[PATCH] [POWERPC] powerpc: Add -mno-spe for ARCH=powerpc builds

[PATCH] [POWERPC] powerpc: Add -mno-spe for ARCH=powerpc builds

[Kumar Gala]

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
---
 arch/powerpc/Makefile |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
index 4e16534..bd87626 100644
--- a/arch/powerpc/Makefile
+++ b/arch/powerpc/Makefile
@@ -107,6 +107,9 @@ endif
 # No AltiVec instruction when building kernel
 KBUILD_CFLAGS += $(call cc-option,-mno-altivec)

+# No SPE instruction when building kernel
+KBUILD_CFLAGS += $(call cc-option,-mno-spe)
+
 # Enable unit-at-a-time mode when possible. It shrinks the
 # kernel considerably.
 KBUILD_CFLAGS += $(call cc-option,-funit-at-a-time)
-- 
1.5.2.4

Re: [PATCH] [POWERPC] powerpc: Add -mno-spe for ARCH=powerpc builds

[Paul Mackerras]

Kumar Gala writes:

> Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

Your commit message doesn't give any reason why you are doing this, or
any explanation of what goes wrong without it.  In fact, the commit
message is completely empty. :)  Please resubmit with a decent commit
message.

Paul.

Re: [PATCH] [POWERPC] powerpc: Add -mno-spe for ARCH=powerpc builds

[Kumar Gala]

On Oct 18, 2007, at 6:19 PM, Paul Mackerras wrote:

> Kumar Gala writes:
>
>> Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
>
> Your commit message doesn't give any reason why you are doing this, or
> any explanation of what goes wrong without it.  In fact, the commit
> message is completely empty. :)  Please resubmit with a decent commit
> message.

I will, just as an FYI I based this on your commit for -mno-altivec  
(which has no rationale for the commit) :)

- k

Re: [PATCH] [POWERPC] powerpc: Add -mno-spe for ARCH=powerpc builds

[Josh Boyer]

On Thu, 18 Oct 2007 22:20:49 -0500
Kumar Gala <galak@kernel.crashing.org> wrote:

> 
> On Oct 18, 2007, at 6:19 PM, Paul Mackerras wrote:
> 
> > Kumar Gala writes:
> >
> >> Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
> >
> > Your commit message doesn't give any reason why you are doing this, or
> > any explanation of what goes wrong without it.  In fact, the commit
> > message is completely empty. :)  Please resubmit with a decent commit
> > message.
> 
> I will, just as an FYI I based this on your commit for -mno-altivec  
> (which has no rationale for the commit) :)

Do as he says, not as he does!  ;)

josh

Re: [PATCH] [POWERPC] powerpc: Add -mno-spe for ARCH=powerpc builds

[Jon Loeliger]

So, like, the other day Kumar Gala mumbled:
> 
> On Oct 18, 2007, at 6:19 PM, Paul Mackerras wrote:
> 
> > Your commit message doesn't give any reason why you are doing this, or
> > any explanation of what goes wrong without it.  In fact, the commit
> > message is completely empty. :)  Please resubmit with a decent commit
> > message.
> 
> I will, just as an FYI I based this on your commit for -mno-altivec  
> (which has no rationale for the commit) :)

Hmmm.  And also, let's not forget that the mail Subject: line
does contribute to the git log commit message as well.

Thanks,
jdl

[POWERPC v2] powerpc: Add -mno-spe for ARCH=powerpc builds

[Kumar Gala]

Newer GCC's are capable of autovectorization for ISA extensions like
AltiVec and SPE.  If we happen to build with one of those compilers we
will get SPE instructions in random kernel code.  Today we only allow
basic interger code in the kernel and FP, AltiVec, or SPE in special
explicit locations that have handled the proper saving and restoring of
the register state (since on uniprocessor we lazy context switch the
register state for FP, AltiVec, and SPE).

-mno-spe disables the compiler for automatically generating SPE
instructions without our knowledge.

---
Hopefully this is up to Paul's double standard :)

(as normal, its in my git tree, posted here for review).

 arch/powerpc/Makefile |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
index 4e16534..bd87626 100644
--- a/arch/powerpc/Makefile
+++ b/arch/powerpc/Makefile
@@ -107,6 +107,9 @@ endif
 # No AltiVec instruction when building kernel
 KBUILD_CFLAGS += $(call cc-option,-mno-altivec)

+# No SPE instruction when building kernel
+KBUILD_CFLAGS += $(call cc-option,-mno-spe)
+
 # Enable unit-at-a-time mode when possible. It shrinks the
 # kernel considerably.
 KBUILD_CFLAGS += $(call cc-option,-funit-at-a-time)
-- 
1.5.2.4