2008-05-29 Richard Guenther <rguenther@suse.de>

	PR tree-optimization/36343
	PR tree-optimization/36346
	PR tree-optimization/36347
	* tree-flow.h (clobber_what_p_points_to): Declare.
	* tree-ssa-structalias.c (set_uids_in_ptset): Whether the
	pointed-to variable is dereferenced is irrelevant to whether
	the pointer can access the pointed-to variable.
	(clobber_what_p_points_to): New function.
	* tree-ssa-alias.c (set_initial_properties): Use it.
	* tree-ssa.c (verify_flow_sensitive_alias_info): Adjust
	call clobber check for NMTs.

	* gcc.c-torture/execute/pr36343.c: New testcase.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@136152 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 15 insertions, 20 deletions

diff --git a/gcc/tree-ssa-alias.c b/gcc/tree-ssa-alias.c
index 4f661543a55..1523aebac17 100644
--- a/gcc/tree-ssa-alias.c
+++ b/gcc/tree-ssa-alias.c
@@ -545,8 +545,14 @@ set_initial_properties (struct alias_info *ai)
     {
       struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
       tree tag = symbol_mem_tag (SSA_NAME_VAR (ptr));
-      
-      if (pi->value_escapes_p)
+
+      /* A pointer that only escapes via a function return does not
+         add to the call clobber or call used solution.
+	 To exclude ESCAPE_TO_PURE_CONST we would need to track
+	 call used variables separately or compute those properly
+	 in the operand scanner.  */
+      if (pi->value_escapes_p
+	  && pi->escape_mask & ~ESCAPE_TO_RETURN)
 	{
 	  /* If PTR escapes then its associated memory tags and
 	     pointed-to variables are call-clobbered.  */
@@ -556,24 +562,13 @@ set_initial_properties (struct alias_info *ai)
 	  if (tag)
 	    mark_call_clobbered (tag, pi->escape_mask);
 
-	  if (pi->pt_vars)
-	    {
-	      bitmap_iterator bi;
-	      unsigned int j;	      
-	      EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, j, bi)
-		{
-		  tree alias = referenced_var (j);
-
-		  /* If you clobber one part of a structure, you
-		     clobber the entire thing.  While this does not make
-		     the world a particularly nice place, it is necessary
-		     in order to allow C/C++ tricks that involve
-		     pointer arithmetic to work.  */
-		  if (!unmodifiable_var_p (alias))
-		    mark_call_clobbered (alias, pi->escape_mask);
-		}
-	    }
-	  else if (pi->pt_anything)
+	  /* Defer to points-to analysis if possible, otherwise
+	     clobber all addressable variables.  Parameters cannot
+	     point to local memory though.
+	     ???  Properly tracking which pointers point to non-local
+	     memory only would make a big difference here.  */
+	  if (!clobber_what_p_points_to (ptr)
+	      && !(pi->escape_mask & ESCAPE_IS_PARM))
 	    {
 	      any_pt_anything = true;
 	      pt_anything_mask |= pi->escape_mask;