[PATCH] D144927: [GVNHoist] don't hoist callbr users into the callbr's block

[Nikita Popov via Phabricator via llvm-commits]

nikic added inline comments.


================
Comment at: llvm/lib/Transforms/Scalar/GVNHoist.cpp:819
+    // the use above the def.
+    if (is_contained(T->users(), Insn))
+      continue;
----------------
nickdesaulniers wrote:
> hiraditya wrote:
> > hiraditya wrote:
> > > I'm assuming there are only a few `T->users` in practice, otherwise linear search on users could be slow.
> > maybe we can check if `Insn` has any operands that are defined by `T`
> > I'm assuming there are only a few T->users in practice
> 
> In practice, only `CallBrInst`'s are terminators that produce values/can even have users.  In practice, the number of users is 1.
> 
> > maybe we can check if Insn has any operands that are defined by T
> 
> Equivalent.
> In practice, only CallBrInst's are terminators that produce values/can even have users.

Invokes also produces values and have users. Though it's possible that those aren't supported by GVNHoist.

> In practice, the number of users is 1.

Hm, why? I'd expect more than one users even for front-end generated IR, depending on number of return values and number of control-flow paths.


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  https://reviews.llvm.org/D144927/new/

https://reviews.llvm.org/D144927