[PATCH] D71093: [InstCombine] Insert instructions before adding them to worklist

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri added a comment.

In D71093#1773021 <https://reviews.llvm.org/D71093#1773021>, @spatel wrote:

> In D71093#1772839 <https://reviews.llvm.org/D71093#1772839>, @lebedev.ri wrote:
>
> > I'm not convinced this is an improvement overall.
> >
> > As a concrete point: we will no longer print the 'new' if said 'new' isn't a new instruction;
> >  as in, printing of new will now depend on the fact that it will be added into worklist,
> >  which won't be the case if we returned preexisting instruction.
>
>
> If we return the existing instruction, don't we always fall down to the else at line 3372 and print it there?


No, because we only get there if we return *the same* instruction we just visited.
I'm talking about the case like:

  %x = mul i8 %y, 42
  %t0 = sub i8 0, %x
  %t1 = sub i8 0, %t0
  
  visit %t1
  ... returned %x
  %x != %t1


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D71093/new/

https://reviews.llvm.org/D71093