pseudo-fix for PR/38984

Paolo Bonzini bonzini@gnu.org
Tue Jan 27 17:02:00 GMT 2009


This is only a pseudo-fix because the testcase also exhibits PR/38985.
The testcase will be fixed in 4.5 thanks to the alias-improvements branch.

The patch however is trivial enough that Richard agreed to put it in 4.4
too.  Fixing PR38985 in time for 4.4.0 also seems not impossible to me.

Bootstrapped/regtested i686-pc-linux-gnu (regtested C only so far; but
there is no testcase outside gcc.dg that tries
-fno-delete-null-pointer-checks).  Ok?

Paolo

2009-01-27  Paolo Bonzini  <bonzini@gnu.org>

	* tree-ssa-structalias.c (get_constraint_for_1): Do not
	use nothing_id if -fno-delete-null-pointer-checks.

Index: tree-ssa-structalias.c
===================================================================
--- tree-ssa-structalias.c      (revision 142960)
+++ tree-ssa-structalias.c      (working copy)
@@ -3030,8 +3030,14 @@ get_constraint_for_1 (tree t, VEC (ce_s,
      happens below, since it will fall into the default case. The only
      case we know something about an integer treated like a pointer is
      when it is the NULL pointer, and then we just say it points to
-     NULL.  */
-  if (TREE_CODE (t) == INTEGER_CST
+     NULL.
+
+     Do not do that if -fno-delete-null-pointer-checks though, because
+     in that case *NULL does not fail, so it _should_ alias *anything.
+     It is not worth adding a new option or renaming the existing one,
+     since this case is relatively obscure.  */
+  if (flag_delete_null_pointer_checks
+      && TREE_CODE (t) == INTEGER_CST
       && integer_zerop (t))
     {
       temp.var = nothing_id;



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