#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*/ exit(int);
char *getenv(char *);
int /*<<< orphan*/ printf(char *, char *);
int /*<<< orphan*/ puts(char *);
int main(int argc, char *argv[]) {
  if (argc != 2) {
    printf("Usage: %s <var>\n", argv[0]);
    exit(1);
  }
  char *var = argv[1];
  char *value = getenv(var);
  if (value != NULL) {
    puts(value);
  }
}


x86 assembly (clang, -O0):
<main>:
push   %rbp
mov    %rsp,%rbp
sub    $0x20,%rsp
movl   $0x0,-0x4(%rbp)
mov    %edi,-0x8(%rbp)
mov    %rsi,-0x10(%rbp)
cmpl   $0x2,-0x8(%rbp)
je     117d <main+0x3d>
mov    -0x10(%rbp),%rax
mov    (%rax),%rsi
lea    0xe92(%rip),%rdi
call   1050 <printf@plt>
mov    $0x1,%edi
call   1060 <exit@plt>
mov    -0x10(%rbp),%rax
mov    0x8(%rax),%rax
mov    %rax,-0x18(%rbp)
mov    -0x18(%rbp),%rdi
call   1030 <getenv@plt>
mov    %rax,-0x20(%rbp)
cmpq   $0x0,-0x20(%rbp)
je     11aa <main+0x6a>
mov    -0x20(%rbp),%rdi
call   1040 <puts@plt>
mov    -0x4(%rbp),%eax
add    $0x20,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<main>:
push   %rax
cmp    $0x2,%edi
jne    1160 <main+0x20>
mov    0x8(%rsi),%rdi
call   1030 <getenv@plt>
test   %rax,%rax
je     115c <main+0x1c>
mov    %rax,%rdi
call   1040 <puts@plt>
xor    %eax,%eax
pop    %rcx
ret
mov    (%rsi),%rsi
lea    0xe96(%rip),%rdi
call   1050 <printf@plt>
mov    $0x1,%edi
call   1060 <exit@plt>

LLVM IR (-O0):
@.str = [17 x i8] c"Usage: %s <var>\0A\00"
define i32 @main(i32 %0, i8** %1) {
%3 = alloca i32
%4 = alloca i32
%5 = alloca i8**
%6 = alloca i8*
%7 = alloca i8*
store i32 0, i32* %3
store i32 %0, i32* %4
store i8** %1, i8*** %5
%8 = load i32, i32* %4
%9 = icmp ne i32 %8, 2
br i1 %9, label %10, label %16
10: ; preds = %2
%11 = load i8**, i8*** %5
%12 = getelementptr inbounds i8*, i8** %11, i64 0
%13 = load i8*, i8** %12
%14 = call i32 @printf(i8* getelementptr inbounds ([17 x i8], [17 x i8]* @.str, i64 0, i64 0), i8* %13)
%15 = call i32 @exit(i32 1)
unreachable
16: ; preds = %2
%17 = load i8**, i8*** %5
%18 = getelementptr inbounds i8*, i8** %17, i64 1
%19 = load i8*, i8** %18
store i8* %19, i8** %6
%20 = load i8*, i8** %6
%21 = call i8* @getenv(i8* %20)
store i8* %21, i8** %7
%22 = load i8*, i8** %7
%23 = icmp ne i8* %22, null
br i1 %23, label %24, label %27
24: ; preds = %16
%25 = load i8*, i8** %7
%26 = call i32 @puts(i8* %25)
br label %27
27: ; preds = %24, %16
%28 = load i32, i32* %3
ret i32 %28
}

LLVM IR (-O2):
@.str = [17 x i8] c"Usage: %s <var>\0A\00"
define i32 @main(i32 %0, i8** nocapture %1) {
%3 = icmp eq i32 %0, 2
br i1 %3, label %8, label %4
4: ; preds = %2
%5 = load i8*, i8** %1
%6 = tail call i32 @printf(i8* getelementptr inbounds ([17 x i8], [17 x i8]* @.str, i64 0, i64 0), i8* %5)
%7 = tail call i32 @exit(i32 1)
unreachable
8: ; preds = %2
%9 = getelementptr inbounds i8*, i8** %1, i64 1
%10 = load i8*, i8** %9
%11 = tail call i8* @getenv(i8* %10)
%12 = icmp eq i8* %11, null
br i1 %12, label %15, label %13
13: ; preds = %8
%14 = tail call i32 @puts(i8* %11)
br label %15
15: ; preds = %13, %8
ret i32 0
}