[PATCH] D103992: [InstCombine / BuildLibCalls] Add parameter attributes from the prototype.

[Reid Kleckner via Phabricator via llvm-commits]

rnk added a comment.

I agree, we probably need to better understand what attributes we are trying to transfer. My guess is that we are trying to transfer call site attributes, things like `noinline`, `alwaysinline`, or other things inferred by optimization. If the call's prototype changes, then copying argument attributes doesn't make any sense and we should re-evaluate doing it in the first place.



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Comment at: llvm/lib/Transforms/Utils/BuildLibCalls.cpp:1222
+    CI->setCallingConv(F->getCallingConv());
+    CI->setAttributes(F->getAttributes());
+  }
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This change is fine: we are taking the attributes from a known callee.


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Comment at: llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp:199
+static void takeAttributesFrom(CallInst *NewCI, CallInst *OrigCI) {
+  NewCI->setAttributes(OrigCI->getAttributes());
+  NewCI->removeAttributes(AttributeList::ReturnIndex,
----------------
This seems questionable. Why not take the parameter attributes from `NewCI`'s callee? What is the value of merging in the attributes from the old call?


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  https://reviews.llvm.org/D103992/new/

https://reviews.llvm.org/D103992