Without newlines at the end, git diff would display:

  No newline at end of file

This is a fairly light-weight traversal and is needed in instrumentation. No need to run the whole `FunctionAttrs` pass at this stage. To avoid layering issues, this patch factors `canRun` and related under Analysis/CFG.

This reverts commit 924384161ffceda08099536dd07a953299a69b53.

This reland addresses the performance regressions seen in #90265 by
retaining the original definition of
`isPotentiallyReachableFromMany(...)` instead of reimplementing it with
`isManyPotentiallyReachableFromMany(...)`.

Fixes #86580

This reverts commit fcf341d3ddfe2289ac88aa3c122b25df8732cc8e.

Causes major compile-time regressions when not using coroutines.

The current logic for using lifetime intrinsics to determine whether a
coroutine alloca should live on the coroutine frame or stack doesn't
consider `llvm.lifetime.end`. As a result, some allocas are incorrectly
placed on the stack even though their lifetimes may outlive the stack.
For example, SimplifyCFG may generate code that drops the corresponding
`llvm.lifetime.end` of an `llvm.lifetime.start`, and that code is
incorrectly handled by the existing logic.

To fix this, new logic is introduced where if an alloca's address is
escaped, and there is a path from an `llvm.lifetime.start` to a
coroutine suspend point (e.g. `llvm.coro.suspend`) without an
`llvm.lifetime.end`, then we know the object lives beyond the suspension
point and therefore must go on the coroutine frame.

Fixes https://github.com/llvm/llvm-project/issues/86580

Accept a const pointer for StopBB. Unfortunately the worklist has
to use non-const pointers due to LoopInfo interaction.

This is a recurring pattern, add an API function for it.

These checks are not specific to the instruction based variant of
isPotentiallyReachable(), they are equally valid for the basic
block based variant. Move them there, to make sure that switching
between the instruction and basic block variants cannot introduce
regressions.