#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 */
scalar_t__ malloc(scalar_t__);
int /*<<< orphan*/ printf(char *, char const *, char const *, char *);
int /*<<< orphan*/ strcat(char *, char const *);
int /*<<< orphan*/ strcpy(char *, char const *);
scalar_t__ strlen(char const *);
char *concat_string(const char *str1, const char *str2) {
  char *concat = (char *)malloc(strlen(str1) + strlen(str2) + 1);
  strcpy(concat, str1);
  strcat(concat, str2);
  printf("Concatenated %s with %s and formed %s.\n", str1, str2, concat);
  return concat;
}


x86 assembly (clang, -O0):
<concat_string>:
push   %rbp
mov    %rsp,%rbp
sub    $0x20,%rsp
mov    %rdi,-0x8(%rbp)
mov    %rsi,-0x10(%rbp)
mov    -0x8(%rbp),%rdi
call   1040 <strlen@plt>
mov    %rax,-0x20(%rbp)
mov    -0x10(%rbp),%rdi
call   1040 <strlen@plt>
mov    -0x20(%rbp),%rdi
add    %rax,%rdi
add    $0x1,%rdi
call   1060 <malloc@plt>
mov    %rax,-0x18(%rbp)
mov    -0x18(%rbp),%rdi
mov    -0x8(%rbp),%rsi
call   1030 <strcpy@plt>
mov    -0x18(%rbp),%rdi
mov    -0x10(%rbp),%rsi
call   1070 <strcat@plt>
mov    -0x8(%rbp),%rsi
mov    -0x10(%rbp),%rdx
mov    -0x18(%rbp),%rcx
lea    0xe49(%rip),%rdi
call   1050 <printf@plt>
mov    -0x18(%rbp),%rax
add    $0x20,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<concat_string>:
push   %r15
push   %r14
push   %r12
push   %rbx
push   %rax
mov    %rsi,%r14
mov    %rdi,%r12
call   1040 <strlen@plt>
mov    %rax,%r15
mov    %r14,%rdi
call   1040 <strlen@plt>
lea    (%r15,%rax,1),%rdi
add    $0x1,%rdi
call   1060 <malloc@plt>
mov    %rax,%rbx
mov    %rax,%rdi
mov    %r12,%rsi
call   1030 <strcpy@plt>
mov    %rbx,%rdi
mov    %r14,%rsi
call   1070 <strcat@plt>
lea    0xe65(%rip),%rdi
mov    %r12,%rsi
mov    %r14,%rdx
mov    %rbx,%rcx
call   1050 <printf@plt>
mov    %rbx,%rax
add    $0x8,%rsp
pop    %rbx
pop    %r12
pop    %r14
pop    %r15
ret

LLVM IR (-O0):
@.str = [40 x i8] c"Concatenated %s with %s and formed %s.\0A\00"
define i8* @concat_string(i8* %0, i8* %1) {
%3 = alloca i8*
%4 = alloca i8*
%5 = alloca i8*
store i8* %0, i8** %3
store i8* %1, i8** %4
%6 = load i8*, i8** %3
%7 = call i64 @strlen(i8* %6)
%8 = load i8*, i8** %4
%9 = call i64 @strlen(i8* %8)
%10 = add nsw i64 %7, %9
%11 = add nsw i64 %10, 1
%12 = call i64 @malloc(i64 %11)
%13 = inttoptr i64 %12 to i8*
store i8* %13, i8** %5
%14 = load i8*, i8** %5
%15 = load i8*, i8** %3
%16 = call i32 @strcpy(i8* %14, i8* %15)
%17 = load i8*, i8** %5
%18 = load i8*, i8** %4
%19 = call i32 @strcat(i8* %17, i8* %18)
%20 = load i8*, i8** %3
%21 = load i8*, i8** %4
%22 = load i8*, i8** %5
%23 = call i32 @printf(i8* getelementptr inbounds ([40 x i8], [40 x i8]* @.str, i64 0, i64 0), i8* %20, i8* %21, i8* %22)
%24 = load i8*, i8** %5
ret i8* %24
}

LLVM IR (-O2):
@.str = [40 x i8] c"Concatenated %s with %s and formed %s.\0A\00"
define i8* @concat_string(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 i64 @malloc(i64 %6)
%8 = inttoptr i64 %7 to i8*
%9 = tail call i32 @strcpy(i8* %8, i8* %0)
%10 = tail call i32 @strcat(i8* %8, i8* %1)
%11 = tail call i32 @printf(i8* getelementptr inbounds ([40 x i8], [40 x i8]* @.str, i64 0, i64 0), i8* %0, i8* %1, i8* %8)
ret i8* %8
}