[all-commits] [llvm/llvm-project] d24a0e: [SCEV] Use constant range of RHS to prove NUW on n...

[Philip Reames via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: d24a0e88576dca1c475a7f48d4361136a46f9b72
      https://github.com/llvm/llvm-project/commit/d24a0e88576dca1c475a7f48d4361136a46f9b72
  Author: Philip Reames <listmail at philipreames.com>
  Date:   2021-11-05 (Fri, 05 Nov 2021)

  Changed paths:
    M llvm/lib/Analysis/ScalarEvolution.cpp
    M llvm/test/Analysis/ScalarEvolution/trip-count-implied-addrec.ll
    M llvm/test/Transforms/IndVarSimplify/finite-exit-comparisons.ll

  Log Message:
  -----------
  [SCEV] Use constant range of RHS to prove NUW on narrow IV in trip count logic

The basic idea here is that given a zero extended narrow IV, we can prove the inner IV to be NUW if we can prove there's a value the inner IV must take before overflow which must exit the loop.

Differential Revision: https://reviews.llvm.org/D109457