[llvm] use multiplication with holes for 32-bit/64-bit clmul fallback (PR #203727)

[Folkert de Vries via llvm-commits]

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@@ -8899,6 +8899,57 @@ SDValue TargetLowering::expandCLMUL(SDNode *Node, SelectionDAG &DAG) const {
     // calculation in BasicTTIImpl::getTypeBasedIntrinsicInstrCost for
     // Intrinsic::clmul.
 
+    // Strategy 4: multiplication with holes.
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folkertdev wrote:

Does it? It's really a scalar implementation that is meant to serve as a better fallback. 

Are there advantages to moving it there?

https://github.com/llvm/llvm-project/pull/203727