[all-commits] [llvm/llvm-project] 334302: [ModuleInliner] Fix the heap maintenance (#69251)

[Kazu Hirata via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 33430205510f4ac82f91728e6289b0412576209c
      https://github.com/llvm/llvm-project/commit/33430205510f4ac82f91728e6289b0412576209c
  Author: Kazu Hirata <kazu at google.com>
  Date:   2023-10-17 (Tue, 17 Oct 2023)

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

  Log Message:
  -----------
  [ModuleInliner] Fix the heap maintenance (#69251)

With expensive checks enabled but without this patch, std::pop_heap
triggers an assertion failure.  This is because:

  updateAndCheckDecreased(Heap.front())

updates the priority associated with Heap.front(), so Heap may no
longer be a valid heap.  The libstdc++ version of std::pop_heap
requires that the entire range be a valid heap even though the core
task of std::pop_heap is just to swap the Heap.front() and
Heap.back().

This patch fixes the problem by:

- calling std::pop_heap to swap Heap.front() and Heap.back(),
- updating the priority of Heap.back(), and
- inserting Heap.back() back into the heap.

We could reduce the number of calls to updateAndCheckDecreased or the
number of elements being moved, but I think it's important to fix the
crash first.

Credit to Ivan Kosarev for identifying the problem and Liqiang Tao for
the analysis and initial version of the patch.