[llvm-dev] Trip count re-computation during Epilog vectorization

[Venkataramanan Kumar via llvm-dev]

Hi,

We are caching TripCount of a loop in
"EpilogueLoopVectorizationInfo.TripCount"  during first pass ( Main Loop)
vectorization.
I see we use the cached value at "emitMinimumVectorEpilogueIterCountCheck"
during the second pass( Epilog Vector loop).

--Snip--
BasicBlock *
EpilogueVectorizerEpilogueLoop::emitMinimumVectorEpilogueIterCountCheck(
    Loop *L, BasicBlock *Bypass, BasicBlock *Insert) {

  assert(EPI.TripCount &&
         "Expected trip count to have been safed in the first pass.");
  assert(
      (!isa<Instruction>(EPI.TripCount) ||
       DT->dominates(cast<Instruction>(EPI.TripCount)->getParent(),
Insert)) &&
      "saved trip count does not dominate insertion point.");
  Value *TC = EPI.TripCount;
 --Snip--

Can  that be used in other places also in second pass?   (*TripCount =
EPI.TripCount*).  In the trunk I see we are recomputing again via
getOrCreateTripCount(L)  during the second pass (Epilog vector loop)
is it guaranteed that trip count will always dominate the epilog vector
loop  and scalar loop ?

regards,
Venkat.
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