Merge pull request #1014 from flang-compiler/jpr-c1b-fix

Make extern weak symbols for type descriptor not defined in translation unit

Author: jeanPerier

flang/lib/Optimizer/CodeGen/CodeGen.cpp

@@ -1172,9 +1172,21 @@ struct EmboxCommonConversion : public FIROpConversion<OP> {
       return rewriter.create<mlir::LLVM::AddressOfOp>(loc, ty,
                                                       global.sym_name());
     }
-    // Builtin derived types have no type descriptors. Return nullptr, that is
-    // what the runtime expects for these types.
-    return rewriter.create<mlir::LLVM::NullOp>(loc, this->voidPtrTy());
+    // The global does not exist in the current translation unit, but may be
+    // defined elsewhere (e.g., type defined in a module).
+    // For now, create a extern_weak symbols (will become nullptr if unresolved)
+    // to support generating code without the front-end generated symbols.
+    // These could be made available_externally to require the symbols to be
+    // defined elsewhere and to cause link-time failure otherwise.
+    auto i8Ty = rewriter.getIntegerType(8);
+    mlir::OpBuilder modBuilder(module.getBodyRegion());
+    // TODO: The symbol should be lowered to constant in lowering, they are read
+    // only.
+    modBuilder.create<mlir::LLVM::GlobalOp>(loc, i8Ty, /*isConstant=*/false,
+                                            mlir::LLVM::Linkage::ExternWeak,
+                                            name, mlir::Attribute{});
+    auto ty = mlir::LLVM::LLVMPointerType::get(i8Ty);
+    return rewriter.create<mlir::LLVM::AddressOfOp>(loc, ty, name);
   }
 
   template <typename BOX>

flang/test/Fir/type-descriptor.fir

@@ -1,13 +1,23 @@
 // RUN: tco -o - %s | FileCheck %s
 
+!type_defined_elsewhere = type !fir.type<_QMsome_moduleTtype_defined_elsewhere{j:i32}>
+fir.global internal @_QFfooEx2 : !fir.box<!fir.heap<!type_defined_elsewhere>> {
+  %0 = fir.zero_bits !fir.heap<!type_defined_elsewhere>
+  %1 = fir.embox %0 : (!fir.heap<!type_defined_elsewhere>) -> !fir.box<!fir.heap<!type_defined_elsewhere>>
+  fir.has_value %1 : !fir.box<!fir.heap<!type_defined_elsewhere>>
+}
+// CHECK: @_QMsome_moduleE.dt.type_defined_elsewhere = extern_weak global i8
+// CHECK: @_QFfooEx2 = internal global { %_QMsome_moduleTtype_defined_elsewhere*, i64, i32, i8, i8, i8, i8, i8*, [1 x i64] }
+// CHECK-SAME: { %_QMsome_moduleTtype_defined_elsewhere* null, i64 ptrtoint (i32* getelementptr (i32, i32* null, i32 1) to i64),
+// CHECK-SAME: i32 20180515, i8 0, i8 34, i8 2, i8 1, i8* @_QMsome_moduleE.dt.type_defined_elsewhere, [1 x i64] undef }
+
 !sometype = type !fir.type<_QFfooTsometype{num:i32,values:!fir.box<!fir.ptr<!fir.array<?x?xf32>>>}>
 fir.global internal @_QFfooE.dt.sometype : i8
 fir.global internal @_QFfooEx : !fir.box<!fir.heap<!sometype>> {
   %0 = fir.zero_bits !fir.heap<!sometype>
   %1 = fir.embox %0 : (!fir.heap<!sometype>) -> !fir.box<!fir.heap<!sometype>>
   fir.has_value %1 : !fir.box<!fir.heap<!sometype>>
 }
-
 // CHECK: @_QFfooEx = internal global { %_QFfooTsometype*, i64, i32, i8, i8, i8, i8, i8*, [1 x i64] }
 // CHECK-SAME: { %_QFfooTsometype* null, i64 ptrtoint (%_QFfooTsometype* getelementptr (%_QFfooTsometype, %_QFfooTsometype* null, i32 1) to i64),
 // CHECK-SAME: i32 20180515, i8 0, i8 34, i8 2, i8 1, i8* @_QFfooE.dt.sometype, [1 x i64] undef }