diff mbox

fix regrename pass to ensure renamings produce valid insns

Message ID 5590624E.8090409@codesourcery.com
State New
Headers show

Commit Message

Sandra Loosemore June 28, 2015, 9:08 p.m. UTC 
On 06/24/2015 09:46 PM, Jeff Law wrote:
> On 06/23/2015 07:00 PM, Sandra Loosemore wrote:
>> On 06/18/2015 11:32 AM, Eric Botcazou wrote:
>>>> The attached patch teaches regrename to validate insns affected by each
>>>> register renaming before making the change.  I can see at least two
>>>> other ways to handle this -- earlier, by rejecting renamings that
>>>> result
>>>> in invalid instructions when it's searching for the best renaming; or
>>>> later, by validating the entire set of renamings as a group instead of
>>>> incrementally for each one -- but doing it all in regname_do_replace
>>>> seems least disruptive and risky in terms of the existing code.
>>>
>>> OK, but the patch looks incomplete, rename_chains should be adjusted
>>> as well,
>>> i.e. regrename_do_replace should now return a boolean.
>>
>> Like this?  I tested this on nios2 and x86_64-linux-gnu, as before, plus
>> built for aarch64-linux-gnu and ran the gcc testsuite.
>>
>> The c6x back end also calls regrename_do_replace.  I am not set up to
>> build or test on that target, and Bernd told me off-list that it would
>> never fail on that target anyway so I have left that code alone.
>>
>> -Sandra
>>
>> regrename-2.log
>>
>>
>> 2015-06-23  Chung-Lin Tang<cltang@codesourcery.com>
>>         Sandra Loosemore<sandra@codesourcery.com>
>>
>>     gcc/
>>     * regrename.h (regrename_do_replace): Change to return bool.
>>     * regrename.c (rename_chains): Check return value of
>>     regname_do_replace.
>>     (regrename_do_replace): Re-validate the modified insns and
>>     return bool status.
>>     * config/aarch64/cortex-a57-fma-steering.c (rename_single_chain):
>>     Update to match rename_chains changes.
> As Eric mentioned, please put an assert to verify that the call from the
> c6x backend never fails.
>
> The regrename and ARM bits are fine.
>
> Do you have a testcase that you can add to the suite?  If so it'd be
> appreciated if you could include that too.
>
> Approved with the c6x assert if a testcase isn't available or
> exceedingly difficult to produce.

Thanks.  I've committed the attached version.

Re the testcase, this fixed 16 FAILs on existing tests in the gcc 
testsuite with the forthcoming nios2 load/store multiple instruction 
support, all assembler errors due to the bad instructions being 
generated.  There's nothing I can do on nios2 for a testcase until I get 
those patches committed (I'm still trying to re-test and tidy them up 
for submission), plus I think the failures are rather fragile -- 
depending on the register allocator choosing an initial register 
numbering that allows peephole optimizers to trigger, etc.  But, I will 
revisit this later and see what I can do.

-Sandra

Comments

Jeff Law July 1, 2015, 5:03 p.m. UTC | #1 
On 06/28/2015 03:08 PM, Sandra Loosemore wrote:
>
> Re the testcase, this fixed 16 FAILs on existing tests in the gcc
> testsuite with the forthcoming nios2 load/store multiple instruction
> support, all assembler errors due to the bad instructions being
> generated.  There's nothing I can do on nios2 for a testcase until I get
> those patches committed (I'm still trying to re-test and tidy them up
> for submission), plus I think the failures are rather fragile --
> depending on the register allocator choosing an initial register
> numbering that allows peephole optimizers to trigger, etc.  But, I will
> revisit this later and see what I can do.
OK.  As long as there's going to be some tests, that works for me.

jeff
diff mbox

Patch

Index: gcc/regrename.c
===================================================================
--- gcc/regrename.c	(revision 225104)
+++ gcc/regrename.c	(working copy)
@@ -496,12 +496,20 @@  rename_chains (void)
 	  continue;
 	}
 
-      if (dump_file)
-	fprintf (dump_file, ", renamed as %s\n", reg_names[best_new_reg]);
-
-      regrename_do_replace (this_head, best_new_reg);
-      tick[best_new_reg] = ++this_tick;
-      df_set_regs_ever_live (best_new_reg, true);
+      if (regrename_do_replace (this_head, best_new_reg))
+	{
+	  if (dump_file)
+	    fprintf (dump_file, ", renamed as %s\n", reg_names[best_new_reg]);
+	  tick[best_new_reg] = ++this_tick;
+	  df_set_regs_ever_live (best_new_reg, true);
+	}
+      else
+	{
+	  if (dump_file)
+	    fprintf (dump_file, ", renaming as %s failed\n",
+		     reg_names[best_new_reg]);
+	  tick[reg] = ++this_tick;
+	}
     }
 }
 
