int main() {
  int fahr, celcius;
  int lower, upper, step;
  lower = 0;
  upper = 300;
  step = 20;
  fahr = lower;
  printf("%s   %s\n", "fahrenheit", "celcius");
  while (fahr <= upper) {
    celcius = fahr2celcius(fahr);
    printf("%10d%s%7d\n", fahr, "  ", celcius);
    fahr = fahr + step;
  }
}


x86 assembly (clang, -O0):
<main>:
push   %rbp
mov    %rsp,%rbp
sub    $0x20,%rsp
movl   $0x0,-0x4(%rbp)
movl   $0x0,-0x10(%rbp)
movl   $0x12c,-0x14(%rbp)
movl   $0x14,-0x18(%rbp)
mov    -0x10(%rbp),%eax
mov    %eax,-0x8(%rbp)
lea    0xeaf(%rip),%rdi
lea    0xeb1(%rip),%rsi
lea    0xeb5(%rip),%rdx
mov    $0x0,%al
call   1030 <printf@plt>
mov    -0x8(%rbp),%eax
cmp    -0x14(%rbp),%eax
jg     11a8 <main+0x88>
mov    -0x8(%rbp),%edi
mov    $0x0,%al
call   1040 <fahr2celcius@plt>
mov    %eax,-0xc(%rbp)
mov    -0x8(%rbp),%esi
mov    -0xc(%rbp),%ecx
lea    0xe90(%rip),%rdi
lea    0xe94(%rip),%rdx
mov    $0x0,%al
call   1030 <printf@plt>
mov    -0x8(%rbp),%eax
add    -0x18(%rbp),%eax
mov    %eax,-0x8(%rbp)
jmp    1166 <main+0x46>
mov    -0x4(%rbp),%eax
add    $0x20,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<main>:
push   %r14
push   %rbx
push   %rax
lea    0xed5(%rip),%rdi
lea    0xed7(%rip),%rsi
lea    0xedb(%rip),%rdx
xor    %eax,%eax
call   1030 <printf@plt>
xor    %edi,%edi
xor    %eax,%eax
call   1040 <fahr2celcius@plt>
lea    0xecc(%rip),%rbx
lea    0xed0(%rip),%r14
mov    %rbx,%rdi
xor    %esi,%esi
mov    %r14,%rdx
mov    %eax,%ecx
xor    %eax,%eax
call   1030 <printf@plt>
mov    $0x14,%edi
xor    %eax,%eax
call   1040 <fahr2celcius@plt>
mov    %rbx,%rdi
mov    $0x14,%esi
mov    %r14,%rdx
mov    %eax,%ecx
xor    %eax,%eax
call   1030 <printf@plt>
mov    $0x28,%edi
xor    %eax,%eax
call   1040 <fahr2celcius@plt>
mov    %rbx,%rdi
mov    $0x28,%esi
mov    %r14,%rdx
mov    %eax,%ecx
xor    %eax,%eax
call   1030 <printf@plt>
mov    $0x3c,%edi
xor    %eax,%eax
call   1040 <fahr2celcius@plt>
mov    %rbx,%rdi
mov    $0x3c,%esi
mov    %r14,%rdx
mov    %eax,%ecx
xor    %eax,%eax
call   1030 <printf@plt>
mov    $0x50,%edi
xor    %eax,%eax
call   1040 <fahr2celcius@plt>
mov    %rbx,%rdi
mov    $0x50,%esi
mov    %r14,%rdx
mov    %eax,%ecx
xor    %eax,%eax
call   1030 <printf@plt>
mov    $0x64,%edi
xor    %eax,%eax
call   1040 <fahr2celcius@plt>
mov    %rbx,%rdi
mov    $0x64,%esi
mov    %r14,%rdx
mov    %eax,%ecx
xor    %eax,%eax
call   1030 <printf@plt>
mov    $0x78,%edi
xor    %eax,%eax
call   1040 <fahr2celcius@plt>
mov    %rbx,%rdi
mov    $0x78,%esi
mov    %r14,%rdx
mov    %eax,%ecx
xor    %eax,%eax
call   1030 <printf@plt>
mov    $0x8c,%edi
xor    %eax,%eax
call   1040 <fahr2celcius@plt>
mov    %rbx,%rdi
mov    $0x8c,%esi
