[PATCH] D47854: [LangRef] Clarify semantics of load metadata.

[Eli Friedman via Phabricator via llvm-commits]

efriedma updated this revision to Diff 151558.
efriedma added a comment.

Actually, move the dereferenceable changes out of this patch; it should all go together, separately.


Repository:
  rL LLVM

https://reviews.llvm.org/D47854

Files:
  docs/LangRef.rst


Index: docs/LangRef.rst
===================================================================
--- docs/LangRef.rst
+++ docs/LangRef.rst
@@ -4933,10 +4933,11 @@
 
 ``range`` metadata may be attached only to ``load``, ``call`` and ``invoke`` of
 integer types. It expresses the possible ranges the loaded value or the value
-returned by the called function at this call site is in. The ranges are
-represented with a flattened list of integers. The loaded value or the value
-returned is known to be in the union of the ranges defined by each consecutive
-pair. Each pair has the following properties:
+returned by the called function at this call site is in. If the loaded or
+returned value is not in the specified range, the behavior is undefined. The
+ranges are represented with a flattened list of integers. The loaded value or
+the value returned is known to be in the union of the ranges defined by each
+consecutive pair. Each pair has the following properties:
 
 -  The type must match the type loaded by the instruction.
 -  The pair ``a,b`` represents the range ``[a,b)``.
@@ -7936,7 +7937,8 @@
 entries. If a load instruction tagged with the ``!invariant.load``
 metadata is executed, the optimizer may assume the memory location
 referenced by the load contains the same value at all points in the
-program where the memory location is known to be dereferenceable.
+program where the memory location is known to be dereferenceable;
+otherwise, the behavior is undefined.
 
 The optional ``!invariant.group`` metadata must reference a single metadata name
  ``<index>`` corresponding to a metadata node with no entries.
@@ -7946,9 +7948,9 @@
 metadata name ``<index>`` corresponding to a metadata node with no
 entries. The existence of the ``!nonnull`` metadata on the
 instruction tells the optimizer that the value loaded is known to
-never be null. This is analogous to the ``nonnull`` attribute
-on parameters and return values. This metadata can only be applied
-to loads of a pointer type.
+never be null. If the value is null at runtime, the behavior is undefined.
+This is analogous to the ``nonnull`` attribute on parameters and return
+values. This metadata can only be applied to loads of a pointer type.
 
 The optional ``!dereferenceable`` metadata must reference a single metadata
 name ``<deref_bytes_node>`` corresponding to a metadata node with one ``i64``
@@ -7975,7 +7977,8 @@
 optimizer that the value loaded is known to be aligned to a boundary specified
 by the integer value in the metadata node. The alignment must be a power of 2.
 This is analogous to the ''align'' attribute on parameters and return values.
-This metadata can only be applied to loads of a pointer type.
+This metadata can only be applied to loads of a pointer type. If the returned
+value is not appropriately aligned at runtime, the behavior is undefined.
 
 Semantics:
 """"""""""


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