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


x86 assembly (clang, -O0):
<convert_aa_int>:
push   %rbp
mov    %rsp,%rbp
mov    %dil,%al
mov    %al,-0x1(%rbp)
movsbl -0x1(%rbp),%eax
add    $0xffffffbf,%eax
mov    %eax,%ecx
mov    %rcx,-0x10(%rbp)
sub    $0x18,%eax
ja     121f <convert_aa_int+0x11f>
mov    -0x10(%rbp),%rax
lea    0xed5(%rip),%rcx
movslq (%rcx,%rax,4),%rax
add    %rcx,%rax
jmp    *%rax
movl   $0x0,-0x8(%rbp)
jmp    121f <convert_aa_int+0x11f>
movl   $0x1,-0x8(%rbp)
jmp    121f <convert_aa_int+0x11f>
movl   $0x2,-0x8(%rbp)
jmp    121f <convert_aa_int+0x11f>
movl   $0x3,-0x8(%rbp)
jmp    121f <convert_aa_int+0x11f>
movl   $0x4,-0x8(%rbp)
jmp    121f <convert_aa_int+0x11f>
movl   $0x5,-0x8(%rbp)
jmp    121f <convert_aa_int+0x11f>
movl   $0x6,-0x8(%rbp)
jmp    121f <convert_aa_int+0x11f>
movl   $0x7,-0x8(%rbp)
jmp    121f <convert_aa_int+0x11f>
movl   $0x8,-0x8(%rbp)
jmp    121f <convert_aa_int+0x11f>
movl   $0x9,-0x8(%rbp)
jmp    121f <convert_aa_int+0x11f>
movl   $0xa,-0x8(%rbp)
jmp    121f <convert_aa_int+0x11f>
movl   $0xb,-0x8(%rbp)
jmp    121f <convert_aa_int+0x11f>
movl   $0xc,-0x8(%rbp)
jmp    121f <convert_aa_int+0x11f>
movl   $0xd,-0x8(%rbp)
jmp    121f <convert_aa_int+0x11f>
movl   $0xe,-0x8(%rbp)
jmp    121f <convert_aa_int+0x11f>
movl   $0xf,-0x8(%rbp)
jmp    121f <convert_aa_int+0x11f>
movl   $0x10,-0x8(%rbp)
jmp    121f <convert_aa_int+0x11f>
movl   $0x11,-0x8(%rbp)
jmp    121f <convert_aa_int+0x11f>
movl   $0x12,-0x8(%rbp)
jmp    121f <convert_aa_int+0x11f>
movl   $0x13,-0x8(%rbp)
mov    -0x8(%rbp),%eax
pop    %rbp
ret

x86 assembly (clang, -O2):
<convert_aa_int>:
add    $0xffffffbf,%edi
xor    %eax,%eax
cmp    $0x18,%edi
ja     1117 <convert_aa_int+0x17>
movslq %edi,%rax
lea    0xeec(%rip),%rcx
mov    (%rcx,%rax,4),%eax
ret

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

LLVM IR (-O2):
@switch.table.convert_aa_int = [25 x i32] [i32 13, i32 0, i32 15, i32 3, i32 5, i32 16, i32 12, i32 6, i32 19, i32 0, i32 1, i32 17, i32 14, i32 2, i32 0, i32 7, i32 4, i32 0, i32 10, i32 11, i32 0, i32 18, i32 9, i32 0, i32 8]
define i32 @convert_aa_int(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 i32], [25 x i32]* @switch.table.convert_aa_int, i64 0, i64 %6
%8 = load i32, i32* %7
br label %9
9: ; preds = %5, %1
%10 = phi i32 [ 0, %1 ], [ %8, %5 ]
ret i32 %10
}