#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 tolower(char const);
int strcasecmp(const char *str1, const char *str2) {
  while (true) {
    int diff = tolower(*str1) - tolower(*str2);
    if (diff != 0 || !*str1 || !*str2) {
      return diff;
    }
    str1 += 1;
    str2 += 1;
  }
}


x86 assembly (clang, -O0):
<strcasecmp>:
push   %rbp
mov    %rsp,%rbp
sub    $0x20,%rsp
mov    %rdi,-0x8(%rbp)
mov    %rsi,-0x10(%rbp)
mov    -0x8(%rbp),%rax
movsbl (%rax),%edi
call   1030 <tolower@plt>
mov    %eax,-0x18(%rbp)
mov    -0x10(%rbp),%rax
movsbl (%rax),%edi
call   1030 <tolower@plt>
mov    %eax,%ecx
mov    -0x18(%rbp),%eax
sub    %ecx,%eax
mov    %eax,-0x14(%rbp)
cmpl   $0x0,-0x14(%rbp)
jne    1169 <strcasecmp+0x59>
mov    -0x8(%rbp),%rax
cmpb   $0x0,(%rax)
je     1169 <strcasecmp+0x59>
mov    -0x10(%rbp),%rax
cmpb   $0x0,(%rax)
jne    1172 <strcasecmp+0x62>
mov    -0x14(%rbp),%eax
add    $0x20,%rsp
pop    %rbp
ret
mov    -0x8(%rbp),%rax
add    $0x1,%rax
mov    %rax,-0x8(%rbp)
mov    -0x10(%rbp),%rax
add    $0x1,%rax
mov    %rax,-0x10(%rbp)
jmp    1120 <strcasecmp+0x10>

x86 assembly (clang, -O2):
<strcasecmp>:
push   %rbp
push   %r15
push   %r14
push   %rbx
push   %rax
mov    %rsi,%r14
mov    %rdi,%r15
movsbl (%rdi),%edi
call   1030 <tolower@plt>
mov    %eax,%ebp
movsbl (%r14),%edi
call   1030 <tolower@plt>
sub    %eax,%ebp
je     1141 <strcasecmp+0x31>
mov    %ebp,%eax
add    $0x8,%rsp
pop    %rbx
pop    %r14
pop    %r15
pop    %rbp
ret
mov    $0x1,%ebx
cs nopw 0x0(%rax,%rax,1)
xor    %ebp,%ebp
cmpb   $0x0,-0x1(%r15,%rbx,1)
je     1134 <strcasecmp+0x24>
cmpb   $0x0,-0x1(%r14,%rbx,1)
je     1134 <strcasecmp+0x24>
movsbl (%r15,%rbx,1),%edi
call   1030 <tolower@plt>
mov    %eax,%ebp
movsbl (%r14,%rbx,1),%edi
call   1030 <tolower@plt>
add    $0x1,%rbx
sub    %eax,%ebp
je     1150 <strcasecmp+0x40>
jmp    1134 <strcasecmp+0x24>

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

LLVM IR (-O2):
define i32 @strcasecmp(i8* nocapture %0, i8* nocapture %1) {
%3 = load i8, i8* %0
%4 = tail call i32 @tolower(i8 signext %3)
%5 = load i8, i8* %1
%6 = tail call i32 @tolower(i8 signext %5)
%7 = sub nsw i32 %4, %6
%8 = icmp eq i32 %7, 0
br i1 %8, label %9, label %26
9: ; preds = %2, %17
%10 = phi i8* [ %19, %17 ], [ %1, %2 ]
%11 = phi i8* [ %18, %17 ], [ %0, %2 ]
%12 = load i8, i8* %11
%13 = icmp eq i8 %12, 0
br i1 %13, label %26, label %14
14: ; preds = %9
%15 = load i8, i8* %10
%16 = icmp eq i8 %15, 0
br i1 %16, label %26, label %17
17: ; preds = %14
%18 = getelementptr inbounds i8, i8* %11, i64 1
%19 = getelementptr inbounds i8, i8* %10, i64 1
%20 = load i8, i8* %18
%21 = tail call i32 @tolower(i8 signext %20)
%22 = load i8, i8* %19
%23 = tail call i32 @tolower(i8 signext %22)
%24 = sub nsw i32 %21, %23
%25 = icmp eq i32 %24, 0
br i1 %25, label %9, label %26
26: ; preds = %17, %9, %14, %2
%27 = phi i32 [ %7, %2 ], [ 0, %14 ], [ 0, %9 ], [ %24, %17 ]
ret i32 %27
}