Fix inliner ICE on alias with flatten attribute [PR92372]

[Jan Hubicka]

Hi,
inliner ICEs upon trying to flatten alias. This patch fixes the ICE
and also adds a warning that flattens on aliases makes no sense.

Testing x86_64-linux in progress, intend to commit it after it finishes
if there are no complains.

gcc/ChangeLog:

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

        PR ipa/92372
        * cgraphunit.c (process_function_and_variable_attributes):
        * ipa-inline.c (ipa_inline):

gcc/testsuite/ChangeLog:

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

        PR ipa/92372
        * gcc.c-torture/pr92372.c: New test.
        * gcc.dg/attr-flatten-1.c: New test.

diff --git a/gcc/cgraphunit.c b/gcc/cgraphunit.c
index fd586366bb9..d7ed405bf2c 100644
--- a/gcc/cgraphunit.c
+++ b/gcc/cgraphunit.c
@@ -851,6 +851,14 @@ process_function_and_variable_attributes (cgraph_node 
*first,
        node = symtab->next_function (node))
     {
       tree decl = node->decl;
+
+      if (node->alias
+         && lookup_attribute ("flatten", DECL_ATTRIBUTES (decl)))
+       {
+         warning_at (DECL_SOURCE_LOCATION (node->decl), OPT_Wattributes,
+                     "%<flatten%>"
+                     " attribute attribute is ignored on aliases");
+       }
       if (DECL_PRESERVE_P (decl))
        node->mark_force_output ();
       else if (lookup_attribute ("externally_visible", DECL_ATTRIBUTES (decl)))
diff --git a/gcc/ipa-inline.c b/gcc/ipa-inline.c
index 6b6ba9aa4b6..302ce16a646 100644
--- a/gcc/ipa-inline.c
+++ b/gcc/ipa-inline.c
@@ -2634,6 +2634,9 @@ ipa_inline (void)
     {
       node = order[i];
       if (node->definition
+         /* Do not try to flatten aliases.  These may happen for example when
+            creating local aliases.  */
+         && !node->alias
          && lookup_attribute ("flatten",
                               DECL_ATTRIBUTES (node->decl)) != NULL)
        order[j--] = order[i];
diff --git a/gcc/testsuite/gcc.c-torture/pr92372.c 
b/gcc/testsuite/gcc.c-torture/pr92372.c
new file mode 100644
index 00000000000..72a13bb16f4
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/pr92372.c
@@ -0,0 +1,16 @@
+int fn2(int);
+int fn3(int);
+
+__attribute__((flatten))
+int fn1(int p1)
+{
+  int a = fn2(p1);
+  return fn3(a);
+}
+__attribute__((flatten))
+int fn4(int p1)
+{
+  int j = fn2(p1);
+  return fn3(j);
+}
+
diff --git a/gcc/testsuite/gcc.dg/attr-flatten-1.c 
b/gcc/testsuite/gcc.dg/attr-flatten-1.c
new file mode 100644
index 00000000000..b2895e1287c
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/attr-flatten-1.c
@@ -0,0 +1,18 @@
+/* { dg-require-alias "" } */
+int fn2(int);
+int fn3(int);
+
+__attribute__((flatten))
+int fn1(int p1)
+{
+  int a = fn2(p1);
+  return fn3(a);
+}
+__attribute__((flatten))
+__attribute__((alias("fn1"))) /* { dg-warning "ignored" } */
+int fn4(int p1);
+int
+test ()
+{
+  return fn4(1);
+}