[RISCV][TTI] Fix crash of non-built-in vector type cost quering.

For the non-built-in vector type, the RISCV cost model cannot handle
this propely. So fall back to the BasicTTI for this situation.

Fixes: #166732

Author: ElvisWang123

llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp

@@ -1683,7 +1683,8 @@ InstructionCost RISCVTTIImpl::getCastInstrCost(unsigned Opcode, Type *Dst,
       !TypeSize::isKnownLE(DL.getTypeSizeInBits(Src),
                            SrcLT.second.getSizeInBits()) ||
       !TypeSize::isKnownLE(DL.getTypeSizeInBits(Dst),
-                           DstLT.second.getSizeInBits()))
+                           DstLT.second.getSizeInBits()) ||
+      SrcLT.first > 1 || DstLT.first > 1)
     return BaseT::getCastInstrCost(Opcode, Dst, Src, CCH, CostKind, I);
 
   // The split cost is handled by the base getCastInstrCost

llvm/test/Analysis/CostModel/RISCV/cast.ll

@@ -6239,3 +6239,13 @@ define void @legalization_crash() {
   fptoui <192 x float> undef to <192 x i1>
   ret void
 }
+
+; Test that BitInt cases won't crash at cost model.
+define void @BitInt_crash() {
+; ZVE64X-LABEL: 'BitInt_crash'
+; ZVE64X-NEXT:  Cost Model: Found an estimated cost of 2043 for instruction: %1 = bitcast <16 x i64> poison to <512 x i2>
+; ZVE64X-NEXT:  Cost Model: Found an estimated cost of 0 for instruction: ret void
+;
+  bitcast <16 x i64> poison to <512 x i2>
+  ret void
+}