mov    %r14,%rdx
mov    %eax,%ecx
xor    %eax,%eax
call   1030 <printf@plt>
mov    $0xa0,%edi
xor    %eax,%eax
call   1040 <fahr2celcius@plt>
mov    %rbx,%rdi
mov    $0xa0,%esi
mov    %r14,%rdx
mov    %eax,%ecx
xor    %eax,%eax
call   1030 <printf@plt>
mov    $0xb4,%edi
xor    %eax,%eax
call   1040 <fahr2celcius@plt>
mov    %rbx,%rdi
mov    $0xb4,%esi
mov    %r14,%rdx
mov    %eax,%ecx
xor    %eax,%eax
call   1030 <printf@plt>
mov    $0xc8,%edi
xor    %eax,%eax
call   1040 <fahr2celcius@plt>
mov    %rbx,%rdi
mov    $0xc8,%esi
mov    %r14,%rdx
mov    %eax,%ecx
xor    %eax,%eax
call   1030 <printf@plt>
mov    $0xdc,%edi
xor    %eax,%eax
call   1040 <fahr2celcius@plt>
mov    %rbx,%rdi
mov    $0xdc,%esi
mov    %r14,%rdx
mov    %eax,%ecx
xor    %eax,%eax
call   1030 <printf@plt>
mov    $0xf0,%edi
xor    %eax,%eax
call   1040 <fahr2celcius@plt>
mov    %rbx,%rdi
mov    $0xf0,%esi
mov    %r14,%rdx
mov    %eax,%ecx
xor    %eax,%eax
call   1030 <printf@plt>
mov    $0x104,%edi
xor    %eax,%eax
call   1040 <fahr2celcius@plt>
mov    %rbx,%rdi
mov    $0x104,%esi
mov    %r14,%rdx
mov    %eax,%ecx
xor    %eax,%eax
call   1030 <printf@plt>
mov    $0x118,%edi
xor    %eax,%eax
call   1040 <fahr2celcius@plt>
mov    %rbx,%rdi
mov    $0x118,%esi
mov    %r14,%rdx
mov    %eax,%ecx
xor    %eax,%eax
call   1030 <printf@plt>
mov    $0x12c,%edi
xor    %eax,%eax
call   1040 <fahr2celcius@plt>
mov    %rbx,%rdi
mov    $0x12c,%esi
mov    %r14,%rdx
mov    %eax,%ecx
xor    %eax,%eax
call   1030 <printf@plt>
xor    %eax,%eax
add    $0x8,%rsp
pop    %rbx
pop    %r14
ret

LLVM IR (-O0):
@.str = [9 x i8] c"%s %s\0A\00"
@.str.1 = [11 x i8] c"fahrenheit\00"
@.str.2 = [8 x i8] c"celcius\00"
@.str.3 = [11 x i8] c"%10d%s%7d\0A\00"
@.str.4 = [3 x i8] c" \00"
define i32 @main() {
%1 = alloca i32
%2 = alloca i32
%3 = alloca i32
%4 = alloca i32
%5 = alloca i32
%6 = alloca i32
store i32 0, i32* %1
store i32 0, i32* %4
store i32 300, i32* %5
store i32 20, i32* %6
%7 = load i32, i32* %4
store i32 %7, i32* %2
%8 = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([9 x i8], [9 x i8]* @.str, i64 0, i64 0), i8* getelementptr inbounds ([11 x i8], [11 x i8]* @.str.1, i64 0, i64 0), i8* getelementptr inbounds ([8 x i8], [8 x i8]* @.str.2, i64 0, i64 0))
br label %9
9: ; preds = %13, %0
%10 = load i32, i32* %2
%11 = load i32, i32* %5
%12 = icmp sle i32 %10, %11
br i1 %12, label %13, label %22
13: ; preds = %9
%14 = load i32, i32* %2
%15 = call i32 (i32, ...) bitcast (i32 (...)* @fahr2celcius to i32 (i32, ...)*)(i32 %14)
store i32 %15, i32* %3
%16 = load i32, i32* %2
%17 = load i32, i32* %3
