[llvm] [SLP][REVEC] Make ShuffleCostEstimator and ShuffleInstructionBuilder can vectorize vector instructions. (PR #99499)

[Han-Kuan Chen via llvm-commits]

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@@ -11641,10 +11642,20 @@ Value *BoUpSLP::gather(ArrayRef<Value *> VL, Value *Root, Type *ScalarTy) {
           V, Ty, !isKnownNonNegative(Scalar, SimplifyQuery(*DL)));
     }
 
-    Vec = Builder.CreateInsertElement(Vec, Scalar, Builder.getInt32(Pos));
-    auto *InsElt = dyn_cast<InsertElementInst>(Vec);
-    if (!InsElt)
-      return Vec;
+    Instruction *InsElt;
+    if (auto *VecTy = dyn_cast<FixedVectorType>(Scalar->getType())) {
+      Vec = InsElt = Builder.CreateInsertVector(
+          Vec->getType(), Vec, V,
+          Builder.getInt64(Pos * VecTy->getNumElements()));
+      auto *II = dyn_cast<IntrinsicInst>(InsElt);
+      if (!(II && II->getIntrinsicID() == Intrinsic::vector_insert))
+        return Vec;
+    } else {
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HanKuanChen wrote:

The else is for `FixedVectorType`. Or are you saying that it always returns `Intrinsic::vector_insert`?

https://github.com/llvm/llvm-project/pull/99499