[llvm-branch-commits] [llvm] [GOFF] Add writing of section symbols (PR #133799)

[Kai Nacke via llvm-branch-commits]

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@@ -0,0 +1,113 @@
+//===- MCGOFFAttributes.h - Attributes of GOFF symbols --------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Defines the various attribute collections defining GOFF symbols.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_MC_MCGOFFATTRIBUTES_H
+#define LLVM_MC_MCGOFFATTRIBUTES_H
+
+#include "llvm/ADT/StringRef.h"
+#include "llvm/BinaryFormat/GOFF.h"
+
+namespace llvm {
+namespace GOFF {
+// An "External Symbol Definition" in the GOFF file has a type, and depending on
+// the type a different subset of the fields is used.
+//
+// Unlike other formats, a 2 dimensional structure is used to define the
+// location of data. For example, the equivalent of the ELF .text section is
+// made up of a Section Definition (SD) and a class (Element Definition; ED).
+// The name of the SD symbol depends on the application, while the class has the
+// predefined name C_CODE/C_CODE64 in AMODE31 and AMODE64 respectively.
+//
+// Data can be placed into this structure in 2 ways. First, the data (in a text
+// record) can be associated with an ED symbol. To refer to data, a Label
+// Definition (LD) is used to give an offset into the data a name. When binding,
+// the whole data is pulled into the resulting executable, and the addresses
+// given by the LD symbols are resolved.
+//
+// The alternative is to use a Part Definition (PR). In this case, the data (in
+// a text record) is associated with the part. When binding, only the data of
+// referenced PRs is pulled into the resulting binary.
+//
+// Both approaches are used, which means that the equivalent of a section in ELF
+// results in 3 GOFF symbols, either SD/ED/LD or SD/ED/PR. Moreover, certain
+// sections are fine with just defining SD/ED symbols. The SymbolMapper takes
+// care of all those details.
+
+// Attributes for SD symbols.
+struct SDAttr {
+  GOFF::ESDTaskingBehavior TaskingBehavior = GOFF::ESD_TA_Unspecified;
+  GOFF::ESDBindingScope BindingScope = GOFF::ESD_BSC_Unspecified;
+};
+
+// Attributes for ED symbols.
+struct EDAttr {
+  bool IsReadOnly = false;
+  GOFF::ESDExecutable Executable = GOFF::ESD_EXE_Unspecified;
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redstar wrote:

There may be no LD. For example, the `B_IDRL` section has only SD and ED.

https://github.com/llvm/llvm-project/pull/133799