2007-05-30 Frank Ch. Eigler <fche@redhat.com>

	PR 4567.
	* staptree.cxx (varuse_collecting_visitor): Add side-effect
	result query functions.
	* elaborate.cxx (dead_stmtexpr_remover::visit_expr_statement):
	Switch to it.
	(dead_assignment_remover::visit_assignment): Skip elision of
	lvalues with side-effects in index exprs.
	* staptree.h: Corresponding changes.

2007-05-30  Frank Ch. Eigler  <fche@redhat.com>

	PR 4567.
	* systemtap.base/optim.stp, optim.exp: New test.

1 files changed, 28 insertions, 0 deletions

diff --git a/staptree.cxx b/staptree.cxx
index daac09cb..8fb41ab6 100644
--- a/staptree.cxx
+++ b/staptree.cxx
@@ -1670,6 +1670,34 @@ varuse_collecting_visitor::visit_delete_statement (delete_statement* s)
   current_lrvalue = last_lrvalue;
 }
 
+bool
+varuse_collecting_visitor::side_effect_free ()
+{
+  return (written.empty() && !embedded_seen);
+}
+
+
+bool
+varuse_collecting_visitor::side_effect_free_wrt (const set<vardecl*>& vars)
+{
+  // A looser notion of side-effect-freeness with respect to a given
+  // list of variables.
+
+  // That's useful because the written list may consist of local
+  // variables of called functions.  But visible side-effects only
+  // occur if the client's locals, or any globals are written-to.
+
+  set<vardecl*> intersection;
+  insert_iterator<set<vardecl*> > int_it (intersection, intersection.begin());
+  set_intersection (written.begin(), written.end(),
+                    vars.begin(), vars.end(),
+                    int_it);
+
+  return (intersection.empty() && !embedded_seen);
+}
+
+
+
 
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