From 554c21f759876a2077f8d91cc90006caa0a1c863 Mon Sep 17 00:00:00 2001
From: Josh Goebel <me@joshgoebel.com>
Date: Sat, 1 Apr 2017 14:40:25 -0400
Subject: [PATCH] make sure we use upper registers

---
 src/Arduboy2.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/Arduboy2.cpp b/src/Arduboy2.cpp
index feb77b7..6eb4f0c 100644
--- a/src/Arduboy2.cpp
+++ b/src/Arduboy2.cpp
@@ -301,10 +301,10 @@ void Arduboy2Base::drawPixel(int16_t x, int16_t y, uint8_t color)
     "adc r31, __zero_reg__\n"
     // load correct bitshift from program RAM
     "lpm %[bit], Z\n"
-    : [row_offset] "=r" (row_offset),
+    : [row_offset] "=a" (row_offset), // upper register (ANDI)
       [bit] "=r" (bit)
     : [width_offset] "r" ((uint8_t)(WIDTH/8)),
-      [y] "r" ((uint8_t)y),
+      [y] "a" ((uint8_t)y), // upper register (ANDI)
       [x] "r" ((uint8_t)x),
       "z" (bitshift_left)
     : "r1", "r0");