Fix cgraph_node::function_symbol availability computation [PR94202]

[Jan Hubicka]

Hi,
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.

Bootstrap/regtest x86_64-linux in progress, plan to commit if succesfull.

gcc/ChangeLog:

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

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

diff --git a/gcc/cgraph.c b/gcc/cgraph.c
index 9f0774f227f..b41dea1fcca 100644
--- a/gcc/cgraph.c
+++ b/gcc/cgraph.c
@@ -3788,16 +3788,13 @@ cgraph_node::function_symbol (enum availability 
*availability,
 
   while (node->thunk.thunk_p)
     {
+      enum availability a;
+
       ref = node;
       node = node->callees->callee;
-      if (availability)
-       {
-         enum availability a;
-         a = node->get_availability (ref);
-         if (a < *availability)
-           *availability = a;
-       }
-      node = node->ultimate_alias_target (availability, ref);
+      node = node->ultimate_alias_target (availability ? &a : NULL, ref);
+      if (availability && a < *availability)
+       *availability = a;
     }
   return node;
 }
@@ -3818,16 +3815,13 @@ cgraph_node::function_or_virtual_thunk_symbol
 
   while (node->thunk.thunk_p && !node->thunk.virtual_offset_p)
     {
+      enum availability a;
+
       ref = node;
       node = node->callees->callee;
-      if (availability)
-       {
-         enum availability a;
-         a = node->get_availability (ref);
-         if (a < *availability)
-           *availability = a;
-       }
-      node = node->ultimate_alias_target (availability, ref);
+      node = node->ultimate_alias_target (availability ? &a : NULL, ref);
+      if (availability && a < *availability)
+       *availability = a;
     }
   return node;
 }
diff --git a/gcc/testsuite/g++.dg/torture/pr94202.C 
b/gcc/testsuite/g++.dg/torture/pr94202.C
new file mode 100644
index 00000000000..ab077368f9f
--- /dev/null
+++ b/gcc/testsuite/g++.dg/torture/pr94202.C
@@ -0,0 +1,21 @@
+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);
+}