[LV] Move collect* calls to LVP::plan() (NFC).

[fhahn]

Summary

Move calls of collect* helpers closer to where the cost-model is used.
Should help simplifying D142669 & D142670.

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

LLVM_DEBUG(
       dbgs() << "LV: Not vectorizing. Inner loops aren't supported in the "
                 "VPlan-native path.\n");
   return VectorizationFactor::Disabled();
 }
 
 std::optional<VectorizationFactor>
 LoopVectorizationPlanner::plan(ElementCount UserVF, unsigned UserIC) {
   assert(OrigLoop->isInnermost() && "Inner loop expected.");
+  CM.collectValuesToIgnore();
+  CM.collectElementTypesForWidening();
+
   FixedScalableVFPair MaxFactors = CM.computeMaxVF(UserVF, UserIC);
   if (!MaxFactors) // Cases that should not to be vectorized nor interleaved.
     return std::nullopt;
 
   // Invalidate interleave groups if all blocks of loop will be predicated.
   if (CM.blockNeedsPredicationForAnyReason(OrigLoop->getHeader()) &&
       !useMaskedInterleavedAccesses(*TTI)) {
     LLVM_DEBUG(
LLVM_DEBUG(dbgs() << "LV: loop not vectorized: cannot prove it is safe to "
                          "reorder floating-point operations\n");
     Hints.emitRemarkWithHints();
     return false;
   }
 
   // Use the cost model.
   LoopVectorizationCostModel CM(SEL, L, PSE, LI, &LVL, *TTI, TLI, DB, AC, ORE,
                                 F, &Hints, IAI);
-  CM.collectValuesToIgnore();
-  CM.collectElementTypesForWidening();
-
   // Use the planner for vectorization.
   LoopVectorizationPlanner LVP(L, LI, TLI, TTI, &LVL, CM, IAI, PSE, Hints, ORE);
 
   // Get user vectorization factor and interleave count.
   ElementCount UserVF = Hints.getWidth();
   unsigned UserIC = Hints.getInterleave();
 
   // Plan how to best vectorize, return the best VF and its cost.