On Thu, May 20, 2021 at 01:24:10PM +0200, Marek Behún wrote: > On ARM, the gd pointer is stored in registers r9 / x18. For this the > -ffixed-r9 / -ffixed-x18 flag is used when compiling, but using global > register variables causes errors when building with LTO, and these > errors are very difficult to overcome. > > Richard Biener says [1]: > Note that global register vars shouldn't be used with LTO and if they > are restricted to just a few compilation units the recommended fix is > to build those CUs without -flto. > > We cannot do this for U-Boot since all CUs use -ffixed-reg flag. > > It seems that with LTO we could in fact store the gd pointer differently > and gain performance or size benefit by allowing the compiler to use > r9 / x18. But this would need more work. > > So for now, when building with LTO, go the clang way, and instead of > declaring gd a global register variable, we make it a function call via > macro. > > [1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68384 > > Signed-off-by: Marek Behún <marek.be...@nic.cz> > Reviewed-by: Simon Glass <s...@chromium.org>
Applied to u-boot/master, thanks! -- Tom
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