[PATCH] D107711: [DAGCombiner] Add target hook function to decide folding (mul (add x, c1), c2)

[Ben Shi via Phabricator via llvm-commits]

benshi001 added inline comments.


================
Comment at: llvm/include/llvm/CodeGen/TargetLowering.h:2086
+  /// The target should check the cost of materializing c1, c2 and c1*c2 into
+  /// registers. If it is not sure about some cases, a default true
+  /// can be returned to let the DAGCombiner decide.
----------------
lebedev.ri wrote:
> 
I think my origin `default true` is right, the default return value should not be false.

Since my hook is called as
```
  if (AddNode.getNode()->hasOneUse() &&
      TLI.isMulAddWithConstProfitable(AddNode, ConstNode))
    return true;
```

So it should return default true for undetermined cases.




CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D107711/new/

https://reviews.llvm.org/D107711