[X86] LowerStore - always split 512-bit concatenated stores (#143426)

All BWI regressions have now been addressed, so remove the special case
handling.

Author: RKSimon

llvm/lib/Target/X86/X86ISelLowering.cpp

@@ -25549,14 +25549,12 @@ static SDValue LowerStore(SDValue Op, const X86Subtarget &Subtarget,
   if (St->isTruncatingStore())
     return SDValue();
 
-  // If this is a 256-bit store of concatenated ops, we are better off splitting
-  // that store into two 128-bit stores. This avoids spurious use of 256-bit ops
-  // and each half can execute independently. Some cores would split the op into
-  // halves anyway, so the concat (vinsertf128) is purely an extra op.
+  // If this is a 256/512-bit store of concatenated ops, we are better off
+  // splitting that store into two half-size stores. This avoids spurious use of
+  // concatenated ops and each half can execute independently. Some cores would
+  // split the op into halves anyway, so the concat is purely an extra op.
   MVT StoreVT = StoredVal.getSimpleValueType();
-  if (StoreVT.is256BitVector() ||
-      ((StoreVT == MVT::v32i16 || StoreVT == MVT::v64i8) &&
-       !Subtarget.hasBWI())) {
+  if (StoreVT.is256BitVector() || StoreVT.is512BitVector()) {
     if (StoredVal.hasOneUse() && isFreeToSplitVector(StoredVal, DAG))
       return splitVectorStore(St, DAG);
     return SDValue();