int encodeAA(char aa) {
  switch (aa) {
  case 'A':
  case 'a':
    return 0;
  case 'R':
  case 'r':
    return 1;
  case 'N':
  case 'n':
    return 2;
  case 'D':
  case 'd':
    return 3;
  case 'C':
  case 'c':
    return 4;
  case 'Q':
  case 'q':
    return 5;
  case 'E':
  case 'e':
    return 6;
  case 'G':
  case 'g':
    return 7;
  case 'H':
  case 'h':
    return 8;
  case 'I':
  case 'i':
    return 9;
  case 'L':
  case 'l':
    return 10;
  case 'K':
  case 'k':
    return 11;
  case 'M':
  case 'm':
    return 12;
  case 'F':
  case 'f':
    return 13;
  case 'P':
  case 'p':
    return 14;
  case 'S':
  case 's':
    return 15;
  case 'T':
  case 't':
    return 16;
  case 'W':
  case 'w':
    return 17;
  case 'Y':
  case 'y':
    return 18;
  case 'V':
  case 'v':
    return 19;
  case 'B':
  case 'b':
    return 20;
  case 'Z':
  case 'z':
    return 21;
  case 'X':
  case 'x':
    return 99;
  case '*':
    return -1;
  default:
    return 99;
  }
}


x86 assembly (clang, -O0):
<encodeAA>:
push   %rbp
mov    %rsp,%rbp
mov    %dil,%al
mov    %al,-0x5(%rbp)
movsbl -0x5(%rbp),%eax
add    $0xffffffd6,%eax
mov    %eax,%ecx
mov    %rcx,-0x10(%rbp)
sub    $0x50,%eax
ja     1254 <encodeAA+0x154>
mov    -0x10(%rbp),%rax
lea    0xed5(%rip),%rcx
movslq (%rcx,%rax,4),%rax
add    %rcx,%rax
jmp    *%rax
movl   $0x0,-0x4(%rbp)
jmp    125b <encodeAA+0x15b>
movl   $0x1,-0x4(%rbp)
jmp    125b <encodeAA+0x15b>
movl   $0x2,-0x4(%rbp)
jmp    125b <encodeAA+0x15b>
movl   $0x3,-0x4(%rbp)
jmp    125b <encodeAA+0x15b>
movl   $0x4,-0x4(%rbp)
jmp    125b <encodeAA+0x15b>
movl   $0x5,-0x4(%rbp)
jmp    125b <encodeAA+0x15b>
movl   $0x6,-0x4(%rbp)
jmp    125b <encodeAA+0x15b>
movl   $0x7,-0x4(%rbp)
jmp    125b <encodeAA+0x15b>
movl   $0x8,-0x4(%rbp)
jmp    125b <encodeAA+0x15b>
movl   $0x9,-0x4(%rbp)
jmp    125b <encodeAA+0x15b>
movl   $0xa,-0x4(%rbp)
jmp    125b <encodeAA+0x15b>
movl   $0xb,-0x4(%rbp)
jmp    125b <encodeAA+0x15b>
movl   $0xc,-0x4(%rbp)
jmp    125b <encodeAA+0x15b>
movl   $0xd,-0x4(%rbp)
jmp    125b <encodeAA+0x15b>
movl   $0xe,-0x4(%rbp)
jmp    125b <encodeAA+0x15b>
movl   $0xf,-0x4(%rbp)
jmp    125b <encodeAA+0x15b>
movl   $0x10,-0x4(%rbp)
jmp    125b <encodeAA+0x15b>
movl   $0x11,-0x4(%rbp)
jmp    125b <encodeAA+0x15b>
movl   $0x12,-0x4(%rbp)
jmp    125b <encodeAA+0x15b>
movl   $0x13,-0x4(%rbp)
jmp    125b <encodeAA+0x15b>
movl   $0x14,-0x4(%rbp)
jmp    125b <encodeAA+0x15b>
movl   $0x15,-0x4(%rbp)
jmp    125b <encodeAA+0x15b>
movl   $0x63,-0x4(%rbp)
jmp    125b <encodeAA+0x15b>
movl   $0xffffffff,-0x4(%rbp)
jmp    125b <encodeAA+0x15b>
movl   $0x63,-0x4(%rbp)
mov    -0x4(%rbp),%eax
pop    %rbp
ret

x86 assembly (clang, -O2):
<encodeAA>:
add    $0xffffffd6,%edi
mov    $0x63,%eax
cmp    $0x50,%edi
ja     111a <encodeAA+0x1a>
movslq %edi,%rax
lea    0xee9(%rip),%rcx
mov    (%rcx,%rax,4),%eax
ret

