char *ss7_ni2str(unsigned char ni) {
  switch (ni) {
  case 0x00:
    return "international";
  case 0x01:
    return "international_spare";
  case 0x02:
    return "national";
  case 0x03:
    return "national_spare";
  default:
    return "Unknown";
  }
}


x86 assembly (clang, -O0):
<ss7_ni2str>:
push   %rbp
mov    %rsp,%rbp
mov    %dil,%al
mov    %al,-0x9(%rbp)
movzbl -0x9(%rbp),%eax
mov    %rax,-0x18(%rbp)
sub    $0x3,%rax
ja     1170 <ss7_ni2str+0x70>
mov    -0x18(%rbp),%rax
lea    0xed9(%rip),%rcx
movslq (%rcx,%rax,4),%rax
add    %rcx,%rax
jmp    *%rax
lea    0xed9(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    117b <ss7_ni2str+0x7b>
lea    0xed7(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    117b <ss7_ni2str+0x7b>
lea    0xebe(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    117b <ss7_ni2str+0x7b>
lea    0xebc(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    117b <ss7_ni2str+0x7b>
lea    0xebb(%rip),%rax
mov    %rax,-0x8(%rbp)
mov    -0x8(%rbp),%rax
pop    %rbp
ret

x86 assembly (clang, -O2):
<ss7_ni2str>:
cmp    $0x3,%dil
ja     1119 <ss7_ni2str+0x19>
movsbq %dil,%rax
lea    0xf1b(%rip),%rcx
movslq (%rcx,%rax,4),%rax
add    %rcx,%rax
ret
lea    0xf02(%rip),%rax
ret

LLVM IR (-O0):
@.str = [14 x i8] c"international\00"
@.str.1 = [20 x i8] c"international_spare\00"
@.str.2 = [9 x i8] c"national\00"
@.str.3 = [15 x i8] c"national_spare\00"
@.str.4 = [8 x i8] c"Unknown\00"
define i8* @ss7_ni2str(i8 zeroext %0) {
%2 = alloca i8*
%3 = alloca i8
store i8 %0, i8* %3
%4 = load i8, i8* %3
%5 = zext i8 %4 to i32
switch i32 %5, label %10 [
i32 0, label %6
i32 1, label %7
i32 2, label %8
i32 3, label %9
]
6: ; preds = %1
store i8* getelementptr inbounds ([14 x i8], [14 x i8]* @.str, i64 0, i64 0), i8** %2
br label %11
7: ; preds = %1
store i8* getelementptr inbounds ([20 x i8], [20 x i8]* @.str.1, i64 0, i64 0), i8** %2
br label %11
8: ; preds = %1
store i8* getelementptr inbounds ([9 x i8], [9 x i8]* @.str.2, i64 0, i64 0), i8** %2
br label %11
9: ; preds = %1
store i8* getelementptr inbounds ([15 x i8], [15 x i8]* @.str.3, i64 0, i64 0), i8** %2
br label %11
10: ; preds = %1
store i8* getelementptr inbounds ([8 x i8], [8 x i8]* @.str.4, i64 0, i64 0), i8** %2
br label %11
11: ; preds = %10, %9, %8, %7, %6
%12 = load i8*, i8** %2
ret i8* %12
}

LLVM IR (-O2):
@.str = [14 x i8] c"international\00"
@.str.1 = [20 x i8] c"international_spare\00"
@.str.2 = [9 x i8] c"national\00"
@.str.3 = [15 x i8] c"national_spare\00"
@.str.4 = [8 x i8] c"Unknown\00"
@reltable.ss7_ni2str = [4 x i32] [i32 trunc (i64 sub (i64 ptrtoint ([14 x i8]* @.str to i64), i64 ptrtoint ([4 x i32]* @reltable.ss7_ni2str to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([20 x i8]* @.str.1 to i64), i64 ptrtoint ([4 x i32]* @reltable.ss7_ni2str to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([9 x i8]* @.str.2 to i64), i64 ptrtoint ([4 x i32]* @reltable.ss7_ni2str to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([15 x i8]* @.str.3 to i64), i64 ptrtoint ([4 x i32]* @reltable.ss7_ni2str to i64)) to i32)]
define i8* @ss7_ni2str(i8 zeroext %0) {
%2 = icmp ult i8 %0, 4
br i1 %2, label %3, label %7
3: ; preds = %1
%4 = sext i8 %0 to i64
%5 = shl i64 %4, 2
%6 = call i8* @llvm.load.relative.i64(i8* bitcast ([4 x i32]* @reltable.ss7_ni2str to i8*), i64 %5)
br label %7
7: ; preds = %1, %3
%8 = phi i8* [ %6, %3 ], [ getelementptr inbounds ([8 x i8], [8 x i8]* @.str.4, i64 0, i64 0), %1 ]
ret i8* %8
}