#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 "";
  }
  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    1195 <concat+0x55>
lea    0xe74(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    11b7 <concat+0x77>
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>
test   %rax,%rax
je     1188 <concat+0x48>
mov    %rax,%rbx
mov    %rax,%rdi
mov    %r15,%rsi
call   1030 <strcpy@plt>
mov    %rbx,%rdi
mov    %r14,%rsi
call   1060 <strcat@plt>
jmp    118f <concat+0x4f>
lea    0xe71(%rip),%rbx
mov    %rbx,%rax
pop    %rbx
pop    %r14
pop    %r15
ret

LLVM IR (-O0):
@.str = [1 x i8] zeroinitializer
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 %17, label %16
16: ; preds = %2
store i8* getelementptr inbounds ([1 x i8], [1 x i8]* @.str, i64 0, i64 0), i8** %3
br label %25
17: ; preds = %2
%18 = load i8*, i8** %6
%19 = load i8*, i8** %4
%20 = call i32 @strcpy(i8* %18, i8* %19)
%21 = load i8*, i8** %6
%22 = load i8*, i8** %5
%23 = call i32 @strcat(i8* %21, i8* %22)
%24 = load i8*, i8** %6
store i8* %24, i8** %3
br label %25
25: ; preds = %17, %16
%26 = load i8*, i8** %3
ret i8* %26
}

LLVM IR (-O2):
@.str = [1 x i8] zeroinitializer
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
%13 = phi i8* [ %7, %9 ], [ getelementptr inbounds ([1 x i8], [1 x i8]* @.str, i64 0, i64 0), %2 ]
ret i8* %13
}