[PATCH] D130728: [SCEV] Iteratively compute ranges for deeply nested expressions.

[Florian Hahn via Phabricator via llvm-commits]

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At the moment, getRangeRef may overflow the stack for very deeply nested
expressions.

This patch introduces a new getRangeRefIter function, which first builds
a worklist of N-ary expressions and phi nodes, followed by their
operands iteratively.

getRangeRef has been extended to also take a Depth argument and it
switches to use getRangeRefIter once the depth reaches a certain
threshold.

This ensures compile-time is not impacted in general. Note that
the iterative algorithm may lead to a slightly different evaluation
order, which could result in slightly worse ranges for cyclic phis.

https://llvm-compile-time-tracker.com/compare.php?from=23c3eb7cdf3478c9db86f6cb5115821a8f0f5f40&to=e0e09fa338e77e53242bfc846e1484350ad79773&stat=instructions

Fixes #49579.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D130728

Files:
  llvm/include/llvm/Analysis/ScalarEvolution.h
  llvm/lib/Analysis/ScalarEvolution.cpp

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