[llvm] [VPlan] Replicate VPScalarIVStepsRecipe by VF outside replicate regions. (PR #170053)

[Florian Hahn via llvm-commits]

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@@ -594,12 +592,33 @@ cloneForLane(VPlan &Plan, VPBuilder &Builder, Type *IdxTy,
                                 /*IsSingleScalar=*/true, /*Mask=*/nullptr,
                                 *RepR, *RepR, RepR->getDebugLoc());
   } else {
-    assert(isa<VPInstruction>(DefR) &&
-           "DefR must be a VPReplicateRecipe or VPInstruction");
+    assert((isa<VPInstruction, VPScalarIVStepsRecipe>(DefR)) &&
+           "DefR must be a VPReplicateRecipe, VPInstruction or "
+           "VPScalarIVStepsRecipe");
     New = DefR->clone();
     for (const auto &[Idx, Op] : enumerate(NewOps)) {
       New->setOperand(Idx, Op);
     }
+    if (auto *Steps = dyn_cast<VPScalarIVStepsRecipe>(New)) {
+      // Skip lane 0: a missing start index is implicitly zero.
+      unsigned KnownLane = Lane.getKnownLane();
+      if (KnownLane != 0) {
+        VPTypeAnalysis TypeInfo(Plan);
+        Type *BaseIVTy = TypeInfo.inferScalarType(DefR->getOperand(0));
+        VPValue *LaneOffset = Plan.getConstantInt(
+            APInt(IdxTy->getScalarSizeInBits(), KnownLane)
+                .sextOrTrunc(BaseIVTy->getScalarSizeInBits()));
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fhahn wrote:

Updated thanks!

https://github.com/llvm/llvm-project/pull/170053