#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 strcmp(const char *s1, const char *s2) {
  while (*s1 == *s2++)
    if (*s1++ == '\0')
      return (0);
  return (*(const unsigned char *)s1 - *(const unsigned char *)(s2 - 1));
}


x86 assembly (clang, -O0):
<strcmp>:
push   %rbp
mov    %rsp,%rbp
mov    %rdi,-0x10(%rbp)
mov    %rsi,-0x18(%rbp)
mov    -0x10(%rbp),%rax
movsbl (%rax),%eax
mov    -0x18(%rbp),%rcx
mov    %rcx,%rdx
add    $0x1,%rdx
mov    %rdx,-0x18(%rbp)
movsbl (%rcx),%ecx
cmp    %ecx,%eax
jne    1159 <strcmp+0x59>
mov    -0x10(%rbp),%rax
mov    %rax,%rcx
add    $0x1,%rcx
mov    %rcx,-0x10(%rbp)
movsbl (%rax),%eax
cmp    $0x0,%eax
jne    1154 <strcmp+0x54>
movl   $0x0,-0x4(%rbp)
jmp    116d <strcmp+0x6d>
jmp    110c <strcmp+0xc>
mov    -0x10(%rbp),%rax
movzbl (%rax),%eax
mov    -0x18(%rbp),%rcx
movzbl -0x1(%rcx),%ecx
sub    %ecx,%eax
mov    %eax,-0x4(%rbp)
mov    -0x4(%rbp),%eax
pop    %rbp
ret

x86 assembly (clang, -O2):
<strcmp>:
xor    %ecx,%ecx
cs nopw 0x0(%rax,%rax,1)
nopl   0x0(%rax)
movzbl (%rdi,%rcx,1),%eax
movzbl (%rsi,%rcx,1),%edx
cmp    %dl,%al
jne    1127 <strcmp+0x27>
add    $0x1,%rcx
test   %eax,%eax
jne    1110 <strcmp+0x10>
xor    %eax,%eax
ret
sub    %edx,%eax
ret

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

LLVM IR (-O2):
define i32 @strcmp(i8* nocapture %0, i8* nocapture %1) {
br label %3
3: ; preds = %9, %2
%4 = phi i8* [ %0, %2 ], [ %11, %9 ]
%5 = phi i8* [ %1, %2 ], [ %10, %9 ]
%6 = load i8, i8* %4
%7 = load i8, i8* %5
%8 = icmp eq i8 %6, %7
br i1 %8, label %9, label %13
9: ; preds = %3
%10 = getelementptr inbounds i8, i8* %5, i64 1
%11 = getelementptr inbounds i8, i8* %4, i64 1
%12 = icmp eq i8 %6, 0
br i1 %12, label %17, label %3
13: ; preds = %3
%14 = zext i8 %6 to i32
%15 = zext i8 %7 to i32
%16 = sub nsw i32 %14, %15
br label %17
17: ; preds = %9, %13
%18 = phi i32 [ %16, %13 ], [ 0, %9 ]
ret i32 %18
}