[all-commits] [llvm/llvm-project] ce7790: [ValueTracking] Limit scan when checking poison UB...

[Nikita Popov via All-commits]

  Branch: refs/heads/release/12.x
  Home:   https://github.com/llvm/llvm-project
  Commit: ce779098006e9de32678f28140f22de7e4a19189
      https://github.com/llvm/llvm-project/commit/ce779098006e9de32678f28140f22de7e4a19189
  Author: Nikita Popov <nikita.ppv at gmail.com>
  Date:   2021-06-14 (Mon, 14 Jun 2021)

  Changed paths:
    M llvm/lib/Analysis/ValueTracking.cpp

  Log Message:
  -----------
  [ValueTracking] Limit scan when checking poison UB (PR50155)

The current code can scan an unlimited number of instructions,
if the containing basic block is very large. The test case from
PR50155 contains a basic block with approximately 100k instructions.

To avoid this, limit the number of instructions we inspect. At
the same time, drop the limit on the number of basic blocks, as
this will be implicitly limited by the number of instructions as
well.

(cherry picked from commit 2cd78686055f1badb9aa55cb95e189548ffc82f0)