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

[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)) {
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ayalz wrote:

then hoist Addr's defining recipe to insert pos, possibly hoisting additional defining recipes as needed? And/or sink loads above member zero to join it.

In general, all members of an interleave group conceptually move to its insert pos, so may as well perform actual movement. This should facilitate subsequent SLP'ing.

Interleave stores are inserted at the last member, so the address of any member should be available there. Interleaved loads are inserted at the first member, so only its address is guaranteed to be available there, although others may as well.

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