[llvm] [SLP]Check if masked gather can be emitted as a serie of loads/insert (PR #83481)

[Simon Pilgrim via llvm-commits]

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@@ -4095,6 +4097,78 @@ static LoadsState canVectorizeLoads(ArrayRef<Value *> VL, const Value *VL0,
         }
       }
     }
+    auto CheckForShuffledLoads = [&](Align CommonAlignment) {
+      unsigned Sz = DL.getTypeSizeInBits(ScalarTy);
+      unsigned MinVF = R.getMinVF(Sz);
+      unsigned MaxVF = std::max<unsigned>(bit_floor(VL.size() / 2), MinVF);
+      MaxVF = std::min(R.getMaximumVF(Sz, Instruction::Load), MaxVF);
+      for (unsigned VF = MaxVF; VF >= MinVF; VF /= 2) {
+        unsigned VectorizedCnt = 0;
+        SmallVector<LoadsState> States;
+        for (unsigned Cnt = 0, End = VL.size(); Cnt + VF <= End;
+             Cnt += VF, ++VectorizedCnt) {
+          ArrayRef<Value *> Slice = VL.slice(Cnt, VF);
+          SmallVector<unsigned> Order;
+          SmallVector<Value *> PointerOps;
+          LoadsState LS =
+              canVectorizeLoads(R, Slice, Slice.front(), TTI, DL, SE, LI, TLI,
+                                Order, PointerOps, /*TryRecursiveCheck=*/false);
+          // Check that the sorted loads are consecutive.
+          if (LS == LoadsState::Gather)
+            break;
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RKSimon wrote:

just return false here?

https://github.com/llvm/llvm-project/pull/83481