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Re: [gimplefe] hacking pass manager


On Tue, Jul 19, 2016 at 10:09 PM, Prasad Ghangal
<prasad.ghangal@gmail.com> wrote:
> On 19 July 2016 at 11:04, Richard Biener <richard.guenther@gmail.com> wrote:
>> On July 18, 2016 11:05:58 PM GMT+02:00, David Malcolm <dmalcolm@redhat.com> wrote:
>>>On Tue, 2016-07-19 at 00:52 +0530, Prasad Ghangal wrote:
>>>> On 19 July 2016 at 00:25, Richard Biener <richard.guenther@gmail.com>
>>>> wrote:
>>>> > On July 18, 2016 8:28:15 PM GMT+02:00, Prasad Ghangal <
>>>> > prasad.ghangal@gmail.com> wrote:
>>>> > > On 15 July 2016 at 16:13, Richard Biener <
>>>> > > richard.guenther@gmail.com>
>>>> > > wrote:
>>>> > > > On Sun, Jul 10, 2016 at 6:13 PM, Prasad Ghangal
>>>> > > > <prasad.ghangal@gmail.com> wrote:
>>>> > > > > On 8 July 2016 at 13:13, Richard Biener <
>>>> > > > > richard.guenther@gmail.com>
>>>> > > wrote:
>>>> > > > > > On Thu, Jul 7, 2016 at 9:45 PM, Prasad Ghangal
>>>> > > <prasad.ghangal@gmail.com> wrote:
>>>> > > > > > > On 6 July 2016 at 14:24, Richard Biener
>>>> > > <richard.guenther@gmail.com> wrote:
>>>> > > > > > > > On Wed, Jul 6, 2016 at 9:51 AM, Prasad Ghangal
>>>> > > <prasad.ghangal@gmail.com> wrote:
>>>> > > > > > > > > On 30 June 2016 at 17:10, Richard Biener
>>>> > > <richard.guenther@gmail.com> wrote:
>>>> > > > > > > > > > On Wed, Jun 29, 2016 at 9:13 PM, Prasad Ghangal
>>>> > > > > > > > > > <prasad.ghangal@gmail.com> wrote:
>>>> > > > > > > > > > > On 29 June 2016 at 22:15, Richard Biener
>>>> > > <richard.guenther@gmail.com> wrote:
>>>> > > > > > > > > > > > On June 29, 2016 6:20:29 PM GMT+02:00,
>>>> > > > > > > > > > > > Prathamesh Kulkarni
>>>> > > <prathamesh.kulkarni@linaro.org> wrote:
>>>> > > > > > > > > > > > > On 18 June 2016 at 12:02, Prasad Ghangal
>>>> > > <prasad.ghangal@gmail.com>
>>>> > > > > > > > > > > > > wrote:
>>>> > > > > > > > > > > > > > Hi,
>>>> > > > > > > > > > > > > >
>>>> > > > > > > > > > > > > > I tried hacking pass manager to execute
>>>> > > > > > > > > > > > > > only given passes.
>>>> > > For this I
>>>> > > > > > > > > > > > > > am adding new member as opt_pass
>>>> > > > > > > > > > > > > > *custom_pass_list to the
>>>> > > function
>>>> > > > > > > > > > > > > > structure to store passes need to execute
>>>> > > > > > > > > > > > > > and providing the
>>>> > > > > > > > > > > > > > custom_pass_list to execute_pass_list()
>>>> > > > > > > > > > > > > > function instead of
>>>> > > all
>>>> > > > > > > > > > > > > passes
>>>> > > > > > > > > > > > > >
>>>> > > > > > > > > > > > > > for test case like-
>>>> > > > > > > > > > > > > >
>>>> > > > > > > > > > > > > > int a;
>>>> > > > > > > > > > > > > > void __GIMPLE (execute ("tree-ccp1", "tree
>>>> > > > > > > > > > > > > > -fre1")) foo()
>>>> > > > > > > > > > > > > > {
>>>> > > > > > > > > > > > > > bb_1:
>>>> > > > > > > > > > > > > >   a = 1 + a;
>>>> > > > > > > > > > > > > > }
>>>> > > > > > > > > > > > > >
>>>> > > > > > > > > > > > > > it will execute only given passes i.e. ccp1
>>>> > > > > > > > > > > > > > and fre1 pass
>>>> > > on the
>>>> > > > > > > > > > > > > function
>>>> > > > > > > > > > > > > >
>>>> > > > > > > > > > > > > > and for test case like -
>>>> > > > > > > > > > > > > >
>>>> > > > > > > > > > > > > > int a;
>>>> > > > > > > > > > > > > > void __GIMPLE (startwith ("tree-ccp1"))
>>>> > > > > > > > > > > > > > foo()
>>>> > > > > > > > > > > > > > {
>>>> > > > > > > > > > > > > > bb_1:
>>>> > > > > > > > > > > > > >   a = 1 + a;
>>>> > > > > > > > > > > > > > }
>>>> > > > > > > > > > > > > >
>>>> > > > > > > > > > > > > > it will act as a entry point to the
>>>> > > > > > > > > > > > > > pipeline and will
>>>> > > execute passes
>>>> > > > > > > > > > > > > > starting from given pass.
>>>> > > > > > > > > > > > > Bike-shedding:
>>>> > > > > > > > > > > > > Would it make sense to have syntax for
>>>> > > > > > > > > > > > > defining pass ranges
>>>> > > to execute
>>>> > > > > > > > > > > > > ?
>>>> > > > > > > > > > > > > for instance:
>>>> > > > > > > > > > > > > void __GIMPLE(execute (pass_start :
>>>> > > > > > > > > > > > > pass_end))
>>>> > > > > > > > > > > > > which would execute all the passes within
>>>> > > > > > > > > > > > > range [pass_start,
>>>> > > pass_end],
>>>> > > > > > > > > > > > > which would be convenient if the range is
>>>> > > > > > > > > > > > > large.
>>>> > > > > > > > > > > >
>>>> > > > > > > > > > > > But it would rely on a particular pass
