#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 MAP_ANONYMOUS;
void *MAP_FAILED;
int MAP_PRIVATE;
int PROT_READ;
int PROT_WRITE;
void *mmap(int /*<<< orphan*/ *, int, int, int, int, int /*<<< orphan*/);
void *allocate_buffer(int size) {
  void *p;
  p = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1,
           0);
  if (p == MAP_FAILED)
    return NULL;
  return p;
}


x86 assembly (clang, -O0):
<allocate_buffer>:
push   %rbp
mov    %rsp,%rbp
sub    $0x20,%rsp
mov    %edi,-0xc(%rbp)
mov    -0xc(%rbp),%esi
mov    0x2ed3(%rip),%rax
mov    (%rax),%edx
mov    0x2ea2(%rip),%rax
or     (%rax),%edx
mov    0x2e91(%rip),%rax
mov    (%rax),%ecx
mov    0x2ea0(%rip),%rax
or     (%rax),%ecx
xor    %eax,%eax
mov    %eax,%edi
mov    $0xffffffff,%r8d
xor    %r9d,%r9d
call   1030 <mmap@plt>
mov    %rax,-0x18(%rbp)
mov    -0x18(%rbp),%rax
mov    0x2e5d(%rip),%rcx
cmp    (%rcx),%rax
jne    1179 <allocate_buffer+0x69>
movq   $0x0,-0x8(%rbp)
jmp    1181 <allocate_buffer+0x71>
mov    -0x18(%rbp),%rax
mov    %rax,-0x8(%rbp)
mov    -0x8(%rbp),%rax
add    $0x20,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<allocate_buffer>:
push   %rbx
mov    %edi,%esi
mov    0x2ede(%rip),%rax
mov    0x2eaf(%rip),%rcx
mov    (%rcx),%edx
or     (%rax),%edx
mov    0x2e9c(%rip),%rax
mov    0x2ead(%rip),%rcx
mov    (%rcx),%ecx
or     (%rax),%ecx
xor    %ebx,%ebx
xor    %edi,%edi
mov    $0xffffffff,%r8d
xor    %r9d,%r9d
call   1030 <mmap@plt>
mov    0x2e70(%rip),%rcx
cmp    (%rcx),%rax
cmove  %rbx,%rax
pop    %rbx
ret

LLVM IR (-O0):
@PROT_READ = global i32 0
@PROT_WRITE = global i32 0
@MAP_PRIVATE = global i32 0
@MAP_ANONYMOUS = global i32 0
@MAP_FAILED = global i8* null
define i8* @allocate_buffer(i32 %0) {
%2 = alloca i8*
%3 = alloca i32
%4 = alloca i8*
store i32 %0, i32* %3
%5 = load i32, i32* %3
%6 = load i32, i32* @PROT_READ
%7 = load i32, i32* @PROT_WRITE
%8 = or i32 %6, %7
%9 = load i32, i32* @MAP_PRIVATE
%10 = load i32, i32* @MAP_ANONYMOUS
%11 = or i32 %9, %10
%12 = call i8* @mmap(i32* null, i32 %5, i32 %8, i32 %11, i32 -1, i32 0)
store i8* %12, i8** %4
%13 = load i8*, i8** %4
%14 = load i8*, i8** @MAP_FAILED
%15 = icmp eq i8* %13, %14
br i1 %15, label %16, label %17
16: ; preds = %1
store i8* null, i8** %2
br label %19
17: ; preds = %1
%18 = load i8*, i8** %4
store i8* %18, i8** %2
br label %19
19: ; preds = %17, %16
%20 = load i8*, i8** %2
ret i8* %20
}

LLVM IR (-O2):
@PROT_READ = global i32 0
@PROT_WRITE = global i32 0
@MAP_PRIVATE = global i32 0
@MAP_ANONYMOUS = global i32 0
@MAP_FAILED = global i8* null
define i8* @allocate_buffer(i32 %0) {
%2 = load i32, i32* @PROT_READ
%3 = load i32, i32* @PROT_WRITE
%4 = or i32 %3, %2
%5 = load i32, i32* @MAP_PRIVATE
%6 = load i32, i32* @MAP_ANONYMOUS
%7 = or i32 %6, %5
%8 = tail call i8* @mmap(i32* null, i32 %0, i32 %4, i32 %7, i32 -1, i32 0)
%9 = load i8*, i8** @MAP_FAILED
%10 = icmp eq i8* %8, %9
%11 = select i1 %10, i8* null, i8* %8
ret i8* %11
}