[llvm-commits] Patch to safely restore optimization to testcase from PR3225 on x86

[Eli Friedman]

On Thu, Dec 18, 2008 at 5:31 PM, Dan Gohman <gohman at apple.com> wrote:
>  > +  if (KnownZero == VTBits) {
>
> If the shift count is known to be all-zero, shouldn't it
> have been simplified already by pre-legalize DAGCombine,
> if not InstCombine?

The masked bits check is only checking the top bit, i.e. whether the
shift amount is < 32 or >= 32.

-Eli