diff mbox

Add force option to find_best_rename_reg in regrename pass

Message ID 002001d00fa4$a3c9f800$eb5de800$@arm.com
State New
Headers show

Commit Message

Thomas Preud'homme Dec. 4, 2014, 9:28 a.m. UTC 
Hi Eric,

Sorry for the delay, for some reasons despite being a recipient the mail
didn't hit my inbox but only my gcc-patches box.

> From: gcc-patches-owner@gcc.gnu.org [mailto:gcc-patches-
> owner@gcc.gnu.org] On Behalf Of Eric Botcazou
> 
> > 2014-11-14  Thomas Preud'homme  <thomas.preudhomme@arm.com>
> >
> >         * regrename.c (find_best_rename_reg): Rename to ...
> >         (find_rename_reg): This. Also add a parameter to skip tick check.
> >         * regrename.h: Likewise.
> >         * config/c6x/c6x.c: Adapt to above renaming.
> 
> Missing function in config/c6x/c6x.c entry.

Here is the proposed ChangeLog entry:

2014-11-26 Thomas Preud'homme thomas.preudhomme@arm.com\

  * regrename.c (find_best_rename_reg): Rename to ...
  (find_rename_reg): This. Also add a parameter to skip tick check.
  * regrename.h: Likewise.
  * config/c6x/c6x.c (try_rename_operands): Adapt to above renaming.

> 
> Please write it like so:
> 
> 	  if (!check_new_reg_p (old_reg, new_reg, this_head,
> *unavailable))
> 	    continue;
> 
> 	  if (!best_rename)
> 	    return new_reg;
> 
> 	  /* In the first pass, we force the renaming of registers that
> 	     don't belong to PREFERRED_CLASS to registers that do, even
> 	     though the latters were used not very long ago.  *
> 	  if ((pass == 0
> 		 && !TEST_HARD_REG_BIT
> (reg_class_contents[preferred_class],
> 					  best_new_reg))
> 		  || tick[best_new_reg] > tick[new_reg]))
> 	    best_new_reg = new_reg;

Oh yes, much better indeed. I should have thought about this. Please find below
the patch reworked as above.


Is this ok for trunk?

Best regards,

Thomas

Comments

Eric Botcazou Dec. 5, 2014, 4:39 p.m. UTC | #1 
> 2014-11-26 Thomas Preud'homme thomas.preudhomme@arm.com\
> 
>   * regrename.c (find_best_rename_reg): Rename to ...
>   (find_rename_reg): This. Also add a parameter to skip tick check.
>   * regrename.h: Likewise.
>   * config/c6x/c6x.c (try_rename_operands): Adapt to above renaming.

OK for mainline, but investigate whether you can better format the 
config/c6x/c6x.c line, for example:

+ best_reg
+   = find_rename_reg (this_head, super_class, &unavailable, old_reg, true);
Thomas Preud'homme Dec. 5, 2014, 6:37 p.m. UTC | #2 
> From: Eric Botcazou [mailto:ebotcazou@adacore.com]
> Sent: Friday, December 05, 2014 4:40 PM
> 
> OK for mainline, but investigate whether you can better format the
> config/c6x/c6x.c line, for example:
> 
> + best_reg
> +   = find_rename_reg (this_head, super_class, &unavailable, old_reg,
> true);

Commited as suggested.

Thanks. Best regards,

Thomas
diff mbox

Patch

diff --git a/gcc/config/c6x/c6x.c b/gcc/config/c6x/c6x.c
index 06319d0..6aca1e3 100644
--- a/gcc/config/c6x/c6x.c
+++ b/gcc/config/c6x/c6x.c
@@ -3513,7 +3513,8 @@  try_rename_operands (rtx_insn *head, rtx_insn *tail, unit_req_table reqs,
   COMPL_HARD_REG_SET (unavailable, reg_class_contents[(int) super_class]);
 
   old_reg = this_head->regno;
-  best_reg = find_best_rename_reg (this_head, super_class, &unavailable, old_reg);
+  best_reg = find_rename_reg (this_head, super_class, &unavailable, old_reg,
+			      true);
 
   regrename_do_replace (this_head, best_reg);
 
diff --git a/gcc/regrename.h b/gcc/regrename.h
index 03b7164..05c78ad 100644
--- a/gcc/regrename.h
+++ b/gcc/regrename.h
@@ -89,8 +89,8 @@  extern void regrename_init (bool);
 extern void regrename_finish (void);
 extern void regrename_analyze (bitmap);
 extern du_head_p regrename_chain_from_id (unsigned int);
-extern int find_best_rename_reg (du_head_p, enum reg_class, HARD_REG_SET *,
-				 int);
+extern int find_rename_reg (du_head_p, enum reg_class, HARD_REG_SET *, int,
+			    bool);
 extern void regrename_do_replace (du_head_p, int);
 
 #endif
diff --git a/gcc/regrename.c b/gcc/regrename.c
index 66f562b..88321d0 100644
--- a/gcc/regrename.c
+++ b/gcc/regrename.c
@@ -357,11 +357,13 @@  check_new_reg_p (int reg ATTRIBUTE_UNUSED, int new_reg,
 /* For the chain THIS_HEAD, compute and return the best register to
    rename to.  SUPER_CLASS is the superunion of register classes in
    the chain.  UNAVAILABLE is a set of registers that cannot be used.
-   OLD_REG is the register currently used for the chain.  */
+   OLD_REG is the register currently used for the chain.  BEST_RENAME
+   controls whether the register chosen must be better than the
+   current one or just respect the given constraint.  */
 
 int
-find_best_rename_reg (du_head_p this_head, enum reg_class super_class,
-		      HARD_REG_SET *unavailable, int old_reg)
+find_rename_reg (du_head_p this_head, enum reg_class super_class,
+		 HARD_REG_SET *unavailable, int old_reg, bool best_rename)
 {
   bool has_preferred_class;
   enum reg_class preferred_class;
@@ -400,15 +402,19 @@  find_best_rename_reg (du_head_p this_head, enum reg_class super_class,
 				    new_reg))
 	    continue;
 
+	  if (!check_new_reg_p (old_reg, new_reg, this_head, *unavailable))
+	    continue;
+
+	  if (!best_rename)
+	    return new_reg;
+
 	  /* In the first pass, we force the renaming of registers that
 	     don't belong to PREFERRED_CLASS to registers that do, even
 	     though the latters were used not very long ago.  */
-	  if (check_new_reg_p (old_reg, new_reg, this_head,
-			       *unavailable)
-	      && ((pass == 0
-		   && !TEST_HARD_REG_BIT (reg_class_contents[preferred_class],
-					  best_new_reg))
-		  || tick[best_new_reg] > tick[new_reg]))
+	  if ((pass == 0
+	      && !TEST_HARD_REG_BIT (reg_class_contents[preferred_class],
+				     best_new_reg))
+	      || tick[best_new_reg] > tick[new_reg])
 	    best_new_reg = new_reg;
 	}
       if (pass == 0 && best_new_reg != old_reg)
@@ -480,8 +486,8 @@  rename_chains (void)
       if (n_uses < 2)
 	continue;
 
-      best_new_reg = find_best_rename_reg (this_head, super_class,
-					   &this_unavailable, reg);
+      best_new_reg = find_rename_reg (this_head, super_class,
+				      &this_unavailable, reg, true);
 
       if (dump_file)
 	{