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

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llvmorg-github-actions[bot] wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clangir

Author: Elio (xiongzile)

<details>
<summary>Changes</summary>

Refer: https://github.com/llvm/llvm-project/issues/192330

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


2 Files Affected:

- (modified) clang/include/clang/CIR/MissingFeatures.h (-1) 
- (modified) clang/lib/CIR/CodeGen/CIRGenItaniumCXXABI.cpp (+3-2) 


``````````diff
diff --git a/clang/include/clang/CIR/MissingFeatures.h b/clang/include/clang/CIR/MissingFeatures.h
index 645fae3e4404d..36093ca35ec01 100644
--- a/clang/include/clang/CIR/MissingFeatures.h
+++ b/clang/include/clang/CIR/MissingFeatures.h
@@ -339,7 +339,6 @@ struct MissingFeatures {
   static bool vlas() { return false; }
   static bool vtableInitialization() { return false; }
   static bool vtableEmitMetadata() { return false; }
-  static bool vtableRelativeLayout() { return false; }
   static bool weakRefReference() { return false; }
   static bool writebacks() { return false; }
   static bool msvcCXXPersonality() { return false; }
diff --git a/clang/lib/CIR/CodeGen/CIRGenItaniumCXXABI.cpp b/clang/lib/CIR/CodeGen/CIRGenItaniumCXXABI.cpp
index 946739d4e1702..48519ddac1a03 100644
--- a/clang/lib/CIR/CodeGen/CIRGenItaniumCXXABI.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenItaniumCXXABI.cpp
@@ -2057,8 +2057,9 @@ mlir::Value CIRGenItaniumCXXABI::getVirtualBaseClassOffset(
 
   mlir::Value vbaseOffset;
   if (cgm.getLangOpts().RelativeCXXABIVTables) {
-    assert(!cir::MissingFeatures::vtableRelativeLayout());
-    cgm.errorNYI(loc, "getVirtualBaseClassOffset: relative layout");
+    vbaseOffset = cgf.getBuilder().createLoad(
+        loc, Address(vbaseOffsetPtr, cgm.sInt32Ty,
+                     CharUnits::fromQuantity(4))); // vbase.offset
   } else {
     mlir::Value offsetPtr = builder.createBitcast(
         vbaseOffsetPtr, builder.getPointerTo(cgm.ptrDiffTy));

``````````

</details>


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