[PATCH] D87668: [GISel] Add new GISel combiners for G_MUL

[Jessica Paquette via Phabricator via llvm-commits]

paquette added a comment.

In the future, can you do a full-context diff? It lets reviewers see the full file.

e.g.

`git show -U999999`



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Comment at: llvm/include/llvm/Target/GlobalISel/Combine.td:441
+// Transform (mul x, 1) -> x
+def mul_by_one: GICombineRule <
+  (defs root:$root),
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This could probably be a `right_identity_one` combine, similar to `right_identity_zero`. Then you can add any other operators where this is true to the `wip_match_opcode` list in a follow-up.


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Comment at: llvm/include/llvm/Target/GlobalISel/Combine.td:453
+  (match (wip_match_opcode G_MUL):$root,
+         [{ return Helper.matchCombineMulByNegativeOne(*${root}, ${matchinfo}); }]),
+  (apply [{ return Helper.applyCombineMulByNegativeOne(*${root}, ${matchinfo}); }])
----------------
Could this use `matchConstantOp`?


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  https://reviews.llvm.org/D87668/new/

https://reviews.llvm.org/D87668