[PATCH] D74320: GlobalISel: Add combine to narrow G_LSHR

[Nicolai Hähnle via Phabricator via llvm-commits]

nhaehnle accepted this revision.
nhaehnle added a comment.
This revision is now accepted and ready to land.

Some nits, but generally LGTM.



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Comment at: llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp:1405-1407
+bool CombinerHelper::matchCombineShiftToUnmerge(MachineInstr &MI,
+                                                unsigned TargetShiftSize,
+                                                unsigned &ShiftVal) {
----------------
Please add a comment describing what this matches.


================
Comment at: llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp:1448
+    Narrowed = Builder.buildLShr(
+      HalfTy, Unmerge.getReg(1),
+      Builder.buildConstant(HalfTy, ShiftVal - Size / 2)).getReg(0);
----------------
This could use `Narrowed` instead of `Unmerge.getReg(1)`.


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  https://reviews.llvm.org/D74320/new/

https://reviews.llvm.org/D74320