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Stop tracking genReturnBB after global morph #97130

Merged
merged 3 commits into from
Jan 20, 2024
Merged

Stop tracking genReturnBB after global morph #97130

merged 3 commits into from
Jan 20, 2024

Commits on Jan 20, 2024

  1. Stop tracking genReturnBB after global morph 

    The `genReturnBB` pointer is set if a merged return block is created
during `fgAddInternal` (so, quite early during compilation). It needs
to be maintained (and the unreferenced block it points to needs to be
kept around) until global morph, which hooks up flow to this block.

After global morph, clear the pointer and don't maintain it; it is no
longer needed. Later code that was checking for it can instead check
for `BBJ_RETURN` blocks or `GT_RETURN` nodes. Also, remove the marking
of the `genReturnBB` block as `BBF_DONT_REMOVE`.

This leads to diffs, as unreachable return blocks get deleted. This can
happen, say, if all other exits are tail calls. If that happens and we're
in a case of needing a profiler hook, then the profile exit hook is also
not needed (it would be unreachable).
    @BruceForstall
    BruceForstall committed Jan 20, 2024
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  2. Allow x86 synchronized methods to have unreachable return blocks 

    The JIT still needs to report an end-of-synchronized-range offset
in the GC info for x86 synchronized methods, so just create a new
label at the end of all blocks. The VM will automatically exit
the synchronization on an exceptional method exit.
    @BruceForstall
    BruceForstall committed Jan 20, 2024
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  3. Create final IG before clearing GC info

    @BruceForstall
    BruceForstall committed Jan 20, 2024
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