re PR debug/52001 (Huge compile-time regression with var-tracking)

PR debug/52001
* cselib.c (preserve_only_constants): Rename to...
(preserve_constants_and_equivs): ... this.  Split out...
(invariant_or_equiv_p): ... this.  Preserve plus expressions
of other preserved expressions too.
(cselib_reset_table): Adjust.
* var-tracking.c (reverse_op): Use canonical value to build
reverse operation.

From-SVN: r184571

gcc/ChangeLog

+2012-02-25  Alexandre Oliva  <aoliva@redhat.com>
+
+	PR debug/52001
+	* cselib.c (preserve_only_constants): Rename to...
+	(preserve_constants_and_equivs): ... this.  Split out...
+	(invariant_or_equiv_p): ... this.  Preserve plus expressions
+	of other preserved expressions too.
+	(cselib_reset_table): Adjust.
+	* var-tracking.c (reverse_op): Use canonical value to build
+	reverse operation.
+
 2012-02-23  Kai Tietz  <ktietz@redhat.com>
 
 	* config/i386/i386.c (ix86_delegitimize_address): Handle

gcc/cselib.c

@@ -383,22 +383,29 @@ cselib_clear_table (void)
   cselib_reset_table (1);
 }
 
-/* Remove from hash table all VALUEs except constants
-   and function invariants.  */
+/* Return TRUE if V is a constant, a function invariant or a VALUE
+   equivalence; FALSE otherwise.  */
 
-static int
-preserve_only_constants (void **x, void *info ATTRIBUTE_UNUSED)
+static bool
+invariant_or_equiv_p (cselib_val *v)
 {
-  cselib_val *v = (cselib_val *)*x;
   struct elt_loc_list *l;
 
+  if (v == cfa_base_preserved_val)
+    return true;
+
+  /* Keep VALUE equivalences around.  */
+  for (l = v->locs; l; l = l->next)
+    if (GET_CODE (l->loc) == VALUE)
+      return true;
+
   if (v->locs != NULL
       && v->locs->next == NULL)
     {
       if (CONSTANT_P (v->locs->loc)
 	  && (GET_CODE (v->locs->loc) != CONST
 	      || !references_value_p (v->locs->loc, 0)))
-	return 1;
+	return true;
       /* Although a debug expr may be bound to different expressions,
 	 we can preserve it as if it was constant, to get unification
 	 and proper merging within var-tracking.  */
@@ -406,24 +413,29 @@ preserve_only_constants (void **x, void *info ATTRIBUTE_UNUSED)
 	  || GET_CODE (v->locs->loc) == DEBUG_IMPLICIT_PTR
 	  || GET_CODE (v->locs->loc) == ENTRY_VALUE
 	  || GET_CODE (v->locs->loc) == DEBUG_PARAMETER_REF)
-	return 1;
-      if (cfa_base_preserved_val)
-	{
-	  if (v == cfa_base_preserved_val)
-	    return 1;
-	  if (GET_CODE (v->locs->loc) == PLUS
-	      && CONST_INT_P (XEXP (v->locs->loc, 1))
-	      && XEXP (v->locs->loc, 0) == cfa_base_preserved_val->val_rtx)
-	    return 1;
-	}
+	return true;
+
+      /* (plus (value V) (const_int C)) is invariant iff V is invariant.  */
+      if (GET_CODE (v->locs->loc) == PLUS
+	  && CONST_INT_P (XEXP (v->locs->loc, 1))
+	  && GET_CODE (XEXP (v->locs->loc, 0)) == VALUE
+	  && invariant_or_equiv_p (CSELIB_VAL_PTR (XEXP (v->locs->loc, 0))))
+	return true;
     }
 
-  /* Keep VALUE equivalences around.  */
-  for (l = v->locs; l; l = l->next)
-    if (GET_CODE (l->loc) == VALUE)
-      return 1;
+  return false;
+}
+
+/* Remove from hash table all VALUEs except constants, function
+   invariants and VALUE equivalences.  */
+
+static int
+preserve_constants_and_equivs (void **x, void *info ATTRIBUTE_UNUSED)
+{
+  cselib_val *v = (cselib_val *)*x;
 
-  htab_clear_slot (cselib_hash_table, x);
+  if (!invariant_or_equiv_p (v))
+    htab_clear_slot (cselib_hash_table, x);
   return 1;
 }
 
@@ -463,7 +475,7 @@ cselib_reset_table (unsigned int num)
     }
 
   if (cselib_preserve_constants)
-    htab_traverse (cselib_hash_table, preserve_only_constants, NULL);
+    htab_traverse (cselib_hash_table, preserve_constants_and_equivs, NULL);
   else
     htab_empty (cselib_hash_table);
 

gcc/var-tracking.c

@@ -5334,6 +5334,10 @@ reverse_op (rtx val, const_rtx expr, rtx insn)
   if (!v || !cselib_preserved_value_p (v))
     return;
 
+  /* Use canonical V to avoid creating multiple redundant expressions
+     for different VALUES equivalent to V.  */
+  v = canonical_cselib_val (v);
+
   /* Adding a reverse op isn't useful if V already has an always valid
      location.  Ignore ENTRY_VALUE, while it is always constant, we should
      prefer non-ENTRY_VALUE locations whenever possible.  */