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Re: [PATCH] MIPS: Add option to pass return address location to _mcount.

To: Richard Sandiford <rdsandiford@googlemail.com>
Subject: Re: [PATCH] MIPS: Add option to pass return address location to _mcount.
From: Wu Zhangjin <wuzhangjin@gmail.com>
Date: Thu, 29 Oct 2009 14:44:34 +0800
Cc: David Daney <ddaney@caviumnetworks.com>, GCC Patches <gcc-patches@gcc.gnu.org>, linux-mips@linux-mips.org, Adam Nemet <anemet@caviumnetworks.com>, rostedt@goodmis.org, Thomas Gleixner <tglx@linutronix.de>, Ralf Baechle <ralf@linux-mips.org>, Nicholas Mc Guire <der.herr@hofr.at>
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Reply-to: wuzhangjin@gmail.com
Sender: linux-mips-bounce@linux-mips.org
Hi,

On Tue, 2009-10-27 at 21:20 +0000, Richard Sandiford wrote:
[...]
> OK with those changes,

Just applied the above changes, and added one more for not getting the
ra_fp_offset when -pg is not enabled:

@@ -9619,6 +9622,9 @@ mips_for_each_saved_gpr_and_fpr (HOST_WIDE_INT
sp_offset,
   for (regno = GP_REG_LAST; regno >= GP_REG_FIRST; regno--)
     if (BITSET_P (cfun->machine->frame.mask, regno - GP_REG_FIRST))
       {
+       /* Record the ra offset for use by mips_function_profiler.  */
+       if (crtl->profile && regno == RETURN_ADDR_REGNUM)
+         cfun->machine->frame.ra_fp_offset = offset + sp_offset;
        mips_save_restore_reg (word_mode, regno, offset, fn);
        offset -= UNITS_PER_WORD;
       }

"crtl->profile &&" was added.

>  thanks, if it passing testing, and if
> Ralf is happy with the linux side.
> 

Just appended that patch with the above changes to the latest gcc 4.5 in
the git repository, and tested it, which works well.

this is the result of a non-leaf function:

ffffffff80243c08 <copy_process>:
ffffffff80243c08:       67bdff40        daddiu  sp,sp,-192
ffffffff80243c0c:       ffbe00b0        sd      s8,176(sp)
ffffffff80243c10:       03a0f02d        move    s8,sp
ffffffff80243c14:       ffbf00b8        sd      ra,184(sp)
[...]
ffffffff80243c38:       3c038021        lui     v1,0x8021
ffffffff80243c3c:       64631530        daddiu  v1,v1,5424
ffffffff80243c40:       03e0082d        move    at,ra
ffffffff80243c44:       0060f809        jalr    v1
ffffffff80243c48:       67ac00b8        daddiu  t0,sp,184 --> Here it is

and for a leaf function:

ffffffff802054d0 <au1k_wait>:
ffffffff802054d0:       67bdfff0        daddiu  sp,sp,-16
ffffffff802054d4:       ffbe0008        sd      s8,8(sp)
ffffffff802054d8:       03a0f02d        move    s8,sp
ffffffff802054dc:       3c038021        lui     v1,0x8021
ffffffff802054e0:       64631530        daddiu  v1,v1,5424
ffffffff802054e4:       03e0082d        move    at,ra
ffffffff802054e8:       0060f809        jalr    v1
ffffffff802054ec:       0000602d        move    t0,zero --> Here it is

and with this new feature, I can safely remove the old
ftrace_get_parent_addr() and add several more instructions to make
function graph tracer work. and also, 'Cause this feature used the
t0($12) register, I must change the temp registers I have used in the
patches of ftrace for MIPS(t0 --> t1, t1 --> t2, t2-> t3...). no more
touch.

The latest revision of this patch will be sent out in the next E-mail,
and also, the -v8 revision of ftrace for MIPS will be sent out with this
new feature of Gcc asap.

Thanks & Regards,
        Wu Zhangjin


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