[llvm] [VPlan] Use pointer to member 0 as VPInterleaveRecipe's pointer arg. (PR #106431)

[Florian Hahn via llvm-commits]

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@@ -1539,9 +1543,39 @@ void VPlanTransforms::createInterleaveGroups(
 
     bool NeedsMaskForGaps =
         IG->requiresScalarEpilogue() && !ScalarEpilogueAllowed;
-    auto *VPIG = new VPInterleaveRecipe(IG, Recipe->getAddr(), StoredValues,
-                                        Recipe->getMask(), NeedsMaskForGaps);
-    VPIG->insertBefore(Recipe);
+
+    Instruction *IRInsertPos = IG->getInsertPos();
+    auto *InsertPos =
+        cast<VPWidenMemoryRecipe>(RecipeBuilder.getRecipe(IRInsertPos));
+    VPRecipeBase *IP = InsertPos;
+
+    // Get or create the start address for the interleave group.
+    auto *Start =
+        cast<VPWidenMemoryRecipe>(RecipeBuilder.getRecipe(IG->getMember(0)));
+    VPValue *Addr = Start->getAddr();
+    if (!VPDT.properlyDominates(Addr->getDefiningRecipe(), InsertPos)) {
+      bool InBounds = false;
+      if (auto *gep = dyn_cast<GetElementPtrInst>(
+              getLoadStorePointerOperand(IRInsertPos)->stripPointerCasts()))
+        InBounds = gep->isInBounds();
+
+      // We cannot re-use the address of the first member because it does not
+      // dominate the insert position. Use the address of the insert position
+      // and create a PtrAdd to adjust the index to start at the first member.
+      APInt Offset(32,
+                   getLoadStoreType(IRInsertPos)->getScalarSizeInBits() / 8 *
+                       IG->getIndex(IRInsertPos),
+                   /*IsSigned=*/true);
+      VPValue *OffsetVPV = Plan.getOrAddLiveIn(
+          ConstantInt::get(IRInsertPos->getParent()->getContext(), -Offset));
+      Addr = new VPInstruction(InsertPos->getAddr(), OffsetVPV, InBounds);
+      Addr->getDefiningRecipe()->insertAfter(InsertPos);
----------------
fhahn wrote:

Thanks, included in this PR.

https://github.com/llvm/llvm-project/pull/106431