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Improve value numbering for casts #59841

Merged
merged 4 commits into from
Oct 15, 2021
Merged

Improve value numbering for casts #59841

merged 4 commits into from
Oct 15, 2021

Commits on Oct 1, 2021

  1. Refactor how casts are VNed, part 1 

    Remove duplication between VNPairForCast
and VNForCast, route the former through
the latter.

Also change the debug output for casts.

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    @SingleAccretion
    SingleAccretion committed Oct 1, 2021
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  2. Refactor how casts are VNed, part 2 

    VN cast helpers just like casts.
This allows them to be folded.

In the past, this was dangerous because some of
the pessimization protected us from undefined
behavior in cases of out-of-bounds conversions,
but now we do not fold such cases anymore.
    @SingleAccretion
    SingleAccretion committed Oct 1, 2021
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  3. Enable VN-based constant propagation for calls 

    This solves some of the regressions seen due to
now-missing CSEs of these helper calls evaluated
as constants by VN.
    @SingleAccretion
    SingleAccretion committed Oct 1, 2021
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  4. Fix VNFuncs for MUL_OVF helpers 

    This fixes the test failures revealed by
the more aggressive constant propagation.

This is very similar to a bug that was recently
fixed where checked casts were treated as non-checked
and could be observed without the assertion propagation
changes as well, with the redundant branches optimization.
    @SingleAccretion
    SingleAccretion committed Oct 1, 2021
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