count;
}


x86 assembly (clang, -O0):
<count_difference>:
push   %rbp
mov    %rsp,%rbp
sub    $0x20,%rsp
mov    %rdi,-0x8(%rbp)
mov    %rsi,-0x10(%rbp)
movl   $0x0,-0x18(%rbp)
movl   $0x0,-0x18(%rbp)
mov    -0x18(%rbp),%eax
mov    %eax,-0x1c(%rbp)
mov    -0x8(%rbp),%rdi
call   1030 <strlen@plt>
mov    %eax,%ecx
mov    -0x1c(%rbp),%eax
cmp    %ecx,%eax
jge    1186 <count_difference+0x76>
mov    -0x8(%rbp),%rax
movslq -0x18(%rbp),%rcx
movsbl (%rax,%rcx,1),%eax
mov    -0x10(%rbp),%rcx
movslq -0x18(%rbp),%rdx
movsbl (%rcx,%rdx,1),%ecx
cmp    %ecx,%eax
je     1173 <count_difference+0x63>
mov    -0x14(%rbp),%eax
add    $0x1,%eax
mov    %eax,-0x14(%rbp)
jmp    1178 <count_difference+0x68>
mov    -0x18(%rbp),%eax
add    $0x1,%eax
mov    %eax,-0x18(%rbp)
jmp    112e <count_difference+0x1e>
mov    -0x14(%rbp),%eax
add    $0x20,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<count_difference>:
push   %rbp
push   %r15
push   %r14
push   %rbx
push   %rax
mov    %rsi,%r14
mov    %rdi,%r15
call   1030 <strlen@plt>
test   %eax,%eax
jle    1155 <count_difference+0x45>
xor    %ebx,%ebx
nopl   0x0(%rax,%rax,1)
movzbl (%r15,%rbx,1),%eax
xor    %ecx,%ecx
cmp    (%r14,%rbx,1),%al
setne  %cl
add    %ecx,%ebp
add    $0x1,%rbx
mov    %r15,%rdi
call   1030 <strlen@plt>
cltq
cmp    %rax,%rbx
jl     1130 <count_difference+0x20>
jmp    1155 <count_difference+0x45>
mov    %ebp,%eax
add    $0x8,%rsp
pop    %rbx
pop    %r14
pop    %r15
pop    %rbp
ret

LLVM IR (-O0):
define i32 @count_difference(i8* %0, i8* %1) {
%3 = alloca i8*
%4 = alloca i8*
%5 = alloca i32
%6 = alloca i32
store i8* %0, i8** %3
store i8* %1, i8** %4
store i32 0, i32* %6
store i32 0, i32* %6
br label %7
7: ; preds = %30, %2
%8 = load i32, i32* %6
%9 = load i8*, i8** %3
%10 = call i32 @strlen(i8* %9)
%11 = icmp slt i32 %8, %10
br i1 %11, label %12, label %33
12: ; preds = %7
%13 = load i8*, i8** %3
%14 = load i32, i32* %6
%15 = sext i32 %14 to i64
%16 = getelementptr inbounds i8, i8* %13, i64 %15
%17 = load i8, i8* %16
%18 = sext i8 %17 to i32
%19 = load i8*, i8** %4
%20 = load i32, i32* %6
%21 = sext i32 %20 to i64
%22 = getelementptr inbounds i8, i8* %19, i64 %21
%23 = load i8, i8* %22
%24 = sext i8 %23 to i32
%25 = icmp ne i32 %18, %24
br i1 %25, label %26, label %29
26: ; preds = %12
%27 = load i32, i32* %5
%28 = add nsw i32 %27, 1
store i32 %28, i32* %5
br label %29
29: ; preds = %26, %12
br label %30
30: ; preds = %29
%31 = load i32, i32* %6
%32 = add nsw i32 %31, 1
store i32 %32, i32* %6
br label %7
33: ; preds = %7
%34 = load i32, i32* %5
ret i32 %34
}

LLVM IR (-O2):
define i32 @count_difference(i8* %0, i8* nocapture %1) {
%3 = tail call i32 @strlen(i8* %0)
%4 = icmp sgt i32 %3, 0
br i1 %4, label %5, label %19
5: ; preds = %2, %5
%6 = phi i64 [ %15, %5 ], [ 0, %2 ]
%7 = phi i32 [ %14, %5 ], [ undef, %2 ]
%8 = getelementptr inbounds i8, i8* %0, i64 %6
%9 = load i8, i8* %8
%10 = getelementptr inbounds i8, i8* %1, i64 %6
%11 = load i8, i8* %10
%12 = icmp ne i8 %9, %11
%13 = zext i1 %12 to i32
%14 = add nsw i32 %7, %13
%15 = add nuw nsw i64 %6, 1
%16 = tail call i32 @strlen(i8* %0)
%17 = sext i32 %16 to i64
%18 = icmp slt i64 %15, %17
br i1 %18, label %5, label %19
19: ; preds = %5, %2
%20 = phi i32 [ undef, %2 ], [ %14, %5 ]
ret i32 %20
}