[PATCH] D33311: [X86] Match bitcast of vsetcc to pmovmsk

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon added inline comments.


================
Comment at: lib/Target/X86/X86ISelLowering.cpp:29020
+  // vxi1 types.
+  if (!LegalTypes && N0.getOpcode() == ISD::SETCC)
+    if (SDValue V = combineBitcastOfSetCC(DAG, SDLoc(N), VT, N0, Subtarget))
----------------
zvi wrote:
> delena wrote:
> > zvi wrote:
> > > delena wrote:
> > > > Can you use if (VT.isInteger() && DAG.ComputeNumSignBits(N) == EltBits) ?
> > > i didn't understand the question. Can you please explain this point?
> > ISD::SETCC is a private case when you know about all-ones or all-zeroes.  DAG.ComputeNumSignBits(N) == EltBits is more general.
> That's a good idea. Do you have an example of such a case?
> 
combineVectorSignBitsTruncation should be a good example - it started with using the 'all bits' of a comparison result and was generalised to use  DAG.ComputeNumSignBits later on


https://reviews.llvm.org/D33311