const char *is_entity(char c) {
  switch (c) {
  case '"':
    return ("&quot;");
  case '\'':
    return ("&apos;");
  case '&':
    return ("&amp;");
  case '<':
    return ("&lt;");
  case '>':
    return ("&gt;");
  }
  return 0;
}


x86 assembly (clang, -O0):
<is_entity>:
push   %rbp
mov    %rsp,%rbp
mov    %dil,%al
mov    %al,-0x9(%rbp)
movsbl -0x9(%rbp),%eax
add    $0xffffffde,%eax
mov    %eax,%ecx
mov    %rcx,-0x18(%rbp)
sub    $0x1c,%eax
ja     1184 <is_entity+0x84>
mov    -0x18(%rbp),%rax
lea    0xed5(%rip),%rcx
movslq (%rcx,%rax,4),%rax
add    %rcx,%rax
jmp    *%rax
lea    0xf39(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    118c <is_entity+0x8c>
lea    0xf30(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    118c <is_entity+0x8c>
lea    0xf27(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    118c <is_entity+0x8c>
lea    0xf1d(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    118c <is_entity+0x8c>
lea    0xf12(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    118c <is_entity+0x8c>
movq   $0x0,-0x8(%rbp)
mov    -0x8(%rbp),%rax
pop    %rbp
ret

x86 assembly (clang, -O2):
<is_entity>:
add    $0xffffffde,%edi
cmp    $0x1c,%edi
ja     1127 <is_entity+0x27>
lea    0xf65(%rip),%rax
lea    0xeea(%rip),%rcx
movslq (%rcx,%rdi,4),%rdx
add    %rcx,%rdx
jmp    *%rdx
lea    0xf5c(%rip),%rax
ret
xor    %eax,%eax
ret
lea    0xf4a(%rip),%rax
ret
lea    0xf4f(%rip),%rax
ret
lea    0xf4c(%rip),%rax
ret

LLVM IR (-O0):
@.str = [7 x i8] c"&quot;\00"
@.str.1 = [7 x i8] c"&apos;\00"
@.str.2 = [6 x i8] c"&amp;\00"
@.str.3 = [5 x i8] c"&lt;\00"
@.str.4 = [5 x i8] c"&gt;\00"
define i8* @is_entity(i8 signext %0) {
%2 = alloca i8*
%3 = alloca i8
store i8 %0, i8* %3
%4 = load i8, i8* %3
%5 = sext i8 %4 to i32
switch i32 %5, label %11 [
i32 34, label %6
i32 39, label %7
i32 38, label %8
i32 60, label %9
i32 62, label %10
]
6: ; preds = %1
store i8* getelementptr inbounds ([7 x i8], [7 x i8]* @.str, i64 0, i64 0), i8** %2
br label %12
7: ; preds = %1
store i8* getelementptr inbounds ([7 x i8], [7 x i8]* @.str.1, i64 0, i64 0), i8** %2
br label %12
8: ; preds = %1
store i8* getelementptr inbounds ([6 x i8], [6 x i8]* @.str.2, i64 0, i64 0), i8** %2
br label %12
9: ; preds = %1
store i8* getelementptr inbounds ([5 x i8], [5 x i8]* @.str.3, i64 0, i64 0), i8** %2
br label %12
10: ; preds = %1
store i8* getelementptr inbounds ([5 x i8], [5 x i8]* @.str.4, i64 0, i64 0), i8** %2
br label %12
11: ; preds = %1
store i8* null, i8** %2
br label %12
12: ; preds = %11, %10, %9, %8, %7, %6
%13 = load i8*, i8** %2
ret i8* %13
}

LLVM IR (-O2):
@.str = [7 x i8] c"&quot;\00"
@.str.1 = [7 x i8] c"&apos;\00"
@.str.2 = [6 x i8] c"&amp;\00"
@.str.3 = [5 x i8] c"&lt;\00"
@.str.4 = [5 x i8] c"&gt;\00"
define i8* @is_entity(i8 signext %0) {
%2 = sext i8 %0 to i32
switch i32 %2, label %7 [
i32 34, label %8
i32 39, label %3
i32 38, label %4
i32 60, label %5
i32 62, label %6
]
3: ; preds = %1
br label %8
4: ; preds = %1
br label %8
5: ; preds = %1
br label %8
6: ; preds = %1
br label %8
7: ; preds = %1
br label %8
8: ; preds = %1, %7, %6, %5, %4, %3
%9 = phi i8* [ null, %7 ], [ getelementptr inbounds ([5 x i8], [5 x i8]* @.str.4, i64 0, i64 0), %6 ], [ getelementptr inbounds ([5 x i8], [5 x i8]* @.str.3, i64 0, i64 0), %5 ], [ getelementptr inbounds ([6 x i8], [6 x i8]* @.str.2, i64 0, i64 0), %4 ], [ getelementptr inbounds ([7 x i8], [7 x i8]* @.str.1, i64 0, i64 0), %3 ], [ getelementptr inbounds ([7 x i8], [7 x i8]* @.str, i64 0, i64 0), %1 ]
ret i8* %9
}