[libcxx-commits] [libcxx] [llvm] [compiler-rt] [clang-tools-extra] [clang] [flang] [libc] [Clang] Generate the GEP instead of adding AST nodes (PR #73730)

[Bill Wendling via libcxx-commits]

================
@@ -3946,6 +4080,32 @@ static Address emitArraySubscriptGEP(CodeGenFunction &CGF, Address addr,
   return Address(eltPtr, CGF.ConvertTypeForMem(eltType), eltAlign);
 }
 
+static bool GetFieldOffsetInBits(CodeGenFunction &CGF, const RecordDecl *RD,
+                                 const FieldDecl *FD, uint64_t &Offset) {
+  ASTContext &Ctx = CGF.getContext();
+  const ASTRecordLayout &Layout = Ctx.getASTRecordLayout(RD);
+  unsigned FieldNo = 0;
+
+  for (const Decl *D : RD->decls()) {
+    if (const auto *Record = dyn_cast<RecordDecl>(D))
+      if (GetFieldOffsetInBits(CGF, Record, FD, Offset)) {
+        Offset += Layout.getFieldOffset(FieldNo);
+        return true;
+      }
+
+    if (const auto *Field = dyn_cast<FieldDecl>(D))
+      if (FD == Field) {
+        Offset += Layout.getFieldOffset(FieldNo);
+        return true;
+      }
+
+    if (isa<FieldDecl>(D))
+      ++FieldNo;
+  }
----------------
bwendling wrote:

If you call `getFieldIndex` for a `FieldDecl` that's not in a top-level of the `RecordDecl`, it will assert. So I need to go through each field one at a time, because the method is broken.

I was planning on adding that to the record layout contexts, but because this patch has been through the wringer, I didn't want to throw yet another reason for people to hate it.

https://github.com/llvm/llvm-project/pull/73730