Re: [COMMITTED] Remove pass counting in VRP.

Re: [COMMITTED] Remove pass counting in VRP.

[David Malcolm]

On Tue, 2023-10-03 at 10:32 -0400, Andrew MacLeod wrote:
> Pass counting in VRP is used to decide when to call early VRP, pass
> the 
> flag to enable warnings, and when the final pass is.
> 
> If you try to add additional passes, this becomes quite fragile. This
> patch simply chooses the pass based on the data pointer passed in,
> and 
> remove the pass counter.   The first FULL VRP pass invokes the
> warning 
> code, and the flag passed in now represents the FINAL pass of VRP.  
> There is no longer a global flag which, as it turns out, wasn't
> working 
> well with the JIT compiler, but when undetected.  (Thanks to dmalcolm
> for helping me sort out what was going on there)
> 
> 
> Bootstraps  on x86_64-pc-linux-gnu with no regressions.   Pushed.

[CCing jit mailing list]

I'm worried that this patch may have "papered over" an issue with
libgccjit.  Specifically:

[...snip...]

> diff --git a/gcc/tree-vrp.cc b/gcc/tree-vrp.cc
> index d7b194f5904..05266dfe34a 100644
> --- a/gcc/tree-vrp.cc
> +++ b/gcc/tree-vrp.cc
> @@ -1120,36 +1120,44 @@ const pass_data pass_data_early_vrp =
>    ( TODO_cleanup_cfg | TODO_update_ssa | TODO_verify_all ),
>  };
>  
> -static int vrp_pass_num = 0;
> +static bool run_warning_pass = true;

I see the global variable "run_warning_pass" starts out true here

>  class pass_vrp : public gimple_opt_pass
>  {
>  public:
>    pass_vrp (gcc::context *ctxt, const pass_data &data_)
> -    : gimple_opt_pass (data_, ctxt), data (data_), warn_array_bounds_p (false),
> -      my_pass (vrp_pass_num++)
> -  {}
> +    : gimple_opt_pass (data_, ctxt), data (data_),
> +      warn_array_bounds_p (false), final_p (false)
> +  {
> +    // Only the frst VRP pass should run warnings.
> +    if (&data == &pass_data_vrp)
> +      {
> +	warn_array_bounds_p = run_warning_pass;
> +	run_warning_pass = false;

...and run_warning_pass affects the member data
pass_vrp::warn_array_bounds_p here, and then becomes false, but nothing
seems to ever reset run_warning_pass back to true.

It seems that with this patch, if libgccjit compiles more than one
gcc_jit_context in the same process, the first context compilation will
warn, whereas subsequent ones in that process won't.

Or did I miss something?

[...snip...]

Thoughts?
Dave

Re: [COMMITTED] Remove pass counting in VRP.

[Andrew MacLeod]

[-- Attachment #1: Type: text/plain, Size: 1090 bytes --]


On 10/3/23 13:02, David Malcolm wrote:
> On Tue, 2023-10-03 at 10:32 -0400, Andrew MacLeod wrote:
>> Pass counting in VRP is used to decide when to call early VRP, pass
>> the
>> flag to enable warnings, and when the final pass is.
>>
>> If you try to add additional passes, this becomes quite fragile. This
>> patch simply chooses the pass based on the data pointer passed in,
>> and
>> remove the pass counter.   The first FULL VRP pass invokes the
>> warning
>> code, and the flag passed in now represents the FINAL pass of VRP.
>> There is no longer a global flag which, as it turns out, wasn't
>> working
>> well with the JIT compiler, but when undetected.  (Thanks to dmalcolm
>> for helping me sort out what was going on there)
>>
>>
>> Bootstraps  on x86_64-pc-linux-gnu with no regressions.   Pushed.
> [CCing jit mailing list]
>
> I'm worried that this patch may have "papered over" an issue with
> libgccjit.  Specifically:

well, that isnt the patch that was checked in :-P

Im not sure how the old version got into the commit note.

Attached is the version checked in.


[-- Attachment #2: pass.diff --]
[-- Type: text/x-patch, Size: 3887 bytes --]

commit 7eb5ce7f58ed4a48641e1786e4fdeb2f7fb8c5ff
Author: Andrew MacLeod <amacleod@redhat.com>
Date:   Thu Sep 28 09:19:32 2023 -0400

    Remove pass counting in VRP.
    
    Rather than using a pass count to decide which parameters are passed to
    VRP, makemit explicit.
    
            * passes.def (pass_vrp): Pass "final pass" flag as parameter.
            * tree-vrp.cc (vrp_pass_num): Remove.
            (pass_vrp::my_pass): Remove.
            (pass_vrp::pass_vrp): Add warn_p as a parameter.
            (pass_vrp::final_p): New.
            (pass_vrp::set_pass_param): Set final_p param.
            (pass_vrp::execute): Call execute_range_vrp with no conditions.
            (make_pass_vrp): Pass additional parameter.
            (make_pass_early_vrp): Ditto.

