[PATCH] D68408: [InstCombine] Negator - sink sinkable negations

[Sanjay Patel via Phabricator via llvm-commits]

spatel added inline comments.


================
Comment at: llvm/lib/Transforms/InstCombine/InstCombineNegator.cpp:180
+  }
+  case Instruction::SDiv:
+    // `sdiv` is negatible if divisor is not undef/INT_MIN/1.
----------------
lebedev.ri wrote:
> nikic wrote:
> > Noticed while looking through the tramp3d-v4 diff: This should be behind a one-use check, to avoid duplicating expensive division instructions.
> I was hesitant about this one indeed, it isn't a typo that one-use check has gone away here,
> because we //generally// consider only instruction count.
> 
> @spatel thoughts?
> 
> But the main, bigger question this touches is:
> "but what if all the uses would get negated by us?
> In future, can we somehow sanely model the whole negatible tree,
> not giving up at non-single-use instructions,
> but defer that to after we've finished building new tree?"
> 
> 
I missed that logic difference, and I'm not getting a reviewable diff of the attached files with llvm-diff or other apps. Can you create an IR example/regression test for that?


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  https://reviews.llvm.org/D68408/new/

https://reviews.llvm.org/D68408