[llvm] [TTI] Don't drop VP intrinsic args when delegating to non-vp equivalent (PR #147677)

[Luke Lau via llvm-commits]

================
@@ -1781,18 +1781,25 @@ class BasicTTIImplBase : public TargetTransformInfoImplCRTPBase<T> {
         assert(ICA.getArgTypes().size() >= 2 &&
                "Expected VPIntrinsic to have Mask and Vector Length args and "
                "types");
+
+        ArrayRef<const Value *> NewArgs = ArrayRef(ICA.getArgs());
+        if (!ICA.isTypeBasedOnly())
+          NewArgs = NewArgs.drop_back(2);
         ArrayRef<Type *> NewTys = ArrayRef(ICA.getArgTypes()).drop_back(2);
 
         // VPReduction intrinsics have a start value argument that their non-vp
         // counterparts do not have, except for the fadd and fmul non-vp
         // counterpart.
         if (VPReductionIntrinsic::isVPReduction(ICA.getID()) &&
             *FID != Intrinsic::vector_reduce_fadd &&
-            *FID != Intrinsic::vector_reduce_fmul)
+            *FID != Intrinsic::vector_reduce_fmul) {
+          if (!ICA.isTypeBasedOnly())
+            NewArgs = NewArgs.drop_front();
           NewTys = NewTys.drop_front();
+        }
----------------
lukel97 wrote:

Yeah it's covered by the existing tests at llvm/test/Analysis/CostModel/RISCV/reduce-fadd/fmul.ll. It just so happens that there's no test diff with that change because the type-based and value-based costing is the same for these intrinsics, i.e. here's the code for the value costing path:

```c++
    case Intrinsic::vector_reduce_add:
    case Intrinsic::vector_reduce_mul:
    case Intrinsic::vector_reduce_and:
    case Intrinsic::vector_reduce_or:
    case Intrinsic::vector_reduce_xor:
    case Intrinsic::vector_reduce_smax:
    case Intrinsic::vector_reduce_smin:
    case Intrinsic::vector_reduce_fmax:
    case Intrinsic::vector_reduce_fmin:
    case Intrinsic::vector_reduce_fmaximum:
    case Intrinsic::vector_reduce_fminimum:
    case Intrinsic::vector_reduce_umax:
    case Intrinsic::vector_reduce_umin: {
      IntrinsicCostAttributes Attrs(IID, RetTy, Args[0]->getType(), FMF, I, 1);
      return getTypeBasedIntrinsicInstrCost(Attrs, CostKind);
    }
```

https://github.com/llvm/llvm-project/pull/147677