[lld] [LLD] Add CLASS syntax to SECTIONS (PR #95323)

[Daniel Thornburgh via llvm-commits]

================
@@ -198,13 +198,52 @@ the current location to a max-page-size boundary, ensuring that the next
 LLD will insert ``.relro_padding`` immediately before the symbol assignment
 using ``DATA_SEGMENT_RELRO_END``.
 
+Section Classes
+~~~~~~~~~~~~~~~
+
+``SECTIONS`` commands can define classes of input sections:
+
+::
+
+  SECTIONS {
+    CLASS(class_name) {
+      input-section-description
+      input-section-description
+      ...
+    }
+  }
+
+Input section descriptions can refer to a class using ``CLASS(class_name)``
+instead of the usual filename and section name patterns. For example:
+
+::
+
+  SECTIONS {
----------------
mysterymath wrote:

I didn't have a particular practical reason to spell them inside `SECTIONS`, just one in terms of mental models. (Well, it's *really* that this design was cribbed wholesale from Roland, but I do agree with it.)  `SECTIONS` naturally namespaces `CLASS`, and class definitions seem more like symbol assignments, `ENTRY`, output section descriptions, and `OVERLAY` than they do the other top level objects (`MEMORY`, `PHDR`, and `VERSION`). There's also a natural analogy between output sections and class definitions, and most output sections are defined in `SECTIONS`.

https://github.com/llvm/llvm-project/pull/95323