const char *func_name(int func) {
  switch (func) {
  case 1:
    return "ANNOUNCE";
  case 2:
    return "REGISTER";
  case 3:
    return "CLIENT_KEY";
  case 4:
    return "REG_CONF";
  case 5:
    return "KEYINFO";
  case 6:
    return "KEYINFO_ACK";
  case 7:
    return "FILEINFO";
  case 8:
    return "FILEINFO_ACK";
  case 9:
    return "FILESEG";
  case 10:
    return "DONE";
  case 11:
    return "STATUS";
  case 12:
    return "COMPLETE";
  case 13:
    return "DONE_CONF";
  case 14:
    return "HB_REQ";
  case 15:
    return "HB_RESP";
  case 16:
    return "KEY_REQ";
  case 17:
    return "PROXY_KEY";
  case 18:
    return "ENCRYPTED";
  case 19:
    return "ABORT";
  case 20:
    return "CONG_CTRL";
  case 21:
    return "CC_ACK";
  default:
    return "UNKNOWN";
  }
}


x86 assembly (clang, -O0):
<func_name>:
push   %rbp
mov    %rsp,%rbp
mov    %edi,-0xc(%rbp)
mov    -0xc(%rbp),%eax
add    $0xffffffff,%eax
mov    %eax,%ecx
mov    %rcx,-0x18(%rbp)
sub    $0x14,%eax
ja     1280 <func_name+0x180>
mov    -0x18(%rbp),%rax
lea    0xed9(%rip),%rcx
movslq (%rcx,%rax,4),%rax
add    %rcx,%rax
jmp    *%rax
lea    0xf1d(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    128b <func_name+0x18b>
lea    0xf16(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    128b <func_name+0x18b>
lea    0xf0f(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    128b <func_name+0x18b>
lea    0xf0a(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    128b <func_name+0x18b>
lea    0xf03(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    128b <func_name+0x18b>
lea    0xefb(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    128b <func_name+0x18b>
lea    0xef7(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    128b <func_name+0x18b>
lea    0xef0(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    128b <func_name+0x18b>
lea    0xeed(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    128b <func_name+0x18b>
lea    0xee5(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    128b <func_name+0x18b>
lea    0xeda(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    128b <func_name+0x18b>
lea    0xed1(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    128b <func_name+0x18b>
lea    0xeca(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    128b <func_name+0x18b>
lea    0xec4(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    128b <func_name+0x18b>
lea    0xebb(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    128b <func_name+0x18b>
lea    0xeb3(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    128b <func_name+0x18b>
lea    0xeab(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    128b <func_name+0x18b>
lea    0xea5(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    128b <func_name+0x18b>
lea    0xe9f(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    128b <func_name+0x18b>
lea    0xe95(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    128b <func_name+0x18b>
lea    0xe8f(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    128b <func_name+0x18b>
lea    0xe86(%rip),%rax
mov    %rax,-0x8(%rbp)
mov    -0x8(%rbp),%rax
pop    %rbp
ret

x86 assembly (clang, -O2):
<func_name>:
add    $0xffffffff,%edi
cmp    $0x14,%edi
ja     111a <func_name+0x1a>
movslq %edi,%rax
lea    0xfb2(%rip),%rcx
movslq (%rcx,%rax,4),%rax
add    %rcx,%rax
ret
lea    0xf98(%rip),%rax
ret

LLVM IR (-O0):
@.str = [9 x i8] c"ANNOUNCE\00"
@.str.1 = [9 x i8] c"REGISTER\00"
@.str.2 = [11 x i8] c"CLIENT_KEY\00"
@.str.3 = [9 x i8] c"REG_CONF\00"
@.str.4 = [8 x i8] c"KEYINFO\00"
@.str.5 = [12 x i8] c"KEYINFO_ACK\00"
@.str.6 = [9 x i8] c"FILEINFO\00"
@.str.7 = [13 x i8] c"FILEINFO_ACK\00"
@.str.8 = [8 x i8] c"FILESEG\00"
@.str.9 = [5 x i8] c"DONE\00"
