[PATCH] D21415: LangRef: Note expectations when loading with extra alignment

[Matt Arsenault via llvm-commits]

arsenm updated this revision to Diff 60920.
arsenm added a comment.

Fix typo. Clarify store rules. Mention sanitizer interference


http://reviews.llvm.org/D21415

Files:
  docs/LangRef.rst

Index: docs/LangRef.rst
===================================================================
--- docs/LangRef.rst
+++ docs/LangRef.rst
@@ -7009,7 +7009,12 @@
 to ensure that the alignment information is correct. Overestimating the
 alignment results in undefined behavior. Underestimating the alignment
 may produce less efficient code. An alignment of 1 is always safe. The
-maximum possible alignment is ``1 << 29``.
+maximum possible alignment is ``1 << 29``. An alignment value higher
+than the size of the loaded type implies memory up to the alignment
+value bytes can be safely loaded without trapping in the default
+address space. Access of the high bytes can interfere with debugging
+tools, so should not be accessed if the function has the
+``sanitize_thread`` or ``sanitize_address`` attributes.
 
 The optional ``!nontemporal`` metadata must reference a single
 metadata name ``<index>`` corresponding to a metadata node with one
@@ -7134,7 +7139,14 @@
 to ensure that the alignment information is correct. Overestimating the
 alignment results in undefined behavior. Underestimating the
 alignment may produce less efficient code. An alignment of 1 is always
-safe. The maximum possible alignment is ``1 << 29``.
+safe. The maximum possible alignment is ``1 << 29``. An alignment
+value higher than the size of the stored type implies memory up to the
+alignment value bytes can be stored to without trapping in the default
+address space. Storing to the higher bytes however may result in data
+races if another thread can access the same address. Introducing a
+data race is not allowed. Storing to the extra bytes is not allowed
+even in situations where a data race is known to not exist if the
+function has the ``sanitize_address`` attribute.
 
 The optional ``!nontemporal`` metadata must reference a single metadata
 name ``<index>`` corresponding to a metadata node with one ``i32`` entry of


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