[libitm] Support Solaris 8 and 9/x86 with Sun as

libitm failed to build on Solaris 8 and 9/x86 with the native assembler,
which lacks support for .hidden.  The following patch deals with that by
explicitly using the PIC code sequence, as inspired by
libffi/src/x86/sysv.S.  It allows libitm to build on i386-pc-solaris2.8,
and testsuite results are even better than those using gas, insofar as

PASS: libitm.c++/eh-1.C execution test

now passes while it fails with gas.  The failure with gas may be due to
the fact that 32-bit Solaris/x86 requires datarel encoding in .eh_frame,
while the .cfi* directives generate pcrel encoding instead.

Ok for mainline?

	Rainer


2011-11-14  Rainer Orth  <ro@CeBiTec.Uni-Bielefeld.DE>

	* config/generic/asmcfi.h: Fix comment.
	* config/x86/sjlj.S (_ITM_beginTransaction): Provide PIC code
	sequence without .hidden support.
	(GTM_longjmp) [__ELF__]: Only use .hidden if
	HAVE_ATTRIBUTE_VISIBILITY.

On 11/16/2011 08:38 AM, Rainer Orth wrote:
> 	* config/generic/asmcfi.h: Fix comment.
> 	* config/x86/sjlj.S (_ITM_beginTransaction): Provide PIC code
> 	sequence without .hidden support.
> 	(GTM_longjmp) [__ELF__]: Only use .hidden if
> 	HAVE_ATTRIBUTE_VISIBILITY.

Nearly ok.

> +	subl	$4, %esp
> +	movl	%ebx, 24(%esp)
> +	call	1f
> +1:	popl	%ebx
> +	addl	$_GLOBAL_OFFSET_TABLE_+[.-1b], %ebx
> +	call	GTM_begin_transaction@PLT
> +	movl	24(%esp), %ebx
> +	addl	$4, %esp

This is overly complicated.  We've saved %ebx at 12(%esp) above.
This should be as simple as

	call	1f
1:	popl	%ebx
	addl	$_GLOBAL_OFFSET_TABLE_+[.-1b], %ebx
	call	GTM_begin_transaction@PLT
	movl	12(%esp), %ebx

It also needs wrapping like

#elif defined(__ELF__)
	...
#else
# error "Unsupported PIC sequence"
#endif

... which will almost certainly immediately fail on Darwin, but
at least not with some reference to @PLT.


r~

On 16 Nov 2011, at 19:12, Richard Henderson wrote:

> On 11/16/2011 08:38 AM, Rainer Orth wrote:
>> 	* config/generic/asmcfi.h: Fix comment.
>> 	* config/x86/sjlj.S (_ITM_beginTransaction): Provide PIC code
>> 	sequence without .hidden support.
>> 	(GTM_longjmp) [__ELF__]: Only use .hidden if
>> 	HAVE_ATTRIBUTE_VISIBILITY.
>
> Nearly ok.
>
>> +	subl	$4, %esp
>> +	movl	%ebx, 24(%esp)
>> +	call	1f
>> +1:	popl	%ebx
>> +	addl	$_GLOBAL_OFFSET_TABLE_+[.-1b], %ebx
>> +	call	GTM_begin_transaction@PLT
>> +	movl	24(%esp), %ebx
>> +	addl	$4, %esp
>
> This is overly complicated.  We've saved %ebx at 12(%esp) above.
> This should be as simple as
>
> 	call	1f
> 1:	popl	%ebx
> 	addl	$_GLOBAL_OFFSET_TABLE_+[.-1b], %ebx
> 	call	GTM_begin_transaction@PLT
> 	movl	12(%esp), %ebx
>
> It also needs wrapping like
>
> #elif defined(__ELF__)
> 	...
> #else
> # error "Unsupported PIC sequence"
> #endif
>
> ... which will almost certainly immediately fail on Darwin, but
> at least not with some reference to @PLT.

we have  the equivalent of hidden on Darwin :

         .private_extern

I will try and get back to this .. been busy with other stuff....

at the moment the two things top issues remaining on Darwn are:

1. underscores for the ASM functions.

.. Darwin's asm will not add an underscore to functions .. so we end  
up with unresolved refs to __ITM_beginTransaction/GTM_...

2. providing a section name for .tm_clone_section that is compatible  
with Mach-o section semantics.

I've hacked around this for my tests by making a target macro, but  
maybe you have some other preference.

Iain