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

[John McCall via libcxx-commits]

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@@ -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;
+  }
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rjmccall wrote:

Let's start by breaking that out as a separate patch.  Just make a method on `ASTRecordLayout` that takes an `IndirectFieldDecl` and recursively adds up the offsets for every step in the path.

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