[llvm] [RISCV] Fix crash when unrolling loop containing vector instructions (PR #83384)

[Shih-Po Hung via llvm-commits]

================
@@ -37,6 +37,9 @@ static cl::opt<unsigned> SLPMaxVF(
 InstructionCost
 RISCVTTIImpl::getRISCVInstructionCost(ArrayRef<unsigned> OpCodes, MVT VT,
                                       TTI::TargetCostKind CostKind) {
+  // Check if the type is valid for all CostKind
+  if (!VT.isVector())
+    return InstructionCost::getInvalid();
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arcbbb wrote:

It is from LoopUnrollPass along the way from TTI.getInstructionCost to TTI.getShuffleCost for
```
%splat.splat.i.i.i = shufflevector <2 x float> zeroinitializer, <2 x float> zeroinitializer, <2 x i32> zeroinitializer
```
The data type is `<2 x float>`, but becomes `float` after `getTypeLegalizationCost(Tp);` then enters getRISCVInstructionCost().
I'm just not sure how a vector type can be generated without a vector support.

If it is true, we might consider checking if the type is still vector after legalization at the beginning of TTI functions which accept vector types.

https://github.com/llvm/llvm-project/pull/83384