#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 */
int /*<<< orphan*/ free(char *);
char *malloc(int);
int /*<<< orphan*/ strcat(char *, char *);
int /*<<< orphan*/ strcpy(char *, char *);
int strlen(char *);
char *concatStrings(char *str1, char *str2) {
  int len = strlen(str1) + strlen(str2) + 2;
  char *newstr = malloc(len);
  strcpy(newstr, str1);
  strcat(newstr, " ");
  strcat(newstr, str2);
  free(str1);
  free(str2);
  return newstr;
}


x86 assembly (clang, -O0):
<concatStrings>:
push   %rbp
mov    %rsp,%rbp
sub    $0x30,%rsp
mov    %rdi,-0x8(%rbp)
mov    %rsi,-0x10(%rbp)
mov    -0x8(%rbp),%rdi
call   1050 <strlen@plt>
mov    %eax,-0x24(%rbp)
mov    -0x10(%rbp),%rdi
call   1050 <strlen@plt>
mov    %eax,%ecx
mov    -0x24(%rbp),%eax
add    %ecx,%eax
add    $0x2,%eax
mov    %eax,-0x14(%rbp)
mov    -0x14(%rbp),%edi
call   1060 <malloc@plt>
mov    %rax,-0x20(%rbp)
mov    -0x20(%rbp),%rdi
mov    -0x8(%rbp),%rsi
call   1040 <strcpy@plt>
mov    -0x20(%rbp),%rdi
lea    0xe5a(%rip),%rsi
call   1070 <strcat@plt>
mov    -0x20(%rbp),%rdi
mov    -0x10(%rbp),%rsi
call   1070 <strcat@plt>
mov    -0x8(%rbp),%rdi
call   1030 <free@plt>
mov    -0x10(%rbp),%rdi
call   1030 <free@plt>
mov    -0x20(%rbp),%rax
add    $0x30,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<concatStrings>:
push   %r15
push   %r14
push   %r12
push   %rbx
push   %rax
mov    %rsi,%r14
mov    %rdi,%r12
call   1050 <strlen@plt>
mov    %eax,%r15d
mov    %r14,%rdi
call   1050 <strlen@plt>
lea    (%r15,%rax,1),%edi
add    $0x2,%edi
call   1060 <malloc@plt>
mov    %rax,%rbx
mov    %rax,%rdi
mov    %r12,%rsi
call   1040 <strcpy@plt>
lea    0xe71(%rip),%rsi
mov    %rbx,%rdi
call   1070 <strcat@plt>
mov    %rbx,%rdi
mov    %r14,%rsi
call   1070 <strcat@plt>
mov    %r12,%rdi
call   1030 <free@plt>
mov    %r14,%rdi
call   1030 <free@plt>
mov    %rbx,%rax
add    $0x8,%rsp
pop    %rbx
pop    %r12
pop    %r14
pop    %r15
ret

LLVM IR (-O0):
@.str = [2 x i8] c" \00"
define i8* @concatStrings(i8* %0, i8* %1) {
%3 = alloca i8*
%4 = alloca i8*
%5 = alloca i32
%6 = alloca i8*
store i8* %0, i8** %3
store i8* %1, i8** %4
%7 = load i8*, i8** %3
%8 = call i32 @strlen(i8* %7)
%9 = load i8*, i8** %4
%10 = call i32 @strlen(i8* %9)
%11 = add nsw i32 %8, %10
%12 = add nsw i32 %11, 2
store i32 %12, i32* %5
%13 = load i32, i32* %5
%14 = call i8* @malloc(i32 %13)
store i8* %14, i8** %6
%15 = load i8*, i8** %6
%16 = load i8*, i8** %3
%17 = call i32 @strcpy(i8* %15, i8* %16)
%18 = load i8*, i8** %6
%19 = call i32 @strcat(i8* %18, i8* getelementptr inbounds ([2 x i8], [2 x i8]* @.str, i64 0, i64 0))
%20 = load i8*, i8** %6
%21 = load i8*, i8** %4
%22 = call i32 @strcat(i8* %20, i8* %21)
%23 = load i8*, i8** %3
%24 = call i32 @free(i8* %23)
%25 = load i8*, i8** %4
%26 = call i32 @free(i8* %25)
%27 = load i8*, i8** %6
ret i8* %27
}

LLVM IR (-O2):
@.str = [2 x i8] c" \00"
define i8* @concatStrings(i8* %0, i8* %1) {
%3 = tail call i32 @strlen(i8* %0)
%4 = tail call i32 @strlen(i8* %1)
%5 = add i32 %3, 2
%6 = add i32 %5, %4
%7 = tail call i8* @malloc(i32 %6)
%8 = tail call i32 @strcpy(i8* %7, i8* %0)
%9 = tail call i32 @strcat(i8* %7, i8* getelementptr inbounds ([2 x i8], [2 x i8]* @.str, i64 0, i64 0))
%10 = tail call i32 @strcat(i8* %7, i8* %1)
%11 = tail call i32 @free(i8* %0)
%12 = tail call i32 @free(i8* %1)
ret i8* %7
}