gcc-10-20200905 is now available

2020-09-05 Thread GCC Administrator via Gcc 
Snapshot gcc-10-20200905 is now available on
  https://gcc.gnu.org/pub/gcc/snapshots/10-20200905/
and on various mirrors, see http://gcc.gnu.org/mirrors.html for details.

This snapshot has been generated from the GCC 10 git branch
with the following options: git://gcc.gnu.org/git/gcc.git branch 
releases/gcc-10 revision 56744d9ed626805bb4ff5f5de7f9bb20d8475adc

You'll find:

 gcc-10-20200905.tar.xz   Complete GCC

  SHA256=53b1acecb1d08062fcf4f4ff3b5644b47a36d5033d5b8473d87dd583ed63daa2
  SHA1=46ae6ed1f3e29a2cf0cb7111efe987322c7be79d

Diffs from 10-20200829 are available in the diffs/ subdirectory.

When a particular snapshot is ready for public consumption the LATEST-10
link is updated and a message is sent to the gcc list.  Please do not use
a snapshot before it has been announced that way.

A couple GIMPLE questions

2020-09-05 Thread Gary Oblock via Gcc 
First off one of the questions just me being curious but
second is quite serious. Note, this is GIMPLE coming
into my optimization and not something I've modified.

Here's the C code:

type_t *
do_comp( type_t *data, size_t len)
{
  type_t *res;
  type_t *x = min_of_x( data, len);
  type_t *y = max_of_y( data, len);

  res = y;
  if ( x < y ) res = 0;
  return res;
}

And here's the resulting GIMPLE:

;; Function do_comp.constprop (do_comp.constprop.0, funcdef_no=5, 
decl_uid=4392, cgraph_uid=3, symbol_order=68) (executed once)

do_comp.constprop (struct type_t * data)
{
  struct type_t * res;
  struct type_t * x;
  struct type_t * y;
  size_t len;

   [local count: 1073741824]:

   [local count: 1073741824]:
  x_2 = min_of_x (data_1(D), 1);
  y_3 = max_of_y (data_1(D), 1);
  if (x_2 < y_3)
goto ; [29.00%]
  else
goto ; [71.00%]

   [local count: 311385128]:

   [local count: 1073741824]:
  # res_4 = PHI 
  return res_4;

}

The silly question first. In the "if" stmt how does GCC
get those probabilities? Which it shows as 29.00% and
71.00%. I believe they should both be 50.00%.

The serious question is what is going on with this phi?
res_4 = PHI 

This makes zero sense practicality wise to me and how is
it supposed to be recognized and used? Note, I really do
need to transform the "0B" into something else for my
structure reorganization optimization.

Thanks,

Gary Oblock




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Re: A couple GIMPLE questions

2020-09-05 Thread Marc Glisse 

On Sat, 5 Sep 2020, Gary Oblock via Gcc wrote:


First off one of the questions just me being curious but
second is quite serious. Note, this is GIMPLE coming
into my optimization and not something I've modified.

Here's the C code:

type_t *
do_comp( type_t *data, size_t len)
{
 type_t *res;
 type_t *x = min_of_x( data, len);
 type_t *y = max_of_y( data, len);

 res = y;
 if ( x < y ) res = 0;
 return res;
}

And here's the resulting GIMPLE:

;; Function do_comp.constprop (do_comp.constprop.0, funcdef_no=5, 
decl_uid=4392, cgraph_uid=3, symbol_order=68) (executed once)

do_comp.constprop (struct type_t * data)
{
 struct type_t * res;
 struct type_t * x;
 struct type_t * y;
 size_t len;

  [local count: 1073741824]:

  [local count: 1073741824]:
 x_2 = min_of_x (data_1(D), 1);
 y_3 = max_of_y (data_1(D), 1);
 if (x_2 < y_3)
   goto ; [29.00%]
 else
   goto ; [71.00%]

  [local count: 311385128]:

  [local count: 1073741824]:
 # res_4 = PHI 
 return res_4;

}

The silly question first. In the "if" stmt how does GCC
get those probabilities? Which it shows as 29.00% and
71.00%. I believe they should both be 50.00%.


See the profile_estimate pass dump. One branch makes the function return 
NULL, which makes gcc guess that it may be a bit less likely than the 
other. Those are heuristics, which are tuned to help on average, but of 
course they are sometimes wrong.



The serious question is what is going on with this phi?
   res_4 = PHI 

This makes zero sense practicality wise to me and how is
it supposed to be recognized and used? Note, I really do
need to transform the "0B" into something else for my
structure reorganization optimization.


That's not a question? Are you asking why PHIs exist at all? They are the 
standard way to represent merging in SSA representations. You can iterate 
on the PHIs of a basic block, etc.



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confidential and proprietary to Ampere Computing or its subsidiaries. It is to 
be used solely for the purpose of furthering the parties' business 
relationship. Any unauthorized review, copying, or distribution of this email 
(or any attachments thereto) is strictly prohibited. If you are not the 
intended recipient, please contact the sender immediately and permanently 
delete the original and any copies of this email and any attachments thereto.


Could you please get rid of this when posting on public mailing lists?

--
Marc Glisse