[llvm] [LangRef] Try to formalize the definition of "odr" in LLVM IR. (PR #92619)

[Fangrui Song via llvm-commits]

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@@ -290,13 +290,17 @@ linkage:
     symbol is weak until linked, if not linked, the symbol becomes null
     instead of being an undefined reference.
 ``linkonce_odr``, ``weak_odr``
-    Some languages allow differing globals to be merged, such as two
-    functions with different semantics. Other languages, such as
-    ``C++``, ensure that only equivalent globals are ever merged (the
-    "one definition rule" --- "ODR"). Such languages can use the
-    ``linkonce_odr`` and ``weak_odr`` linkage types to indicate that the
-    global will only be merged with equivalent globals. These linkage
-    types are otherwise the same as their non-``odr`` versions.
+    The ``odr`` suffix indicates that all globals defined with the given name
+    are equivalent, along the lines of the C++ "one definition rule" ("ODR").
+    Informally, this means we can inline functions and fold loads of constants.
+
+    Formally, use the following definition: when an ``odr`` function is
+    called, one of the definitions is non-deterministically chosen to run. For
+    ``odr`` variables, if the value any byte is not equal in all initializers,
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MaskRay wrote:

typo: if any byte in the value?

https://github.com/llvm/llvm-project/pull/92619