EH and powerpc

EH and powerpc

[jeroen dobbelaere xe44 7682]

Hello,

I'm trying to use a crosscompilation version of egcs for powerpc.
This works fine, but it uses sjsl exceptions (which adds runtime
overhead).

Is there a way to use the powerpc as target without sjsl exceptions 
(but still with exceptions) ?

It seems that the definition of INCOMING_RETURN_ADDR_RTX is missing.
(in gcc/defaults.h :

/* If we have a definition of INCOMING_RETURN_ADDR_RTX, assume that
   the rest of the DWARF 2 frame unwind support is also provided.  */
#if !defined (DWARF2_UNWIND_INFO) && defined (INCOMING_RETURN_ADDR_RTX)
#define DWARF2_UNWIND_INFO 1
#endif
)


DWARF2_UNWIND_INFO is not set anywhere in gcc/config/rs6000
as INCOMING_RETURN_ADDR_RTX.

This results in '__throw' and other stuff not being included in
libgcc.a

(oh yes, this is with egcs-980302)

Greetings,

Jeroen Dobbelaere

Re: EH and powerpc

[Jim Wilson]

	Is there a way to use the powerpc as target without sjsl exceptions 
	(but still with exceptions) ?

As you have already figured out, there is no alternative to sjlj until someone
adds DWARF2 frame unwind support to the powerpc port.  So far this has been 
done for the mips, sparc, i386, and m68k port.  I don't know if there is
an explanation anywhere of how to do this, but you can look at the existing
supported ports for clues.  In particular, look at the FUNCTION_PROLOGUE,
FUNCTION_EPILOGUE macros, and the prologue/epilogue named patterns in the md
file, and see the support for RTX_FRAME_RELATED_P and dwarf2out_do_frame in
them.  See also the DWARF_* macros in the tm.h file.

Jim

Re: EH and powerpc

[H.J. Lu]

> 
> 	Is there a way to use the powerpc as target without sjsl exceptions 
> 	(but still with exceptions) ?
> 
> As you have already figured out, there is no alternative to sjlj until someone
> adds DWARF2 frame unwind support to the powerpc port.  So far this has been 
> done for the mips, sparc, i386, and m68k port.  I don't know if there is
> an explanation anywhere of how to do this, but you can look at the existing
> supported ports for clues.  In particular, look at the FUNCTION_PROLOGUE,
> FUNCTION_EPILOGUE macros, and the prologue/epilogue named patterns in the md
> file, and see the support for RTX_FRAME_RELATED_P and dwarf2out_do_frame in
> them.  See also the DWARF_* macros in the tm.h file.
> 

How hard to add DWARF2 unwind to alpha/ELF?


-- 
H.J. Lu (hjl@gnu.org)

Re: EH and powerpc

[Jim Wilson]

	How hard to add DWARF2 unwind to alpha/ELF?

I have never added DWARF2 unwind support to a port, so I don't know how
difficult this task is.  I would guess that it is a few days if you already
have a good understanding of the basics involved (Dwarf2 debug info, frame
layout and how it is constructed).

Jim