[LV] Fix missing precomptueCosts() in emitInvalidCostRemarks().

We should always update the SkipComputation set in VPCostContext before VPlan.cost().

This patch prevent assertion of in-loop reduction in the `VPReductionRecipe::computeCost()` and other
potentail assertions of partially implemented VPlan-based cost model.

Author: ElvisWang123

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

@@ -4363,6 +4363,7 @@ void LoopVectorizationPlanner::emitInvalidCostRemarks(
     for (ElementCount VF : Plan->vectorFactors()) {
       VPCostContext CostCtx(CM.TTI, *CM.TLI, Legal->getWidestInductionType(),
                             CM);
+      precomputeCosts(*Plan, VF, CostCtx);
       auto Iter = vp_depth_first_deep(Plan->getVectorLoopRegion()->getEntry());
       for (VPBasicBlock *VPBB : VPBlockUtils::blocksOnly<VPBasicBlock>(Iter)) {
         for (auto &R : *VPBB) {

llvm/test/Transforms/LoopVectorize/reduction-inloop.ll

@@ -1,5 +1,7 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
 ; RUN: opt < %s -passes=loop-vectorize,dce,instcombine -force-vector-interleave=1 -force-vector-width=4 -prefer-inloop-reductions -S | FileCheck %s
+; Check remark analysis runs successfully.
+; RUN: opt < %s -passes=loop-vectorize,dce,instcombine -force-vector-interleave=1 -force-vector-width=4 -prefer-inloop-reductions -pass-remarks-analysis=loop-vectorize -S
 
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"