char *str_lvl(int lvl) {
  switch (lvl) {
  case 0:
    return "FTD";
  case 1:
    return "DBG";
  case 2:
    return "EVT";
  case 3:
    return "WRN";
  case 4:
    return "ERR";
  default:
    "???";
  }
}


x86 assembly (clang, -O0):
<str_lvl>:
push   %rbp
mov    %rsp,%rbp
mov    %edi,-0xc(%rbp)
mov    -0xc(%rbp),%eax
mov    %rax,-0x18(%rbp)
sub    $0x4,%rax
ja     117c <str_lvl+0x7c>
mov    -0x18(%rbp),%rax
lea    0xedd(%rip),%rcx
movslq (%rcx,%rax,4),%rax
add    %rcx,%rax
jmp    *%rax
lea    0xee1(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1181 <str_lvl+0x81>
lea    0xed5(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1181 <str_lvl+0x81>
lea    0xec9(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1181 <str_lvl+0x81>
lea    0xebd(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1181 <str_lvl+0x81>
lea    0xeb1(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1181 <str_lvl+0x81>
jmp    1181 <str_lvl+0x81>
mov    -0x8(%rbp),%rax
pop    %rbp
ret

x86 assembly (clang, -O2):
<str_lvl>:
add    $0xffffffff,%edi
cmp    $0x3,%edi
ja     111a <str_lvl+0x1a>
movslq %edi,%rax
lea    0xf02(%rip),%rcx
movslq (%rcx,%rax,4),%rax
add    %rcx,%rax
ret
lea    0xedf(%rip),%rax
ret

LLVM IR (-O0):
@.str = [4 x i8] c"FTD\00"
@.str.1 = [4 x i8] c"DBG\00"
@.str.2 = [4 x i8] c"EVT\00"
@.str.3 = [4 x i8] c"WRN\00"
@.str.4 = [4 x i8] c"ERR\00"
@.str.5 = [4 x i8] c"???\00"
define i8* @str_lvl(i32 %0) {
%2 = alloca i8*
%3 = alloca i32
store i32 %0, i32* %3
%4 = load i32, i32* %3
switch i32 %4, label %10 [
i32 0, label %5
i32 1, label %6
i32 2, label %7
i32 3, label %8
i32 4, label %9
]
5: ; preds = %1
store i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str, i64 0, i64 0), i8** %2
br label %11
6: ; preds = %1
store i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str.1, i64 0, i64 0), i8** %2
br label %11
7: ; preds = %1
store i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str.2, i64 0, i64 0), i8** %2
br label %11
8: ; preds = %1
store i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str.3, i64 0, i64 0), i8** %2
br label %11
9: ; preds = %1
store i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str.4, i64 0, i64 0), i8** %2
br label %11
10: ; preds = %1
br label %11
11: ; preds = %5, %6, %7, %8, %9, %10
%12 = load i8*, i8** %2
ret i8* %12
}

LLVM IR (-O2):
@.str = [4 x i8] c"FTD\00"
@.str.1 = [4 x i8] c"DBG\00"
@.str.2 = [4 x i8] c"EVT\00"
@.str.3 = [4 x i8] c"WRN\00"
@.str.4 = [4 x i8] c"ERR\00"
@reltable.str_lvl = [4 x i32] [i32 trunc (i64 sub (i64 ptrtoint ([4 x i8]* @.str.1 to i64), i64 ptrtoint ([4 x i32]* @reltable.str_lvl to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([4 x i8]* @.str.2 to i64), i64 ptrtoint ([4 x i32]* @reltable.str_lvl to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([4 x i8]* @.str.3 to i64), i64 ptrtoint ([4 x i32]* @reltable.str_lvl to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([4 x i8]* @.str.4 to i64), i64 ptrtoint ([4 x i32]* @reltable.str_lvl to i64)) to i32)]
define i8* @str_lvl(i32 %0) {
%2 = add i32 %0, -1
%3 = icmp ult i32 %2, 4
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 ([4 x i32]* @reltable.str_lvl to i8*), i64 %6)
br label %8
8: ; preds = %4, %1
%9 = phi i8* [ getelementptr inbounds ([4 x i8], [4 x i8]* @.str, i64 0, i64 0), %1 ], [ %7, %4 ]
ret i8* %9
}