@.str.10 = [7 x i8] c"STATUS\00"
@.str.11 = [9 x i8] c"COMPLETE\00"
@.str.12 = [10 x i8] c"DONE_CONF\00"
@.str.13 = [7 x i8] c"HB_REQ\00"
@.str.14 = [8 x i8] c"HB_RESP\00"
@.str.15 = [8 x i8] c"KEY_REQ\00"
@.str.16 = [10 x i8] c"PROXY_KEY\00"
@.str.17 = [10 x i8] c"ENCRYPTED\00"
@.str.18 = [6 x i8] c"ABORT\00"
@.str.19 = [10 x i8] c"CONG_CTRL\00"
@.str.20 = [7 x i8] c"CC_ACK\00"
@.str.21 = [8 x i8] c"UNKNOWN\00"
define i8* @func_name(i32 %0) {
%2 = alloca i8*
%3 = alloca i32
store i32 %0, i32* %3
%4 = load i32, i32* %3
switch i32 %4, label %26 [
i32 1, label %5
i32 2, label %6
i32 3, label %7
i32 4, label %8
i32 5, label %9
i32 6, label %10
i32 7, label %11
i32 8, label %12
i32 9, label %13
i32 10, label %14
i32 11, label %15
i32 12, label %16
i32 13, label %17
i32 14, label %18
i32 15, label %19
i32 16, label %20
i32 17, label %21
i32 18, label %22
i32 19, label %23
i32 20, label %24
i32 21, label %25
]
5: ; preds = %1
store i8* getelementptr inbounds ([9 x i8], [9 x i8]* @.str, i64 0, i64 0), i8** %2
br label %27
6: ; preds = %1
store i8* getelementptr inbounds ([9 x i8], [9 x i8]* @.str.1, i64 0, i64 0), i8** %2
br label %27
7: ; preds = %1
store i8* getelementptr inbounds ([11 x i8], [11 x i8]* @.str.2, i64 0, i64 0), i8** %2
br label %27
8: ; preds = %1
store i8* getelementptr inbounds ([9 x i8], [9 x i8]* @.str.3, i64 0, i64 0), i8** %2
br label %27
9: ; preds = %1
store i8* getelementptr inbounds ([8 x i8], [8 x i8]* @.str.4, i64 0, i64 0), i8** %2
br label %27
10: ; preds = %1
store i8* getelementptr inbounds ([12 x i8], [12 x i8]* @.str.5, i64 0, i64 0), i8** %2
br label %27
11: ; preds = %1
store i8* getelementptr inbounds ([9 x i8], [9 x i8]* @.str.6, i64 0, i64 0), i8** %2
br label %27
12: ; preds = %1
store i8* getelementptr inbounds ([13 x i8], [13 x i8]* @.str.7, i64 0, i64 0), i8** %2
br label %27
13: ; preds = %1
store i8* getelementptr inbounds ([8 x i8], [8 x i8]* @.str.8, i64 0, i64 0), i8** %2
br label %27
14: ; preds = %1
store i8* getelementptr inbounds ([5 x i8], [5 x i8]* @.str.9, i64 0, i64 0), i8** %2
br label %27
15: ; preds = %1
store i8* getelementptr inbounds ([7 x i8], [7 x i8]* @.str.10, i64 0, i64 0), i8** %2
br label %27
16: ; preds = %1
store i8* getelementptr inbounds ([9 x i8], [9 x i8]* @.str.11, i64 0, i64 0), i8** %2
br label %27
17: ; preds = %1
store i8* getelementptr inbounds ([10 x i8], [10 x i8]* @.str.12, i64 0, i64 0), i8** %2
br label %27
18: ; preds = %1
store i8* getelementptr inbounds ([7 x i8], [7 x i8]* @.str.13, i64 0, i64 0), i8** %2
br label %27
19: ; preds = %1
store i8* getelementptr inbounds ([8 x i8], [8 x i8]* @.str.14, i64 0, i64 0), i8** %2
br label %27
20: ; preds = %1
store i8* getelementptr inbounds ([8 x i8], [8 x i8]* @.str.15, i64 0, i64 0), i8** %2
br label %27
21: ; preds = %1
store i8* getelementptr inbounds ([10 x i8], [10 x i8]* @.str.16, i64 0, i64 0), i8** %2
br label %27
22: ; preds = %1
store i8* getelementptr inbounds ([10 x i8], [10 x i8]* @.str.17, i64 0, i64 0), i8** %2
br label %27
23: ; preds = %1
store i8* getelementptr inbounds ([6 x i8], [6 x i8]* @.str.18, i64 0, i64 0), i8** %2
br label %27
24: ; preds = %1
store i8* getelementptr inbounds ([10 x i8], [10 x i8]* @.str.19, i64 0, i64 0), i8** %2
br label %27
25: ; preds = %1
store i8* getelementptr inbounds ([7 x i8], [7 x i8]* @.str.20, i64 0, i64 0), i8** %2
br label %27
26: ; preds = %1
store i8* getelementptr inbounds ([8 x i8], [8 x i8]* @.str.21, i64 0, i64 0), i8** %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, %5
%28 = load i8*, i8** %2
ret i8* %28
}

LLVM IR (-O2):
@.str = [9 x i8] c"ANNOUNCE\00"
@.str.1 = [9 x i8] c"REGISTER\00"
@.str.2 = [11 x i8] c"CLIENT_KEY\00"
@.str.3 = [9 x i8] c"REG_CONF\00"
@.str.4 = [8 x i8] c"KEYINFO\00"
