[llvm] [LLVM] Add `Type::getTruncatedType()` and use it in Intrinsics.cpp (PR #196239)

[Nikita Popov via llvm-commits]

================
@@ -70,6 +70,14 @@ class IntegerType : public Type {
     return Type::getIntNTy(getContext(), 2 * getScalarSizeInBits());
   }
 
+  /// Returns type half as wide the input type.
+  IntegerType *getTruncatedType() const {
+    unsigned BitWidth = getScalarSizeInBits();
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nikic wrote:

```suggestion
    unsigned BitWidth = getBitWidth();
```


https://github.com/llvm/llvm-project/pull/196239