[PATCH] D143787: [X86] Add new pass `X86FixupInstTuning` for fixing up machine-instruction selection.

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon added a comment.

Probably better for this first patch to add the pass and the inital vpermilps -> vshufps/vshufd fold, the scheduler based unpckpd fold can be added in a followup



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Comment at: llvm/lib/Target/X86/X86FixupInstTuning.cpp:84
+    }
+    return 0.0;
+  };
----------------
It'd be better to return Optional<double> instead of 0.0 for failed matches (and return nullopt here)


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  https://reviews.llvm.org/D143787/new/

https://reviews.llvm.org/D143787