Bootstrap is broken with BOOT_CFLAGS="-g -O2 -fgraphite-identity".
Fixed: trunk now passes bootstrap on amd64-linux with BOOT_CFLAGS="-g -O2 -fgraphite-identity" all default languages. I will prepare a patch for the graphite branch to enable -fgraphite-identity by default in -O2 or higher. PR38499 is another bug, to be fixed later, that appears for BOOT_CFLAGS="-g -O2 -floop-block".