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Date: Mon, 29 Aug 2016 20:41:00 -0000
From: Segher Boessenkool <segher@kernel.crashing.org>
To: Steven Bosscher <stevenb.gcc@gmail.com>
Cc: GCC Patches <gcc-patches@gcc.gnu.org>, Paolo Bonzini <bonzini@gnu.org>,        Seongbae Park <seongbae.park@gmail.com>,        Kenneth Zadeck <zadeck@naturalbridge.com>
Subject: Re: [PATCH] df: Keep return address register undefined until epilogue_completed
Message-ID: <20160829204121.GB22842@gate.crashing.org>
References: <c6b7f1d6bfb232511d9e0a3467bd87db65e27b6b.1472488939.git.segher@kernel.crashing.org> <CABu31nNY=8qaWgdtVA2Mc9J+zjm5HL+J--XNVKU4Zxx6h9QNyA@mail.gmail.com>
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On Mon, Aug 29, 2016 at 10:19:25PM +0200, Steven Bosscher wrote:
> On Mon, Aug 29, 2016 at 6:50 PM, Segher Boessenkool wrote:
> > This patch changes that so that that def is only added after
> > epilogue_completed.
> ...
> > Does this work on all other targets?
> 
> Guessing: not for targets where INCOMING_RETURN_ADDR_RTX is the stack register?
> That'd be at least h8300, rl78, and rx.

The stack pointer is always added (earlier in this function):

  /* The always important stack pointer.  */
  bitmap_set_bit (entry_block_defs, STACK_POINTER_REGNUM);

so that isn't it.

History suggests it was a fix (or workaround) for a problem on ia64,
but I might well have that wrong.


Segher