[llvm] [VPlan] Introduce recipes for VP loads and stores. (PR #87816)

[via llvm-commits]

================
@@ -1203,43 +1203,52 @@ static VPActiveLaneMaskPHIRecipe *addVPLaneMaskPhiAndUpdateExitBranch(
   return LaneMaskPhi;
 }
 
-/// Replaces (ICMP_ULE, WideCanonicalIV, backedge-taken-count) pattern using
-/// the given \p Idiom.
-static void
-replaceHeaderPredicateWith(VPlan &Plan, VPValue &Idiom,
-                           function_ref<bool(VPUser &, unsigned)> Cond = {}) {
+/// Collect all VPValues representing a header mask through the (ICMP_ULE,
+/// WideCanonicalIV, backedge-taken-count) pattern.
+/// TODO: Introduce explicit recipe for header-mask instead of searching
+/// for the header-mask pattern manually.
+static SmallVector<VPValue *> collectAllHeaderMasks(VPlan &Plan) {
+  SmallVector<VPValue *> WideCanonicalIVs;
   auto *FoundWidenCanonicalIVUser =
       find_if(Plan.getCanonicalIV()->users(),
               [](VPUser *U) { return isa<VPWidenCanonicalIVRecipe>(U); });
-  if (FoundWidenCanonicalIVUser == Plan.getCanonicalIV()->users().end())
-    return;
-  auto *WideCanonicalIV =
-      cast<VPWidenCanonicalIVRecipe>(*FoundWidenCanonicalIVUser);
-  // Walk users of WideCanonicalIV and replace all compares of the form
-  // (ICMP_ULE, WideCanonicalIV, backedge-taken-count) with
-  // the given idiom VPValue.
+  assert(count_if(Plan.getCanonicalIV()->users(),
+                  [](VPUser *U) { return isa<VPWidenCanonicalIVRecipe>(U); }) <=
+             1 &&
+         "Must at most one VPWideCanonicalIVRecipe");
----------------
ayalz wrote:

```suggestion
         "Must be at most one VPWideCanonicalIVRecipe");
```

https://github.com/llvm/llvm-project/pull/87816