#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 *malloc(size_t);
int /*<<< orphan*/ strcat(char *, char *);
int /*<<< orphan*/ strcpy(char *, char *);
size_t strlen(char *);
char *concat(char *s1, char *s2) {
  size_t l1, l2;
  char *result;
  l1 = strlen(s1);
  l2 = strlen(s2);
  if (NULL == (result = malloc((l1 + l2 + 1) * sizeof(char)))) {
    return NULL;
  }
  strcpy(result, s1);
  strcat(result, s2);
  return result;
}


x86 assembly (clang, -O0):
<concat>:
push   %rbp
mov    %rsp,%rbp
sub    $0x30,%rsp
mov    %rdi,-0x10(%rbp)
mov    %rsi,-0x18(%rbp)
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    -0x20(%rbp),%rdi
add    -0x28(%rbp),%rdi
add    $0x1,%rdi
shl    $0x0,%rdi
call   1050 <malloc@plt>
mov    %rax,%rcx
mov    %rcx,-0x30(%rbp)
xor    %eax,%eax
cmp    %rcx,%rax
jne    119e <concat+0x5e>
movq   $0x0,-0x8(%rbp)
jmp    11c0 <concat+0x80>
mov    -0x30(%rbp),%rdi
mov    -0x10(%rbp),%rsi
call   1030 <strcpy@plt>
mov    -0x30(%rbp),%rdi
mov    -0x18(%rbp),%rsi
call   1060 <strcat@plt>
mov    -0x30(%rbp),%rax
mov    %rax,-0x8(%rbp)
mov    -0x8(%rbp),%rax
add    $0x30,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<concat>:
push   %r15
push   %r14
push   %rbx
mov    %rsi,%r14
mov    %rdi,%r15
call   1040 <strlen@plt>
mov    %rax,%rbx
mov    %r14,%rdi
call   1040 <strlen@plt>
lea    (%rbx,%rax,1),%rdi
add    $0x1,%rdi
call   1050 <malloc@plt>
mov    %rax,%rbx
test   %rax,%rax
je     1186 <concat+0x46>
mov    %rbx,%rdi
mov    %r15,%rsi
call   1030 <strcpy@plt>
mov    %rbx,%rdi
mov    %r14,%rsi
call   1060 <strcat@plt>
mov    %rbx,%rax
pop    %rbx
pop    %r14
pop    %r15
ret

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

LLVM IR (-O2):
define i8* @concat(i8* %0, i8* %1) {
%3 = tail call i64 @strlen(i8* dereferenceable(1) %0)
%4 = tail call i64 @strlen(i8* dereferenceable(1) %1)
%5 = add i64 %3, 1
%6 = add i64 %5, %4
%7 = tail call i8* @malloc(i64 %6)
%8 = icmp eq i8* %7, null
br i1 %8, label %12, label %9
9: ; preds = %2
%10 = tail call i32 @strcpy(i8* %7, i8* %0)
%11 = tail call i32 @strcat(i8* %7, i8* %1)
br label %12
12: ; preds = %2, %9
ret i8* %7
}