Re: PATCH: [5 Regression] r219037 caused FAIL: gcc.dg/pr44194-1.c

[John David Anglin <dave dot anglin at bell dot net>]

On 2015-01-03, at 2:48 PM, H.J. Lu wrote:

> On Sat, Jan 3, 2015 at 9:35 AM, John David Anglin
> <dave@hiauly1.hia.nrc.ca> wrote:
>> On Wed, 31 Dec 2014, H.J. Lu wrote:
>> 
>>> -      /* Arguments for a sibling call that are pushed to memory are passed
>>> -      using the incoming argument pointer of the current function.  These
>>> -      may or may not be frame related depending on the target.  Since
>>> -      argument pointer related stores are not currently tracked, we treat
>>> -      a sibling call as though it does a wild read.  */
>>> -      if (SIBLING_CALL_P (insn))
>>> +      if (targetm.sibcall_wild_read_p (insn))
>>>      {
>>>        add_wild_read (bb_info);
>>>        return;
>> 
>> Instead of falling through to code designed to handle normal calls, it
>> would be better to treat them separately.  Potentially, there are other
>> optimizations that may be applicable.  If a sibcall doesn't read from
>> the frame, add_non_frame_wild_read() can be called.  This would restore
>> the x86 optimization.
>> 
> 
> That will a new optimization.  I am trying to restore the old behavior on
> x86 with minimum impact in stage 3.


Not really.  In gcc.dg/pr44194-1.c, the sibcall was not a const function and this case
was covered by this hunk of code:

      else
        /* Every other call, including pure functions, may read any memory
           that is not relative to the frame.  */
        add_non_frame_wild_read (bb_info);

Dave
--
John David Anglin	dave.anglin@bell.net