[clang] [CIR] Upstream handling of integral-to-pointer casts (PR #161653)

[Andy Kaylor via cfe-commits]

================
@@ -1889,6 +1889,25 @@ mlir::Value ScalarExprEmitter::VisitCastExpr(CastExpr *ce) {
     }
     return v;
   }
+  case CK_IntegralToPointer: {
+    auto DestCIRTy = cgf.convertType(destTy);
+    mlir::Value Src = Visit(const_cast<Expr *>(subExpr));
+
+    // Properly resize by casting to an int of the same size as the pointer.
+    // Clang's IntegralToPointer includes 'bool' as the source, but in CIR
+    // 'bool' is not an integral type.  So check the source type to get the
+    // correct CIR conversion.
+    auto MiddleTy = cgf.cgm.getDataLayout().getIntPtrType(DestCIRTy);
+    auto MiddleVal = builder.createCast(subExpr->getType()->isBooleanType()
+                                            ? cir::CastKind::bool_to_int
+                                            : cir::CastKind::integral,
+                                        Src, MiddleTy);
+
+    if (cgf.cgm.getCodeGenOpts().StrictVTablePointers)
+      llvm_unreachable("NYI");
----------------
andykaylor wrote:

```suggestion
      cgf.cgm.errorNYI(subExpr->getSourceRange(), "IntegralToPointer: strict vtable pointers");
```
We handle NYI cases differently upstream than in the incubator. Whenever possible, we call `errorNYI`.

https://github.com/llvm/llvm-project/pull/161653