#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 */
char tolower(char const);
char *strtolower(char *dest, const char *src) {
  const char *p;
  char *q;
  for (p = src, q = dest; *p != '\0'; p++, q++) {
    *q = tolower(*p);
  }
  *q = '\0';
  return dest;
}


x86 assembly (clang, -O0):
<strtolower>:
push   %rbp
mov    %rsp,%rbp
sub    $0x20,%rsp
mov    %rdi,-0x8(%rbp)
mov    %rsi,-0x10(%rbp)
mov    -0x10(%rbp),%rax
mov    %rax,-0x18(%rbp)
mov    -0x8(%rbp),%rax
mov    %rax,-0x20(%rbp)
mov    -0x18(%rbp),%rax
movsbl (%rax),%eax
cmp    $0x0,%eax
je     1171 <strtolower+0x61>
mov    -0x18(%rbp),%rax
movsbl (%rax),%edi
call   1030 <tolower@plt>
mov    %al,%cl
mov    -0x20(%rbp),%rax
mov    %cl,(%rax)
mov    -0x18(%rbp),%rax
add    $0x1,%rax
mov    %rax,-0x18(%rbp)
mov    -0x20(%rbp),%rax
add    $0x1,%rax
mov    %rax,-0x20(%rbp)
jmp    1130 <strtolower+0x20>
mov    -0x20(%rbp),%rax
movb   $0x0,(%rax)
mov    -0x8(%rbp),%rax
add    $0x20,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<strtolower>:
push   %r15
push   %r14
push   %rbx
mov    %rdi,%r14
mov    (%rsi),%al
mov    %rdi,%rbx
test   %al,%al
je     114a <strtolower+0x3a>
mov    %rsi,%r15
add    $0x1,%r15
mov    %r14,%rbx
nopl   0x0(%rax,%rax,1)
movsbl %al,%edi
call   1030 <tolower@plt>
mov    %al,(%rbx)
add    $0x1,%rbx
movzbl (%r15),%eax
add    $0x1,%r15
test   %al,%al
jne    1130 <strtolower+0x20>
movb   $0x0,(%rbx)
mov    %r14,%rax
pop    %rbx
pop    %r14
pop    %r15
ret

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

LLVM IR (-O2):
define i8* @strtolower(i8* returned writeonly %0, i8* nocapture %1) {
%3 = load i8, i8* %1
%4 = icmp eq i8 %3, 0
br i1 %4, label %14, label %5
5: ; preds = %2, %5
%6 = phi i8 [ %12, %5 ], [ %3, %2 ]
%7 = phi i8* [ %11, %5 ], [ %0, %2 ]
%8 = phi i8* [ %10, %5 ], [ %1, %2 ]
%9 = tail call signext i8 @tolower(i8 signext %6)
store i8 %9, i8* %7
%10 = getelementptr inbounds i8, i8* %8, i64 1
%11 = getelementptr inbounds i8, i8* %7, i64 1
%12 = load i8, i8* %10
%13 = icmp eq i8 %12, 0
br i1 %13, label %14, label %5
14: ; preds = %5, %2
%15 = phi i8* [ %0, %2 ], [ %11, %5 ]
store i8 0, i8* %15
ret i8* %0
}