[PATCH] D82550: [SLPVectorizer] handle vectorized lib functions

[Alexey Bataev via Phabricator via llvm-commits]

ABataev added inline comments.


================
Comment at: llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp:5121
+    if (I->mayReadOrWriteMemory() && !isSideeffectIntrinsic(I) &&
+        !isVectorizableLibFunctionCall(I)) {
       // Update the linked list of memory accessing instructions.
----------------
sanwou01 wrote:
> ABataev wrote:
> > Why do you need to exclude vectorizable library functions here?
> For "normal" function calls, we have to assume that the functions may read or write memory any location in memory, which may alias memory read or written by another instruction in the same bundle. For functions with vector variants, we should be able to assume that they are pure: they won't write to memory (except when the function takes pointer arguments, which I'm not handling correctly now that I think about it; I'll fix that up).
> 
> Actually, the calculateDependencies function below might be the less-surprising place to handle this.
Then it is better to add correct attributes to such functions. Special processing may lead to problems later.


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  https://reviews.llvm.org/D82550/new/

https://reviews.llvm.org/D82550