const char *exception_mnemonic(int vector) {
  switch (vector) {
  case 0:
    return "#DE";
  case 1:
    return "#DB";
  case 2:
    return "#NMI";
  case 3:
    return "#BP";
  case 4:
    return "#OF";
  case 5:
    return "#BR";
  case 6:
    return "#UD";
  case 7:
    return "#NM";
  case 8:
    return "#DF";
  case 10:
    return "#TS";
  case 11:
    return "#NP";
  case 12:
    return "#SS";
  case 13:
    return "#GP";
  case 14:
    return "#PF";
  case 16:
    return "#MF";
  case 17:
    return "#AC";
  case 18:
    return "#MC";
  case 19:
    return "#XM";
  default:
    return "#??";
  }
}


x86 assembly (clang, -O0):
<exception_mnemonic>:
push   %rbp
mov    %rsp,%rbp
mov    %edi,-0xc(%rbp)
mov    -0xc(%rbp),%eax
mov    %rax,-0x18(%rbp)
sub    $0x13,%rax
ja     124c <exception_mnemonic+0x14c>
mov    -0x18(%rbp),%rax
lea    0xedd(%rip),%rcx
movslq (%rcx,%rax,4),%rax
add    %rcx,%rax
jmp    *%rax
lea    0xf1d(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1257 <exception_mnemonic+0x157>
lea    0xf11(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1257 <exception_mnemonic+0x157>
lea    0xf05(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1257 <exception_mnemonic+0x157>
lea    0xefa(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1257 <exception_mnemonic+0x157>
lea    0xeee(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1257 <exception_mnemonic+0x157>
lea    0xee2(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1257 <exception_mnemonic+0x157>
lea    0xed6(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1257 <exception_mnemonic+0x157>
lea    0xeca(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1257 <exception_mnemonic+0x157>
lea    0xebe(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1257 <exception_mnemonic+0x157>
lea    0xeb2(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1257 <exception_mnemonic+0x157>
lea    0xea6(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1257 <exception_mnemonic+0x157>
lea    0xe9a(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1257 <exception_mnemonic+0x157>
lea    0xe8e(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1257 <exception_mnemonic+0x157>
lea    0xe82(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1257 <exception_mnemonic+0x157>
lea    0xe76(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1257 <exception_mnemonic+0x157>
lea    0xe6a(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1257 <exception_mnemonic+0x157>
lea    0xe5e(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1257 <exception_mnemonic+0x157>
lea    0xe52(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1257 <exception_mnemonic+0x157>
lea    0xe46(%rip),%rax
mov    %rax,-0x8(%rbp)
mov    -0x8(%rbp),%rax
pop    %rbp
ret

x86 assembly (clang, -O2):
<exception_mnemonic>:
cmp    $0x13,%edi
ja     1117 <exception_mnemonic+0x17>
movslq %edi,%rax
lea    0xf41(%rip),%rcx
movslq (%rcx,%rax,4),%rax
add    %rcx,%rax
ret
lea    0xf2b(%rip),%rax
ret

LLVM IR (-O0):
@.str = [4 x i8] c"#DE\00"
@.str.1 = [4 x i8] c"#DB\00"
@.str.2 = [5 x i8] c"#NMI\00"
@.str.3 = [4 x i8] c"#BP\00"
@.str.4 = [4 x i8] c"#OF\00"
@.str.5 = [4 x i8] c"#BR\00"
@.str.6 = [4 x i8] c"#UD\00"
@.str.7 = [4 x i8] c"#NM\00"
@.str.8 = [4 x i8] c"#DF\00"
@.str.9 = [4 x i8] c"#TS\00"
@.str.10 = [4 x i8] c"#NP\00"
@.str.11 = [4 x i8] c"#SS\00"
@.str.12 = [4 x i8] c"#GP\00"
@.str.13 = [4 x i8] c"#PF\00"
@.str.14 = [4 x i8] c"#MF\00"
@.str.15 = [4 x i8] c"#AC\00"
@.str.16 = [4 x i8] c"#MC\00"
@.str.17 = [4 x i8] c"#XM\00"
@.str.18 = [4 x i8] c"#??\00"
define i8* @exception_mnemonic(i32 %0) {
%2 = alloca i8*
%3 = alloca i32
store i32 %0, i32* %3
%4 = load i32, i32* %3
switch i32 %4, label %23 [
i32 0, label %5
i32 1, label %6
i32 2, label %7
i32 3, label %8
i32 4, label %9
i32 5, label %10
i32 6, label %11
i32 7, label %12
i32 8, label %13
i32 10, label %14
i32 11, label %15
i32 12, label %16
i32 13, label %17
i32 14, label %18
i32 16, label %19
i32 17, label %20
i32 18, label %21
i32 19, label %22
]
5: ; preds = %1
store i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str, i64 0, i64 0), i8** %2
br label %24
6: ; preds = %1
store i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str.1, i64 0, i64 0), i8** %2
br label %24
7: ; preds = %1
store i8* getelementptr inbounds ([5 x i8], [5 x i8]* @.str.2, i64 0, i64 0), i8** %2
br label %24
8: ; preds = %1
store i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str.3, i64 0, i64 0), i8** %2
br label %24
9: ; preds = %1
store i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str.4, i64 0, i64 0), i8** %2
br label %24
10: ; preds = %1
store i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str.5, i64 0, i64 0), i8** %2
br label %24
11: ; preds = %1
store i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str.6, i64 0, i64 0), i8** %2
br label %24
12: ; preds = %1
store i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str.7, i64 0, i64 0), i8** %2
br label %24
13: ; preds = %1
store i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str.8, i64 0, i64 0), i8** %2
br label %24
14: ; preds = %1
store i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str.9, i64 0, i64 0), i8** %2
br label %24
15: ; preds = %1
store i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str.10, i64 0, i64 0), i8** %2
br label %24
16: ; preds = %1
store i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str.11, i64 0, i64 0), i8** %2
br label %24
17: ; preds = %1
store i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str.12, i64 0, i64 0), i8** %2
br label %24
18: ; preds = %1
store i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str.13, i64 0, i64 0), i8** %2
br label %24
19: ; preds = %1
store i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str.14, i64 0, i64 0), i8** %2
br label %24
20: ; preds = %1
store i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str.15, i64 0, i64 0), i8** %2
br label %24
21: ; preds = %1
store i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str.16, i64 0, i64 0), i8** %2
br label %24
22: ; preds = %1
store i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str.17, i64 0, i64 0), i8** %2
br label %24
23: ; preds = %1
store i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str.18, i64 0, i64 0), i8** %2
br label %24
24: ; preds = %23, %22, %21, %20, %19, %18, %17, %16, %15, %14, %13, %12, %11, %10, %9, %8, %7, %6, %5
%25 = load i8*, i8** %2
ret i8* %25
}

