6502: optimise the top byte check to avoid a shift

diff --git a/Kernel/cpu-6502/cpu.h b/Kernel/cpu-6502/cpu.h
index 9c3ce28..aa10486 100644 (file)
--- a/Kernel/cpu-6502/cpu.h
+++ b/Kernel/cpu-6502/cpu.h
@@ -65,3 +65,7 @@ typedef union {            /* this structure is endian dependent */
 
 /* cc65 really wants register tags on struct pointers used repeatedly */
 #define regptr register
+
+/* CC65 is bright enough to partly optimise this but not fully so do it
+   by hand */
+#define HIBYTE32(x)    (((uint8_t *)&(x))[3])