63358eaff6
log2(1) is 0 and log2(0) is -1. If we have the int64_t 0xffffffff then log2(0xffffffff >> 31) = log2(0x1) = 0, so the current reduction code would not shift. That's a bad idea, though, since 0xffffffff when interpreted as an int32_t would become a negative number. We need to always shift one more than the current code does to get a safe reduction. This also means we can get rid of another compare/branch since -1 is the smallest result log2() can return, so the shift can no longer go negative now. Signed-off-by: Julius Werner <jwerner@chromium.org> Change-Id: Ib1eb6364c35c26924804261c02171139cdbd1034 Reviewed-on: https://review.coreboot.org/c/coreboot/+/42845 Tested-by: build bot (Jenkins) <no-reply@coreboot.org> Reviewed-by: Yu-Ping Wu <yupingso@google.com> Reviewed-by: Joel Kitching <kitching@google.com> Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net> |
||
---|---|---|
.. | ||
arch | ||
bin | ||
configs | ||
crypto | ||
curses | ||
drivers | ||
gdb | ||
include | ||
libc | ||
libcbfs | ||
liblz4 | ||
liblzma | ||
libpci | ||
sample | ||
tests | ||
Doxyfile | ||
Kconfig | ||
LICENSE_GPL | ||
LICENSES | ||
Makefile | ||
Makefile.inc | ||
README |
------------------------------------------------------------------------------- libpayload README ------------------------------------------------------------------------------- libpayload is a minimal library to support standalone payloads that can be booted with firmware like coreboot. It handles the setup code, and provides common C library symbols such as malloc() and printf(). Note: This is _not_ a standard library for use with an operating system, rather it's only useful for coreboot payload development! See https://www.coreboot.org for details on coreboot. Installation ------------ $ git clone https://review.coreboot.org/coreboot.git $ cd coreboot/payloads/libpayload $ make menuconfig $ make $ make install (optional, will install into ./install per default) On x86 systems, libpayload will always be 32-bit even if your host OS runs in 64-bit, so you might have to install the 32-bit libgcc version. On Debian systems you'd do 'apt-get install gcc-multilib' for example. Run 'make distclean' before switching boards. This command will remove your current .config file, so you need 'make menuconfig' again or 'make defconfig' in order to set up configuration. Default configuration is based on 'configs/defconfig'. See the configs/ directory for examples of configuration. Usage ----- Here's an example of a very simple payload (hello.c) and how to build it: #include <libpayload.h> int main(void) { printf("Hello, world!\n"); return 0; } Building the payload using the 'lpgcc' compiler wrapper: $ lpgcc -o hello.elf hello.c Please see the sample/ directory for details. Website and Mailing List ------------------------ The main website is https://www.coreboot.org/Libpayload. For additional information, patches, and discussions, please join the coreboot mailing list at https://www.coreboot.org/Mailinglist, where most libpayload developers are subscribed. Copyright and License --------------------- See LICENSES.