[PATCH] D57243: GlobalISel: Allow bitcount ops to have different result type

[Daniel Sanders via Phabricator via llvm-commits]

dsanders added a comment.

In D57243#1385507 <https://reviews.llvm.org/D57243#1385507>, @qcolombet wrote:

> >   Personally, I'd like to replace the LegalizationAction with a function pointer that just performs the desired change and have a standard library of actions that can be called for the common changes. 
>
> @dsanders didn't we try something like that for ISel and the performance was terrible?


You're thinking of the hundreds-thousands of single-use lambdas that were generated. It was the ugly temporary code that was used to inject multiple statements inside an if-statement condition and looked like this:

  if ([&](...) {
      if (!...) return false;
      if (!...) return false;
      if (!...) return false;
      if (!...) return false;
      return true;
      }(Arg1, Arg2)) {
        ...
  }

The legalizer is already done the way I'm talking about on the rule matching side and performance was marginally better on average than the old setAction() interface.


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