Re: [GCC RFC]A new and simple pass merging paired load store instructions

[Oleg Endo <oleg dot endo at t-online dot de>]

On Fri, 2014-05-16 at 18:10 +0800, Bin.Cheng wrote:
> On Thu, May 15, 2014 at 6:31 PM, Oleg Endo <oleg.endo@t-online.de> wrote:
> >
> > How about the following.
> > Instead of adding new hooks and inserting the pass to the general pass list, make the new
> > pass class take the necessary callback functions directly.  Then targets can just instantiate
> > the pass, passing their impl of the callbacks, and insert the pass object into the pass list at
> > a place that fits best for the target.

> Oh, I don't know we can do this in GCC.  But yes, a target may want to
> run it at some place that fits best for the target.
> 

I think it's better than trying to come up with a scheme that so-so fits
all.  My idea would look like:

// merge_paired_loadstore.h
class merge_paired_loadstore : public rtl_opt_pass
{
public:
  struct delegate
  {
    virtual bool merge_paired_loadstore (rtx x, rtx y, ...) = 0;
    ...
  };

  merge_paired_loadstore (gcc::context* ctx, const char* name,
                          delegate* d);
  ...
};

// <target>.cc

#include "merge_paired_loadstore.h"

static struct target_merge_loadstore_delegate :
merge_paired_loadstore::delegate
{
  virtual bool merge_paired_loadstore (...)
  {
     // code as if this was a freestanding target hook function
  };
} g_merge_loadstore_delegate;


static void <target>_register_passes (void)
{
  register_pass (
    new merge_paired_loadstore (g, "merge_ls",          
                                &g_merge_loadstore_delegate),
    PASS_POS_INSERT_AFTER, "other pass", 1);
}


Then, later, maybe sometime in the future, if there's something like a
class target, it'd look like:

class my_target : public target,
                  merge_paired_loadstore::delegate
{
   ... 

   virtual bool merge_paired_loadstore (...);
};

Maybe it's a bit far fetched at the moment, but it would be a start.

Cheers,
Oleg