Re: regclass speedup

[Mike Stump <mstump at apple dot com>]

On Wednesday, January 15, 2003, at 12:46 AM, Richard Henderson wrote:
> On Fri, Jan 10, 2003 at 01:17:38PM -0800, Mike Stump wrote:
> > Here is a little one that avoids re-initializing for regclass.  Speeds
> > up regclass by about 88% for one of my compiles (Finder_FE).  The only
> > issue may be, can any of the things that influence auto-inc or 
> > auto-dec
> > availability change from function to function?
> Couple o' things.  First, there is a comment,
>
>   /* Initialize information about which register classes can be used 
> for
>      pseudos that are auto-incremented or auto-decremented.  It would
>      seem better to put this in init_reg_sets, but we need to be able
>      to allocate rtx, which we can't do that early.  */
Comment updated.

> which appears to be false now -- init_reg_sets is called
> after init_ggc.  So it appears as if we can just move the
> code rather than creating the late_regclass_init.
Done.  I kept as much of the original temporal ordering as possible and 
put it last in the per compilation unit init code.  I also kept it easy 
to move around, just in case people want to defer the code, or move it 
later, and to keep functions reasonably sized.

> Second,
>
>       rtx r = gen_rtx_REG (VOIDmode, 0);
>             REGNO (r) = j;
>                   PUT_MODE (r, m);
>
> this is a no-no.  We cannot randomly modify register rtxs
> we get back from gen_rtx_REG.  It may be shared.  We should
> be using gen_rtx_raw_REG instead.
Latent bug...  I also fixed this.

Retesting now, ok otherwise?  Ok for 3.3 branch as well?


2003-01-23  Mike Stump  <mrs@apple.com>

        * regclass.c (init_reg_autoinc): New function.
        (regclass): Move initialization of forbidden_inc_dec_class from 
here...
        (init_regs): to here.  Avoids reinitialization for each 
function, saving time.

Doing diffs in regclass.c.~1~:
*** regclass.c.~1~      Thu Jan 23 09:53:18 2003
--- regclass.c  Thu Jan 23 09:53:39 2003
*************** init_regs ()
*** 578,583 ****
--- 578,585 ----
    init_reg_sets_1 ();

    init_reg_modes ();
+
+   init_reg_autoinc ();
  }

  /* Initialize some fake stack-frame MEM references for use in
*************** scan_one_insn (insn, pass)
*** 1143,1179 ****
    return insn;
  }

! /* This is a pass of the compiler that scans all instructions
!    and calculates the preferred class for each pseudo-register.
!    This information can be accessed later by calling 
`reg_preferred_class'.
!    This pass comes just before local register allocation.  */

  void
! regclass (f, nregs, dump)
!      rtx f;
!      int nregs;
!      FILE *dump;
  {
-   rtx insn;
-   int i;
-   int pass;
-
-   init_recog ();
-
-   costs = (struct costs *) xmalloc (nregs * sizeof (struct costs));
-
  #ifdef FORBIDDEN_INC_DEC_CLASSES
!
!   in_inc_dec = (char *) xmalloc (nregs);
!
!   /* Initialize information about which register classes can be used 
for
!      pseudos that are auto-incremented or auto-decremented.  It would
!      seem better to put this in init_reg_sets, but we need to be able
!      to allocate rtx, which we can't do that early.  */

    for (i = 0; i < N_REG_CLASSES; i++)
      {
!       rtx r = gen_rtx_REG (VOIDmode, 0);
        enum machine_mode m;
        int j;

--- 1145,1162 ----
    return insn;
  }

! /* Initialize information about which register classes can be used for
!    pseudos that are auto-incremented or auto-decremented.  */

  void
! init_reg_autoinc ()
  {
  #ifdef FORBIDDEN_INC_DEC_CLASSES
!   int i;

    for (i = 0; i < N_REG_CLASSES; i++)
      {
!       rtx r = gen_rtx_raw_REG (VOIDmode, 0);
        enum machine_mode m;
        int j;

*************** regclass (f, nregs, dump)
*** 1213,1218 ****
--- 1196,1227 ----
                }
          }
      }
+ #endif /* FORBIDDEN_INC_DEC_CLASSES */
+ }
+
+ /* This is a pass of the compiler that scans all instructions
+    and calculates the preferred class for each pseudo-register.
+    This information can be accessed later by calling 
`reg_preferred_class'.
+    This pass comes just before local register allocation.  */
+
+ void
+ regclass (f, nregs, dump)
+      rtx f;
+      int nregs;
+      FILE *dump;
+ {
+   rtx insn;
+   int i;
+   int pass;
+
+   init_recog ();
+
+   costs = (struct costs *) xmalloc (nregs * sizeof (struct costs));
+
+ #ifdef FORBIDDEN_INC_DEC_CLASSES
+
+   in_inc_dec = (char *) xmalloc (nregs);
+
  #endif /* FORBIDDEN_INC_DEC_CLASSES */

    /* Normally we scan the insns once and determine the best class to 
use for
--------------

Attachment: regclass.diffs
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