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

[via llvm-commits]

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@@ -1203,43 +1203,54 @@ 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 = {}) {
+/// Collet all VPValues representing a header mask through the (ICMP_ULE,
+/// WideCanonicalIV, backedge-taken-count) pattern.
+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.
+  if (FoundWidenCanonicalIVUser != Plan.getCanonicalIV()->users().end()) {
+    auto *WideCanonicalIV =
+        cast<VPWidenCanonicalIVRecipe>(*FoundWidenCanonicalIVUser);
+    assert(all_of(Plan.getCanonicalIV()->users(),
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ayalz wrote:

nit: would `count_if() <= 1` before and next to `find_if()` be clearer than `all_of()`?

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