[PATCH] D85504: [Reassociate] [PowerPC] stop common out mul factors if fma is preferred on target

[Sanjay Patel via Phabricator via llvm-commits]

spatel added a comment.

The reassociate pass (like instcombine) is supposed to be a target-independent canonicalization pass:

    // This pass reassociates commutative expressions in an order that is designed
    // to promote better constant propagation, GCSE, LICM, PRE, etc.
  		

So it's intentionally avoiding using TTI/TLI and trying not to do all forms of reassociation. As Roman mentioned, see D67383 <https://reviews.llvm.org/D67383> as an example of a possible TTI-aware reassociation pass.

So either we need to reverse this in DAGCombine and/or PPC-specific codegen, or we need to make an argument that the canonicalization does not make sense in general (for FP only?).


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https://reviews.llvm.org/D85504