[PATCH] D82444: [SLP] Make sure instructions are ordered when computing spill cost.

[Valeriy Dmitriev via Phabricator via llvm-commits]

vdmitrie added inline comments.


================
Comment at: llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp:3777
+  llvm::stable_sort(OrderedScalars, [this](Instruction *A, Instruction *B) {
+    return !DT->dominates(A, B);
+  });
----------------
There is a problem with this predicate function.
MSFT STL implementation of stable_sort asserts that if predicate returned true
then it must return false when operands are swapped.
But (A dom B) == false does not necessarily mean that (B dom A) == true.
Instead: (A dom B) ==true means that (B dom A) == false.
Rewriting it like this solves this issue:
    return DT->dominates(B, A);


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  https://reviews.llvm.org/D82444/new/

https://reviews.llvm.org/D82444