const char *dbg_version(unsigned val) {
  switch (val) {
  case 0b0001:
    return "v6";
  case 0b0010:
    return "v6.1";
  case 0b0011:
    return "v7 full";
  case 0b0100:
    return "v7 basic";
  case 0b0101:
    return "v7.1";
  case 0b0110:
    return "v8";
  case 0b0111:
    return "v8.1";
  case 0b1000:
    return "v8.2";
  }
  return "???";
}


x86 assembly (clang, -O0):
<dbg_version>:
push   %rbp
mov    %rsp,%rbp
mov    %edi,-0xc(%rbp)
mov    -0xc(%rbp),%eax
add    $0xffffffff,%eax
mov    %eax,%ecx
mov    %rcx,-0x18(%rbp)
sub    $0x7,%eax
ja     11b0 <dbg_version+0xb0>
mov    -0x18(%rbp),%rax
lea    0xed9(%rip),%rcx
movslq (%rcx,%rax,4),%rax
add    %rcx,%rax
jmp    *%rax
lea    0xee9(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    11bb <dbg_version+0xbb>
lea    0xedc(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    11bb <dbg_version+0xbb>
lea    0xed1(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    11bb <dbg_version+0xbb>
lea    0xec9(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    11bb <dbg_version+0xbb>
lea    0xec2(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    11bb <dbg_version+0xbb>
lea    0xeb7(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    11bb <dbg_version+0xbb>
lea    0xeaa(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    11bb <dbg_version+0xbb>
lea    0xe9f(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    11bb <dbg_version+0xbb>
lea    0xe94(%rip),%rax
mov    %rax,-0x8(%rbp)
mov    -0x8(%rbp),%rax
pop    %rbp
ret

x86 assembly (clang, -O2):
<dbg_version>:
add    $0xffffffff,%edi
cmp    $0x7,%edi
ja     111a <dbg_version+0x1a>
movslq %edi,%rax
lea    0xf1e(%rip),%rcx
movslq (%rcx,%rax,4),%rax
add    %rcx,%rax
ret
lea    0xf0a(%rip),%rax
ret

LLVM IR (-O0):
@.str = [3 x i8] c"v6\00"
@.str.1 = [5 x i8] c"v6.1\00"
@.str.2 = [8 x i8] c"v7 full\00"
@.str.3 = [9 x i8] c"v7 basic\00"
@.str.4 = [5 x i8] c"v7.1\00"
@.str.5 = [3 x i8] c"v8\00"
@.str.6 = [5 x i8] c"v8.1\00"
@.str.7 = [5 x i8] c"v8.2\00"
@.str.8 = [4 x i8] c"???\00"
define i8* @dbg_version(i32 %0) {
%2 = alloca i8*
%3 = alloca i32
store i32 %0, i32* %3
%4 = load i32, i32* %3
switch i32 %4, label %13 [
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
]
5: ; preds = %1
store i8* getelementptr inbounds ([3 x i8], [3 x i8]* @.str, i64 0, i64 0), i8** %2
br label %14
6: ; preds = %1
store i8* getelementptr inbounds ([5 x i8], [5 x i8]* @.str.1, i64 0, i64 0), i8** %2
br label %14
7: ; preds = %1
store i8* getelementptr inbounds ([8 x i8], [8 x i8]* @.str.2, i64 0, i64 0), i8** %2
br label %14
8: ; preds = %1
store i8* getelementptr inbounds ([9 x i8], [9 x i8]* @.str.3, i64 0, i64 0), i8** %2
br label %14
9: ; preds = %1
store i8* getelementptr inbounds ([5 x i8], [5 x i8]* @.str.4, i64 0, i64 0), i8** %2
br label %14
10: ; preds = %1
store i8* getelementptr inbounds ([3 x i8], [3 x i8]* @.str.5, i64 0, i64 0), i8** %2
br label %14
11: ; preds = %1
store i8* getelementptr inbounds ([5 x i8], [5 x i8]* @.str.6, i64 0, i64 0), i8** %2
br label %14
12: ; preds = %1
store i8* getelementptr inbounds ([5 x i8], [5 x i8]* @.str.7, i64 0, i64 0), i8** %2
br label %14
13: ; preds = %1
store i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str.8, i64 0, i64 0), i8** %2
br label %14
14: ; preds = %13, %12, %11, %10, %9, %8, %7, %6, %5
%15 = load i8*, i8** %2
ret i8* %15
}

LLVM IR (-O2):
@.str = [3 x i8] c"v6\00"
@.str.1 = [5 x i8] c"v6.1\00"
@.str.2 = [8 x i8] c"v7 full\00"
@.str.3 = [9 x i8] c"v7 basic\00"
@.str.4 = [5 x i8] c"v7.1\00"
@.str.5 = [3 x i8] c"v8\00"
@.str.6 = [5 x i8] c"v8.1\00"
@.str.7 = [5 x i8] c"v8.2\00"
@.str.8 = [4 x i8] c"???\00"
@reltable.dbg_version = [8 x i32] [i32 trunc (i64 sub (i64 ptrtoint ([3 x i8]* @.str to i64), i64 ptrtoint ([8 x i32]* @reltable.dbg_version to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([5 x i8]* @.str.1 to i64), i64 ptrtoint ([8 x i32]* @reltable.dbg_version to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([8 x i8]* @.str.2 to i64), i64 ptrtoint ([8 x i32]* @reltable.dbg_version to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([9 x i8]* @.str.3 to i64), i64 ptrtoint ([8 x i32]* @reltable.dbg_version to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([5 x i8]* @.str.4 to i64), i64 ptrtoint ([8 x i32]* @reltable.dbg_version to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([3 x i8]* @.str.5 to i64), i64 ptrtoint ([8 x i32]* @reltable.dbg_version to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([5 x i8]* @.str.6 to i64), i64 ptrtoint ([8 x i32]* @reltable.dbg_version to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([5 x i8]* @.str.7 to i64), i64 ptrtoint ([8 x i32]* @reltable.dbg_version to i64)) to i32)]
define i8* @dbg_version(i32 %0) {
%2 = add i32 %0, -1
%3 = icmp ult i32 %2, 8
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 ([8 x i32]* @reltable.dbg_version to i8*), i64 %6)
br label %8
8: ; preds = %1, %4
%9 = phi i8* [ %7, %4 ], [ getelementptr inbounds ([4 x i8], [4 x i8]* @.str.8, i64 0, i64 0), %1 ]
ret i8* %9
}