char ui2hex(unsigned char ui) {
  switch (ui) {
  case 0x0: {
    return ('0');
  }
  case 0x1: {
    return ('1');
  }
  case 0x2: {
    return ('2');
  }
  case 0x3: {
    return ('3');
  }
  case 0x4: {
    return ('4');
  }
  case 0x5: {
    return ('5');
  }
  case 0x6: {
    return ('6');
  }
  case 0x7: {
    return ('7');
  }
  case 0x8: {
    return ('8');
  }
  case 0x9: {
    return ('9');
  }
  case 0xa: {
    return ('A');
  }
  case 0xb: {
    return ('B');
  }
  case 0xc: {
    return ('C');
  }
  case 0xd: {
    return ('D');
  }
  case 0xe: {
    return ('E');
  }
  case 0xf: {
    return ('F');
  }
  }
  return (' ');
}


x86 assembly (clang, -O0):
<ui2hex>:
push   %rbp
mov    %rsp,%rbp
mov    %dil,%al
mov    %al,-0x2(%rbp)
movzbl -0x2(%rbp),%eax
mov    %rax,-0x10(%rbp)
sub    $0xf,%rax
ja     11c0 <ui2hex+0xc0>
mov    -0x10(%rbp),%rax
lea    0xed9(%rip),%rcx
movslq (%rcx,%rax,4),%rax
add    %rcx,%rax
jmp    *%rax
movb   $0x30,-0x1(%rbp)
jmp    11c4 <ui2hex+0xc4>
movb   $0x31,-0x1(%rbp)
jmp    11c4 <ui2hex+0xc4>
movb   $0x32,-0x1(%rbp)
jmp    11c4 <ui2hex+0xc4>
movb   $0x33,-0x1(%rbp)
jmp    11c4 <ui2hex+0xc4>
movb   $0x34,-0x1(%rbp)
jmp    11c4 <ui2hex+0xc4>
movb   $0x35,-0x1(%rbp)
jmp    11c4 <ui2hex+0xc4>
movb   $0x36,-0x1(%rbp)
jmp    11c4 <ui2hex+0xc4>
movb   $0x37,-0x1(%rbp)
jmp    11c4 <ui2hex+0xc4>
movb   $0x38,-0x1(%rbp)
jmp    11c4 <ui2hex+0xc4>
movb   $0x39,-0x1(%rbp)
jmp    11c4 <ui2hex+0xc4>
movb   $0x41,-0x1(%rbp)
jmp    11c4 <ui2hex+0xc4>
movb   $0x42,-0x1(%rbp)
jmp    11c4 <ui2hex+0xc4>
movb   $0x43,-0x1(%rbp)
jmp    11c4 <ui2hex+0xc4>
movb   $0x44,-0x1(%rbp)
jmp    11c4 <ui2hex+0xc4>
movb   $0x45,-0x1(%rbp)
jmp    11c4 <ui2hex+0xc4>
movb   $0x46,-0x1(%rbp)
jmp    11c4 <ui2hex+0xc4>
movb   $0x20,-0x1(%rbp)
movsbl -0x1(%rbp),%eax
pop    %rbp
ret

x86 assembly (clang, -O2):
<ui2hex>:
mov    $0x20,%al
cmp    $0xf,%dil
ja     1116 <ui2hex+0x16>
movsbq %dil,%rax
lea    0xeed(%rip),%rcx
mov    (%rax,%rcx,1),%al
ret

LLVM IR (-O0):
define signext i8 @ui2hex(i8 zeroext %0) {
%2 = alloca i8
%3 = alloca i8
store i8 %0, i8* %3
%4 = load i8, i8* %3
%5 = zext i8 %4 to i32
switch i32 %5, label %22 [
i32 0, label %6
i32 1, label %7
i32 2, label %8
i32 3, label %9
i32 4, label %10
i32 5, label %11
i32 6, label %12
i32 7, label %13
i32 8, label %14
i32 9, label %15
i32 10, label %16
i32 11, label %17
i32 12, label %18
i32 13, label %19
i32 14, label %20
i32 15, label %21
]
6: ; preds = %1
store i8 48, i8* %2
br label %23
7: ; preds = %1
store i8 49, i8* %2
br label %23
8: ; preds = %1
store i8 50, i8* %2
br label %23
9: ; preds = %1
store i8 51, i8* %2
br label %23
10: ; preds = %1
store i8 52, i8* %2
br label %23
11: ; preds = %1
store i8 53, i8* %2
br label %23
12: ; preds = %1
store i8 54, i8* %2
br label %23
13: ; preds = %1
store i8 55, i8* %2
br label %23
14: ; preds = %1
store i8 56, i8* %2
br label %23
15: ; preds = %1
store i8 57, i8* %2
br label %23
16: ; preds = %1
store i8 65, i8* %2
br label %23
17: ; preds = %1
store i8 66, i8* %2
br label %23
18: ; preds = %1
store i8 67, i8* %2
br label %23
19: ; preds = %1
store i8 68, i8* %2
br label %23
20: ; preds = %1
store i8 69, i8* %2
br label %23
21: ; preds = %1
store i8 70, i8* %2
br label %23
22: ; preds = %1
store i8 32, i8* %2
br label %23
23: ; preds = %22, %21, %20, %19, %18, %17, %16, %15, %14, %13, %12, %11, %10, %9, %8, %7, %6
%24 = load i8, i8* %2
ret i8 %24
}

LLVM IR (-O2):
@switch.table.ui2hex = [16 x i8] c"0123456789ABCDEF"
define signext i8 @ui2hex(i8 zeroext %0) {
%2 = icmp ult i8 %0, 16
br i1 %2, label %3, label %7
3: ; preds = %1
%4 = sext i8 %0 to i64
%5 = getelementptr inbounds [16 x i8], [16 x i8]* @switch.table.ui2hex, i64 0, i64 %4
%6 = load i8, i8* %5
br label %7
7: ; preds = %1, %3
%8 = phi i8 [ %6, %3 ], [ 32, %1 ]
ret i8 %8
}