[PATCH] D87883: [X86] Add support for calling SimplifyDemandedBits on the input of PDEP with a constant mask.

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon accepted this revision.
RKSimon added a comment.
This revision is now accepted and ready to land.

LGTM - the logic makes sense to me - maybe add equivalent code into X86TTIImpl::simplifyDemandedUseBitsIntrinsic ? We already have pdep/pext constant folding support in instcombine



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Comment at: llvm/lib/Target/X86/X86ISelLowering.cpp:34039
+    // operand since bits can only map to the same or higher bit position.
+    Known.Zero.setLowBits(Known2.countMinTrailingZeros());
+    break;
----------------
It might be worth moving this into a KnownBits::DepositBits helper - IIRC RISCV has a similar instruction being finalised - maybe also move the instcombine constant folding handling into APInt ?


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