[rtems commit] rtems: Add RTEMS_ALIGN_DOWN()

[Sebastian Huber]

Module:    rtems
Branch:    master
Commit:    641b31a48d48c59ef73c47a225f1012b11e0eea7
Changeset: http://git.rtems.org/rtems/commit/?id=641b31a48d48c59ef73c47a225f1012b11e0eea7

Author:    Sebastian Huber <sebastian.huber at embedded-brains.de>
Date:      Wed Sep 16 10:33:52 2020 +0200

rtems: Add RTEMS_ALIGN_DOWN()

Update #3959.
Update #4074.

---

 cpukit/include/rtems/score/basedefs.h | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/cpukit/include/rtems/score/basedefs.h b/cpukit/include/rtems/score/basedefs.h
index 5a7e4e4..4d16c88 100644
--- a/cpukit/include/rtems/score/basedefs.h
+++ b/cpukit/include/rtems/score/basedefs.h
@@ -220,6 +220,21 @@
 #endif
 
 /**
+ * @brief Returns the specified value aligned down to the specified alignment.
+ *
+ * @param _value is the value to align down.
+ *
+ * @param _alignment is the desired alignment in bytes.  The alignment shall be
+ *   a power of two, otherwise the returned value is undefined.  The alignment
+ *   parameter is evaluated twice.
+ *
+ * @return The specified value aligned down to the specified alignment is
+ *   returned.
+ */
+#define RTEMS_ALIGN_DOWN( _value, _alignment ) \
+  ( ( _value ) & ~( ( _alignment ) - 1 ) )
+
+/**
  * @brief Instructs the compiler to enforce the specified alignment.
  */
 #if defined(__GNUC__)