PR10274 Fix exelib -O3 testcase.

The testcase now uses noinline, an empty asm statement and a volatile
variable to prevent the function getting inlined, being totally unrolled
or the recursive call being replaced with an inner-iteration.

This does defeat part of the testcase though, which was testing unwinding
through an optimized recursive function. But it seems the best we can do.

* testsuite/systemtap.exelib/exelib.exp: Add -O3 to the mix.
* testsuite/systemtap.exelib/uprobes_exe.c: Use volatile bar and mark
  main_func noinline.
* testsuite/systemtap.exelib/uprobes_lib.c: Use volatile foo and mark
  lib_func noinline.

1 files changed, 13 insertions, 4 deletions

diff --git a/testsuite/systemtap.exelib/uprobes_lib.c b/testsuite/systemtap.exelib/uprobes_lib.c
index 25297b6b..072a1d61 100644
--- a/testsuite/systemtap.exelib/uprobes_lib.c
+++ b/testsuite/systemtap.exelib/uprobes_lib.c
@@ -7,15 +7,24 @@
  * later version.
  */
 
-void
+// volatile static variable to prevent folding of lib_func
+static volatile int foo;
+
+// Marked noinline and has an empty asm statement to prevent inlining
+// or optimizing away totally.
+int
+__attribute__((noinline))
 lib_func (int bar)
 {
-  if (bar > 1)
-    lib_func (bar - 1);
+  asm ("");
+  if (bar - foo > 0)
+    foo = lib_func (bar - foo);
+  return foo;
 }
 
 void
 lib_main ()
 {
-  lib_func (3);
+  foo = 1;
+  foo = lib_func (3);
 }