3ee826594a
LazyBlockFrequenceInfoPass, LazyBranchProbabilityInfoPass and LoopAccessLegacyAnalysis all cache pointers to their nestled required analysis passes. One need to use addRequiredTransitive to describe that the nestled passes can't be freed until those analysis passes no longer are used themselves. There is still a bit of a mess considering the getLazyBPIAnalysisUsage and getLazyBFIAnalysisUsage functions. Those functions are used from both Transform, CodeGen and Analysis passes. I figure it is OK to use addRequiredTransitive also when being used from Transform and CodeGen passes. On the other hand, I figure we must do it when used from other Analysis passes. So using addRequiredTransitive should be more correct here. An alternative solution would be to add a bool option in those functions to let the user tell if it is a analysis pass or not. Since those lazy passes will be obsolete when new PM has conquered the world I figure we can leave it like this right now. Intention with the patch is to fix PR49950. It at least solves the problem for the reproducer in PR49950. However, that reproducer need five passes in a specific order, so there are lots of various "solutions" that could avoid the crash without actually fixing the root cause. This is a reapply of commit3655f0757f, that was reverted in33ff3c2049due to problems with assertions in the polly lit tests. That problem is supposed to be solved by also adjusting ScopPass to explicitly preserve LazyBlockFrequencyInfo and LazyBranchProbabilityInfo (it already preserved OptimizationRemarkEmitter which depends on those lazy passes). Differential Revision: https://reviews.llvm.org/D100958
Analysis Opportunities:
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In test/Transforms/LoopStrengthReduce/quadradic-exit-value.ll, the
ScalarEvolution expression for %r is this:
{1,+,3,+,2}<loop>
Outside the loop, this could be evaluated simply as (%n * %n), however
ScalarEvolution currently evaluates it as
(-2 + (2 * (trunc i65 (((zext i64 (-2 + %n) to i65) * (zext i64 (-1 + %n) to i65)) /u 2) to i64)) + (3 * %n))
In addition to being much more complicated, it involves i65 arithmetic,
which is very inefficient when expanded into code.
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In formatValue in test/CodeGen/X86/lsr-delayed-fold.ll,
ScalarEvolution is forming this expression:
((trunc i64 (-1 * %arg5) to i32) + (trunc i64 %arg5 to i32) + (-1 * (trunc i64 undef to i32)))
This could be folded to
(-1 * (trunc i64 undef to i32))
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