[BFI] Use CallbackVH to notify BFI about deletion of basic blocks

Authored by DaniilSuchkov on Mar 5 2020, 3:32 AM.


[BFI] Use CallbackVH to notify BFI about deletion of basic blocks

With AssertingVHs instead of bare pointers in
BlockFrequencyInfoImpl::Nodes (but without CallbackVHs) ~1/36 of all
tests ran by make check fail. It means that there are users of BFI that
delete basic blocks while keeping BFI. Some of those transformations add
new basic blocks, so if a new basic block happens to be allocated at
address where an already deleted block was and we don't explicitly set
block frequency for that new block, BFI will report some non-default
frequency for the block even though frequency for the block was never
set. Inliner is an example of a transformation that adds and removes BBs
while querying and updating BFI.
With this patch, thanks to updates via CallbackVH, BFI won't keep stale
pointers in its Nodes map.

This is a resubmission of 408349a25d0f5a012003f84c95b49bcc7782fa70 with
fixed MSVC compilation errors.

Reviewers: davidxl, yamauchi, asbirlea, fhahn, fedor.sergeev

Reviewed-By: asbirlea, davidxl

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D75341

Event Timeline

Apparently, it breaks MSVC buildbots too, but it does it in a way I can't comprehend: looks like after my change MSVC instantiates all methods of BlockFrequencyInfoImpl, including ones that weren't instantiated before and which are incorrect for <MachineBasicBlock> instantiation. I don't have access to MSVC, so there's no way I'll figure out what's wrong with it and fix it.