From 6618346148aec206393880c269bd0e464d2d29f5 Mon Sep 17 00:00:00 2001
From: Scott Lahteine <sourcetree@thinkyhead.com>
Date: Sat, 18 Mar 2017 10:18:40 -0500
Subject: [PATCH] Patches to work around "register spill" compiler bug

---
 Marlin/temperature.cpp | 13 +++++++++++++
 Marlin/temperature.h   |  3 ++-
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/Marlin/temperature.cpp b/Marlin/temperature.cpp
index af76edb0f..883133806 100644
--- a/Marlin/temperature.cpp
+++ b/Marlin/temperature.cpp
@@ -24,6 +24,8 @@
  * temperature.cpp - temperature control
  */
 
+
+
 #include "Marlin.h"
 #include "ultralcd.h"
 #include "temperature.h"
@@ -666,6 +668,17 @@ float Temperature::get_pid_output(int e) {
  *  - Apply filament width to the extrusion rate (may move)
  *  - Update the heated bed PID output value
  */
+
+/**
+ * The following line SOMETIMES results in the dreaded "unable to find a register to spill in class 'POINTER_REGS'"
+ * compile error.
+ *    thermal_runaway_protection(&thermal_runaway_state_machine[e], &thermal_runaway_timer[e], current_temperature[e], target_temperature[e], e, THERMAL_PROTECTION_PERIOD, THERMAL_PROTECTION_HYSTERESIS);
+ *
+ * This is due to a bug in the C++ compiler used by the Arduino IDE from 1.6.10 to at least 1.8.1.
+ *
+ * The work around is to add the compiler flag "__attribute__((__optimize__("O2")))" to the declaration for manage_heater()
+ */
+//void Temperature::manage_heater()  __attribute__((__optimize__("O2")));
 void Temperature::manage_heater() {
 
   if (!temp_meas_ready) return;
diff --git a/Marlin/temperature.h b/Marlin/temperature.h
index e59214844..d6451554f 100644
--- a/Marlin/temperature.h
+++ b/Marlin/temperature.h
@@ -241,7 +241,8 @@ class Temperature {
     /**
      * Call periodically to manage heaters
      */
-    static void manage_heater();
+    //static void manage_heater(); // changed to address compiler error
+    static void manage_heater()  __attribute__((__optimize__("O2")));
 
     /**
      * Preheating hotends