short char2AA(char ch) {
  switch (ch) {
  case 'C':
    return 0;
  case 'G':
    return 1;
  case 'P':
    return 2;
  case 'S':
    return 3;
  case 'A':
    return 4;
  case 'T':
    return 5;
  case 'D':
    return 6;
  case 'E':
    return 7;
  case 'N':
    return 8;
  case 'Q':
    return 9;
  case 'H':
    return 10;
  case 'K':
    return 11;
  case 'R':
    return 12;
  case 'V':
    return 13;
  case 'M':
    return 14;
  case 'I':
    return 15;
  case 'L':
    return 16;
  case 'F':
    return 17;
  case 'Y':
    return 18;
  case 'W':
    return 19;
  default:
    return 0;
  }
}


x86 assembly (clang, -O0):
<char2AA>:
push   %rbp
mov    %rsp,%rbp
mov    %dil,%al
mov    %al,-0x3(%rbp)
movsbl -0x3(%rbp),%eax
add    $0xffffffbf,%eax
mov    %eax,%ecx
mov    %rcx,-0x10(%rbp)
sub    $0x18,%eax
ja     1210 <char2AA+0x110>
mov    -0x10(%rbp),%rax
lea    0xed5(%rip),%rcx
movslq (%rcx,%rax,4),%rax
add    %rcx,%rax
jmp    *%rax
movw   $0x0,-0x2(%rbp)
jmp    1216 <char2AA+0x116>
movw   $0x1,-0x2(%rbp)
jmp    1216 <char2AA+0x116>
movw   $0x2,-0x2(%rbp)
jmp    1216 <char2AA+0x116>
movw   $0x3,-0x2(%rbp)
jmp    1216 <char2AA+0x116>
movw   $0x4,-0x2(%rbp)
jmp    1216 <char2AA+0x116>
movw   $0x5,-0x2(%rbp)
jmp    1216 <char2AA+0x116>
movw   $0x6,-0x2(%rbp)
jmp    1216 <char2AA+0x116>
movw   $0x7,-0x2(%rbp)
jmp    1216 <char2AA+0x116>
movw   $0x8,-0x2(%rbp)
jmp    1216 <char2AA+0x116>
movw   $0x9,-0x2(%rbp)
jmp    1216 <char2AA+0x116>
movw   $0xa,-0x2(%rbp)
jmp    1216 <char2AA+0x116>
movw   $0xb,-0x2(%rbp)
jmp    1216 <char2AA+0x116>
movw   $0xc,-0x2(%rbp)
jmp    1216 <char2AA+0x116>
movw   $0xd,-0x2(%rbp)
jmp    1216 <char2AA+0x116>
movw   $0xe,-0x2(%rbp)
jmp    1216 <char2AA+0x116>
movw   $0xf,-0x2(%rbp)
jmp    1216 <char2AA+0x116>
movw   $0x10,-0x2(%rbp)
jmp    1216 <char2AA+0x116>
movw   $0x11,-0x2(%rbp)
jmp    1216 <char2AA+0x116>
movw   $0x12,-0x2(%rbp)
jmp    1216 <char2AA+0x116>
movw   $0x13,-0x2(%rbp)
jmp    1216 <char2AA+0x116>
movw   $0x0,-0x2(%rbp)
movswl -0x2(%rbp),%eax
pop    %rbp
ret

x86 assembly (clang, -O2):
<char2AA>:
add    $0xffffffbf,%edi
cmp    $0x18,%edi
ja     1117 <char2AA+0x17>
movslq %edi,%rax
lea    0xeee(%rip),%rcx
movzwl (%rcx,%rax,2),%eax
ret
xor    %eax,%eax
ret

LLVM IR (-O0):
define signext i16 @char2AA(i8 signext %0) {
%2 = alloca i16
%3 = alloca i8
store i8 %0, i8* %3
%4 = load i8, i8* %3
%5 = sext i8 %4 to i32
switch i32 %5, label %26 [
i32 67, label %6
i32 71, label %7
i32 80, label %8
i32 83, label %9
i32 65, label %10
i32 84, label %11
i32 68, label %12
i32 69, label %13
i32 78, label %14
i32 81, label %15
i32 72, label %16
i32 75, label %17
i32 82, label %18
i32 86, label %19
i32 77, label %20
i32 73, label %21
i32 76, label %22
i32 70, label %23
i32 89, label %24
i32 87, label %25
]
6: ; preds = %1
store i16 0, i16* %2
br label %27
7: ; preds = %1
store i16 1, i16* %2
br label %27
8: ; preds = %1
store i16 2, i16* %2
br label %27
9: ; preds = %1
store i16 3, i16* %2
br label %27
10: ; preds = %1
store i16 4, i16* %2
br label %27
11: ; preds = %1
store i16 5, i16* %2
br label %27
12: ; preds = %1
store i16 6, i16* %2
br label %27
13: ; preds = %1
store i16 7, i16* %2
br label %27
14: ; preds = %1
store i16 8, i16* %2
br label %27
15: ; preds = %1
store i16 9, i16* %2
br label %27
16: ; preds = %1
store i16 10, i16* %2
br label %27
17: ; preds = %1
store i16 11, i16* %2
br label %27
18: ; preds = %1
store i16 12, i16* %2
br label %27
19: ; preds = %1
store i16 13, i16* %2
br label %27
20: ; preds = %1
store i16 14, i16* %2
br label %27
21: ; preds = %1
store i16 15, i16* %2
br label %27
22: ; preds = %1
store i16 16, i16* %2
br label %27
23: ; preds = %1
store i16 17, i16* %2
br label %27
24: ; preds = %1
store i16 18, i16* %2
br label %27
25: ; preds = %1
store i16 19, i16* %2
br label %27
26: ; preds = %1
store i16 0, i16* %2
br label %27
27: ; preds = %26, %25, %24, %23, %22, %21, %20, %19, %18, %17, %16, %15, %14, %13, %12, %11, %10, %9, %8, %7, %6
%28 = load i16, i16* %2
ret i16 %28
}

LLVM IR (-O2):
@switch.table.char2AA = [25 x i16] [i16 4, i16 0, i16 0, i16 6, i16 7, i16 17, i16 1, i16 10, i16 15, i16 0, i16 11, i16 16, i16 14, i16 8, i16 0, i16 2, i16 9, i16 12, i16 3, i16 5, i16 0, i16 13, i16 19, i16 0, i16 18]
define signext i16 @char2AA(i8 signext %0) {
%2 = sext i8 %0 to i32
%3 = add nsw i32 %2, -65
%4 = icmp ult i32 %3, 25
br i1 %4, label %5, label %9
5: ; preds = %1
%6 = sext i32 %3 to i64
%7 = getelementptr inbounds [25 x i16], [25 x i16]* @switch.table.char2AA, i64 0, i64 %6
%8 = load i16, i16* %7
br label %9
9: ; preds = %5, %1
%10 = phi i16 [ 0, %1 ], [ %8, %5 ]
ret i16 %10
}