altos/scheme: Work around gcc 7.2.0 optimization bug in memory manager

[fw/altos] / src / scheme / ao_scheme_mem.c

diff --git a/src/scheme/ao_scheme_mem.c b/src/scheme/ao_scheme_mem.c
index 3659d3ec4a7fa331312bc96f856183c071c148aa..94275451b10419fefbaa4e0e3be317a47b9e0752 100644 (file)
--- a/src/scheme/ao_scheme_mem.c
+++ b/src/scheme/ao_scheme_mem.c
@@ -623,6 +623,20 @@ ao_scheme_collect(uint8_t style)
                        top += size;
                }
 
+               /* Short-circuit the rest of the loop when all of the
+                * found objects aren't moving. This isn't strictly
+                * necessary as the rest of the loop is structured to
+                * work in this case, but GCC 7.2.0 with optimization
+                * greater than 2 generates incorrect code for this...
+                */
+               if (i == AO_SCHEME_NCHUNK) {
+                       chunk_low = chunk_high;
+#if DBG_MEM_STATS
+                       loops++;
+#endif
+                       continue;
+               }
+
                /*
                 * Limit amount of chunk array used in mapping moves
                 * to the active region