const char *mpool_strerror(const int error) {
  switch (error) {
  case 1:
    return "no error";
    break;
  case 2:
    return "function argument is null";
    break;
  case 3:
    return "function argument is invalid";
    break;
  case 4:
    return "invalid mpool pointer";
    break;
  case 5:
    return "mpool structure was overwritten";
    break;
  case 6:
    return "could not get system page-size";
    break;
  case 7:
    return "could not open /dev/zero";
    break;
  case 8:
    return "no memory available";
    break;
  case 9:
    return "problems with mmap";
    break;
  case 10:
    return "error processing requested size";
    break;
  case 11:
    return "allocation exceeds pool max size";
    break;
  case 12:
    return "invalid memory address";
    break;
  case 13:
    return "memory lower bounds overwritten";
    break;
  case 14:
    return "memory block not found in pool";
    break;
  case 15:
    return "memory address has already been freed";
    break;
  case 16:
    return "invalid internal block status";
    break;
  case 17:
    return "invalid internal free address";
    break;
  case 18:
    return "sbrk did not return contiguous memory";
    break;
  case 19:
    return "no available pages left in pool";
    break;
  case 20:
    return "system alloc function failed";
    break;
  case 21:
    return "user pointer admin space overwritten";
    break;
  default:
    break;
  }
  return "invalid error code";
}


x86 assembly (clang, -O0):
<mpool_strerror>:
push   %rbp
mov    %rsp,%rbp
mov    %edi,-0xc(%rbp)
mov    -0xc(%rbp),%eax
add    $0xffffffff,%eax
mov    %eax,%ecx
mov    %rcx,-0x18(%rbp)
sub    $0x14,%eax
ja     1280 <mpool_strerror+0x180>
mov    -0x18(%rbp),%rax
lea    0xed9(%rip),%rcx
movslq (%rcx,%rax,4),%rax
add    %rcx,%rax
jmp    *%rax
lea    0xf1d(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1290 <mpool_strerror+0x190>
lea    0xf16(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1290 <mpool_strerror+0x190>
lea    0xf20(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1290 <mpool_strerror+0x190>
lea    0xf2d(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1290 <mpool_strerror+0x190>
lea    0xf33(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1290 <mpool_strerror+0x190>
lea    0xf43(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1290 <mpool_strerror+0x190>
lea    0xf52(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1290 <mpool_strerror+0x190>
lea    0xf5b(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1290 <mpool_strerror+0x190>
lea    0xf5f(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1290 <mpool_strerror+0x190>
lea    0xf62(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1290 <mpool_strerror+0x190>
lea    0xf72(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1290 <mpool_strerror+0x190>
lea    0xf83(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1290 <mpool_strerror+0x190>
lea    0xf8a(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1290 <mpool_strerror+0x190>
lea    0xf9a(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1290 <mpool_strerror+0x190>
lea    0xfa9(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1290 <mpool_strerror+0x190>
lea    0xfbf(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1290 <mpool_strerror+0x190>
lea    0xfcd(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1290 <mpool_strerror+0x190>
lea    0xfdb(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1290 <mpool_strerror+0x190>
lea    0xff1(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1290 <mpool_strerror+0x190>
lea    0x1001(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1290 <mpool_strerror+0x190>
lea    0x100e(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    1290 <mpool_strerror+0x190>
jmp    1285 <mpool_strerror+0x185>
lea    0x101e(%rip),%rax
mov    %rax,-0x8(%rbp)
mov    -0x8(%rbp),%rax
pop    %rbp
ret

x86 assembly (clang, -O2):
<mpool_strerror>:
add    $0xffffffff,%edi
cmp    $0x14,%edi
ja     111a <mpool_strerror+0x1a>
movslq %edi,%rax
lea    0x115a(%rip),%rcx
movslq (%rcx,%rax,4),%rax
add    %rcx,%rax
ret
lea    0x1135(%rip),%rax
ret

LLVM IR (-O0):
@.str = [9 x i8] c"no error\00"
@.str.1 = [26 x i8] c"function argument is null\00"
@.str.2 = [29 x i8] c"function argument is invalid\00"
@.str.3 = [22 x i8] c"invalid mpool pointer\00"
