From: Richard Guenther <rguenther@suse.de>
Date: Mon, 4 Jul 2011 13:25:21 +0000 (+0000)
Subject: backport: re PR tree-optimization/49115 (invalid return value optimization (?) when... 
X-Git-Tag: releases/gcc-4.5.4~557
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=69d2b841467f404658e05d6ebfabda1628f21811;p=thirdparty%2Fgcc.git

backport: re PR tree-optimization/49115 (invalid return value optimization (?) when exception is thrown and caught)

2011-07-04  Richard Guenther  <rguenther@suse.de>

        Backport from mainline
        2011-05-23  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/49115
	* tree-ssa-dce.c (mark_aliased_reaching_defs_necessary_1): Likewise.

	* g++.dg/torture/pr49115.C: New testcase.

From-SVN: r175812
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 4bd7435ec8f6..440ce2a85af0 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,11 @@
+2011-07-04  Richard Guenther  <rguenther@suse.de>
+
+	Backport from mainline
+	2011-05-23  Richard Guenther  <rguenther@suse.de>
+
+	PR tree-optimization/49115
+	* tree-ssa-dce.c (mark_aliased_reaching_defs_necessary_1): Likewise.
+
 2011-07-04  Richard Guenther  <rguenther@suse.de>
 
 	PR tree-optimization/49615
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index a88b2f23b770..babb1fc487ac 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,11 @@
+2011-07-04  Richard Guenther  <rguenther@suse.de>
+
+	Backport from mainline
+	2011-05-23  Richard Guenther  <rguenther@suse.de>
+
+	PR tree-optimization/49115
+	* g++.dg/torture/pr49115.C: New testcase.
+
 2011-07-04  Richard Guenther  <rguenther@suse.de>
 
 	PR tree-optimization/49615
diff --git a/gcc/testsuite/g++.dg/torture/pr49115.C b/gcc/testsuite/g++.dg/torture/pr49115.C
new file mode 100644
index 000000000000..c4cce21ba5d9
--- /dev/null
+++ b/gcc/testsuite/g++.dg/torture/pr49115.C
@@ -0,0 +1,25 @@
+// { dg-do run }
+
+extern "C" void abort (void);
+struct MyException {};
+struct Data {
+    int nr;
+    Data() : nr(66) {}
+};
+Data __attribute__((noinline,noclone)) getData(int i)
+{
+  if (i) throw MyException();
+  Data data;
+  data.nr = i;
+  return data;
+}
+int main(int, char **)
+{
+  Data data;
+  try {
+      data = getData(1);
+  } catch (MyException& e) {
+      if (data.nr != 66)
+	abort ();
+  }
+}
diff --git a/gcc/tree-ssa-dce.c b/gcc/tree-ssa-dce.c
index f0e8a34f4cfa..220f8c49aae3 100644
--- a/gcc/tree-ssa-dce.c
+++ b/gcc/tree-ssa-dce.c
@@ -509,7 +509,14 @@ mark_aliased_reaching_defs_necessary_1 (ao_ref *ref, tree vdef, void *data)
 
   /* If the stmt lhs kills ref, then we can stop walking.  */
   if (gimple_has_lhs (def_stmt)
-      && TREE_CODE (gimple_get_lhs (def_stmt)) != SSA_NAME)
+      && TREE_CODE (gimple_get_lhs (def_stmt)) != SSA_NAME
+      /* The assignment is not necessarily carried out if it can throw
+         and we can catch it in the current function where we could inspect
+	 the previous value.
+         ???  We only need to care about the RHS throwing.  For aggregate
+	 assignments or similar calls and non-call exceptions the LHS
+	 might throw as well.  */
+      && !stmt_can_throw_internal (def_stmt))
     {
       tree base, lhs = gimple_get_lhs (def_stmt);
       HOST_WIDE_INT size, offset, max_size;