%18 = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([11 x i8], [11 x i8]* @.str.3, i64 0, i64 0), i32 %16, i8* getelementptr inbounds ([3 x i8], [3 x i8]* @.str.4, i64 0, i64 0), i32 %17)
%19 = load i32, i32* %2
%20 = load i32, i32* %6
%21 = add nsw i32 %19, %20
store i32 %21, i32* %2
br label %9
22: ; preds = %9
%23 = load i32, i32* %1
ret i32 %23
}

LLVM IR (-O2):
@.str = [9 x i8] c"%s %s\0A\00"
@.str.1 = [11 x i8] c"fahrenheit\00"
@.str.2 = [8 x i8] c"celcius\00"
@.str.3 = [11 x i8] c"%10d%s%7d\0A\00"
@.str.4 = [3 x i8] c" \00"
define i32 @main() {
%1 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([9 x i8], [9 x i8]* @.str, i64 0, i64 0), i8* getelementptr inbounds ([11 x i8], [11 x i8]* @.str.1, i64 0, i64 0), i8* getelementptr inbounds ([8 x i8], [8 x i8]* @.str.2, i64 0, i64 0))
%2 = tail call i32 (i32, ...) bitcast (i32 (...)* @fahr2celcius to i32 (i32, ...)*)(i32 0)
%3 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([11 x i8], [11 x i8]* @.str.3, i64 0, i64 0), i32 0, i8* getelementptr inbounds ([3 x i8], [3 x i8]* @.str.4, i64 0, i64 0), i32 %2)
%4 = tail call i32 (i32, ...) bitcast (i32 (...)* @fahr2celcius to i32 (i32, ...)*)(i32 20)
%5 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([11 x i8], [11 x i8]* @.str.3, i64 0, i64 0), i32 20, i8* getelementptr inbounds ([3 x i8], [3 x i8]* @.str.4, i64 0, i64 0), i32 %4)
%6 = tail call i32 (i32, ...) bitcast (i32 (...)* @fahr2celcius to i32 (i32, ...)*)(i32 40)
%7 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([11 x i8], [11 x i8]* @.str.3, i64 0, i64 0), i32 40, i8* getelementptr inbounds ([3 x i8], [3 x i8]* @.str.4, i64 0, i64 0), i32 %6)
%8 = tail call i32 (i32, ...) bitcast (i32 (...)* @fahr2celcius to i32 (i32, ...)*)(i32 60)
%9 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([11 x i8], [11 x i8]* @.str.3, i64 0, i64 0), i32 60, i8* getelementptr inbounds ([3 x i8], [3 x i8]* @.str.4, i64 0, i64 0), i32 %8)
%10 = tail call i32 (i32, ...) bitcast (i32 (...)* @fahr2celcius to i32 (i32, ...)*)(i32 80)
%11 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([11 x i8], [11 x i8]* @.str.3, i64 0, i64 0), i32 80, i8* getelementptr inbounds ([3 x i8], [3 x i8]* @.str.4, i64 0, i64 0), i32 %10)
%12 = tail call i32 (i32, ...) bitcast (i32 (...)* @fahr2celcius to i32 (i32, ...)*)(i32 100)
%13 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([11 x i8], [11 x i8]* @.str.3, i64 0, i64 0), i32 100, i8* getelementptr inbounds ([3 x i8], [3 x i8]* @.str.4, i64 0, i64 0), i32 %12)
%14 = tail call i32 (i32, ...) bitcast (i32 (...)* @fahr2celcius to i32 (i32, ...)*)(i32 120)
%15 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([11 x i8], [11 x i8]* @.str.3, i64 0, i64 0), i32 120, i8* getelementptr inbounds ([3 x i8], [3 x i8]* @.str.4, i64 0, i64 0), i32 %14)
