[PATCH] D135700: [DAGCombine] Simplify (truncate (build_pair x, y)) -> (truncate x) or x

[Krzysztof Parzyszek via Phabricator via llvm-commits]

kparzysz added a comment.

In D135700#3885112 <https://reviews.llvm.org/D135700#3885112>, @RKSimon wrote:

> What do you want to do next - merge your local branch Hexagon patch into trunk?

Sorry, missed this comment.  The Hexagon-specific code is already merged.  As for this, I was planning to fix the x86 codegen to get this case, but I haven't had time to do it yet.  I believe this only applies to extending loads, where the consumer accesses the extension bits, and only when the consumer can be modified to access the memory directly.  Only existing patterns/selections would need to be updated, because without such explicit change from using register to memory this patch wouldn't have any effect on the code size.


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