[llvm] [X86][AVX] Match v4f64 blend from shuffle of scalar values. (PR #135753)

[Simon Pilgrim via llvm-commits]

================
@@ -9040,6 +9040,39 @@ X86TargetLowering::LowerBUILD_VECTOR(SDValue Op, SelectionDAG &DAG) const {
   MVT OpEltVT = Op.getOperand(0).getSimpleValueType();
   unsigned NumElems = Op.getNumOperands();
 
+  // Match BUILD_VECTOR of scalars that we can lower to X86ISD::BLENDI via
+  // shuffles.
----------------
RKSimon wrote:

Needs to be put in a helper method - similar to lowerBuildVectorAsBroadcast

https://github.com/llvm/llvm-project/pull/135753