>>>> > > > > > > > > > > > pipeline, f.e.
>>>> > > pass-start appearing before pass-end.
>>>> > > > > > > > > > > >
>>>> > > > > > > > > > > > Currently control doesn't work 100% as it only
>>>> > > > > > > > > > > > replaces
>>>> > > all_optimizations but not lowering passes or early opts, nor IPA
>>>> > > opts.
>>>> > > > > > > > > > > >
>>>> > > > > > > > > > >
>>>> > > > > > > > > > > Each pass needs GIMPLE in some specific form. So
>>>> > > > > > > > > > > I am letting
>>>> > > lowering
>>>> > > > > > > > > > > and early opt passes to execute. I think we have
>>>> > > > > > > > > > > to execute
>>>> > > some
>>>> > > > > > > > > > > passes (like cfg) anyway to represent GIMPLE into
>>>> > > > > > > > > > > proper form
>>>> > > > > > > > > >
>>>> > > > > > > > > > Yes, that's true.  Note that early opt passes only
>>>> > > > > > > > > > optimize but
>>>> > > we need
>>>> > > > > > > > > > pass_build_ssa_passes at least (for into-SSA).  For
>>>> > > > > > > > > > proper
>>>> > > unit-testing
>>>> > > > > > > > > > of GIMPLE passes we do need to guard off early opts
>>>> > > > > > > > > > somehow
>>>> > > > > > > > > > (I guess a simple if (flag_gimple && cfun
>>>> > > > > > > > > > ->custom_pass_list)
>>>> > > would do
>>>> > > > > > > > > > that).
>>>> > > > > > > > > >
>>>> > > > > > > > > > Then there is of course the question about IPA
>>>> > > > > > > > > > passes which I
>>>> > > think is
>>>> > > > > > > > > > somewhat harder (one could always disable all IPA
>>>> > > > > > > > > > passes
>>>> > > manually
>>>> > > > > > > > > > via flags of course or finally have a global
>>>> > > > > > > > > > -fipa/no-ipa like
>>>> > > most
>>>> > > > > > > > > > other compilers).
>>>> > > > > > > > > >
>>>> > > > > > > > > Can we iterate through all ipa passes and do
>>>> > > > > > > > > -fdisable-ipa-pass
>>>> > > or
>>>> > > > > > > > > -fenable-ipa-pass equivalent for each?
>>>> > > > > > > >
>>>> > > > > > > > We could do that, yes.  But let's postpone this issue.
>>>> > > > > > > >  I think
>>>> > > that
>>>> > > > > > > > startwith is going to be most useful and rather than
>>>> > > > > > > > constructing
>>>> > > > > > > > a pass list for it "native" support for it in the pass
>>>> > > > > > > > manager is
>>>> > > > > > > > likely to produce better results (add a 'startwith'
>>>> > > > > > > > member
>>>> > > alongside
>>>> > > > > > > > the pass list member and if it is set the pass manager
>>>> > > > > > > > skips all
>>>> > > > > > > > passes that do not match 'startwith' and once it
>>>> > > > > > > > reaches it it
>>>> > > clears
>>>> > > > > > > > the field).
>>>> > > > > > > >
>>>> > > > > > > > In the future I hope we can get away from a static pass
>>>> > > > > > > > list and
>>>> > > more
>>>> > > > > > > > towards rule-driven pass execution (we have all those
>>>> > > > > > > > PROP_*
>>>> > > stuff
>>>> > > > > > > > already but it isn't really used for example).  But
>>>> > > > > > > > well, that
>>>> > > would be
>>>> > > > > > > > a separate GSoC project ;)
>>>> > > > > > > >
>>>> > > > > > > > IMHO startwith will provide everything needed for unit
>>>> > > > > > > > -testing.
>>>> > > We can
>>>> > > > > > > > add a flag on whether further passes should be executed
>>>> > > > > > > > or not
>>>> > > and
>>>> > > > > > > > even a pass list like execute ("ccp1", "fre") can be
>>>> > > > > > > > implemented
>>>> > > by
>>>> > > > > > > > startwith ccp1 and then from there executing the rest
>>>> > > > > > > > of the
>>>> > > passes in the
>>>> > > > > > > > list and stopping at the end.
>>>> > > > > > > >
>>>> > > > > > > > As said, unit-testing should exercise a single pass if
>>>> > > > > > > > we can
>>>> > > control
>>>> > > > > > > > its input.
>>>> > > > > > > >
>>>> > > > > > > In this patch I am skipping execution of passes until
>>>> > > pass_startwith
>>>> > > > > > > is found. Unlike previous build, now pass manager
>>>> > > > > > > executes all
>>>> > > passes
>>>> > > > > > > in pipeline starting from pass_startwith instead of just
>>>> > > > > > > sub
>>>> > > passes.
>>>> > > > > >
>>>> > > > > > That looks good.  I wonder if
>>>> > > > > >
>>>> > > > > > +  if (startwith_p && cfun->startwith)
>>>> > > > > > +    {
>>>> > > > > > +      if (pass->name == cfun->pass_startwith->name
>>>> > > > > > +         || pass->name == "*clean_state")
>>>> > > > > >
>>>> > > > > > need better be strcmp ()s though.  Also the early
>>>> > > > > > optimization
>>>> > > pipeline
