void Get_Hour_Min(when, hour, min) char *when;
int *hour;
int *min;
{
  int hour_min;
  int just_min = 0;
  switch (sscanf(when, "%d:%d", &hour_min, &just_min)) {
  case 1:
    *hour = hour_min / 100;
    *min = hour_min % 100;
    break;
  case 2:
    *hour = hour_min;
    *min = just_min;
    break;
  default:
    Usage();
  }
  if (hour_min < 0 || just_min < 0 || *min > 59)
    Usage();
}


x86 assembly (clang, -O0):
<Get_Hour_Min>:
push   %rbp
mov    %rsp,%rbp
sub    $0x30,%rsp
mov    %rdi,-0x8(%rbp)
mov    %rsi,-0x10(%rbp)
mov    %rdx,-0x18(%rbp)
movl   $0x0,-0x20(%rbp)
mov    -0x8(%rbp),%rdi
lea    0xeba(%rip),%rsi
xor    %eax,%eax
lea    -0x1c(%rbp),%rdx
lea    -0x20(%rbp),%rcx
call   1040 <sscanf@plt>
mov    %eax,%ecx
mov    %ecx,-0x24(%rbp)
sub    $0x1,%eax
je     1179 <Get_Hour_Min+0x59>
jmp    1168 <Get_Hour_Min+0x48>
mov    -0x24(%rbp),%eax
sub    $0x2,%eax
je     11a2 <Get_Hour_Min+0x82>
jmp    11b9 <Get_Hour_Min+0x99>
mov    -0x1c(%rbp),%eax
mov    $0x64,%ecx
cltd
idiv   %ecx
mov    %eax,%ecx
mov    -0x10(%rbp),%rax
mov    %ecx,(%rax)
mov    -0x1c(%rbp),%eax
mov    $0x64,%ecx
cltd
idiv   %ecx
mov    -0x18(%rbp),%rax
mov    %edx,(%rax)
jmp    11c0 <Get_Hour_Min+0xa0>
mov    -0x1c(%rbp),%ecx
mov    -0x10(%rbp),%rax
mov    %ecx,(%rax)
mov    -0x20(%rbp),%ecx
mov    -0x18(%rbp),%rax
mov    %ecx,(%rax)
jmp    11c0 <Get_Hour_Min+0xa0>
mov    $0x0,%al
call   1030 <Usage@plt>
cmpl   $0x0,-0x1c(%rbp)
jl     11e1 <Get_Hour_Min+0xc1>
cmpl   $0x0,-0x20(%rbp)
jl     11e1 <Get_Hour_Min+0xc1>
mov    -0x18(%rbp),%rax
cmpl   $0x3b,(%rax)
jle    11e8 <Get_Hour_Min+0xc8>
mov    $0x0,%al
call   1030 <Usage@plt>
add    $0x30,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<Get_Hour_Min>:
push   %r14
push   %rbx
push   %rax
mov    %rdx,%r14
mov    %rsi,%rbx
movl   $0x0,(%rsp)
lea    0xec8(%rip),%rsi
lea    0x4(%rsp),%rdx
mov    %rsp,%rcx
xor    %eax,%eax
call   1040 <sscanf@plt>
cmp    $0x2,%eax
je     117c <Get_Hour_Min+0x5c>
cmp    $0x1,%eax
jne    118e <Get_Hour_Min+0x6e>
movslq 0x4(%rsp),%rax
imul   $0x51eb851f,%rax,%rcx
mov    %rcx,%rdx
shr    $0x3f,%rdx
sar    $0x25,%rcx
add    %edx,%ecx
mov    %ecx,(%rbx)
imul   $0x64,%ecx,%ecx
mov    %eax,%edx
sub    %ecx,%edx
mov    %edx,(%r14)
test   %eax,%eax
jns    119d <Get_Hour_Min+0x7d>
jmp    11a9 <Get_Hour_Min+0x89>
mov    0x4(%rsp),%eax
mov    %eax,(%rbx)
mov    (%rsp),%ecx
mov    %ecx,(%r14)
test   %eax,%eax
jns    119d <Get_Hour_Min+0x7d>
jmp    11a9 <Get_Hour_Min+0x89>
xor    %eax,%eax
call   1030 <Usage@plt>
mov    0x4(%rsp),%eax
test   %eax,%eax
js     11a9 <Get_Hour_Min+0x89>
cmpl   $0x0,(%rsp)
js     11a9 <Get_Hour_Min+0x89>
cmpl   $0x3c,(%r14)
jl     11b0 <Get_Hour_Min+0x90>
xor    %eax,%eax
call   1030 <Usage@plt>
add    $0x8,%rsp
pop    %rbx
pop    %r14
ret

