Recent compilers can detect and inline manually-written bswap code,
but GCC 4.2.1 (the last GPLv2 version) cannot and generates really
awful code. Depending on how the compiler is configured, it might
also not want to generate bswap because it was not in i386. Using
asm is fine because TCG knows about bswap and all processors with
virtualization extensions also do.
Reported-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Recent GCC compiles linuxboot_dma.c to 921 bytes, while CentOS 6 needs
1029 and clang needs 1527. Because the size of the ROM, rounded to the
next 512 bytes, must match, this causes the API to break between a <1K
ROM and one that is bigger.
We want to make the ROM 1.5 KB in size, but it's better to make clang
produce leaner ROMs, because currently it is worryingly close to the limit.
To fix this prevent clang's happy inlining (which -Os cannot prevent).
This only requires adding a noinline attribute.
Second, the patch makes sure that the ROM has enough padding to prevent
ABI breakage on different compilers. The size is now hardcoded in the file
that is passed to signrom.py, as was the case before commit 6f71b77
("scripts/signrom.py: Allow option ROM checksum script to write the size
header.", 2016-05-23); signrom.py however will still pad the input to
the requested size. This ensures that the padding goes beyond the
next multiple of 512 if necessary, and also avoids the need for
-fno-toplevel-reorder which clang doesn't support. signrom.py can then
error out if the requested size is too small for the actual size of the
compiled ROM.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This optionrom is based on linuxboot.S.
Signed-off-by: Marc Marí <markmb@redhat.com>
Signed-off-by: Richard W.M. Jones <rjones@redhat.com>
Message-Id: <1464027093-24073-2-git-send-email-rjones@redhat.com>
[Add -fno-toplevel-reorder, support clang without -m16. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
