[PATCH] D68651: [InstCombine] Signed saturation patterns

[Krzysztof Parzyszek via Phabricator via llvm-commits]

kparzysz added a comment.

I'm in favor of treating signed saturation as canonical.  The issue in delaying detection of such cases to instruction selection is the volatility of the IR: there is no guarantee that the IR will remain in the same form (expected by isel) from one day to the next.  For example, some optimization may decide to just promote the operations to the wider type and only do the extension/truncate once, depending on how many saturating operations may be near one another.  Handling this variability in isel is just not feasible.


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  https://reviews.llvm.org/D68651/new/

https://reviews.llvm.org/D68651