[PATCH] powerpc: put the gpr sabe/restore functions in their own section

[PATCH] powerpc: put the gpr sabe/restore functions in their own section

[Stephen Rothwell]

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This allows the linker to know that calls to them do not need to switch
TOC and stop errors like the following when linking large configurations:

powerpc64-linux-ld: drivers/built-in.o: In function `.gpiochip_is_requested':
(.text+0x4): sibling call optimization to `_savegpr0_29' does not allow automatic multiple TOCs; recompile with -mminimal-toc or -fno-optimize-sibling-calls, or make `_savegpr0_29' extern

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
---
 arch/powerpc/lib/crtsavres.S |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/lib/crtsavres.S b/arch/powerpc/lib/crtsavres.S
index 1c893f0..b2c68ce 100644
--- a/arch/powerpc/lib/crtsavres.S
+++ b/arch/powerpc/lib/crtsavres.S
@@ -41,12 +41,13 @@
 #include <asm/ppc_asm.h>
 
 	.file	"crtsavres.S"
-	.section ".text"
 
 #ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE
 
 #ifndef CONFIG_PPC64
 
+	.section ".text"
+
 /* Routines for saving integer registers, called by the compiler.  */
 /* Called with r11 pointing to the stack header word of the caller of the */
 /* function, just beyond the end of the integer save area.  */
@@ -232,6 +233,8 @@ _GLOBAL(_rest32gpr_31_x)
 
 #else /* CONFIG_PPC64 */
 
+	.section ".text.save.restore","ax",@progbits
+
 .globl	_savegpr0_14
 _savegpr0_14:
 	std	r14,-144(r1)
-- 
1.7.10.280.gaa39

-- 
Cheers,
Stephen Rothwell                    sfr@canb.auug.org.au

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Re: [PATCH] powerpc: put the gpr sabe/restore functions in their own section

[Michael Ellerman]

On Fri, 2012-07-06 at 17:09 +1000, Stephen Rothwell wrote:
> This allows the linker to know that calls to them do not need to switch
> TOC and stop errors like the following when linking large configurations:

>  arch/powerpc/lib/crtsavres.S |    5 ++++-

You didn't make any change to the linker script? How does this section
get in there? I don't see a .text* anywhere?

> diff --git a/arch/powerpc/lib/crtsavres.S b/arch/powerpc/lib/crtsavres.S
> index 1c893f0..b2c68ce 100644
> --- a/arch/powerpc/lib/crtsavres.S
> +++ b/arch/powerpc/lib/crtsavres.S
> @@ -41,12 +41,13 @@
>  #include <asm/ppc_asm.h>
>  
>  	.file	"crtsavres.S"
> -	.section ".text"
>  
>  #ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE
>  
>  #ifndef CONFIG_PPC64
>  
> +	.section ".text"
> +
>  /* Routines for saving integer registers, called by the compiler.  */
>  /* Called with r11 pointing to the stack header word of the caller of the */
>  /* function, just beyond the end of the integer save area.  */
> @@ -232,6 +233,8 @@ _GLOBAL(_rest32gpr_31_x)
>  
>  #else /* CONFIG_PPC64 */
>  
> +	.section ".text.save.restore","ax",@progbits
> +
>  .globl	_savegpr0_14
>  _savegpr0_14:
>  	std	r14,-144(r1)

Any reason to not put the 32-bit versions in the same section? AFAICS
nothing in that file uses the TOC. 

cheers

Re: [PATCH] powerpc: put the gpr sabe/restore functions in their own section

[Stephen Rothwell]

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Hi Michael,

On Sat, 07 Jul 2012 16:55:21 +1000 Michael Ellerman <michael@ellerman.id.au> wrote:
>
> On Fri, 2012-07-06 at 17:09 +1000, Stephen Rothwell wrote:
> > This allows the linker to know that calls to them do not need to switch
> > TOC and stop errors like the following when linking large configurations:
> 
> >  arch/powerpc/lib/crtsavres.S |    5 ++++-
> 
> You didn't make any change to the linker script? How does this section
> get in there? I don't see a .text* anywhere?

Yeah.  ld just seems to figure it out (I note that we also have sections
called .text.unlikely and .text.startup).

> > diff --git a/arch/powerpc/lib/crtsavres.S b/arch/powerpc/lib/crtsavres.S
> > index 1c893f0..b2c68ce 100644
> > --- a/arch/powerpc/lib/crtsavres.S
> > +++ b/arch/powerpc/lib/crtsavres.S
> > @@ -41,12 +41,13 @@
> >  #include <asm/ppc_asm.h>
> >  
> >  	.file	"crtsavres.S"
> > -	.section ".text"
> >  
> >  #ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE
> >  
> >  #ifndef CONFIG_PPC64
> >  
> > +	.section ".text"
> > +
> >  /* Routines for saving integer registers, called by the compiler.  */
> >  /* Called with r11 pointing to the stack header word of the caller of the */
> >  /* function, just beyond the end of the integer save area.  */
> > @@ -232,6 +233,8 @@ _GLOBAL(_rest32gpr_31_x)
> >  
> >  #else /* CONFIG_PPC64 */
> >  
> > +	.section ".text.save.restore","ax",@progbits
> > +
> >  .globl	_savegpr0_14
> >  _savegpr0_14:
> >  	std	r14,-144(r1)
> 
> Any reason to not put the 32-bit versions in the same section? AFAICS
> nothing in that file uses the TOC. 

32 bit does not use a toc (apparently).  And I figured to make the
minimal change to the output.

-- 
Cheers,
Stephen Rothwell                    sfr@canb.auug.org.au

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