char *get_rng_type_desc(int rng_type) {
  char *rv = "Unrecognized RNG type";
  switch (rng_type) {
  case 1:
    rv = "psdes";
    break;
  case 2:
    rv = "/dev/urandom";
    break;
  case 3:
    rv = "rand48";
    break;
  case 4:
    rv = "Mersenne twister";
    break;
  }
  return rv;
}


x86 assembly (clang, -O0):
<get_rng_type_desc>:
push   %rbp
mov    %rsp,%rbp
mov    %edi,-0x4(%rbp)
lea    0xf02(%rip),%rax
mov    %rax,-0x10(%rbp)
mov    -0x4(%rbp),%eax
add    $0xffffffff,%eax
mov    %eax,%ecx
mov    %rcx,-0x18(%rbp)
sub    $0x3,%eax
ja     1176 <get_rng_type_desc+0x76>
mov    -0x18(%rbp),%rax
lea    0xece(%rip),%rcx
movslq (%rcx,%rax,4),%rax
add    %rcx,%rax
jmp    *%rax
lea    0xee4(%rip),%rax
mov    %rax,-0x10(%rbp)
jmp    1176 <get_rng_type_desc+0x76>
lea    0xeda(%rip),%rax
mov    %rax,-0x10(%rbp)
jmp    1176 <get_rng_type_desc+0x76>
lea    0xed7(%rip),%rax
mov    %rax,-0x10(%rbp)
jmp    1176 <get_rng_type_desc+0x76>
lea    0xece(%rip),%rax
mov    %rax,-0x10(%rbp)
mov    -0x10(%rbp),%rax
pop    %rbp
ret

x86 assembly (clang, -O2):
<get_rng_type_desc>:
add    $0xffffffff,%edi
cmp    $0x3,%edi
ja     111a <get_rng_type_desc+0x1a>
movslq %edi,%rax
lea    0xf32(%rip),%rcx
movslq (%rcx,%rax,4),%rax
add    %rcx,%rax
ret
lea    0xedf(%rip),%rax
ret

LLVM IR (-O0):
@.str = [22 x i8] c"Unrecognized RNG type\00"
@.str.1 = [6 x i8] c"psdes\00"
@.str.2 = [13 x i8] c"/dev/urandom\00"
@.str.3 = [7 x i8] c"rand48\00"
@.str.4 = [17 x i8] c"Mersenne twister\00"
define i8* @get_rng_type_desc(i32 %0) {
%2 = alloca i32
%3 = alloca i8*
store i32 %0, i32* %2
store i8* getelementptr inbounds ([22 x i8], [22 x i8]* @.str, i64 0, i64 0), i8** %3
%4 = load i32, i32* %2
switch i32 %4, label %9 [
i32 1, label %5
i32 2, label %6
i32 3, label %7
i32 4, label %8
]
5: ; preds = %1
store i8* getelementptr inbounds ([6 x i8], [6 x i8]* @.str.1, i64 0, i64 0), i8** %3
br label %9
6: ; preds = %1
store i8* getelementptr inbounds ([13 x i8], [13 x i8]* @.str.2, i64 0, i64 0), i8** %3
br label %9
7: ; preds = %1
store i8* getelementptr inbounds ([7 x i8], [7 x i8]* @.str.3, i64 0, i64 0), i8** %3
br label %9
8: ; preds = %1
store i8* getelementptr inbounds ([17 x i8], [17 x i8]* @.str.4, i64 0, i64 0), i8** %3
br label %9
9: ; preds = %1, %8, %7, %6, %5
%10 = load i8*, i8** %3
ret i8* %10
}

LLVM IR (-O2):
@.str = [22 x i8] c"Unrecognized RNG type\00"
@.str.1 = [6 x i8] c"psdes\00"
@.str.2 = [13 x i8] c"/dev/urandom\00"
@.str.3 = [7 x i8] c"rand48\00"
@.str.4 = [17 x i8] c"Mersenne twister\00"
@reltable.get_rng_type_desc = [4 x i32] [i32 trunc (i64 sub (i64 ptrtoint ([6 x i8]* @.str.1 to i64), i64 ptrtoint ([4 x i32]* @reltable.get_rng_type_desc to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([13 x i8]* @.str.2 to i64), i64 ptrtoint ([4 x i32]* @reltable.get_rng_type_desc to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([7 x i8]* @.str.3 to i64), i64 ptrtoint ([4 x i32]* @reltable.get_rng_type_desc to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([17 x i8]* @.str.4 to i64), i64 ptrtoint ([4 x i32]* @reltable.get_rng_type_desc to i64)) to i32)]
define i8* @get_rng_type_desc(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.get_rng_type_desc to i8*), i64 %6)
br label %8
8: ; preds = %4, %1
%9 = phi i8* [ getelementptr inbounds ([22 x i8], [22 x i8]* @.str, i64 0, i64 0), %1 ], [ %7, %4 ]
ret i8* %9
}