const char *runcmd_strerror(int code) {
  switch (code) {
  case (-1):
    return "pipe() or open() failed";
  case (-2):
    return "memory allocation failed";
  case (-3):
    return "command too complicated";
  case (-4):
    return "failed to fork()";
  case (-5):
    return "invalid parameters";
  case (-6):
    return "wait() failed";
  }
  return "unknown";
}


x86 assembly (clang, -O0):
<runcmd_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    $0x5,%eax
ja     1190 <runcmd_strerror+0x90>
mov    -0x18(%rbp),%rax
lea    0xed9(%rip),%rcx
movslq (%rcx,%rax,4),%rax
add    %rcx,%rax
jmp    *%rax
lea    0xee1(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    119b <runcmd_strerror+0x9b>
lea    0xee9(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    119b <runcmd_strerror+0x9b>
lea    0xef2(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    119b <runcmd_strerror+0x9b>
lea    0xefa(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    119b <runcmd_strerror+0x9b>
lea    0xefb(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    119b <runcmd_strerror+0x9b>
lea    0xefe(%rip),%rax
mov    %rax,-0x8(%rbp)
jmp    119b <runcmd_strerror+0x9b>
lea    0xefc(%rip),%rax
mov    %rax,-0x8(%rbp)
mov    -0x8(%rbp),%rax
pop    %rbp
ret

x86 assembly (clang, -O2):
<runcmd_strerror>:
cmp    $0xfffffffa,%edi
jb     111a <runcmd_strerror+0x1a>
add    $0x6,%edi
movslq %edi,%rax
lea    0xf72(%rip),%rcx
movslq (%rcx,%rax,4),%rax
add    %rcx,%rax
ret
lea    0xf5a(%rip),%rax
ret

LLVM IR (-O0):
@.str = [24 x i8] c"pipe() or open() failed\00"
@.str.1 = [25 x i8] c"memory allocation failed\00"
@.str.2 = [24 x i8] c"command too complicated\00"
@.str.3 = [17 x i8] c"failed to fork()\00"
@.str.4 = [19 x i8] c"invalid parameters\00"
@.str.5 = [14 x i8] c"wait() failed\00"
@.str.6 = [8 x i8] c"unknown\00"
define i8* @runcmd_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 -1, label %5
i32 -2, label %6
i32 -3, label %7
i32 -4, label %8
i32 -5, label %9
i32 -6, label %10
]
5: ; preds = %1
store i8* getelementptr inbounds ([24 x i8], [24 x i8]* @.str, i64 0, i64 0), i8** %2
br label %12
6: ; preds = %1
store i8* getelementptr inbounds ([25 x i8], [25 x i8]* @.str.1, i64 0, i64 0), i8** %2
br label %12
7: ; preds = %1
store i8* getelementptr inbounds ([24 x i8], [24 x i8]* @.str.2, i64 0, i64 0), i8** %2
br label %12
8: ; preds = %1
store i8* getelementptr inbounds ([17 x i8], [17 x i8]* @.str.3, i64 0, i64 0), i8** %2
br label %12
9: ; preds = %1
store i8* getelementptr inbounds ([19 x i8], [19 x i8]* @.str.4, i64 0, i64 0), i8** %2
br label %12
10: ; preds = %1
store i8* getelementptr inbounds ([14 x i8], [14 x i8]* @.str.5, i64 0, i64 0), i8** %2
br label %12
11: ; preds = %1
store i8* getelementptr inbounds ([8 x i8], [8 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 = [24 x i8] c"pipe() or open() failed\00"
@.str.1 = [25 x i8] c"memory allocation failed\00"
@.str.2 = [24 x i8] c"command too complicated\00"
@.str.3 = [17 x i8] c"failed to fork()\00"
@.str.4 = [19 x i8] c"invalid parameters\00"
@.str.5 = [14 x i8] c"wait() failed\00"
@.str.6 = [8 x i8] c"unknown\00"
@reltable.runcmd_strerror = [6 x i32] [i32 trunc (i64 sub (i64 ptrtoint ([14 x i8]* @.str.5 to i64), i64 ptrtoint ([6 x i32]* @reltable.runcmd_strerror to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([19 x i8]* @.str.4 to i64), i64 ptrtoint ([6 x i32]* @reltable.runcmd_strerror to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([17 x i8]* @.str.3 to i64), i64 ptrtoint ([6 x i32]* @reltable.runcmd_strerror to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([24 x i8]* @.str.2 to i64), i64 ptrtoint ([6 x i32]* @reltable.runcmd_strerror to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([25 x i8]* @.str.1 to i64), i64 ptrtoint ([6 x i32]* @reltable.runcmd_strerror to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([24 x i8]* @.str to i64), i64 ptrtoint ([6 x i32]* @reltable.runcmd_strerror to i64)) to i32)]
define i8* @runcmd_strerror(i32 %0) {
%2 = icmp ugt i32 %0, -7
br i1 %2, label %3, label %8
3: ; preds = %1
%4 = add i32 %0, 6
%5 = sext i32 %4 to i64
%6 = shl i64 %5, 2
%7 = call i8* @llvm.load.relative.i64(i8* bitcast ([6 x i32]* @reltable.runcmd_strerror to i8*), i64 %6)
br label %8
8: ; preds = %1, %3
%9 = phi i8* [ %7, %3 ], [ getelementptr inbounds ([8 x i8], [8 x i8]* @.str.6, i64 0, i64 0), %1 ]
ret i8* %9
}