[PATCH] D115757: [SLP]Generalize cost model.

[Alexey Bataev via Phabricator via llvm-commits]

ABataev added inline comments.


================
Comment at: llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp:5840
+    if (!I)
+      return true;
     auto *Op = cast<Instruction>(V)->getOperand(OpIdx);
----------------
RKSimon wrote:
> ABataev wrote:
> > RKSimon wrote:
> > > true?
> > Here is my idea. Generally speaking, here we can have only undef/poison or just a pointer (as part of getelementpr node) currently (maybe, need to add an assert). I thought that because of that we can treat its (virtual) operand as power-of-2, since it can be any value. Thoughts?
> Still not sure about this - this undef case is fine, but the GEP I can imagine might not work in all special cases.
> 
> How good is return isa<UndefValue>(V); instead?
GetElementPtr may have just a pointer, which is not a GEP instructions.
Say, we have this:
```
void @foo(ptr %v) {
...
load %v
%n = getelementptr i32, ptr v, 1
load %n
...
}
```
and we may have a ПУЗ node which includes {%v, %n}. Here %v is not a GEP though still part of the GEP node and we consider as `gentlementptr ptr %v, 0`.


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  https://reviews.llvm.org/D115757/new/

https://reviews.llvm.org/D115757