[llvm] [DAG] Add MVT::widenIntegerElementType and MVT::widenIntegerVectorElementType (PR #206850)

[Simon Pilgrim via llvm-commits]

================
@@ -265,6 +265,28 @@ namespace llvm {
       return MVT::getVectorVT(EltVT, EltCnt * 2);
     }
 
+    // Return a VT for an Integer type doubled in size
+    MVT widenIntegerElementType() const {
+      assert(isScalarInteger() && "Not an integer MVT!");
----------------
RKSimon wrote:

Yes, so it'd work something like:
```
MVT WideSVT = DAG.getIntegerVT(VT.getScalarSizeInBIts() * 2));
return changeElementType(WideSVT);
```

https://github.com/llvm/llvm-project/pull/206850