#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(scalar_t__);
int /*<<< orphan*/ strcat(char *, char const *);
int /*<<< orphan*/ strcpy(char *, char const *);
scalar_t__ strlen(char const *);
char *concat(const char *s1, const char *s2) {
  char *result = malloc(strlen(s1) + strlen(s2) + 1);
  if (!result)
    return result;
  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,-0x28(%rbp)
mov    -0x18(%rbp),%rdi
call   1040 <strlen@plt>
mov    -0x28(%rbp),%rdi
add    %rax,%rdi
add    $0x1,%rdi
call   1050 <malloc@plt>
mov    %rax,-0x20(%rbp)
cmpq   $0x0,-0x20(%rbp)
jne    1192 <concat+0x52>
mov    -0x20(%rbp),%rax
mov    %rax,-0x8(%rbp)
jmp    11b4 <concat+0x74>
mov    -0x20(%rbp),%rdi
mov    -0x10(%rbp),%rsi
call   1030 <strcpy@plt>
mov    -0x20(%rbp),%rdi
mov    -0x18(%rbp),%rsi
call   1060 <strcat@plt>
mov    -0x20(%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 i8*
store i8* %0, i8** %4
store i8* %1, i8** %5
%7 = load i8*, i8** %4
%8 = call i64 @strlen(i8* %7)
%9 = load i8*, i8** %5
%10 = call i64 @strlen(i8* %9)
%11 = add nsw i64 %8, %10
%12 = add nsw i64 %11, 1
%13 = call i8* @malloc(i64 %12)
store i8* %13, i8** %6
%14 = load i8*, i8** %6
%15 = icmp ne i8* %14, null
br i1 %15, label %18, label %16
16: ; preds = %2
%17 = load i8*, i8** %6
store i8* %17, i8** %3
br label %26
18: ; preds = %2
%19 = load i8*, i8** %6
%20 = load i8*, i8** %4
%21 = call i32 @strcpy(i8* %19, i8* %20)
%22 = load i8*, i8** %6
%23 = load i8*, i8** %5
%24 = call i32 @strcat(i8* %22, i8* %23)
%25 = load i8*, i8** %6
store i8* %25, i8** %3
br label %26
26: ; preds = %18, %16
%27 = load i8*, i8** %3
ret i8* %27
}

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
}