coroutines: Update TREE_SIDE_EFFECTS on inserted bind exprs.

There are several places where we insert bind expressions while
making the coroutine AST transforms.  These should be marked as
having side-effects where relevant, which had been omitted.  This
leads to at least one failure in the cppcoros test suite, where a loop
body is dropped in gimplification because it is not marked.

gcc/cp/ChangeLog:

2020-05-08  Iain Sandoe  <iain@sandoe.co.uk>

	PR c++/95003
	* coroutines.cc (build_actor_fn): Ensure that bind scopes
	are marked as having side-effects where necessary.
	(replace_statement_captures): Likewise.
	(morph_fn_to_coro): Likewise.

gcc/testsuite/ChangeLog:

2020-05-08  Iain Sandoe  <iain@sandoe.co.uk>

	PR c++/95003
	* g++.dg/coroutines/torture/pr95003.C: New test.

2 files changed, 55 insertions, 0 deletions

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 2381a1c80f9..69c3cac3d71 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2020-05-08  Iain Sandoe  <iain@sandoe.co.uk>
+
+	PR c++/95003
+	* g++.dg/coroutines/torture/pr95003.C: New test.
+
 2020-05-08  Nathan Sidwell  <nathan@acm.org>
 
 	* gcc.dg/cpp/counter-[23].c: Move to c-c+_-common/cpp.
diff --git a/gcc/testsuite/g++.dg/coroutines/torture/pr95003.C b/gcc/testsuite/g++.dg/coroutines/torture/pr95003.C
new file mode 100644
index 00000000000..eda785827ec
--- /dev/null
+++ b/gcc/testsuite/g++.dg/coroutines/torture/pr95003.C
@@ -0,0 +1,50 @@
+// { dg-do run }
+
+#include "../coro.h"
+#include "../coro1-ret-int-yield-int.h"
+
+// This tests that, when we insert bind scopes to contain variables that
+// have been promoted from compiler temporaries to extend their lifetimes
+// to a containing full expression, the inserted bind scopes have their
+// tree-side-effects set.
+
+struct Awaitable {
+  int v;
+  Awaitable (int _v) : v(_v) {}
+  bool await_ready() { return false; }
+  void await_suspend(std::coroutine_handle<coro1::promise_type>) {}
+  int await_resume() { return v; }
+  auto operator co_await() { return *this; }
+};
+
+coro1
+my_coro
+(int x)
+{
+  int sum = 0;
+  for (unsigned i = 0; i < 100; ++i) {
+    sum += co_await Awaitable{x+1};
+  }
+  co_return sum;
+}
+
+int main ()
+{
+  PRINT ("main: create coro1");
+  struct coro1 f_coro = my_coro (0);
+
+  PRINT ("main: OK -- looping");
+
+  do {
+    f_coro.handle.resume();
+  } while (!f_coro.handle.done());
+
+  int y = f_coro.handle.promise().get_value();
+  if (y != 100)
+    {
+      PRINTF ("main: y is wrong : %d, should be 100\n", y);
+      abort ();
+    }
+  puts ("main: done");
+  return 0;
+}