simplification to HClampToUint8

simplification to HClampToUint8

* src/hydrogen-instructions.h (HClampToUint8): Don't mark as having
  flexible representation; instead the output is always an Integer32.
  There is no input representation restriction, so we can still perform
  input-specific truncation.

I tested by looking at the --print-code of

var a = PixelArray(1000000)
function fill(a,x) { for (var i=0; i<a.len; i++) a[i] = x; }

Seems to optimize fine both for double and integer inputs.  But perhaps
there is a better test, for which the original code does better, and
this is a bogus patch.

Committed: http://code.google.com/p/v8/source/detail?r=8650

[wingo, 2011-07-13 17:19:31]

I'm not sure about this one, but the old code wasn't clear either and had a
TODO.

[danno, 2011-07-14 08:46:36]

LGTM.

This is the right approach. It is in fact what HToInt32 does, which serves a
similar purpose.

[wingo, 2011-07-14 15:55:59]

Thanks for the review.  It need a commiter to land, at your leisure.

[wingo, 2011-07-14 16:10:14]

I see now that you had already landed it; thanks!  Apologies for the noise.