[PATCH] D73744: [SCEV] SCEVExpander::isHighCostExpansionHelper(): cost-model min/max (PR44668)

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri created this revision.
lebedev.ri added reviewers: reames, mkazantsev, wmi, sanjoy.
lebedev.ri added a project: LLVM.
Herald added subscribers: javed.absar, hiraditya.
lebedev.ri added a parent revision: D73741: [SCEV] SCEVExpander::isHighCostExpansionHelper(): cost-model polynomial recurrence.

Previosly we simply always said that `SCEVMinMaxExpr` is too costly to expand.
But this isn't really true, it expands into just a comparison+swap pair.
And again much like with add/mul, there will be one less such pair
than the number of operands. And we need to count the cost of operands themselves.

This does change a number of testcases, and as far as i can tell,
all of these changes are improvements, in the sense that
we fixed up more latches to do the [in]equality comparison.

This concludes cost-modelling changes, no other SCEV expressions exist as of now.

This is a part of addressing PR44668 <https://bugs.llvm.org/show_bug.cgi?id=44668>.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D73744

Files:
  llvm/lib/Analysis/ScalarEvolutionExpander.cpp
  llvm/test/Transforms/IndVarSimplify/elim-extend.ll
  llvm/test/Transforms/IndVarSimplify/eliminate-comparison.ll
  llvm/test/Transforms/IndVarSimplify/eliminate-trunc.ll
  llvm/test/Transforms/IndVarSimplify/full_widening.ll
  llvm/test/Transforms/IndVarSimplify/iv-widen.ll
  llvm/test/Transforms/IndVarSimplify/lftr-multi-exit.ll
  llvm/test/Transforms/IndVarSimplify/lftr-reuse.ll
  llvm/test/Transforms/IndVarSimplify/loop-invariant-conditions.ll
  llvm/test/Transforms/IndVarSimplify/widen-loop-comp.ll
  llvm/test/Transforms/LoopVectorize/X86/float-induction-x86.ll

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