[llvm] [LangRef] Clarify definition of fragments and debug intrinsics (PR #82019)

[Felipe de Azevedo Piovezan via llvm-commits]

================
@@ -130,6 +130,40 @@ debugging information influences optimization passes then it will be reported
 as a failure.  See :doc:`TestingGuide` for more information on LLVM test
 infrastructure and how to run various tests.
 
+.. _variables_and_variable_fragments:
+
+Variables and Variable Fragments
+================================
+
+Source language variables (or just "variables") are represented by `local
+variable <LangRef.html#dilocalvariable>`_ and `global variable
+<LangRef.html#diglobalvariable>`_ metadata nodes.
+
+When variables are not allocated to contiguous memory or to a single LLVM value
+the metadata must record enough information to describe each "piece" or
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felipepiovezan wrote:

Could we say "described by a single expression" then? IIRC when we have multiple fragments, each fragment is described by its own expression (and its own intrinsic)

https://github.com/llvm/llvm-project/pull/82019