[PATCH] D105806: [LV] Print remark when loop cannot be vectorized due to invalid costs.

[Sander de Smalen via Phabricator via llvm-commits]

sdesmalen added inline comments.


================
Comment at: llvm/lib/Transforms/Vectorize/LoopVectorize.cpp:6115
+    // Sort/group per instruction
+    llvm::sort(InvalidCosts, [](InstructionVFPair &A, InstructionVFPair &B) {
+      ElementCountComparator ECC;
----------------
thakis wrote:
> …maybe this needs to be a stable_sort() instead?
Doh! The latest issue seems caused by the change in rGdc7bdc1e7121693df112f2fdb11cc6b88580ba4b :

  const Instruction *AI = A.first, *BI = B.first;
  if (AI->getParent() != BI->getParent())
    return AI->getParent() < BI->getParent();   // pointer comparison

I considered writing:

  if (AI->getParent() != BI->getParent())
    return false;

So that `AI < BI == false` && `BI < AI == false` and that stable_sort would keep it in place, but this doesn't work in practice.
I didn't think of a more suitable way to order the blocks (the dominator tree is not part of CostModel, so I also can't use that).

Any tips?


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  https://reviews.llvm.org/D105806/new/

https://reviews.llvm.org/D105806