[llvm] [VPlan] Use target's index type for {First,Last}ActiveLane instead of i64 (PR #186361)

[Ramkumar Ramachandra via llvm-commits]

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@@ -25,6 +25,10 @@ using namespace VPlanPatternMatch;
 #define DEBUG_TYPE "vplan"
 
 VPTypeAnalysis::VPTypeAnalysis(const VPlan &Plan) : Ctx(Plan.getContext()) {
+  const DataLayout &DL =
+      Plan.getScalarHeader()->getIRBasicBlock()->getDataLayout();
+  IndexTy = DL.getIndexType(PointerType::get(Plan.getContext(), 0));
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artagnon wrote:

Couldn't we could have the ptr type accepted as an argument, make the DL available, and pass `PointerType::get(Plan.getContext(), DL.getAllocaAddrSpace())` for this use-case?

https://github.com/llvm/llvm-project/pull/186361