re PR tree-optimization/90316 (large compile time increase in opt / alias stmt…

re PR tree-optimization/90316 (large compile time increase in opt / alias stmt walking for Go example)

2019-05-07  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/90316
	* tree-ssa-pre.c (translate_vuse_through_block): When
	same_valid is NULL do not bother to search for a virtual
	PHI continuation.
	(phi_translate_1): When operands changed we cannot keep
	the same value-number so do not bother to ask whether
	that's possible from translate_vuse_through_block.

From-SVN: r270944

gcc/ChangeLog

+2019-05-07  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/90316
+	* tree-ssa-pre.c (translate_vuse_through_block): When
+	same_valid is NULL do not bother to search for a virtual
+	PHI continuation.
+	(phi_translate_1): When operands changed we cannot keep
+	the same value-number so do not bother to ask whether
+	that's possible from translate_vuse_through_block.
+
 2019-05-07  Martin Liska  <mliska@suse.cz>
 
 	* bitmap.c (bitmap_register): Come up with

gcc/tree-ssa-pre.c

@@ -1146,7 +1146,8 @@ translate_vuse_through_block (vec<vn_reference_op_s> operands,
   edge e = NULL;
   bool use_oracle;
 
-  *same_valid = true;
+  if (same_valid)
+    *same_valid = true;
 
   if (gimple_bb (phi) != phiblock)
     return vuse;
@@ -1179,7 +1180,7 @@ translate_vuse_through_block (vec<vn_reference_op_s> operands,
 
   if (e)
     {
-      if (use_oracle)
+      if (use_oracle && same_valid)
 	{
 	  bitmap visited = NULL;
 	  /* Try to find a vuse that dominates this phi node by skipping
@@ -1191,13 +1192,9 @@ translate_vuse_through_block (vec<vn_reference_op_s> operands,
 	}
       else
 	vuse = NULL_TREE;
-      if (!vuse)
-	{
-	  /* If we didn't find any, the value ID can't stay the same,
-	     but return the translated vuse.  */
-	  *same_valid = false;
-	  vuse = PHI_ARG_DEF (phi, e->dest_idx);
-	}
+      /* If we didn't find any, the value ID can't stay the same.  */
+      if (!vuse && same_valid)
+	*same_valid = false;
       /* ??? We would like to return vuse here as this is the canonical
          upmost vdef that this reference is associated with.  But during
 	 insertion of the references into the hash tables we only ever
@@ -1535,7 +1532,8 @@ phi_translate_1 (bitmap_set_t dest,
 						    ? newoperands : operands,
 						    ref->set, ref->type,
 						    vuse, phiblock, pred,
-						    &same_valid);
+						    changed
+						    ? NULL : &same_valid);
 	    if (newvuse == NULL_TREE)
 	      {
 		newoperands.release ();