[llvm] [SelectionDAG] Add computeKnownBits support for ISD::STEP_VECTOR (PR #80452)
Luke Lau via llvm-commits
llvm-commits at lists.llvm.org
Fri Feb 2 09:32:55 PST 2024
================
@@ -3110,6 +3110,19 @@ KnownBits SelectionDAG::computeKnownBits(SDValue Op, const APInt &DemandedElts,
}
break;
}
+ case ISD::STEP_VECTOR: {
+ const APInt &Step = Op.getConstantOperandAPInt(0);
+
+ if (Step.isPowerOf2())
+ Known.Zero.setLowBits(Step.logBase2());
+
+ const Function &F = getMachineFunction().getFunction();
+ const APInt MaxNumElts = getVScaleRange(&F, BitWidth).getUnsignedMax() *
----------------
lukel97 wrote:
Yeah, I did a quick check that * does indeed perform wrapping. But forgot to actually bail if it overflows.
https://github.com/llvm/llvm-project/pull/80452
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