[PATCH u-boot v4 00/36] U-Boot LTO (Sandbox + Some ARM boards)

[Tom Rini]

On Tue, Jun 01, 2021 at 06:55:52PM +0200, Heinrich Schuchardt wrote:
> On 6/1/21 6:22 PM, Marek Behún wrote:
> > On Tue, 1 Jun 2021 16:59:52 +0200
> > Patrick DELAUNAY <patrick.delaunay at foss.st.com> wrote:
> > 
> > > Hi Marek,
> > > 
> > > I am trying to activate CONFIG_LTO for STMicroelectronics stm32mp15
> > > platform
> > > 
> > > (stm32mp15_trusted_defconfig and stm32mp15_basic_defconfig).
> > > 
> > > 
> > > The config stm32mp15_basic_defconfig, with SPL supported failed to
> > > boot
> > > 
> > > with gcc-arm-9.2-2019.12.
> > > 
> > > because a weak function is not correctly handle between
> > > 
> > > 1/ ./arch/arm/lib/cache-cp15.c: 96
> > > 
> > >       __weak void dram_bank_mmu_setup(int bank);
> > > 
> > > 2/ the stm32mp implementation in
> > > 
> > >      arch/arm/mach-stm32mp/cpu.c:62
> > > 
> > >      void dram_bank_mmu_setup(int bank)
> > > 
> > > => The used function in SPL is the cache library, not the stm32mp
> > > function.
> > > 
> > >         and SPL boot it OK when I remove the function in the cache
> > > library...
> > > 
> > > 
> > > And the issue is also solved with I use a more recent version
> > > 
> > > gcc-arm-10.2-2020.11 on my PC.
> > > 
> > > 
> > > Do you see the same kind of issue for old version of gcc ?
> > > 
> > > 
> > > Do you think CONFIG_LTO require a more recent version of gcc that
> > > 
> > > the minimal version required by U-Boot  because I don't see this
> > > information
> > > 
> > > in the serie?
> > 
> > I only tried compiling with older versions in the CI.
> > 
> > On the devices for which I tested it I only compiled with newer gcc
> > (10.2.0) since it is the stable version on my system.
> > 
> > But yeah, I suggest to use newer GCC for LTO.
> > 
> > Marek
> > 
> 
> gcc (Debian 11-20210327-1) 11.0.1 compiles stm32mp15_basic_defconfig
> with CONFIG_LTO=y.

It's run-time not compile time that shows the problem however as gcc-9.x
sounds like it has a problem with LTO and weak functions.

-- 
Tom
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