[PATCH] D141022: [SelectionDAG] Improve codegen for udiv by constant if any divisors are 1.

[Roman Lebedev via Phabricator via llvm-commits]

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

LG, thanks.
There may be similar opportunity at least in the `urem==C` expansion.

> DAGCombiner is unable to fold srl X, <0, undef> to X

This seems like a somewhat straight-forward missing optimization?
Although, then the second element becomes non-poison in the result.



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Comment at: llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp:6067
+      PostShift = DAG.getConstant(magics.PostShift, dl, ShSVT);
+      NPQFactor = DAG.getConstant(magics.IsAdd ? APInt::getOneBitSet(EltBits, EltBits - 1) : APInt::getZero(EltBits), dl, SVT);
+      UseNPQ |= magics.IsAdd;
----------------
Not clang-formatted


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https://reviews.llvm.org/D141022