[Help-smalltalk] [PATCH 2/4] embedded: Allow to disable the prefetching.

[Holger Hans Peter Freyther]

Disabling the prefetching is a win on arm9 (arm926ejs, e.g. TI
Davinci DM644x). This was benchmarked using the simple Bench.st
benchmark.

2013-04-28  Holger Hans Peter Freyther  <address@hidden>

        * libgst/gstpriv.h: Allow to disable the DO_PREFETCH.
---
 configure.ac     |    9 +++++++++
 libgst/ChangeLog |    4 ++++
 libgst/gstpriv.h |    3 ++-
 3 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index fbf1ce9..e0cb5e6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -655,6 +655,15 @@ if test "$enable_preemption" != no; then
     [Define to enable preemptive multitasking of Smalltalk processes])
 fi
 
+AC_ARG_ENABLE(prefetch,
+[  --disable-prefetch      disable memory prefetch macros], ,
+enable_prefetch=yes)
+
+if test "$enable_prefetch" != no; then
+  AC_DEFINE(ENABLE_PREFETCH, 1,
+    [Define to enable usage of __builtin_prefetch])
+fi
+
 GST_ARG_ENABLE_MODULES([Blox,TCP])
 
 dnl 
diff --git a/libgst/ChangeLog b/libgst/ChangeLog
index 4abaa9a..f952307 100644
--- a/libgst/ChangeLog
+++ b/libgst/ChangeLog
@@ -1,3 +1,7 @@
+2013-04-28  Holger Hans Peter Freyther  <address@hidden>
+
+       * libgst/gstpriv.h: Allow to disable the DO_PREFETCH.
+
 2013-04-25  Holger Hans Peter Freyther  <address@hidden>
 
        * libgst/md-config.h: Add cases for the ARM architecture.
diff --git a/libgst/gstpriv.h b/libgst/gstpriv.h
index 7127438..b3d100f 100644
--- a/libgst/gstpriv.h
+++ b/libgst/gstpriv.h
@@ -175,7 +175,8 @@
 #define PREF_T2 8
 #define PREF_NTA 12
 
-#if GNUC_PREREQ (3, 1)
+/* the prefetch is a loss on on a ARM9 (TI Davinci), hack it out */
+#if defined(ENABLE_PREFETCH) && GNUC_PREREQ (3, 1)
 #define DO_PREFETCH(x, distance, k) \
   __builtin_prefetch (((char *) (x)) \
                      + (((k) & PREF_BACKWARDS ? -(distance) : (distance)) \
-- 
1.7.10.4