From 30263a7389d5c2712536b74656193708bbc64d49 Mon Sep 17 00:00:00 2001
From: "Frank Ch. Eigler" <fche@elastic.org>
Date: Tue, 23 Feb 2010 20:31:00 -0500
Subject: PR11005: @defined($tvar) predicate, part 1

* staptree.h (defined_op): New class.
* all files: Extend all visitors as appropriate, mostly
  dummy/pass-through implementation.
* parse.cxx (parse_target_symbol): New function, factored out
  of parse_symbol().
  (parse_define_op): New function.
* NEWS: Mention it.
* parse.h: Corresponding changes.
* tapsets.cxx (var_expanding_visitor::visit_defined_op):
  Implement @defined() semantics.
  (dwarf_var_expanding_visitor::visit_target_symbol): Adjust.
* tapset-utrace.c (visit_target_symbol_arg): Avoid crashes
  on $argZZZ.
* tapsets.cxx (sdt_var_expanding_visitor): Ditto.
* semok/thirtysix.stp: New test.
---
 elaborate.cxx | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

(limited to 'elaborate.cxx')

diff --git a/elaborate.cxx b/elaborate.cxx
index 88a856c2..127e0bda 100644
--- a/elaborate.cxx
+++ b/elaborate.cxx
@@ -1243,6 +1243,7 @@ semantic_pass_symbols (systemtap_session& s)
 }
 
 
+
 // Keep unread global variables for probe end value display.
 void add_global_var_display (systemtap_session& s)
 {
@@ -2609,6 +2610,7 @@ struct void_statement_reducer: public update_visitor
   void visit_print_format (print_format* e);
   void visit_target_symbol (target_symbol* e);
   void visit_cast_op (cast_op* e);
+  void visit_defined_op (defined_op* e);
 
   // these are a bit hairy to grok due to the intricacies of indexables and
   // stats, so I'm chickening out and skipping them...
@@ -2947,6 +2949,23 @@ void_statement_reducer::visit_cast_op (cast_op* e)
 }
 
 
+void
+void_statement_reducer::visit_defined_op (defined_op* e)
+{
+  // When the result of a @defined operation isn't needed, just elide
+  // it entirely.  Its operand $expression must already be
+  // side-effect-free.
+
+  if (session.verbose>2)
+    clog << "Eliding unused check " << *e->tok << endl;
+
+  relaxed_p = false;
+  e = 0;
+  provide (e);
+}
+
+
+
 void semantic_pass_opt5 (systemtap_session& s, bool& relaxed_p)
 {
   // Let's simplify statements with unused computed values.
@@ -3575,6 +3594,13 @@ typeresolution_info::visit_target_symbol (target_symbol* e)
 }
 
 
+void
+typeresolution_info::visit_defined_op (defined_op* e)
+{
+  throw semantic_error("unexpected @defined", e->tok);
+}
+
+
 void
 typeresolution_info::visit_cast_op (cast_op* e)
 {
-- 
cgit