[llvm-commits] [PATCH] Compress Repeated Byte Output

[David A. Greene]

Chris Lattner <clattner at apple.com> writes:

> On Aug 26, 2011, at 10:48 AM, David Greene wrote:
>
>> 
>> Emit a repeated sequence of bytes using .zero.  This saves an enormous
>> amount of asm file space for certain programs.
>> ---
>
> In addition to the return, please remove these two cases, which are handled below with the generic code:
>
> +    if (CI->isZero())
> +      return 0;
> +    if (CI->isAllOnesValue())
> +      return 0xfful;

Ok.  I was trying to speed up common cases.

>
>
> +    uint8_t Byte = Value & 0xffull;
>
> What's up with the ULL suffixes here and UL elsewhere?  Please use
> capital suffixes if you want to keep them.  I'd recommend just
> replacing this with uint8_t(Value) which is more explicit.

ULL because Value is a 64-bit quantity.  But yeah, a cast should work.

> +    if (Size == 1)
> +      return Byte;
>
> Please remove this, it isn't doing anything.

Ok.

> Your ConstantInt handling code still doesn't handle i11's.  You need
> to ensure that we have a multiple of 8 bits and a power of 2 (to avoid
> tail padding being ignored).

Didn't know we have such things.  Will fix.


> +    return Byte;
> +  }
> +  else if 
>
> No need for the else.

Right.

> +  else if (const ConstantArray *CA = dyn_cast<ConstantArray>(V)) {
> +    // Make sure all array elements are sequences of the same repeated
> +    // byte.
> +    int Byte = -1;
> +    for (int i = 0, e = CA->getNumOperands(); i != e; ++i) {
>
> This is awkward.  Just peel off one iteration:

All right.

                             -Dave