[all-commits] [llvm/llvm-project] 7021b4: [ConstraintElim] Try to get induction step/start/f...

[Florian Hahn via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 7021b428656d283626e9ab3c1a81795c1f6c7086
      https://github.com/llvm/llvm-project/commit/7021b428656d283626e9ab3c1a81795c1f6c7086
  Author: Florian Hahn <flo at fhahn.com>
  Date:   2026-07-15 (Wed, 15 Jul 2026)

  Changed paths:
    M llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
    M llvm/test/Transforms/ConstraintElimination/induction-nowrap-from-scev-not-ir.ll
    M llvm/test/Transforms/ConstraintElimination/monotonic-int-phis-wrapping.ll

  Log Message:
  -----------
  [ConstraintElim] Try to get induction step/start/flags from IR (NFC-ish) (#209284)

Handle the common integer inductions where the increment is plain add
PN, C by looking at IR instead of querying SCEV. There's effectively no
re-use between SCEV expression created in ConstraintElimination, and
handling simple cases in IR can avoid unnecessary, expensive SCEV
queries.

Should be NFC-ish. We miss trivial folding of the start value (see
regressed test), but that should not happen in end-to-end pipeline.

Improves compile-time for some workloads, ClamAV, mafft:
https://llvm-compile-time-tracker.com/compare.php?from=b8ba3c2b72cb53268129bbecfeb4ba7ec5b8d831&to=2bede223d3ec3ed6e2e9654b635258c50e4e90df&stat=instructions%3Au

I am working on follow-up changes that will handle more cases, where
avoiding unnecessary queries will be more important.

PR: https://github.com/llvm/llvm-project/pull/209284



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