char *idx_format_name(int fmt) {
  switch (fmt) {
  case 0:
    return "csi";
  case 1:
    return "bai";
  case 2:
    return "tbi";
  case 3:
    return "crai";
  default:
    return "unknown";
  }
}


x86 assembly (clang, -O0):
<idx_format_name>:
push   %rbp
mov    %rsp,%rbp
mov    %edi,-0xc(%rbp)
mov    -0xc(%rbp),%eax
mov    %rax,-0x18(%rbp)
sub    $0x3,%rax
ja     116c <idx_format_name+0x6c>
mov    -0x18(%rbp),%rax
lea    0xedd(%rip),%rcx
movslq (%rcx,%rax,4),%rax
add    %rcx,%rax
jmp    *%rax
lea    0xedd(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1177 <idx_format_name+0x77>
lea    0xed1(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1177 <idx_format_name+0x77>
lea    0xec5(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1177 <idx_format_name+0x77>
lea    0xeb9(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1177 <idx_format_name+0x77>
lea    0xeae(%rip),%rax
mov    %rax,-0x8(%rbp)
mov    -0x8(%rbp),%rax
pop    %rbp
ret

x86 assembly (clang, -O2):
<idx_format_name>:
cmp    $0x3,%edi
ja     1117 <idx_format_name+0x17>
movslq %edi,%rax
lea    0xf0d(%rip),%rcx
movslq (%rcx,%rax,4),%rax
add    %rcx,%rax
ret
lea    0xef3(%rip),%rax
ret

LLVM IR (-O0):
@.str = [4 x i8] c"csi\00"
@.str.1 = [4 x i8] c"bai\00"
@.str.2 = [4 x i8] c"tbi\00"
@.str.3 = [5 x i8] c"crai\00"
@.str.4 = [8 x i8] c"unknown\00"
define i8* @idx_format_name(i32 %0) {
%2 = alloca i8*
%3 = alloca i32
store i32 %0, i32* %3
%4 = load i32, i32* %3
switch i32 %4, label %9 [
i32 0, label %5
i32 1, label %6
i32 2, label %7
i32 3, label %8
]
5: ; preds = %1
store i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str, i64 0, i64 0), i8** %2
br label %10
6: ; preds = %1
store i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str.1, i64 0, i64 0), i8** %2
br label %10
7: ; preds = %1
store i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str.2, i64 0, i64 0), i8** %2
br label %10
8: ; preds = %1
store i8* getelementptr inbounds ([5 x i8], [5 x i8]* @.str.3, i64 0, i64 0), i8** %2
br label %10
9: ; preds = %1
store i8* getelementptr inbounds ([8 x i8], [8 x i8]* @.str.4, i64 0, i64 0), i8** %2
br label %10
10: ; preds = %9, %8, %7, %6, %5
%11 = load i8*, i8** %2
ret i8* %11
}

LLVM IR (-O2):
@.str = [4 x i8] c"csi\00"
@.str.1 = [4 x i8] c"bai\00"
@.str.2 = [4 x i8] c"tbi\00"
@.str.3 = [5 x i8] c"crai\00"
@.str.4 = [8 x i8] c"unknown\00"
@reltable.idx_format_name = [4 x i32] [i32 trunc (i64 sub (i64 ptrtoint ([4 x i8]* @.str to i64), i64 ptrtoint ([4 x i32]* @reltable.idx_format_name to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([4 x i8]* @.str.1 to i64), i64 ptrtoint ([4 x i32]* @reltable.idx_format_name to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([4 x i8]* @.str.2 to i64), i64 ptrtoint ([4 x i32]* @reltable.idx_format_name to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([5 x i8]* @.str.3 to i64), i64 ptrtoint ([4 x i32]* @reltable.idx_format_name to i64)) to i32)]
define i8* @idx_format_name(i32 %0) {
%2 = icmp ult i32 %0, 4
br i1 %2, label %3, label %7
3: ; preds = %1
%4 = sext i32 %0 to i64
%5 = shl i64 %4, 2
%6 = call i8* @llvm.load.relative.i64(i8* bitcast ([4 x i32]* @reltable.idx_format_name 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
}