LLVM IR (-O0):
define i32 @encodeAA(i8 signext %0) {
%2 = alloca i32
%3 = alloca i8
store i8 %0, i8* %3
%4 = load i8, i8* %3
%5 = sext i8 %4 to i32
switch i32 %5, label %30 [
i32 65, label %6
i32 97, label %6
i32 82, label %7
i32 114, label %7
i32 78, label %8
i32 110, label %8
i32 68, label %9
i32 100, label %9
i32 67, label %10
i32 99, label %10
i32 81, label %11
i32 113, label %11
i32 69, label %12
i32 101, label %12
i32 71, label %13
i32 103, label %13
i32 72, label %14
i32 104, label %14
i32 73, label %15
i32 105, label %15
i32 76, label %16
i32 108, label %16
i32 75, label %17
i32 107, label %17
i32 77, label %18
i32 109, label %18
i32 70, label %19
i32 102, label %19
i32 80, label %20
i32 112, label %20
i32 83, label %21
i32 115, label %21
i32 84, label %22
i32 116, label %22
i32 87, label %23
i32 119, label %23
i32 89, label %24
i32 121, label %24
i32 86, label %25
i32 118, label %25
i32 66, label %26
i32 98, label %26
i32 90, label %27
i32 122, label %27
i32 88, label %28
i32 120, label %28
i32 42, label %29
]
6: ; preds = %1, %1
store i32 0, i32* %2
br label %31
7: ; preds = %1, %1
store i32 1, i32* %2
br label %31
8: ; preds = %1, %1
store i32 2, i32* %2
br label %31
9: ; preds = %1, %1
store i32 3, i32* %2
br label %31
10: ; preds = %1, %1
store i32 4, i32* %2
br label %31
11: ; preds = %1, %1
store i32 5, i32* %2
br label %31
12: ; preds = %1, %1
store i32 6, i32* %2
br label %31
13: ; preds = %1, %1
store i32 7, i32* %2
br label %31
14: ; preds = %1, %1
store i32 8, i32* %2
br label %31
15: ; preds = %1, %1
store i32 9, i32* %2
br label %31
16: ; preds = %1, %1
store i32 10, i32* %2
br label %31
17: ; preds = %1, %1
store i32 11, i32* %2
br label %31
18: ; preds = %1, %1
store i32 12, i32* %2
br label %31
19: ; preds = %1, %1
store i32 13, i32* %2
br label %31
20: ; preds = %1, %1
store i32 14, i32* %2
br label %31
21: ; preds = %1, %1
store i32 15, i32* %2
br label %31
22: ; preds = %1, %1
store i32 16, i32* %2
br label %31
23: ; preds = %1, %1
store i32 17, i32* %2
br label %31
24: ; preds = %1, %1
store i32 18, i32* %2
br label %31
25: ; preds = %1, %1
store i32 19, i32* %2
br label %31
26: ; preds = %1, %1
store i32 20, i32* %2
br label %31
27: ; preds = %1, %1
store i32 21, i32* %2
br label %31
28: ; preds = %1, %1
store i32 99, i32* %2
br label %31
29: ; preds = %1
store i32 -1, i32* %2
br label %31
30: ; preds = %1
store i32 99, i32* %2
br label %31
31: ; preds = %30, %29, %28, %27, %26, %25, %24, %23, %22, %21, %20, %19, %18, %17, %16, %15, %14, %13, %12, %11, %10, %9, %8, %7, %6
%32 = load i32, i32* %2
ret i32 %32
}

LLVM IR (-O2):
@switch.table.encodeAA = [81 x i32] [i32 -1, i32 99, i32 99, i32 99, i32 99, i32 99, i32 99, i32 99, i32 99, i32 99, i32 99, i32 99, i32 99, i32 99, i32 99, i32 99, i32 99, i32 99, i32 99, i32 99, i32 99, i32 99, i32 99, i32 0, i32 20, i32 4, i32 3, i32 6, i32 13, i32 7, i32 8, i32 9, i32 99, i32 11, i32 10, i32 12, i32 2, i32 99, i32 14, i32 5, i32 1, i32 15, i32 16, i32 99, i32 19, i32 17, i32 99, i32 18, i32 21, i32 99, i32 99, i32 99, i32 99, i32 99, i32 99, i32 0, i32 20, i32 4, i32 3, i32 6, i32 13, i32 7, i32 8, i32 9, i32 99, i32 11, i32 10, i32 12, i32 2, i32 99, i32 14, i32 5, i32 1, i32 15, i32 16, i32 99, i32 19, i32 17, i32 99, i32 18, i32 21]
define i32 @encodeAA(i8 signext %0) {
%2 = sext i8 %0 to i32
%3 = add nsw i32 %2, -42
%4 = icmp ult i32 %3, 81
br i1 %4, label %5, label %9
5: ; preds = %1
%6 = sext i32 %3 to i64
%7 = getelementptr inbounds [81 x i32], [81 x i32]* @switch.table.encodeAA, i64 0, i64 %6
%8 = load i32, i32* %7
br label %9
9: ; preds = %1, %5
%10 = phi i32 [ %8, %5 ], [ 99, %1 ]
ret i32 %10
}