[PATCH] D31758: Invariant.group and mustalias docs fixes

[Piotr Padlewski via Phabricator via llvm-commits]

Prazek created this revision.

Alias analysis would like to know that
invariant.group.barrier returns pointer that mustalias,
but this can't imply that we can replace one pointer with another


https://reviews.llvm.org/D31758

Files:
  docs/AliasAnalysis.rst
  docs/LangRef.rst


Index: docs/LangRef.rst
===================================================================
--- docs/LangRef.rst
+++ docs/LangRef.rst
@@ -5118,6 +5118,19 @@
    !0 = !{!"magic ptr"}
    !1 = !{!"other ptr"}
 
+Because `invariant.group` is tied to the SSA value of the pointer operand,
+replacing one pointer by another based on `mustalias` returned from Alias
+Analysis can't be done without discarding the `invariant.group` metadata.
+.. code-block:: llvm
+  %v = load i8, i8* %x, !invariant.group !0
+  ; if %x mustalias %y then we can replace the above instruction with
+  %v = load i8, i8* %y
+
+Where replacing by SSA values equivalence is not required to discard
+`invariant.group` metadata.
+
+
+
 '``type``' Metadata
 ^^^^^^^^^^^^^^^^^^^
 
Index: docs/AliasAnalysis.rst
===================================================================
--- docs/AliasAnalysis.rst
+++ docs/AliasAnalysis.rst
@@ -136,7 +136,7 @@
 
 The ``MustAlias`` response may only be returned if the two memory objects are
 guaranteed to always start at exactly the same location. A ``MustAlias``
-response implies that the pointers compare equal.
+response not implies that the pointers compare equal.
 
 The ``getModRefInfo`` methods
 -----------------------------


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