[PATCH] Improve in_array_bounds_p

[Richard Biener]

yOn Fri, 10 Jul 2015, Richard Biener wrote:

> 
> I was just testing the patch below which runs into latent issues when
> building libjava (at least)...
> 
> /space/rguenther/src/svn/trunk/libjava/java/lang/natClassLoader.cc: In 
> function Β‘java::lang::Class* _Jv_FindClassInCache(_Jv_Utf8Const*)Β’:
> /space/rguenther/src/svn/trunk/libjava/java/lang/natClassLoader.cc:97:1: 
> error:BB 3 last statement has incorrectly set lp
>  _Jv_FindClassInCache (_Jv_Utf8Const *name)
>  ^
> /space/rguenther/src/svn/trunk/libjava/java/lang/natClassLoader.cc:97:1: 
> internal compiler error: verify_flow_info failed
> 0x8e2132 verify_flow_info()
>         /space/rguenther/src/svn/trunk/gcc/cfghooks.c:261
> 
> so I have to debug that first.

It's stmts no longer throwing after VRP setting a value-range on
an array index for example.  I've addressed this in the revised
patch below which teaches CFG cleanup to deal with this (it
already removes dead EH edges and makes similar adjustments for
noreturn calls).

>  Still IMHO the patch makes sense apart
> from the ugly need to go through a INTEGER_CST tree when converting
> a wide_int to a widest_int (ugh).  Any wide-int folks around that
> can suggest something better here (reason: the two integers we compare
> do not have to have the same type/precision - see tree_int_cst_lt
> which also uses widest_ints).

This issue still remains.

Bootstrap and regtest running on x86_64-unknown-linux-gnu.

Richard.

2015-07-10  Richard Biener  <rguenther@suse.de>

	* tree-eh.c (in_array_bounds_p): Use value-range information
	when available.
	* tree-cfgcleanup.c (cleanup_control_flow_bb): Clean stmts
	from stale EH info.

Index: gcc/tree-eh.c
===================================================================
--- gcc/tree-eh.c	(revision 225655)
+++ gcc/tree-eh.c	(working copy)
@@ -2532,8 +2532,11 @@ in_array_bounds_p (tree ref)
 {
   tree idx = TREE_OPERAND (ref, 1);
   tree min, max;
+  wide_int idx_min, idx_max;
 
-  if (TREE_CODE (idx) != INTEGER_CST)
+  if (TREE_CODE (idx) != INTEGER_CST
+      && (TREE_CODE (idx) != SSA_NAME
+	  || get_range_info (idx, &idx_min, &idx_max) != VR_RANGE))
     return false;
 
   min = array_ref_low_bound (ref);
@@ -2544,11 +2547,26 @@ in_array_bounds_p (tree ref)
       || TREE_CODE (max) != INTEGER_CST)
     return false;
 
-  if (tree_int_cst_lt (idx, min)
-      || tree_int_cst_lt (max, idx))
-    return false;
+  if (TREE_CODE (idx) == INTEGER_CST)
+    {
+      if (tree_int_cst_lt (idx, min)
+	  || tree_int_cst_lt (max, idx))
+	return false;
+
+      return true;
+    }
+  else
+    {
+      if (wi::lts_p (wi::to_widest (wide_int_to_tree (TREE_TYPE (idx),
+						      idx_min)),
+		     wi::to_widest (min))
+	  || wi::lts_p (wi::to_widest (max),
+			wi::to_widest (wide_int_to_tree (TREE_TYPE (idx),
+							 idx_max))))
+	return false;
 
-  return true;
+      return true;
+    }
 }
 
 /* Returns true if it is possible to prove that the range of
Index: gcc/tree-cfgcleanup.c
===================================================================
--- gcc/tree-cfgcleanup.c	(revision 225662)
+++ gcc/tree-cfgcleanup.c	(working copy)
@@ -256,6 +256,14 @@ cleanup_control_flow_bb (basic_block bb)
            && remove_fallthru_edge (bb->succs))
     retval = true;
 
+  /* If a stmt may no longer throw, remove it from the EH tables
+     and cleanup dead EH edges.  */
+  else if (maybe_clean_eh_stmt (stmt))
+    {
+      gimple_purge_dead_eh_edges (bb);
+      retval = true;
+    }
+
   return retval;
 }