#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*/ O_RDWR;
int open(char *, int /*<<< orphan*/);
int /*<<< orphan*/ printf(char *, ...);
int /*<<< orphan*/ read(int, char *, int);
int main() {
  char buff1[100] = {};
  int fd = open("/dev/my_driver", O_RDWR);
  read(fd, buff1, 100);
  printf("Reading from Device : ");
  printf("%s\n", buff1);
}


x86 assembly (clang, -O0):
<main>:
push   %rbp
mov    %rsp,%rbp
sub    $0x80,%rsp
lea    -0x70(%rbp),%rdi
xor    %esi,%esi
mov    $0x64,%edx
call   1040 <memset@plt>
mov    0x2e86(%rip),%rax
mov    (%rax),%esi
lea    0xe95(%rip),%rdi
call   1060 <open@plt>
mov    %eax,-0x74(%rbp)
mov    -0x74(%rbp),%edi
lea    -0x70(%rbp),%rsi
mov    $0x64,%edx
call   1050 <read@plt>
lea    0xe84(%rip),%rdi
mov    $0x0,%al
call   1030 <printf@plt>
lea    -0x70(%rbp),%rsi
lea    0xe89(%rip),%rdi
mov    $0x0,%al
call   1030 <printf@plt>
xor    %eax,%eax
add    $0x80,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<main>:
push   %rbx
sub    $0x70,%rsp
xorps  %xmm0,%xmm0
movaps %xmm0,0x50(%rsp)
movaps %xmm0,0x40(%rsp)
movaps %xmm0,0x30(%rsp)
movaps %xmm0,0x20(%rsp)
movaps %xmm0,0x10(%rsp)
movaps %xmm0,(%rsp)
movl   $0x0,0x60(%rsp)
mov    0x2e74(%rip),%rax
mov    (%rax),%esi
lea    0xe83(%rip),%rdi
call   1060 <open@plt>
mov    %rsp,%rbx
mov    %eax,%edi
mov    %rbx,%rsi
mov    $0x64,%edx
call   1050 <read@plt>
lea    0xe74(%rip),%rdi
xor    %eax,%eax
call   1040 <printf@plt>
mov    %rbx,%rdi
call   1030 <puts@plt>
xor    %eax,%eax
add    $0x70,%rsp
pop    %rbx
ret

LLVM IR (-O0):
@.str = [15 x i8] c"/dev/my_driver\00"
@O_RDWR = global i32 0
@.str.1 = [23 x i8] c"Reading from Device : \00"
@.str.2 = [4 x i8] c"%s\0A\00"
define i32 @main() {
%1 = alloca [100 x i8]
%2 = alloca i32
%3 = bitcast [100 x i8]* %1 to i8*
%4 = load i32, i32* @O_RDWR
%5 = call i32 @open(i8* getelementptr inbounds ([15 x i8], [15 x i8]* @.str, i64 0, i64 0), i32 %4)
store i32 %5, i32* %2
%6 = load i32, i32* %2
%7 = getelementptr inbounds [100 x i8], [100 x i8]* %1, i64 0, i64 0
%8 = call i32 @read(i32 %6, i8* %7, i32 100)
%9 = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([23 x i8], [23 x i8]* @.str.1, i64 0, i64 0))
%10 = getelementptr inbounds [100 x i8], [100 x i8]* %1, i64 0, i64 0
%11 = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str.2, i64 0, i64 0), i8* %10)
ret i32 0
}

LLVM IR (-O2):
@.str = [15 x i8] c"/dev/my_driver\00"
@O_RDWR = global i32 0
@.str.1 = [23 x i8] c"Reading from Device : \00"
define i32 @main() {
%1 = alloca [100 x i8]
%2 = getelementptr inbounds [100 x i8], [100 x i8]* %1, i64 0, i64 0
%3 = load i32, i32* @O_RDWR
%4 = tail call i32 @open(i8* getelementptr inbounds ([15 x i8], [15 x i8]* @.str, i64 0, i64 0), i32 %3)
%5 = call i32 @read(i32 %4, i8* %2, i32 100)
%6 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([23 x i8], [23 x i8]* @.str.1, i64 0, i64 0))
%7 = call i32 @puts(i8* %2)
ret i32 0
}