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[TargetLowering] SimplifyDemandedBits - just call computeKnownBits for BUILD_VECTOR cases.

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Don't do this locally, computeKnownBits does this better (and can handle non-constant cases as well).

A next step would be to actually simplify non-constant elements - building on what we already do in SimplifyDemandedVectorElts.

llvm-svn: 365309
This commit is contained in:
Simon Pilgrim 2019-07-08 11:00:39 +00:00
parent 2b509d6922
commit 3a3945c8c9
1 changed files with 3 additions and 23 deletions
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26
lib/CodeGen/SelectionDAG/TargetLowering.cpp
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@ -639,29 +639,9 @@ bool TargetLowering::SimplifyDemandedBits(
break;
}
case ISD::BUILD_VECTOR:
// Collect the known bits that are shared by every constant vector element.
Known.Zero.setAllBits(); Known.One.setAllBits();
for (SDValue SrcOp : Op->ops()) {
if (!isa<ConstantSDNode>(SrcOp)) {
// We can only handle all constant values - bail out with no known bits.
Known = KnownBits(BitWidth);
return false;
}
Known2.One = cast<ConstantSDNode>(SrcOp)->getAPIntValue();
Known2.Zero = ~Known2.One;
// BUILD_VECTOR can implicitly truncate sources, we must handle this.
if (Known2.One.getBitWidth() != BitWidth) {
assert(Known2.getBitWidth() > BitWidth &&
"Expected BUILD_VECTOR implicit truncation");
Known2 = Known2.trunc(BitWidth);
}
// Known bits are the values that are shared by every element.
// TODO: support per-element known bits.
Known.One &= Known2.One;
Known.Zero &= Known2.Zero;
}
// Collect the known bits that are shared by every demanded element.
// TODO: Call SimplifyDemandedBits for non-constant demanded elements.
Known = TLO.DAG.computeKnownBits(Op, DemandedElts, Depth);
return false; // Don't fall through, will infinitely loop.
case ISD::LOAD: {
LoadSDNode *LD = cast<LoadSDNode>(Op);