From d40a4f4bc38a1116ff040a01bd80265cfe9e4550 Mon Sep 17 00:00:00 2001
From: Joseph Heenan <joseph@heenan.me.uk>
Date: Sat, 13 Aug 2016 06:51:30 +0000
Subject: [PATCH 1/2] #104 Fix compile failing on raspberry pi 3

When we test if the compiler options work, we didn't test for the
possibility of the compiler crashing which unfortunately it does on
the raspberry pi 3 - crashing in this case means returning exit code
134 (i.e. SIGABRT).

Change the test so that instead of testing for one particular failure,
we invert and test for success - treating everything else as failure.
---
 configure.ac | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/configure.ac b/configure.ac
index a256f3d4..29e443fd 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1045,11 +1045,11 @@ rm -f $TMPO
 rm -f $TMPC
 
 
-if test "x${TMP}" = "x1" ; then
+if test "x${TMP}" = "x0" ; then
+	echo "CPU optimization: $CPU_OPTIONS"
+else
 	CPU_OPTIONS=""
 	echo "No CPU optimizations will be added"
-else
-	echo "CPU optimization: $CPU_OPTIONS"
 fi
 
 else

From c7ca2af868b79ece35ed521e9e6d4ed7a8cbcc84 Mon Sep 17 00:00:00 2001
From: Joseph Heenan <joseph@heenan.me.uk>
Date: Sat, 13 Aug 2016 07:22:10 +0000
Subject: [PATCH 2/2] Fix #104 Use optimal compilation options on Raspberry Pi
 3
MIME-Version: 1.0
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Content-Transfer-Encoding: 8bit

gcc on the raspberry pi 3 crashes when called from our configure
script, and even in simpler cases:

$ gcc -mcpu=native -march=native
*** Error in `gcc': double free or corruption (top): 0x0190dbc0 ***
Aborted

So we need to add explicit optimisation options if we want to build an
optimal binary on the Pi 3.

As per:

https://www.element14.com/community/community/raspberry-pi/blog/2016/02/29/the-most-comprehensive-raspberry-pi-comparison-benchmark-ever

the raspberry pi 3 is an armv8, but cpuinfo incorrectly reports it as
an armv7. So we can’t detect the CPU using /proc/cpuinfo.

Instead we use /proc/device-tree/model, which explicit has the
Raspberry PI type in it, e.g. “Raspberry Pi 3 Model B Rev 1.2”.

https://www.raspberrypi.org/forums/viewtopic.php?t=144115&p=952479
lists hopefully correct optimal gcc flags, namely:

Some basic options that should be the defaults anyway:-
-mfloat-abi=hard -mlittle-endian -munaligned-access
(confirmed; these are the defaults)

Pi1 -mcpu=arm1176jzf-s  -mfpu=vfp
Pi2 -mcpu=cortex-a7  -mfpu=neon-vfpv4
Pi3 -mcpu=cortex-a53  -mfpu=neon-fp-armv8
---
 configure.ac | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index 29e443fd..458735e6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -845,7 +845,18 @@ if test "${OPTIMIZECPU}" = "yes"; then
 # Try to autodetect cpu type
 CPU_NAME="unknown"
 CPU_TYPE="unknown"
-if test -e "/proc/cpuinfo" ; then
+if test -e "/proc/device-tree/model"; then
+    # explicit test for RPI3 as /proc/cpuinfo reports armv7 even though
+    # it is armv8
+    RPI3=`grep "Raspberry Pi 3 Model" /proc/device-tree/model`
+    if test "x${RPI3}" != "x"; then
+        CPU_NAME="Raspberry Pi 3"
+        CPU_TYPE="Raspberry Pi 3"
+	CPU_OPTIONS="-mcpu=cortex-a53 -mfpu=neon-fp-armv8"
+    fi
+fi
+
+if test "x${CPU_TYPE}" = "xunknown" && test -e "/proc/cpuinfo" ; then
 	intel[[30]]="-march=i386"
 	intel[[32]]="-march=i386"
 	intel[[34]]="-march=i386"