LLVM IR (-O2):
@.str = [4 x i8] c"#DE\00"
@.str.1 = [4 x i8] c"#DB\00"
@.str.2 = [5 x i8] c"#NMI\00"
@.str.3 = [4 x i8] c"#BP\00"
@.str.4 = [4 x i8] c"#OF\00"
@.str.5 = [4 x i8] c"#BR\00"
@.str.6 = [4 x i8] c"#UD\00"
@.str.7 = [4 x i8] c"#NM\00"
@.str.8 = [4 x i8] c"#DF\00"
@.str.9 = [4 x i8] c"#TS\00"
@.str.10 = [4 x i8] c"#NP\00"
@.str.11 = [4 x i8] c"#SS\00"
@.str.12 = [4 x i8] c"#GP\00"
@.str.13 = [4 x i8] c"#PF\00"
@.str.14 = [4 x i8] c"#MF\00"
@.str.15 = [4 x i8] c"#AC\00"
@.str.16 = [4 x i8] c"#MC\00"
@.str.17 = [4 x i8] c"#XM\00"
@.str.18 = [4 x i8] c"#??\00"
@reltable.exception_mnemonic = [20 x i32] [i32 trunc (i64 sub (i64 ptrtoint ([4 x i8]* @.str to i64), i64 ptrtoint ([20 x i32]* @reltable.exception_mnemonic to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([4 x i8]* @.str.1 to i64), i64 ptrtoint ([20 x i32]* @reltable.exception_mnemonic to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([5 x i8]* @.str.2 to i64), i64 ptrtoint ([20 x i32]* @reltable.exception_mnemonic to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([4 x i8]* @.str.3 to i64), i64 ptrtoint ([20 x i32]* @reltable.exception_mnemonic to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([4 x i8]* @.str.4 to i64), i64 ptrtoint ([20 x i32]* @reltable.exception_mnemonic to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([4 x i8]* @.str.5 to i64), i64 ptrtoint ([20 x i32]* @reltable.exception_mnemonic to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([4 x i8]* @.str.6 to i64), i64 ptrtoint ([20 x i32]* @reltable.exception_mnemonic to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([4 x i8]* @.str.7 to i64), i64 ptrtoint ([20 x i32]* @reltable.exception_mnemonic to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([4 x i8]* @.str.8 to i64), i64 ptrtoint ([20 x i32]* @reltable.exception_mnemonic to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([4 x i8]* @.str.18 to i64), i64 ptrtoint ([20 x i32]* @reltable.exception_mnemonic to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([4 x i8]* @.str.9 to i64), i64 ptrtoint ([20 x i32]* @reltable.exception_mnemonic to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([4 x i8]* @.str.10 to i64), i64 ptrtoint ([20 x i32]* @reltable.exception_mnemonic to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([4 x i8]* @.str.11 to i64), i64 ptrtoint ([20 x i32]* @reltable.exception_mnemonic to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([4 x i8]* @.str.12 to i64), i64 ptrtoint ([20 x i32]* @reltable.exception_mnemonic to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([4 x i8]* @.str.13 to i64), i64 ptrtoint ([20 x i32]* @reltable.exception_mnemonic to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([4 x i8]* @.str.18 to i64), i64 ptrtoint ([20 x i32]* @reltable.exception_mnemonic to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([4 x i8]* @.str.14 to i64), i64 ptrtoint ([20 x i32]* @reltable.exception_mnemonic to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([4 x i8]* @.str.15 to i64), i64 ptrtoint ([20 x i32]* @reltable.exception_mnemonic to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([4 x i8]* @.str.16 to i64), i64 ptrtoint ([20 x i32]* @reltable.exception_mnemonic to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([4 x i8]* @.str.17 to i64), i64 ptrtoint ([20 x i32]* @reltable.exception_mnemonic to i64)) to i32)]
define i8* @exception_mnemonic(i32 %0) {
%2 = icmp ult i32 %0, 20
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 ([20 x i32]* @reltable.exception_mnemonic to i8*), i64 %5)
br label %7
7: ; preds = %1, %3
%8 = phi i8* [ %6, %3 ], [ getelementptr inbounds ([4 x i8], [4 x i8]* @.str.18, i64 0, i64 0), %1 ]
ret i8* %8
}