@.str.4 = [32 x i8] c"mpool structure was overwritten\00"
@.str.5 = [31 x i8] c"could not get system page-size\00"
@.str.6 = [25 x i8] c"could not open /dev/zero\00"
@.str.7 = [20 x i8] c"no memory available\00"
@.str.8 = [19 x i8] c"problems with mmap\00"
@.str.9 = [32 x i8] c"error processing requested size\00"
@.str.10 = [33 x i8] c"allocation exceeds pool max size\00"
@.str.11 = [23 x i8] c"invalid memory address\00"
@.str.12 = [32 x i8] c"memory lower bounds overwritten\00"
@.str.13 = [31 x i8] c"memory block not found in pool\00"
@.str.14 = [38 x i8] c"memory address has already been freed\00"
@.str.15 = [30 x i8] c"invalid internal block status\00"
@.str.16 = [30 x i8] c"invalid internal free address\00"
@.str.17 = [38 x i8] c"sbrk did not return contiguous memory\00"
@.str.18 = [32 x i8] c"no available pages left in pool\00"
@.str.19 = [29 x i8] c"system alloc function failed\00"
@.str.20 = [37 x i8] c"user pointer admin space overwritten\00"
@.str.21 = [19 x i8] c"invalid error code\00"
define i8* @mpool_strerror(i32 %0) {
%2 = alloca i8*
%3 = alloca i32
store i32 %0, i32* %3
%4 = load i32, i32* %3
switch i32 %4, label %26 [
i32 1, label %5
i32 2, label %6
i32 3, label %7
i32 4, label %8
i32 5, label %9
i32 6, label %10
i32 7, label %11
i32 8, label %12
i32 9, label %13
i32 10, label %14
i32 11, label %15
i32 12, label %16
i32 13, label %17
i32 14, label %18
i32 15, label %19
i32 16, label %20
i32 17, label %21
i32 18, label %22
i32 19, label %23
i32 20, label %24
i32 21, label %25
]
5: ; preds = %1
store i8* getelementptr inbounds ([9 x i8], [9 x i8]* @.str, i64 0, i64 0), i8** %2
br label %28
6: ; preds = %1
store i8* getelementptr inbounds ([26 x i8], [26 x i8]* @.str.1, i64 0, i64 0), i8** %2
br label %28
7: ; preds = %1
store i8* getelementptr inbounds ([29 x i8], [29 x i8]* @.str.2, i64 0, i64 0), i8** %2
br label %28
8: ; preds = %1
store i8* getelementptr inbounds ([22 x i8], [22 x i8]* @.str.3, i64 0, i64 0), i8** %2
br label %28
9: ; preds = %1
store i8* getelementptr inbounds ([32 x i8], [32 x i8]* @.str.4, i64 0, i64 0), i8** %2
br label %28
10: ; preds = %1
store i8* getelementptr inbounds ([31 x i8], [31 x i8]* @.str.5, i64 0, i64 0), i8** %2
br label %28
11: ; preds = %1
store i8* getelementptr inbounds ([25 x i8], [25 x i8]* @.str.6, i64 0, i64 0), i8** %2
br label %28
12: ; preds = %1
store i8* getelementptr inbounds ([20 x i8], [20 x i8]* @.str.7, i64 0, i64 0), i8** %2
br label %28
13: ; preds = %1
store i8* getelementptr inbounds ([19 x i8], [19 x i8]* @.str.8, i64 0, i64 0), i8** %2
br label %28
14: ; preds = %1
store i8* getelementptr inbounds ([32 x i8], [32 x i8]* @.str.9, i64 0, i64 0), i8** %2
br label %28
15: ; preds = %1
store i8* getelementptr inbounds ([33 x i8], [33 x i8]* @.str.10, i64 0, i64 0), i8** %2
br label %28
16: ; preds = %1
store i8* getelementptr inbounds ([23 x i8], [23 x i8]* @.str.11, i64 0, i64 0), i8** %2
br label %28
17: ; preds = %1
store i8* getelementptr inbounds ([32 x i8], [32 x i8]* @.str.12, i64 0, i64 0), i8** %2
br label %28
18: ; preds = %1
store i8* getelementptr inbounds ([31 x i8], [31 x i8]* @.str.13, i64 0, i64 0), i8** %2
br label %28
19: ; preds = %1
store i8* getelementptr inbounds ([38 x i8], [38 x i8]* @.str.14, i64 0, i64 0), i8** %2
br label %28
20: ; preds = %1
store i8* getelementptr inbounds ([30 x i8], [30 x i8]* @.str.15, i64 0, i64 0), i8** %2
br label %28
21: ; preds = %1
store i8* getelementptr inbounds ([30 x i8], [30 x i8]* @.str.16, i64 0, i64 0), i8** %2
br label %28
22: ; preds = %1
store i8* getelementptr inbounds ([38 x i8], [38 x i8]* @.str.17, i64 0, i64 0), i8** %2
br label %28
23: ; preds = %1
store i8* getelementptr inbounds ([32 x i8], [32 x i8]* @.str.18, i64 0, i64 0), i8** %2
br label %28
24: ; preds = %1
store i8* getelementptr inbounds ([29 x i8], [29 x i8]* @.str.19, i64 0, i64 0), i8** %2
br label %28
25: ; preds = %1
store i8* getelementptr inbounds ([37 x i8], [37 x i8]* @.str.20, i64 0, i64 0), i8** %2
br label %28
26: ; preds = %1
br label %27
27: ; preds = %26
store i8* getelementptr inbounds ([19 x i8], [19 x i8]* @.str.21, i64 0, i64 0), i8** %2
br label %28
28: ; preds = %27, %25, %24, %23, %22, %21, %20, %19, %18, %17, %16, %15, %14, %13, %12, %11, %10, %9, %8, %7, %6, %5
%29 = load i8*, i8** %2
ret i8* %29
}

LLVM IR (-O2):
@.str = [9 x i8] c"no error\00"
