================
@@ -2744,6 +2702,12 @@ class VPSingleDefBundleRecipe : public VPSingleDefRecipe
{
/// vector operands, performing a reduction.add on the result, and adding
/// the scalar result to a chain.
MulAccumulateReduction,
+ /// Represent an inloop multiply-accumulate reduction, multiplying the
+ /// extended vector operands, negating the multiplication, performing a
+ /// reduction.add
+ /// on the result, and adding
+ /// the scalar result to a chain.
+ ExtNegatedMulAccumulateReduction,
----------------
sdesmalen-arm wrote:
This looks like something that is currently not yet supported for InLoop
reductions. Because you're trying to align the PartialReductions with other
reductions, we need to add support for `sub` reductions as well to InLoop
reductions. I'd suggest pulling that out into a separate PR (and rebasing this
one on top of that).
This will require a few changes:
* `RecurrenceDescriptor::getReductionOpChain` does not recognise sub-reductions
at the moment, which will need fixing. The reason for that is described in one
of the comments:
```
// [..] Subs are also currently not allowed (which are usually
// treated as part of a add reduction) as they are expected to generally be
// more expensive than out-of-loop reductions, and need to be costed more
// carefully.
```
Because you're adding a cost-model for those here, we can now handle
sub-reductions as well.
* When the `VPReductionRecipe` is created in
`LoopVectorizationPlanner::adjustRecipesForReductions`, for in-loop
sub-reductions we'd need to add a `sub(0, VecOp)` similar to how we do this for
partial reductions.
When we finally properly merge the two implementations, the special code we
currently have for partial reductions to insert the `sub` can be removed, in
favour of the code that we'd need to add for in-loop reductions. (FWIW, that is
not something I'm suggesting to do as part of this PR, but rather as a future
follow-up)
https://github.com/llvm/llvm-project/pull/146073
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