%16 = tail call i32 (i32, ...) bitcast (i32 (...)* @fahr2celcius to i32 (i32, ...)*)(i32 140)
%17 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([11 x i8], [11 x i8]* @.str.3, i64 0, i64 0), i32 140, i8* getelementptr inbounds ([3 x i8], [3 x i8]* @.str.4, i64 0, i64 0), i32 %16)
%18 = tail call i32 (i32, ...) bitcast (i32 (...)* @fahr2celcius to i32 (i32, ...)*)(i32 160)
%19 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([11 x i8], [11 x i8]* @.str.3, i64 0, i64 0), i32 160, i8* getelementptr inbounds ([3 x i8], [3 x i8]* @.str.4, i64 0, i64 0), i32 %18)
%20 = tail call i32 (i32, ...) bitcast (i32 (...)* @fahr2celcius to i32 (i32, ...)*)(i32 180)
%21 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([11 x i8], [11 x i8]* @.str.3, i64 0, i64 0), i32 180, i8* getelementptr inbounds ([3 x i8], [3 x i8]* @.str.4, i64 0, i64 0), i32 %20)
%22 = tail call i32 (i32, ...) bitcast (i32 (...)* @fahr2celcius to i32 (i32, ...)*)(i32 200)
%23 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([11 x i8], [11 x i8]* @.str.3, i64 0, i64 0), i32 200, i8* getelementptr inbounds ([3 x i8], [3 x i8]* @.str.4, i64 0, i64 0), i32 %22)
%24 = tail call i32 (i32, ...) bitcast (i32 (...)* @fahr2celcius to i32 (i32, ...)*)(i32 220)
%25 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([11 x i8], [11 x i8]* @.str.3, i64 0, i64 0), i32 220, i8* getelementptr inbounds ([3 x i8], [3 x i8]* @.str.4, i64 0, i64 0), i32 %24)
%26 = tail call i32 (i32, ...) bitcast (i32 (...)* @fahr2celcius to i32 (i32, ...)*)(i32 240)
%27 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([11 x i8], [11 x i8]* @.str.3, i64 0, i64 0), i32 240, i8* getelementptr inbounds ([3 x i8], [3 x i8]* @.str.4, i64 0, i64 0), i32 %26)
%28 = tail call i32 (i32, ...) bitcast (i32 (...)* @fahr2celcius to i32 (i32, ...)*)(i32 260)
%29 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([11 x i8], [11 x i8]* @.str.3, i64 0, i64 0), i32 260, i8* getelementptr inbounds ([3 x i8], [3 x i8]* @.str.4, i64 0, i64 0), i32 %28)
%30 = tail call i32 (i32, ...) bitcast (i32 (...)* @fahr2celcius to i32 (i32, ...)*)(i32 280)
%31 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([11 x i8], [11 x i8]* @.str.3, i64 0, i64 0), i32 280, i8* getelementptr inbounds ([3 x i8], [3 x i8]* @.str.4, i64 0, i64 0), i32 %30)
%32 = tail call i32 (i32, ...) bitcast (i32 (...)* @fahr2celcius to i32 (i32, ...)*)(i32 300)
%33 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([11 x i8], [11 x i8]* @.str.3, i64 0, i64 0), i32 300, i8* getelementptr inbounds ([3 x i8], [3 x i8]* @.str.4, i64 0, i64 0), i32 %32)
ret i32 0
}