[polly] r262607 - [DOC] Add more documentation about the different element type support

[Johannes Doerfert via llvm-commits]

Author: jdoerfert
Date: Thu Mar  3 05:33:30 2016
New Revision: 262607

URL: http://llvm.org/viewvc/llvm-project?rev=262607&view=rev
Log:
[DOC] Add more documentation about the different element type support


Modified:
    polly/trunk/docs/ReleaseNotes.rst

Modified: polly/trunk/docs/ReleaseNotes.rst
URL: http://llvm.org/viewvc/llvm-project/polly/trunk/docs/ReleaseNotes.rst?rev=262607&r1=262606&r2=262607&view=diff
==============================================================================
--- polly/trunk/docs/ReleaseNotes.rst (original)
+++ polly/trunk/docs/ReleaseNotes.rst Thu Mar  3 05:33:30 2016
@@ -26,6 +26,29 @@ can model and optimize such code.
       }
     }
 
+
+If the accesses are not aligned with the size of the access type we model them
+as multiple accesses to an array of smaller elements. This is especially
+usefull for structs containing different typed elements as accesses to them are
+represented using only one base pointer, namely the ``struct`` itself.  In the
+example below the accesses to ``s`` are all modeled as if ``s`` was a single
+char array because the accesses to ``s->A`` and ``s->B`` are not aligned with
+their respective type size (both are off-by-one due to the ``char`` field in
+the ``struct``).
+
+.. code-block:: c
+
+    struct S {
+      char Offset;
+      int A[100];
+      double B[100];
+    };
+
+    void struct_accesses(struct S *s) {
+      for (long i = 0; i < 100; i++)
+        s->B[i] += s->A[i];
+    }
+
 Update of the isl math library
 ------------------------------