#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);
char toupper(char);
void strtoupper(char *to_upper) {
  int i;
  for (i = 0; to_upper[i] != '\0'; i++)
    to_upper[i] = tolower(to_upper[i]);
  to_upper[0] = toupper(to_upper[0]);
}


x86 assembly (clang, -O0):
<strtoupper>:
push   %rbp
mov    %rsp,%rbp
sub    $0x10,%rsp
mov    %rdi,-0x8(%rbp)
movl   $0x0,-0xc(%rbp)
mov    -0x8(%rbp),%rax
movslq -0xc(%rbp),%rcx
movsbl (%rax,%rcx,1),%eax
cmp    $0x0,%eax
je     1174 <strtoupper+0x54>
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    1133 <strtoupper+0x13>
mov    -0x8(%rbp),%rax
movsbl (%rax),%edi
call   1030 <toupper@plt>
mov    %al,%cl
mov    -0x8(%rbp),%rax
mov    %cl,(%rax)
add    $0x10,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<strtoupper>:
push   %r14
push   %rbx
push   %rax
mov    %rdi,%r14
mov    (%rdi),%al
test   %al,%al
je     115b <strtoupper+0x3b>
lea    0x1(%r14),%rbx
cs nopw 0x0(%rax,%rax,1)
nopl   0x0(%rax,%rax,1)
movsbl %al,%edi
call   1040 <tolower@plt>
mov    %al,-0x1(%rbx)
movzbl (%rbx),%eax
add    $0x1,%rbx
test   %al,%al
jne    1140 <strtoupper+0x20>
mov    (%r14),%al
jmp    115d <strtoupper+0x3d>
xor    %eax,%eax
movsbl %al,%edi
call   1030 <toupper@plt>
mov    %al,(%r14)
add    $0x8,%rsp
pop    %rbx
pop    %r14
ret

LLVM IR (-O0):
define void @strtoupper(i8* %0) {
%2 = alloca i8*
%3 = alloca i32
store i8* %0, i8** %2
store i32 0, i32* %3
br label %4
4: ; preds = %23, %1
%5 = load i8*, i8** %2
%6 = load i32, i32* %3
%7 = sext i32 %6 to i64
%8 = getelementptr inbounds i8, i8* %5, i64 %7
%9 = load i8, i8* %8
%10 = sext i8 %9 to i32
%11 = icmp ne i32 %10, 0
br i1 %11, label %12, label %26
12: ; preds = %4
%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 %4
26: ; preds = %4
%27 = load i8*, i8** %2
%28 = getelementptr inbounds i8, i8* %27, i64 0
%29 = load i8, i8* %28
%30 = call signext i8 @toupper(i8 signext %29)
%31 = load i8*, i8** %2
%32 = getelementptr inbounds i8, i8* %31, i64 0
store i8 %30, i8* %32
ret void
}

LLVM IR (-O2):
define void @strtoupper(i8* nocapture %0) {
%2 = load i8, i8* %0
%3 = icmp eq i8 %2, 0
br i1 %3, label %15, label %4
4: ; preds = %1, %4
%5 = phi i64 [ %9, %4 ], [ 0, %1 ]
%6 = phi i8 [ %11, %4 ], [ %2, %1 ]
%7 = phi i8* [ %10, %4 ], [ %0, %1 ]
%8 = tail call signext i8 @tolower(i8 signext %6)
store i8 %8, i8* %7
%9 = add nuw i64 %5, 1
%10 = getelementptr inbounds i8, i8* %0, i64 %9
%11 = load i8, i8* %10
%12 = icmp eq i8 %11, 0
br i1 %12, label %13, label %4
13: ; preds = %4
%14 = load i8, i8* %0
br label %15
15: ; preds = %13, %1
%16 = phi i8 [ %14, %13 ], [ 0, %1 ]
%17 = tail call signext i8 @toupper(i8 signext %16)
store i8 %17, i8* %0
ret void
}