[PATCH] D41860: [CallSiteSplitting] Support splitting of blocks with instrs before call.

[Florian Hahn via Phabricator via llvm-commits]

fhahn added a comment.

> If getUserCost is supposed to represent only the code size (I believe so), then we may need to introduce a new target hook to handle sdiv properly in getOperationCost(). @hfinkel might have better idea about it.

I am not entirely sure, but it looks like for most instructions, `getUserCost` delegates to `getOperationCost`, which per default marks sdiv & co as expensive. In any case, the patch uses

  TTI.getInstructionCost(&InstBeforeCall,
                                     TargetTransformInfo::TCK_CodeSize);

so in case the code size cost becomes more accurate, we should pick it up.



================
Comment at: lib/Transforms/Scalar/CallSiteSplitting.cpp:85
+                                  "their cost is below DuplicationThreshold"),
+                         cl::init(50));
+
----------------
junbuml wrote:
> Considering that TCC_Basic is 1, don't you think 50 is too aggressive? For me, the conservative enough default should be TCC_Expensive. 
Yeah, that was left over from testing, sorry about that!


https://reviews.llvm.org/D41860