[ConstraintElim] Bound IVs by compares of the phi in header/latch. (#226297) Extend addInfoForInductions to add bounds for IVs when the phi is compared in the header or latch: In that case, every iteration taking the backedge checked PN ContinuePred B, which guarantees PN != B for NE and LT predicates. For an increment by one, PN != B together with StartValue <= B (added precondition) imply PN <= B. Alive2 Proofs: * icmp ult in header: https://alive2.llvm.org/ce/z/x37Uvm * icmp slt in header: https://alive2.llvm.org/ce/z/ibnn5k * icmp ne in header: https://alive2.llvm.org/ce/z/wLRfZe Triggers in a number of additional cases on https://github.com/dtcxzyw/llvm-opt-benchmark-nightly/pull/1431. As-is, this comes with a slight compile-time increase: * stage1-O3: +0.04% * stage1-ReleaseThinLTO: +0.03% * stage1-ReleaseLTO-g: +0.03% * stage1-aarch64-O3: +0.02% * stage2-O3: +0.03% https://llvm-compile-time-tracker.com/compare.php?from=ea9f4c16ec59a210753b6e5dd23e6b0ee0a8542c&to=56c848df9c9a711d71987d4771c6914f582b83bf&stat=instructions:u PR: https://github.com/llvm/llvm-project/pull/226297
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