LLVM IR (-O0):
@.str = [6 x i8] c"%d:%d\00"
define void @Get_Hour_Min(i8* %0, i32* %1, i32* %2) {
%4 = alloca i8*
%5 = alloca i32*
%6 = alloca i32*
%7 = alloca i32
%8 = alloca i32
store i8* %0, i8** %4
store i32* %1, i32** %5
store i32* %2, i32** %6
store i32 0, i32* %8
%9 = load i8*, i8** %4
%10 = call i32 (i8*, i8*, ...) @sscanf(i8* %9, i8* getelementptr inbounds ([6 x i8], [6 x i8]* @.str, i64 0, i64 0), i32* %7, i32* %8)
switch i32 %10, label %23 [
i32 1, label %11
i32 2, label %18
]
11: ; preds = %3
%12 = load i32, i32* %7
%13 = sdiv i32 %12, 100
%14 = load i32*, i32** %5
store i32 %13, i32* %14
%15 = load i32, i32* %7
%16 = srem i32 %15, 100
%17 = load i32*, i32** %6
store i32 %16, i32* %17
br label %25
18: ; preds = %3
%19 = load i32, i32* %7
%20 = load i32*, i32** %5
store i32 %19, i32* %20
%21 = load i32, i32* %8
%22 = load i32*, i32** %6
store i32 %21, i32* %22
br label %25
23: ; preds = %3
%24 = call i32 (...) @Usage()
br label %25
25: ; preds = %23, %18, %11
%26 = load i32, i32* %7
%27 = icmp slt i32 %26, 0
br i1 %27, label %35, label %28
28: ; preds = %25
%29 = load i32, i32* %8
%30 = icmp slt i32 %29, 0
br i1 %30, label %35, label %31
31: ; preds = %28
%32 = load i32*, i32** %6
%33 = load i32, i32* %32
%34 = icmp sgt i32 %33, 59
br i1 %34, label %35, label %37
35: ; preds = %31, %28, %25
%36 = call i32 (...) @Usage()
br label %37
37: ; preds = %35, %31
ret void
}

LLVM IR (-O2):
@.str = [6 x i8] c"%d:%d\00"
define void @Get_Hour_Min(i8* nocapture %0, i32* nocapture writeonly %1, i32* nocapture %2) {
%4 = alloca i32
%5 = alloca i32
%6 = bitcast i32* %4 to i8*
%7 = bitcast i32* %5 to i8*
store i32 0, i32* %5
%8 = call i32 (i8*, i8*, ...) @sscanf(i8* %0, i8* getelementptr inbounds ([6 x i8], [6 x i8]* @.str, i64 0, i64 0), i32* %4, i32* %5)
switch i32 %8, label %16 [
i32 1, label %9
i32 2, label %13
]
9: ; preds = %3
%10 = load i32, i32* %4
%11 = sdiv i32 %10, 100
store i32 %11, i32* %1
%12 = srem i32 %10, 100
store i32 %12, i32* %2
br label %19
13: ; preds = %3
%14 = load i32, i32* %4
store i32 %14, i32* %1
%15 = load i32, i32* %5
store i32 %15, i32* %2
br label %19
16: ; preds = %3
%17 = call i32 (...) @Usage()
%18 = load i32, i32* %4
br label %19
19: ; preds = %16, %13, %9
%20 = phi i32 [ %18, %16 ], [ %14, %13 ], [ %10, %9 ]
%21 = icmp slt i32 %20, 0
%22 = load i32, i32* %5
%23 = icmp slt i32 %22, 0
%24 = select i1 %21, i1 true, i1 %23
br i1 %24, label %28, label %25
25: ; preds = %19
%26 = load i32, i32* %2
%27 = icmp sgt i32 %26, 59
br i1 %27, label %28, label %30
28: ; preds = %25, %19
%29 = call i32 (...) @Usage()
br label %30
30: ; preds = %28, %25
ret void
}