const char *rumavl_strerror(int errno) {
  switch (errno) {
  case 0:
    return "Operation successful";
  case (-1):
    return "Invalid argument to function";
  case (-2):
    return "Insufficient memory to complete operation";
  case (-3):
    return "Entry does not exist";
  case (-5):
    return "No more entries in range";
  case (-6):
    return "Entry already exists";
  }
  return "UNKNOWN ERROR";
}


x86 assembly (clang, -O0):
<rumavl_strerror>:
push   %rbp
mov    %rsp,%rbp
mov    %edi,-0xc(%rbp)
mov    -0xc(%rbp),%eax
add    $0x6,%eax
mov    %eax,%ecx
mov    %rcx,-0x18(%rbp)
sub    $0x6,%eax
ja     1190 <rumavl_strerror+0x90>
mov    -0x18(%rbp),%rax
lea    0xed9(%rip),%rcx
movslq (%rcx,%rax,4),%rax
add    %rcx,%rax
jmp    *%rax
lea    0xee5(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    119b <rumavl_strerror+0x9b>
lea    0xeea(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    119b <rumavl_strerror+0x9b>
lea    0xef7(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    119b <rumavl_strerror+0x9b>
lea    0xf11(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    119b <rumavl_strerror+0x9b>
lea    0xf16(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    119b <rumavl_strerror+0x9b>
lea    0xf1f(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    119b <rumavl_strerror+0x9b>
lea    0xf24(%rip),%rax
mov    %rax,-0x8(%rbp)
mov    -0x8(%rbp),%rax
pop    %rbp
ret

x86 assembly (clang, -O2):
<rumavl_strerror>:
add    $0x6,%edi
cmp    $0x6,%edi
ja     111a <rumavl_strerror+0x1a>
movslq %edi,%rax
lea    0xf9e(%rip),%rcx
movslq (%rcx,%rax,4),%rax
add    %rcx,%rax
ret
lea    0xf7e(%rip),%rax
ret

LLVM IR (-O0):
@.str = [21 x i8] c"Operation successful\00"
@.str.1 = [29 x i8] c"Invalid argument to function\00"
@.str.2 = [42 x i8] c"Insufficient memory to complete operation\00"
@.str.3 = [21 x i8] c"Entry does not exist\00"
@.str.4 = [25 x i8] c"No more entries in range\00"
@.str.5 = [21 x i8] c"Entry already exists\00"
@.str.6 = [14 x i8] c"UNKNOWN ERROR\00"
define i8* @rumavl_strerror(i32 %0) {
%2 = alloca i8*
%3 = alloca i32
store i32 %0, i32* %3
%4 = load i32, i32* %3
switch i32 %4, label %11 [
i32 0, label %5
i32 -1, label %6
i32 -2, label %7
i32 -3, label %8
i32 -5, label %9
i32 -6, label %10
]
5: ; preds = %1
store i8* getelementptr inbounds ([21 x i8], [21 x i8]* @.str, i64 0, i64 0), i8** %2
br label %12
6: ; preds = %1
store i8* getelementptr inbounds ([29 x i8], [29 x i8]* @.str.1, i64 0, i64 0), i8** %2
br label %12
7: ; preds = %1
store i8* getelementptr inbounds ([42 x i8], [42 x i8]* @.str.2, i64 0, i64 0), i8** %2
br label %12
8: ; preds = %1
store i8* getelementptr inbounds ([21 x i8], [21 x i8]* @.str.3, i64 0, i64 0), i8** %2
br label %12
9: ; preds = %1
store i8* getelementptr inbounds ([25 x i8], [25 x i8]* @.str.4, i64 0, i64 0), i8** %2
br label %12
10: ; preds = %1
store i8* getelementptr inbounds ([21 x i8], [21 x i8]* @.str.5, i64 0, i64 0), i8** %2
br label %12
11: ; preds = %1
store i8* getelementptr inbounds ([14 x i8], [14 x i8]* @.str.6, i64 0, i64 0), i8** %2
br label %12
12: ; preds = %11, %10, %9, %8, %7, %6, %5
%13 = load i8*, i8** %2
ret i8* %13
}

LLVM IR (-O2):
@.str = [21 x i8] c"Operation successful\00"
@.str.1 = [29 x i8] c"Invalid argument to function\00"
@.str.2 = [42 x i8] c"Insufficient memory to complete operation\00"
@.str.3 = [21 x i8] c"Entry does not exist\00"
@.str.4 = [25 x i8] c"No more entries in range\00"
@.str.5 = [21 x i8] c"Entry already exists\00"
@.str.6 = [14 x i8] c"UNKNOWN ERROR\00"
@reltable.rumavl_strerror = [7 x i32] [i32 trunc (i64 sub (i64 ptrtoint ([21 x i8]* @.str.5 to i64), i64 ptrtoint ([7 x i32]* @reltable.rumavl_strerror to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([25 x i8]* @.str.4 to i64), i64 ptrtoint ([7 x i32]* @reltable.rumavl_strerror to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([14 x i8]* @.str.6 to i64), i64 ptrtoint ([7 x i32]* @reltable.rumavl_strerror to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([21 x i8]* @.str.3 to i64), i64 ptrtoint ([7 x i32]* @reltable.rumavl_strerror to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([42 x i8]* @.str.2 to i64), i64 ptrtoint ([7 x i32]* @reltable.rumavl_strerror to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([29 x i8]* @.str.1 to i64), i64 ptrtoint ([7 x i32]* @reltable.rumavl_strerror to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([21 x i8]* @.str to i64), i64 ptrtoint ([7 x i32]* @reltable.rumavl_strerror to i64)) to i32)]
define i8* @rumavl_strerror(i32 %0) {
%2 = add i32 %0, 6
%3 = icmp ult i32 %2, 7
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 ([7 x i32]* @reltable.rumavl_strerror to i8*), i64 %6)
br label %8
8: ; preds = %1, %4
%9 = phi i8* [ %7, %4 ], [ getelementptr inbounds ([14 x i8], [14 x i8]* @.str.6, i64 0, i64 0), %1 ]
ret i8* %9
}