#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*/ memcpy(char *, char const *, scalar_t__);
scalar_t__ strlen(char const *);
char *strdup(const char *s) {
  char *d;
  if (s == NULL)
    return NULL;
  if ((d = malloc(strlen(s) + 1)) == NULL)
    return NULL;
  memcpy(d, s, strlen(s) + 1);
  return d;
}


x86 assembly (clang, -O0):
<strdup>:
push   %rbp
mov    %rsp,%rbp
sub    $0x30,%rsp
mov    %rdi,-0x10(%rbp)
cmpq   $0x0,-0x10(%rbp)
jne    1154 <strdup+0x24>
movq   $0x0,-0x8(%rbp)
jmp    11b9 <strdup+0x89>
mov    -0x10(%rbp),%rdi
call   1030 <strlen@plt>
mov    %rax,%rdi
add    $0x1,%rdi
call   1050 <malloc@plt>
mov    %rax,-0x18(%rbp)
cmp    $0x0,%rax
jne    1184 <strdup+0x54>
movq   $0x0,-0x8(%rbp)
jmp    11b9 <strdup+0x89>
mov    -0x18(%rbp),%rax
mov    %rax,-0x28(%rbp)
mov    -0x10(%rbp),%rax
mov    %rax,-0x20(%rbp)
mov    -0x10(%rbp),%rdi
call   1030 <strlen@plt>
mov    -0x28(%rbp),%rdi
mov    -0x20(%rbp),%rsi
mov    %rax,%rdx
add    $0x1,%rdx
call   1040 <memcpy@plt>
mov    -0x18(%rbp),%rax
mov    %rax,-0x8(%rbp)
mov    -0x8(%rbp),%rax
add    $0x30,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<strdup>:
push   %r15
push   %r14
push   %rbx
test   %rdi,%rdi
je     1169 <strdup+0x39>
mov    %rdi,%r14
call   1030 <strlen@plt>
mov    %rax,%rbx
add    $0x1,%rbx
mov    %rbx,%rdi
call   1050 <malloc@plt>
test   %rax,%rax
je     1169 <strdup+0x39>
mov    %rax,%r15
mov    %rax,%rdi
mov    %r14,%rsi
mov    %rbx,%rdx
call   1040 <memcpy@plt>
jmp    116c <strdup+0x3c>
xor    %r15d,%r15d
mov    %r15,%rax
pop    %rbx
pop    %r14
pop    %r15
ret

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

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