diff --git a/gcc/passes.def b/gcc/passes.def
index 4110a472914..2bafd60bbfb 100644
--- a/gcc/passes.def
+++ b/gcc/passes.def
@@ -221,7 +221,7 @@ along with GCC; see the file COPYING3.  If not see
       NEXT_PASS (pass_fre, true /* may_iterate */);
       NEXT_PASS (pass_merge_phi);
       NEXT_PASS (pass_thread_jumps_full, /*first=*/true);
-      NEXT_PASS (pass_vrp, true /* warn_array_bounds_p */);
+      NEXT_PASS (pass_vrp, false /* final_p*/);
       NEXT_PASS (pass_dse);
       NEXT_PASS (pass_dce);
       /* pass_stdarg is always run and at this point we execute
@@ -348,7 +348,7 @@ along with GCC; see the file COPYING3.  If not see
       NEXT_PASS (pass_dominator, false /* may_peel_loop_headers_p */);
       NEXT_PASS (pass_strlen);
       NEXT_PASS (pass_thread_jumps_full, /*first=*/false);
-      NEXT_PASS (pass_vrp, false /* warn_array_bounds_p */);
+      NEXT_PASS (pass_vrp, true /* final_p */);
       /* Run CCP to compute alignment and nonzero bits.  */
       NEXT_PASS (pass_ccp, true /* nonzero_p */);
       NEXT_PASS (pass_warn_restrict);
diff --git a/gcc/tree-vrp.cc b/gcc/tree-vrp.cc
index d7b194f5904..4f8c7745461 100644
--- a/gcc/tree-vrp.cc
+++ b/gcc/tree-vrp.cc
@@ -1120,36 +1120,32 @@ const pass_data pass_data_early_vrp =
   ( TODO_cleanup_cfg | TODO_update_ssa | TODO_verify_all ),
 };
 
-static int vrp_pass_num = 0;
 class pass_vrp : public gimple_opt_pass
 {
 public:
-  pass_vrp (gcc::context *ctxt, const pass_data &data_)
-    : gimple_opt_pass (data_, ctxt), data (data_), warn_array_bounds_p (false),
-      my_pass (vrp_pass_num++)
-  {}
+  pass_vrp (gcc::context *ctxt, const pass_data &data_, bool warn_p)
+    : gimple_opt_pass (data_, ctxt), data (data_),
+      warn_array_bounds_p (warn_p), final_p (false)
+    { }
 
   /* opt_pass methods: */
-  opt_pass * clone () final override { return new pass_vrp (m_ctxt, data); }
+  opt_pass * clone () final override
+    { return new pass_vrp (m_ctxt, data, false); }
   void set_pass_param (unsigned int n, bool param) final override
     {
       gcc_assert (n == 0);
-      warn_array_bounds_p = param;
+      final_p = param;
     }
   bool gate (function *) final override { return flag_tree_vrp != 0; }
   unsigned int execute (function *fun) final override
     {
-      // Early VRP pass.
-      if (my_pass == 0)
-	return execute_ranger_vrp (fun, /*warn_array_bounds_p=*/false, false);
-
-      return execute_ranger_vrp (fun, warn_array_bounds_p, my_pass == 2);
+      return execute_ranger_vrp (fun, warn_array_bounds_p, final_p);
     }
 
  private:
   const pass_data &data;
   bool warn_array_bounds_p;
-  int my_pass;
+  bool final_p;
 }; // class pass_vrp
 
 const pass_data pass_data_assumptions =
@@ -1219,13 +1215,13 @@ public:
 gimple_opt_pass *
 make_pass_vrp (gcc::context *ctxt)
 {
-  return new pass_vrp (ctxt, pass_data_vrp);
+  return new pass_vrp (ctxt, pass_data_vrp, true);
 }
 
 gimple_opt_pass *
 make_pass_early_vrp (gcc::context *ctxt)
 {
-  return new pass_vrp (ctxt, pass_data_early_vrp);
+  return new pass_vrp (ctxt, pass_data_early_vrp, false);
 }
 
 gimple_opt_pass *

Re: [COMMITTED] Remove pass counting in VRP.

[David Malcolm]

On Tue, 2023-10-03 at 13:11 -0400, Andrew MacLeod wrote:
> 
> On 10/3/23 13:02, David Malcolm wrote:
> > On Tue, 2023-10-03 at 10:32 -0400, Andrew MacLeod wrote:
> > > Pass counting in VRP is used to decide when to call early VRP,
> > > pass
> > > the
> > > flag to enable warnings, and when the final pass is.
> > > 
> > > If you try to add additional passes, this becomes quite fragile.
> > > This
> > > patch simply chooses the pass based on the data pointer passed
> > > in,
> > > and
> > > remove the pass counter.   The first FULL VRP pass invokes the
> > > warning
> > > code, and the flag passed in now represents the FINAL pass of
> > > VRP.
> > > There is no longer a global flag which, as it turns out, wasn't
> > > working
> > > well with the JIT compiler, but when undetected.  (Thanks to
> > > dmalcolm
> > > for helping me sort out what was going on there)
> > > 
> > > 
> > > Bootstraps  on x86_64-pc-linux-gnu with no regressions.   Pushed.
> > [CCing jit mailing list]
> > 
> > I'm worried that this patch may have "papered over" an issue with
> > libgccjit.  Specifically:
> 
> well, that isnt the patch that was checked in :-P

Aha!  That makes much more sense.  I took a look at
https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=7eb5ce7f58ed4a48641e1786e4fdeb2f7fb8c5ff
and yes, that looks like it will work with libgccjit

Thanks for clarifying (and for fixing the issue)
Dave

> 
> Im not sure how the old version got into the commit note.
> 
> Attached is the version checked in.
>