Fix cgraph_node::function_symbol availability compuattion [PR94202]

this fixes ICE in inliner cache sanity check which is caused by very old
bug in visibility calculation in cgraph_node::function_symbol and
cgraph_node::function_or_virtual_thunk_symbol.

In the testcase there is indirect call to a thunk. At begining we correctly
see that its body as AVAIL_AVAILABLE but later we inline into the thunk and
this turns it to AVAIL_INTERPOSABLE.

This is because function_symbol incorrectly overwrites availability parameter
by availability of the alias used in the call within thunk, which is a local
alias.

gcc/ChangeLog:

2020-03-19  Jan Hubicka  <hubicka@ucw.cz>

	PR ipa/94202
	* cgraph.c (cgraph_node::function_symbol): Fix availability computation.
	(cgraph_node::function_or_virtual_thunk_symbol): Likewise.

gcc/testsuite/ChangeLog:

2020-03-19  Jan Hubicka  <hubicka@ucw.cz>

	PR ipa/94202
	* g++.dg/torture/pr94202.C: New test.

1 files changed, 22 insertions, 0 deletions

diff --git a/gcc/testsuite/g++.dg/torture/pr94202.C b/gcc/testsuite/g++.dg/torture/pr94202.C
new file mode 100644
index 0000000..5ed3dcb
--- /dev/null
+++ b/gcc/testsuite/g++.dg/torture/pr94202.C
@@ -0,0 +1,22 @@
+// { dg-additional-options "-w" }
+struct S1 {
+  virtual ~S1();
+  virtual void v();
+};
+struct S2: S1 {};
+struct S3: S1, S2 { void v(); };
+struct S4: S3 { void v(); };
+void S4::v() { S3::v(); }
+struct R {
+  S1 * m;
+  void f(S2 * x) {
+    static_cast<S1 *>(x)->v();
+    x->v();
+    m = x;
+  }
+};
+void f() {
+  R r;
+  r.f(new S4);
+  r.f(new S3);
+}