[PATCH] D113577: [SCEV] Support rewriting ZExt expressions with loop guard info.

[Florian Hahn via Phabricator via llvm-commits]

fhahn created this revision.
fhahn added reviewers: reames, nikic, mkazantsev.
Herald added subscribers: javed.absar, hiraditya.
fhahn requested review of this revision.
Herald added a project: LLVM.

So far, applying loop guard information has been restricted to
SCEVUnknown. In a few cases, like PR40961 and PR52464, this leads to
SCEV failing to determine tight upper bounds for the backedge taken
count.

This patch adjusts SCEVLoopGuardRewriter and applyLoopGuards to support
re-writing ZExt expressions.

This fixes PR40961. PR52464 requires a follow-up patch, which I will
share soon.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D113577

Files:
  llvm/lib/Analysis/ScalarEvolution.cpp
  llvm/test/Analysis/ScalarEvolution/max-backedge-taken-count-guard-info-rewrite-expressions.ll

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