[PATCH] D153963: [InstCombine] Fold add of select and zext/sext of select condition

[Noah Goldstein via Phabricator via llvm-commits]

goldstein.w.n added a comment.

Can you add alive2 link for this? I think it also works a lot more binops than just `add`. If so, can you split to a helper so it can be used elsewhere.



================
Comment at: llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp:1488
+  // select A, T_C + 1, F_C (for Z = zext A)
+  // select A, T_C - 1, F_C (for Z = sext A)
+  // Take into account the negation as well.
----------------
I had a lot of trouble following this comment can you make say:

```
(select cond, (add X, 1), X)
   -> (add X, (zext cond))
```

then some format for sext.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D153963/new/

https://reviews.llvm.org/D153963