On 14.06.2018 12:55, Christian Borntraeger wrote: > > On 06/14/2018 10:48 AM, Thomas Huth wrote: >> Since we're storing the firmware blobs in the QEMU git repository, it >> would be nice if the blobs would be a little bit smaller. By using -Os >> and -fno-asynchronous-unwind-tables the size of the s390-ccw.img can be >> decreased by ca. 4kB, and the size of s390-netboot.img even by ca. 45kB. >> The change of speed of the firmware should not really matter compared to >> a binary that has been compiled with -O2 since the firmware still starts >> very fast. > > >> >> Signed-off-by: Thomas Huth <[email protected]> >> --- >> pc-bios/s390-ccw/Makefile | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/pc-bios/s390-ccw/Makefile b/pc-bios/s390-ccw/Makefile >> index 439e3cc..f22a5ca 100644 >> --- a/pc-bios/s390-ccw/Makefile >> +++ b/pc-bios/s390-ccw/Makefile >> @@ -13,6 +13,7 @@ OBJECTS = start.o main.o bootmap.o jump2ipl.o sclp.o >> menu.o \ >> virtio.o virtio-scsi.o virtio-blkdev.o libc.o >> >> QEMU_CFLAGS := $(filter -W%, $(QEMU_CFLAGS)) >> +QEMU_CFLAGS += -Os -fno-asynchronous-unwind-tables > > Hmm, it looks like that the O2 comes after Os for me (which would override > Os). > > cc -iquote /home/cborntra/REPOS/qemu/build/. -iquote . -iquote > /home/cborntra/REPOS/qemu/tcg -iquote /home/cborntra/REPOS/qemu/tcg/s390 > -I/home/cborntra/REPOS/qemu/linux-headers > -I/home/cborntra/REPOS/qemu/build/linux-headers -iquote . -iquote > /home/cborntra/REPOS/qemu -iquote /home/cborntra/REPOS/qemu/accel/tcg -iquote > /home/cborntra/REPOS/qemu/include -Werror -Wstrict-prototypes > -Wredundant-decls -Wall -Wundef -Wwrite-strings -Wmissing-prototypes > -Wexpansion-to-defined -Wendif-labels -Wno-shift-negative-value > -Wno-missing-include-dirs -Wempty-body -Wnested-externs -Wformat-security > -Wformat-y2k -Winit-self -Wignored-qualifiers -Wold-style-declaration > -Wold-style-definition -Wtype-limits -Os -fno-asynchronous-unwind-tables > -ffreestanding -fno-delete-null-pointer-checks -msoft-float -march=z900 -fPIE > -fno-strict-aliasing -fno-stack-protector -MMD -MP -MT libc.o -MF ./libc.d > -O2 -g -c -o libc.o /home/cborntra/REPOS/qemu/pc-bios/s390-ccw/libc.c > > so the effect is only because of the -fno-asynchronous-unwind-tables.
Ugh, you're right - at least for the objects for s390-ccw.img. Seems like the -O2 comes from "CFLAGS" and not from "QEMU_CFLAGS" here, so the flags should be added to the CFLAGS variable instead. Actually, I was only looking at the object files from s390-netboot.img, and the libc files from SLOF get *only* compiled with QEMU_CFLAGS there (see LIBC_CFLAGS in netboot.mak). So the huge part of the s390-netboot.img binary got compiled without optimizations so far! That's why I was seeing such a big improvement there! Wow, I wonder why we did not notice this before... Anyway, I'll send a v2 to fix these issues. Thomas
