#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 *);
char tolower(char);
void lower(char *str) {
  int i;
  if (str != NULL) {
    for (i = 0; i < strlen(str); i++) {
      str[i] = tolower(str[i]);
    }
  }
}


x86 assembly (clang, -O0):
<lower>:
push   %rbp
mov    %rsp,%rbp
sub    $0x10,%rsp
mov    %rdi,-0x8(%rbp)
cmpq   $0x0,-0x8(%rbp)
je     118b <lower+0x6b>
movl   $0x0,-0xc(%rbp)
mov    -0xc(%rbp),%eax
mov    %eax,-0x10(%rbp)
mov    -0x8(%rbp),%rdi
call   1030 <strlen@plt>
mov    %eax,%ecx
mov    -0x10(%rbp),%eax
cmp    %ecx,%eax
jge    1186 <lower+0x66>
mov    -0x8(%rbp),%rax
movslq -0xc(%rbp),%rcx
movsbl (%rax,%rcx,1),%edi
call   1040 <tolower@plt>
mov    %al,%dl
mov    -0x8(%rbp),%rax
movslq -0xc(%rbp),%rcx
mov    %dl,(%rax,%rcx,1)
mov    -0xc(%rbp),%eax
add    $0x1,%eax
mov    %eax,-0xc(%rbp)
jmp    113e <lower+0x1e>
jmp    118b <lower+0x6b>
add    $0x10,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<lower>:
push   %r14
push   %rbx
push   %rax
test   %rdi,%rdi
je     1161 <lower+0x41>
mov    %rdi,%r14
call   1030 <strlen@plt>
test   %eax,%eax
jle    1161 <lower+0x41>
xor    %ebx,%ebx
nopw   0x0(%rax,%rax,1)
movsbl (%r14,%rbx,1),%edi
call   1040 <tolower@plt>
mov    %al,(%r14,%rbx,1)
add    $0x1,%rbx
mov    %r14,%rdi
call   1030 <strlen@plt>
cltq
cmp    %rax,%rbx
jl     1140 <lower+0x20>
add    $0x8,%rsp
pop    %rbx
pop    %r14
ret

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

LLVM IR (-O2):
define void @lower(i8* %0) {
%2 = icmp eq i8* %0, null
br i1 %2, label %15, label %3
3: ; preds = %1
%4 = tail call i32 @strlen(i8* %0)
%5 = icmp sgt i32 %4, 0
br i1 %5, label %6, label %15
6: ; preds = %3, %6
%7 = phi i64 [ %11, %6 ], [ 0, %3 ]
%8 = getelementptr inbounds i8, i8* %0, i64 %7
%9 = load i8, i8* %8
%10 = tail call signext i8 @tolower(i8 signext %9)
store i8 %10, i8* %8
%11 = add nuw nsw i64 %7, 1
%12 = tail call i32 @strlen(i8* %0)
%13 = sext i32 %12 to i64
%14 = icmp slt i64 %11, %13
br i1 %14, label %6, label %15
15: ; preds = %6, %3, %1
ret void
}