@.str.1 = [26 x i8] c"function argument is null\00"
@.str.2 = [29 x i8] c"function argument is invalid\00"
@.str.3 = [22 x i8] c"invalid mpool pointer\00"
@.str.4 = [32 x i8] c"mpool structure was overwritten\00"
@.str.5 = [31 x i8] c"could not get system page-size\00"
@.str.6 = [25 x i8] c"could not open /dev/zero\00"
@.str.7 = [20 x i8] c"no memory available\00"
@.str.8 = [19 x i8] c"problems with mmap\00"
@.str.9 = [32 x i8] c"error processing requested size\00"
@.str.10 = [33 x i8] c"allocation exceeds pool max size\00"
@.str.11 = [23 x i8] c"invalid memory address\00"
@.str.12 = [32 x i8] c"memory lower bounds overwritten\00"
@.str.13 = [31 x i8] c"memory block not found in pool\00"
@.str.14 = [38 x i8] c"memory address has already been freed\00"
@.str.15 = [30 x i8] c"invalid internal block status\00"
@.str.16 = [30 x i8] c"invalid internal free address\00"
@.str.17 = [38 x i8] c"sbrk did not return contiguous memory\00"
@.str.18 = [32 x i8] c"no available pages left in pool\00"
@.str.19 = [29 x i8] c"system alloc function failed\00"
@.str.20 = [37 x i8] c"user pointer admin space overwritten\00"
@.str.21 = [19 x i8] c"invalid error code\00"
@reltable.mpool_strerror = [21 x i32] [i32 trunc (i64 sub (i64 ptrtoint ([9 x i8]* @.str to i64), i64 ptrtoint ([21 x i32]* @reltable.mpool_strerror to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([26 x i8]* @.str.1 to i64), i64 ptrtoint ([21 x i32]* @reltable.mpool_strerror to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([29 x i8]* @.str.2 to i64), i64 ptrtoint ([21 x i32]* @reltable.mpool_strerror to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([22 x i8]* @.str.3 to i64), i64 ptrtoint ([21 x i32]* @reltable.mpool_strerror to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([32 x i8]* @.str.4 to i64), i64 ptrtoint ([21 x i32]* @reltable.mpool_strerror to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([31 x i8]* @.str.5 to i64), i64 ptrtoint ([21 x i32]* @reltable.mpool_strerror to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([25 x i8]* @.str.6 to i64), i64 ptrtoint ([21 x i32]* @reltable.mpool_strerror to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([20 x i8]* @.str.7 to i64), i64 ptrtoint ([21 x i32]* @reltable.mpool_strerror to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([19 x i8]* @.str.8 to i64), i64 ptrtoint ([21 x i32]* @reltable.mpool_strerror to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([32 x i8]* @.str.9 to i64), i64 ptrtoint ([21 x i32]* @reltable.mpool_strerror to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([33 x i8]* @.str.10 to i64), i64 ptrtoint ([21 x i32]* @reltable.mpool_strerror to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([23 x i8]* @.str.11 to i64), i64 ptrtoint ([21 x i32]* @reltable.mpool_strerror to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([32 x i8]* @.str.12 to i64), i64 ptrtoint ([21 x i32]* @reltable.mpool_strerror to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([31 x i8]* @.str.13 to i64), i64 ptrtoint ([21 x i32]* @reltable.mpool_strerror to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([38 x i8]* @.str.14 to i64), i64 ptrtoint ([21 x i32]* @reltable.mpool_strerror to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([30 x i8]* @.str.15 to i64), i64 ptrtoint ([21 x i32]* @reltable.mpool_strerror to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([30 x i8]* @.str.16 to i64), i64 ptrtoint ([21 x i32]* @reltable.mpool_strerror to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([38 x i8]* @.str.17 to i64), i64 ptrtoint ([21 x i32]* @reltable.mpool_strerror to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([32 x i8]* @.str.18 to i64), i64 ptrtoint ([21 x i32]* @reltable.mpool_strerror to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([29 x i8]* @.str.19 to i64), i64 ptrtoint ([21 x i32]* @reltable.mpool_strerror to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([37 x i8]* @.str.20 to i64), i64 ptrtoint ([21 x i32]* @reltable.mpool_strerror to i64)) to i32)]
define i8* @mpool_strerror(i32 %0) {
%2 = add i32 %0, -1
%3 = icmp ult i32 %2, 21
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 ([21 x i32]* @reltable.mpool_strerror to i8*), i64 %6)
br label %8
8: ; preds = %1, %4
%9 = phi i8* [ %7, %4 ], [ getelementptr inbounds ([19 x i8], [19 x i8]* @.str.21, i64 0, i64 0), %1 ]
ret i8* %9
}