It turns out that some toolchains which support MIPS R6 don't support
the -mcompact-branches flag to specify compact branch behaviour. Default
to not providing the -mcompact-branch option to the compiler such that
we can build with such toolchains.
Signed-off-by: Paul Burton <[email protected]>
Reported-by: kbuild test robot <[email protected]>
Fixes: c1a0e9bc885d ("MIPS: Allow compact branch policy to be changed")
Cc: stable <[email protected]> # v4.4+
---
arch/mips/Kconfig.debug | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/arch/mips/Kconfig.debug b/arch/mips/Kconfig.debug
index f0e314c..e91b3d1 100644
--- a/arch/mips/Kconfig.debug
+++ b/arch/mips/Kconfig.debug
@@ -117,7 +117,15 @@ if CPU_MIPSR6
choice
prompt "Compact branch policy"
- default MIPS_COMPACT_BRANCHES_OPTIMAL
+ default MIPS_COMPACT_BRANCHES_DEFAULT
+
+config MIPS_COMPACT_BRANCHES_DEFAULT
+ bool "Toolchain Default (don't specify)"
+ help
+ Don't pass the -mcompact-branches flag to the compiler, allowing it
+ to use its default (generally "optimal"). This is particularly
+ useful for early R6-supporting toolchains which don't support the
+ -mcompact-branches flag.
config MIPS_COMPACT_BRANCHES_NEVER
bool "Never (force delay slot branches)"
--
2.8.0
On Fri, 22 Apr 2016, Paul Burton wrote:
> It turns out that some toolchains which support MIPS R6 don't support
> the -mcompact-branches flag to specify compact branch behaviour. Default
> to not providing the -mcompact-branch option to the compiler such that
> we can build with such toolchains.
Good idea overall, one further suggestion below.
> diff --git a/arch/mips/Kconfig.debug b/arch/mips/Kconfig.debug
> index f0e314c..e91b3d1 100644
> --- a/arch/mips/Kconfig.debug
> +++ b/arch/mips/Kconfig.debug
> @@ -117,7 +117,15 @@ if CPU_MIPSR6
>
> choice
> prompt "Compact branch policy"
> - default MIPS_COMPACT_BRANCHES_OPTIMAL
> + default MIPS_COMPACT_BRANCHES_DEFAULT
> +
> +config MIPS_COMPACT_BRANCHES_DEFAULT
> + bool "Toolchain Default (don't specify)"
> + help
> + Don't pass the -mcompact-branches flag to the compiler, allowing it
> + to use its default (generally "optimal"). This is particularly
> + useful for early R6-supporting toolchains which don't support the
> + -mcompact-branches flag.
>
> config MIPS_COMPACT_BRANCHES_NEVER
> bool "Never (force delay slot branches)"
How about making the option depend on DEBUG_KERNEL and maybe making it an
umbrella setting to hide details from users who do not want to be
bothered, i.e. something like:
config MIPS_COMPACT_BRANCHES_OVERRIDE
bool "Override the toolchain default for compact branch policy"
depends on DEBUG_KERNEL
default n
[...]
if MIPS_COMPACT_BRANCHES_OVERRIDE
choice
prompt "Compact branch policy"
default MIPS_COMPACT_BRANCHES_OPTIMAL
[...]
endif # MIPS_COMPACT_BRANCHES_OVERRIDE
?
Maciej
On Fri, Apr 22, 2016 at 04:56:02PM +0100, Maciej W. Rozycki wrote:
> On Fri, 22 Apr 2016, Paul Burton wrote:
>
> > It turns out that some toolchains which support MIPS R6 don't support
> > the -mcompact-branches flag to specify compact branch behaviour. Default
> > to not providing the -mcompact-branch option to the compiler such that
> > we can build with such toolchains.
>
> Good idea overall, one further suggestion below.
>
> > diff --git a/arch/mips/Kconfig.debug b/arch/mips/Kconfig.debug
> > index f0e314c..e91b3d1 100644
> > --- a/arch/mips/Kconfig.debug
> > +++ b/arch/mips/Kconfig.debug
> > @@ -117,7 +117,15 @@ if CPU_MIPSR6
> >
> > choice
> > prompt "Compact branch policy"
> > - default MIPS_COMPACT_BRANCHES_OPTIMAL
> > + default MIPS_COMPACT_BRANCHES_DEFAULT
> > +
> > +config MIPS_COMPACT_BRANCHES_DEFAULT
> > + bool "Toolchain Default (don't specify)"
> > + help
> > + Don't pass the -mcompact-branches flag to the compiler, allowing it
> > + to use its default (generally "optimal"). This is particularly
> > + useful for early R6-supporting toolchains which don't support the
> > + -mcompact-branches flag.
> >
> > config MIPS_COMPACT_BRANCHES_NEVER
> > bool "Never (force delay slot branches)"
>
> How about making the option depend on DEBUG_KERNEL and maybe making it an
> umbrella setting to hide details from users who do not want to be
> bothered, i.e. something like:
>
> config MIPS_COMPACT_BRANCHES_OVERRIDE
> bool "Override the toolchain default for compact branch policy"
> depends on DEBUG_KERNEL
> default n
Although note that "default n" is redundant.
Cheers
James
> [...]
> if MIPS_COMPACT_BRANCHES_OVERRIDE
> choice
> prompt "Compact branch policy"
> default MIPS_COMPACT_BRANCHES_OPTIMAL
> [...]
> endif # MIPS_COMPACT_BRANCHES_OVERRIDE
>
> ?
>
> Maciej
>