[LLVMdev] computeMaskedBitsforTargetNode

Eli Friedman eli.friedman at gmail.com
Thu Nov 20 18:47:21 PST 2008

On Thu, Nov 20, 2008 at 6:19 PM, Villmow, Micah <Micah.Villmow at amd.com> wrote:
> Can someone explain what this function is supposed to do? I've looked at
> PowerPC, Sparc, etc.. and can't really figure out what I should be doing
> here.

It's an optimization: it allows the target-independent passes like
DAGCombine to get information about which bits of a value are known at
compile-time to be set or known to be unset.  The conservative
assumption is that nothing is known, so the default implementation is
always correct.


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