[PATCH] D27129: [SelectionDAG] Add partial BITCAST support to computeKnownBits

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon created this revision.
RKSimon added reviewers: eli.friedman, majnemer, craig.topper, spatel, andreadb.
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Adds support for bitcasting a 'small element' vector to 'large element' scalar/vector (e.g. v16i8 to v4i32 or v2i32 to i64), which is required for PR30845. We extract the knownbits for each 'small element' part and concatenate the results together.

I have the code ready for 'large element' scalar/vector to 'small element' vector bitcasting as well if you think it worth adding to this patch now before we have any useful test cases.


Repository:
  rL LLVM

https://reviews.llvm.org/D27129

Files:
  lib/CodeGen/SelectionDAG/SelectionDAG.cpp
  test/CodeGen/X86/pmul.ll

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