@@ -927,7 +935,13 @@  regrename_analyze (bitmap bb_mask)
     bb->aux = NULL;
 }
 
-void
+/* Attempt to replace all uses of the register in the chain beginning with
+   HEAD with REG.  Returns true on success and false if the replacement is
+   rejected because the insns would not validate.  The latter can happen
+   e.g. if a match_parallel predicate enforces restrictions on register
+   numbering in its subpatterns.  */
+
+bool
 regrename_do_replace (struct du_head *head, int reg)
 {
   struct du_chain *chain;
@@ -941,22 +955,26 @@  regrename_do_replace (struct du_head *he
       int reg_ptr = REG_POINTER (*chain->loc);
 
       if (DEBUG_INSN_P (chain->insn) && REGNO (*chain->loc) != base_regno)
-	INSN_VAR_LOCATION_LOC (chain->insn) = gen_rtx_UNKNOWN_VAR_LOC ();
+	validate_change (chain->insn, &(INSN_VAR_LOCATION_LOC (chain->insn)),
+			 gen_rtx_UNKNOWN_VAR_LOC (), true);
       else
 	{
-	  *chain->loc = gen_raw_REG (GET_MODE (*chain->loc), reg);
+	  validate_change (chain->insn, chain->loc, 
+			   gen_raw_REG (GET_MODE (*chain->loc), reg), true);
 	  if (regno >= FIRST_PSEUDO_REGISTER)
 	    ORIGINAL_REGNO (*chain->loc) = regno;
 	  REG_ATTRS (*chain->loc) = attr;
 	  REG_POINTER (*chain->loc) = reg_ptr;
 	}
-
-      df_insn_rescan (chain->insn);
     }
 
+  if (!apply_change_group ())
+    return false;
+
   mode = GET_MODE (*head->first->loc);
   head->regno = reg;
   head->nregs = hard_regno_nregs[reg][mode];
+  return true;
 }
 
 
Index: gcc/regrename.h
===================================================================
--- gcc/regrename.h	(revision 225104)
+++ gcc/regrename.h	(working copy)
@@ -91,6 +91,6 @@  extern void regrename_analyze (bitmap);
 extern du_head_p regrename_chain_from_id (unsigned 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);
+extern bool regrename_do_replace (du_head_p, int);
 
 #endif
Index: gcc/config/aarch64/cortex-a57-fma-steering.c
===================================================================
--- gcc/config/aarch64/cortex-a57-fma-steering.c	(revision 225104)
+++ gcc/config/aarch64/cortex-a57-fma-steering.c	(working copy)
@@ -289,11 +289,19 @@  rename_single_chain (du_head_p head, HAR
       return false;
     }
 
-  if (dump_file)
-    fprintf (dump_file, ", renamed as %s\n", reg_names[best_new_reg]);
-
-  regrename_do_replace (head, best_new_reg);
-  df_set_regs_ever_live (best_new_reg, true);
+  if (regrename_do_replace (head, best_new_reg))
+    {
+      if (dump_file)
+	fprintf (dump_file, ", renamed as %s\n", reg_names[best_new_reg]);
+      df_set_regs_ever_live (best_new_reg, true);
+    }
+  else
+    {
+      if (dump_file)
+	fprintf (dump_file, ", renaming as %s failed\n",
+		 reg_names[best_new_reg]);
+      return false;
+    }
   return true;
 }
 
Index: gcc/config/c6x/c6x.c
===================================================================
--- gcc/config/c6x/c6x.c	(revision 225104)
+++ gcc/config/c6x/c6x.c	(working copy)
@@ -3516,7 +3516,7 @@  try_rename_operands (rtx_insn *head, rtx
   best_reg =
     find_rename_reg (this_head, super_class, &unavailable, old_reg, true);
 
-  regrename_do_replace (this_head, best_reg);
+  gcc_assert (regrename_do_replace (this_head, best_reg));
 
   count_unit_reqs (new_reqs, head, PREV_INSN (tail));
   merge_unit_reqs (new_reqs);
@@ -3529,7 +3529,7 @@  try_rename_operands (rtx_insn *head, rtx
 	       unit_req_imbalance (reqs), unit_req_imbalance (new_reqs));
     }
   if (unit_req_imbalance (new_reqs) > unit_req_imbalance (reqs))
-    regrename_do_replace (this_head, old_reg);
+    gcc_assert (regrename_do_replace (this_head, old_reg));
   else
     memcpy (reqs, new_reqs, sizeof (unit_req_table));