[PATCH, CHKP, PR ipa/71624] Fix local.can_change_signature computation for instrumentation thunk callees

[Ilya Enkovich]

Hi,

This patch sets local.can_change_signature to false for instrumentation
thunk callees.  We have two reasons for that:
  - We don't support modification of instrumentation thunks
  - We don't actually emit instrumentation thunk and therefore its
signature should be in sync with callee

This patch should prevent incorrect IPA optimizations on instrumneted
functions.

Bootstrapped and tested on x86_64-unknown-linux-gnu.  I'm going to apply
it to trunk and gcc-6-btanch.

@Honza, do you think this a valid fix to prevent invalid code modifications?

Thanks,
Ilya
--
gcc/

2016-06-27  Ilya Enkovich  <ilya.enkov...@intel.com>

        * ipa-inline-analysis.c (compute_inline_parameters): Set
        local.can_change_signature to false for intrumentation
        thunk callees.

gcc/testsuite/

2016-06-27  Ilya Enkovich  <ilya.enkov...@intel.com>

        * g++.dg/pr71624.C: New test.


diff --git a/gcc/ipa-inline-analysis.c b/gcc/ipa-inline-analysis.c
index 5d67218..da29d22 100644
--- a/gcc/ipa-inline-analysis.c
+++ b/gcc/ipa-inline-analysis.c
@@ -3017,6 +3017,16 @@ compute_inline_parameters (struct cgraph_node *node, 
bool early)
               node->local.can_change_signature = !e;
             }
         }
+       /* Functions called by instrumentation thunk can't change signature
+         because instrumentation thunk modification is not supported.  */
+       if (node->local.can_change_signature)
+        for (e = node->callers; e; e = e->next_caller)
+          if (e->caller->thunk.thunk_p
+              && e->caller->thunk.add_pointer_bounds_args)
+            {
+              node->local.can_change_signature = false;
+              break;
+            }
        estimate_function_body_sizes (node, early);
        pop_cfun ();
      }
diff --git a/gcc/testsuite/g++.dg/pr71624.C b/gcc/testsuite/g++.dg/pr71624.C
new file mode 100644
index 0000000..94a75cd
--- /dev/null
+++ b/gcc/testsuite/g++.dg/pr71624.C
@@ -0,0 +1,35 @@
+/* PR71624 */
+// { dg-do compile { target i?86-*-* x86_64-*-* } }
+/* { dg-options "-fcheck-pointer-bounds -mmpx -O2" } */
+
+class c1
+{
+public:
+  virtual int fn1 () const;
+  int fn2 (const int *) const;
+};
+
+class c2
+{
+  int fn1 ();
+  c1 obj;
+};
+
+int
+c1::fn1 () const
+{
+  return 0;
+}
+
+int
+c1::fn2 (const int *) const
+{
+  return this->fn1 ();
+}
+
+int
+c2::fn1 ()
+{
+  return obj.fn2 (0);
+}
+