>>>> > > > > > should be executed with startwith support as well.
>>>> > > > > >
>>>> > > > >
>>>> > > > > This patch adds startwith support for early opt passes. But
>>>> > > > > for
>>>> > > > > starting from some passes (like asan0, optimized) in
>>>> > > > > all_passes
>>>> > > > > pipeline, it falils at verify_curr_properties in
>>>> > > > > execute_one_pass
>>>> > > ().
>>>> > > > > I wonder if we need to update properties after skipping each
>>>> > > > > pass
>>>> > > >
>>>> > > > Yeah, it's not possible to start at arbitrary points with
>>>> > > > skipping
>>>> > > passes
>>>> > > > that provide a required property.  I suspect it's good enough
>>>> > > > that
>>>> > > we'll
>>>> > > > ICE if that happens.
>>>> > > >
>>>> > > > I see you are working on the dump-file side a bit now.  What is
>>>> > > > still
>>>> > > > missing after you got support for PHIs is parsing of SSA names.
>>>> > > > Without this unit-testing will be difficult at best.
>>>> > > >
>>>> > > > I think what we need to do is simplify the job of the parser
>>>> > > > and
>>>> > > > make the syntax we use to print SSA names a bit different.
>>>> > > > So rather than printing VAR_VERSION we need to choose a
>>>> > > > letter that is not part of a valid identifier before VERSION,
>>>> > > > like a dot '.'.  Thus we'd have i.1 instead of i_1 and we'd
>>>> > > > have
>>>> > > > .2 instead of _2 for an anonymous SSA name.  The advantage
>>>> > > > for non-anonymous names is that we can properly re-use the
>>>> > > > C frontends decl handling for declaring and looking up 'i'.
>>>> > > > The disadvantage is that for anonymous SSA names this isn't
>>>> > > > so easy which means we could choose to not support those
>>>> > > > for the moment and require fake decls for them.  In fact
>>>> > > > into-SSA will do the correct thing if we just treat them as
>>>> > > > decls,
>>>> > > > thus continue to dump them as _VERSION.
>>>> > > >
>>>> > >
>>>> > > I am little confused here about parsing 'i.1' because lexer drops
>>>> > > DOT
>>>> > > token for syntax like NAME.NUMBER . Hence instead of 'i.1' parser
>>>> > > receives 'i1'
>>>> >
>>>> > Are you sure? You should get three tokens, one for 'i', one for the
>>>> > dot and
>>>> > One for '1'.  You'd lookup the first via the C frontend symbol
>>>> > table only.
>>>> >
>>>>
>>>> Yes, I was also expecting that. For syntax like 'a.b' (ie name.name)
>>>> it gives proper 3 tokens but for syntax like 'a.1' it produces only
>>>> 2.
>>>>
>>>> This is what I observed while debugging "int a.1;"
>>>>
>>>> (gdb) print *c_parser_peek_nth_token (parser, 1)
>>>> $3 = {type = CPP_KEYWORD, id_kind = C_ID_NONE, keyword = RID_INT,
>>>>   pragma_kind = PRAGMA_NONE, location = 242114, value =
>>>> 0x7ffff65c82d0}
>>>> (gdb) print *c_parser_peek_nth_token (parser, 2)
>>>> $4 = {type = CPP_NAME, id_kind = C_ID_ID, keyword = RID_MAX,
>>>>   pragma_kind = PRAGMA_NONE, location = 242240, value =
>>>> 0x7ffff66d0b90}
>>>> (gdb) print *c_parser_peek_nth_token (parser, 3)
>>>> $5 = {type = CPP_NUMBER, id_kind = C_ID_NONE, keyword = RID_MAX,
>>>>   pragma_kind = PRAGMA_NONE, location = 242273, value =
>>>> 0x7ffff66e0030}
>>>
>>>What is the number?  I'm wondering if it's somehow been lexed as a
>>>decimal ".1" i.e. if the "." is somehow being treated as part of the
>>>CPP_NUMBER.
>>
>
> Yes, the token '.1' is treated as CPP_NUMBER
>
>> Ah, possible...
>>
>>>FWIW, I find hacking in calls to "inform" very useful for seeing what
>>>each token is (assuming that caret printing isn't disabled).
>>>
>>>  (gdb) call inform ($3->location, "")
>>>  (gdb) call inform ($4->location, "")
>>>  (gdb) call inform ($5
>>>->location, "")
>>>
>>>etc
>>>
>>>BTW, does it have to be '.' as the SSA_NAME separator?  Could it be a
>>>different character e.g. '@' or something else that's non-legal in C?
>>
>> It doesn't have to be '.', but sth visually not too disturbing would be nice.  If we don't go with '.' We can as well try to parse the SSA version from i_1, leaving the ambiguity with it being a valid C identifier.
>>
>
> As special characters are not valid in C, I am using 'a..1' as syntax
> for ssa name. For parsing I am using
> +      lhs.value = make_ssa_name_fn (cfun,
> +                                   lookup_name (c_parser_peek_token
> (parser)->value),
> +                                   NULL);
> Now for passing ssa name into __PHI, how can we lookup for particular ssa name.
> Or is there other better method to do it?

