#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 */
size_t strlen(char const *);
scalar_t__ strncmp(char const *, char const *, size_t);
int starts_with(const char *str, const char *prefix) {
  if (!str || !prefix)
    return 0;
  size_t lenstr = strlen(str);
  size_t lenprefix = strlen(prefix);
  if (lenprefix > lenstr)
    return 0;
  return strncmp(str, prefix, lenprefix) == 0;
}


x86 assembly (clang, -O0):
<starts_with>:
push   %rbp
mov    %rsp,%rbp
sub    $0x30,%rsp
mov    %rdi,-0x10(%rbp)
mov    %rsi,-0x18(%rbp)
cmpq   $0x0,-0x10(%rbp)
je     1146 <starts_with+0x26>
cmpq   $0x0,-0x18(%rbp)
jne    1152 <starts_with+0x32>
movl   $0x0,-0x4(%rbp)
jmp    11a6 <starts_with+0x86>
mov    -0x10(%rbp),%rdi
call   1040 <strlen@plt>
mov    %rax,-0x20(%rbp)
mov    -0x18(%rbp),%rdi
call   1040 <strlen@plt>
mov    %rax,-0x28(%rbp)
mov    -0x28(%rbp),%rax
cmp    -0x20(%rbp),%rax
jbe    1186 <starts_with+0x66>
movl   $0x0,-0x4(%rbp)
jmp    11a6 <starts_with+0x86>
mov    -0x10(%rbp),%rdi
mov    -0x18(%rbp),%rsi
mov    -0x28(%rbp),%rdx
call   1030 <strncmp@plt>
cmp    $0x0,%rax
sete   %al
and    $0x1,%al
movzbl %al,%eax
mov    %eax,-0x4(%rbp)
mov    -0x4(%rbp),%eax
add    $0x30,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<starts_with>:
push   %rbp
push   %r15
push   %r14
push   %rbx
push   %rax
xor    %r14d,%r14d
test   %rdi,%rdi
je     1167 <starts_with+0x47>
mov    %rsi,%rbx
test   %rsi,%rsi
je     1167 <starts_with+0x47>
mov    %rdi,%rbp
call   1040 <strlen@plt>
mov    %rax,%r15
mov    %rbx,%rdi
call   1040 <strlen@plt>
cmp    %r15,%rax
ja     1167 <starts_with+0x47>
mov    %rbp,%rdi
mov    %rbx,%rsi
mov    %rax,%rdx
call   1030 <strncmp@plt>
xor    %r14d,%r14d
test   %rax,%rax
sete   %r14b
mov    %r14d,%eax
add    $0x8,%rsp
pop    %rbx
pop    %r14
pop    %r15
pop    %rbp
ret

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

LLVM IR (-O2):
define i32 @starts_with(i8* %0, i8* %1) {
%3 = icmp ne i8* %0, null
%4 = icmp ne i8* %1, null
%5 = and i1 %3, %4
br i1 %5, label %6, label %14
6: ; preds = %2
%7 = tail call i64 @strlen(i8* %0)
%8 = tail call i64 @strlen(i8* %1)
%9 = icmp ugt i64 %8, %7
br i1 %9, label %14, label %10
10: ; preds = %6
%11 = tail call i64 @strncmp(i8* %0, i8* %1, i64 %8)
%12 = icmp eq i64 %11, 0
%13 = zext i1 %12 to i32
br label %14
14: ; preds = %10, %6, %2
%15 = phi i32 [ 0, %2 ], [ %13, %10 ], [ 0, %6 ]
ret i32 %15
}