Revert "[x86] fold vector (X > -1) & Y to shift+andn"

Authored by hans on Mon, Nov 15, 3:07 AM.


Revert "[x86] fold vector (X > -1) & Y to shift+andn"

This casued assertion failures:

void llvm::SelectionDAG::ReplaceAllUsesWith(llvm::SDNode *, llvm::SDNode *):
Assertion `(!From->hasAnyUseOfValue(i) || From->getValueType(i) == To->getValueType(i))
&& "Cannot use this version of ReplaceAllUsesWith!"' failed.

See comment on the code review.

(Had to update some expectations in test/CodeGen/X86/vselect-zero.ll
manually due to other changes having landed after the reverted one.)

and (pcmpgt X, -1), Y --> pandn (vsrai X, BitWidth-1), Y

This avoids the -1 constant vector in favor of an arithmetic shift
instruction if it exists (the ISA is still not complete after all
these years...).

We catch this pattern late in combining by matching PCMPGT, so it
should not interfere with more general folds.

Differential Revision: https://reviews.llvm.org/D113603

This reverts commit bf5748a1af0d2f6f9396d9dc6ac89d15de41eee7.