@.str.5 = [12 x i8] c"KEYINFO_ACK\00"
@.str.6 = [9 x i8] c"FILEINFO\00"
@.str.7 = [13 x i8] c"FILEINFO_ACK\00"
@.str.8 = [8 x i8] c"FILESEG\00"
@.str.9 = [5 x i8] c"DONE\00"
@.str.10 = [7 x i8] c"STATUS\00"
@.str.11 = [9 x i8] c"COMPLETE\00"
@.str.12 = [10 x i8] c"DONE_CONF\00"
@.str.13 = [7 x i8] c"HB_REQ\00"
@.str.14 = [8 x i8] c"HB_RESP\00"
@.str.15 = [8 x i8] c"KEY_REQ\00"
@.str.16 = [10 x i8] c"PROXY_KEY\00"
@.str.17 = [10 x i8] c"ENCRYPTED\00"
@.str.18 = [6 x i8] c"ABORT\00"
@.str.19 = [10 x i8] c"CONG_CTRL\00"
@.str.20 = [7 x i8] c"CC_ACK\00"
@.str.21 = [8 x i8] c"UNKNOWN\00"
@reltable.func_name = [21 x i32] [i32 trunc (i64 sub (i64 ptrtoint ([9 x i8]* @.str to i64), i64 ptrtoint ([21 x i32]* @reltable.func_name to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([9 x i8]* @.str.1 to i64), i64 ptrtoint ([21 x i32]* @reltable.func_name to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([11 x i8]* @.str.2 to i64), i64 ptrtoint ([21 x i32]* @reltable.func_name to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([9 x i8]* @.str.3 to i64), i64 ptrtoint ([21 x i32]* @reltable.func_name to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([8 x i8]* @.str.4 to i64), i64 ptrtoint ([21 x i32]* @reltable.func_name to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([12 x i8]* @.str.5 to i64), i64 ptrtoint ([21 x i32]* @reltable.func_name to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([9 x i8]* @.str.6 to i64), i64 ptrtoint ([21 x i32]* @reltable.func_name to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([13 x i8]* @.str.7 to i64), i64 ptrtoint ([21 x i32]* @reltable.func_name to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([8 x i8]* @.str.8 to i64), i64 ptrtoint ([21 x i32]* @reltable.func_name to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([5 x i8]* @.str.9 to i64), i64 ptrtoint ([21 x i32]* @reltable.func_name to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([7 x i8]* @.str.10 to i64), i64 ptrtoint ([21 x i32]* @reltable.func_name to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([9 x i8]* @.str.11 to i64), i64 ptrtoint ([21 x i32]* @reltable.func_name to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([10 x i8]* @.str.12 to i64), i64 ptrtoint ([21 x i32]* @reltable.func_name to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([7 x i8]* @.str.13 to i64), i64 ptrtoint ([21 x i32]* @reltable.func_name to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([8 x i8]* @.str.14 to i64), i64 ptrtoint ([21 x i32]* @reltable.func_name to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([8 x i8]* @.str.15 to i64), i64 ptrtoint ([21 x i32]* @reltable.func_name to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([10 x i8]* @.str.16 to i64), i64 ptrtoint ([21 x i32]* @reltable.func_name to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([10 x i8]* @.str.17 to i64), i64 ptrtoint ([21 x i32]* @reltable.func_name to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([6 x i8]* @.str.18 to i64), i64 ptrtoint ([21 x i32]* @reltable.func_name to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([10 x i8]* @.str.19 to i64), i64 ptrtoint ([21 x i32]* @reltable.func_name to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([7 x i8]* @.str.20 to i64), i64 ptrtoint ([21 x i32]* @reltable.func_name to i64)) to i32)]
define i8* @func_name(i32 %0) {
%2 = add i32 %0, -1
%3 = icmp ult i32 %2, 21
br i1 %3, label %4, label %8
4: ; preds = %1
%5 = sext i32 %2 to i64
%6 = shl i64 %5, 2
%7 = call i8* @llvm.load.relative.i64(i8* bitcast ([21 x i32]* @reltable.func_name to i8*), i64 %6)
br label %8
8: ; preds = %1, %4
%9 = phi i8* [ %7, %4 ], [ getelementptr inbounds ([8 x i8], [8 x i8]* @.str.21, i64 0, i64 0), %1 ]
ret i8* %9
}