[clang] [CIR] Relative vtable layout for virtual base offset (PR #195025)

[via cfe-commits]

================
@@ -2057,8 +2057,11 @@ mlir::Value CIRGenItaniumCXXABI::getVirtualBaseClassOffset(
 
   mlir::Value vbaseOffset;
   if (cgm.getLangOpts().RelativeCXXABIVTables) {
-    assert(!cir::MissingFeatures::vtableRelativeLayout());
-    cgm.errorNYI(loc, "getVirtualBaseClassOffset: relative layout");
+    mlir::Value offsetPtr = builder.createBitcast(
----------------
xiongzile wrote:

I noticed there are several other places guarded by this feature.

Should I aim to implement full support in this patch？

https://github.com/llvm/llvm-project/pull/195025