Note that with this you need to preserve SSA versions as used in the source
(the 1 in a..1).  If you can do that (see below) the way to lookup an SSA name
is simply calling 'ssa_name (version)' with version being an integer with the
version number.

make_ssa_name will simply allocate the next available SSA version so
you'll need to add an interface that allows you allocation of a specific
SSA version.  Like with sth similar to

Index: gcc/tree-ssanames.c
===================================================================
--- gcc/tree-ssanames.c (revision 238512)
+++ gcc/tree-ssanames.c (working copy)
@@ -255,7 +255,7 @@
    used without a preceding definition).  */

 tree
-make_ssa_name_fn (struct function *fn, tree var, gimple *stmt)
+make_ssa_name_fn (struct function *fn, tree var, gimple *stmt, int version)
 {
   tree t;
   use_operand_p imm;
@@ -265,8 +265,17 @@
              || TREE_CODE (var) == RESULT_DECL
              || (TYPE_P (var) && is_gimple_reg_type (var)));

+  if (version != 0)
+    {
+      t = make_node (SSA_NAME);
+      SSA_NAME_VERSION (t) = version;
+      vec_safe_grow_cleared (SSANAMES (fn), version + 1);
+      gcc_assert ((*SSANAMES (fn))[version] == NULL);
+      (*SSANAMES (fn))[version] = t;
+      ssa_name_nodes_created++;
+    }
   /* If our free list has an element, then use it.  */
-  if (!vec_safe_is_empty (FREE_SSANAMES (fn)))
+  else if (!vec_safe_is_empty (FREE_SSANAMES (fn)))
     {
       t = FREE_SSANAMES (fn)->pop ();
       ssa_name_nodes_reused++;
Index: gcc/tree-ssanames.h
===================================================================
--- gcc/tree-ssanames.h (revision 237253)
+++ gcc/tree-ssanames.h (working copy)
@@ -79,7 +79,7 @@
 extern void init_ssanames (struct function *, int);
 extern void fini_ssanames (struct function *);
 extern void ssanames_print_statistics (void);
-extern tree make_ssa_name_fn (struct function *, tree, gimple *);
+extern tree make_ssa_name_fn (struct function *, tree, gimple *, int);
 extern void release_ssa_name_fn (struct function *, tree);
 extern bool get_ptr_info_alignment (struct ptr_info_def *, unsigned int *,
                                    unsigned int *);

where you can then do sth like

  ssaname = ssa_name (version);
  if (!ssaname)
    ssaname = make_ssa_name_fn (cfun, lookup_name (...), NULL, version);

to either lookup an existing or allocate a new SSA name of the desired version.

Just for some bike-shedding, I don't like using '..' too much ;)

Richard.

>
>> Richard.
>>
>>>Dave
>>
>>


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