[PATCH] Do not allow to inline ifunc resolvers (PR ipa/81128).

["Martin Liška" <mliska@suse.cz>]

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Hello.

Currently ifunc is interpreted as normal alias by IPA optimizations. That's problematic
as should not consider ifunc alias as candidate for inlining, or redirection.

Patch can bootstrap on ppc64le-redhat-linux and survives regression tests.
And survives MVC tests on x86_64-linux-gnu.

Ready to be installed?
Martin

gcc/ChangeLog:

2017-06-22  Martin Liska  <mliska@suse.cz>

	* ipa-inline.c (can_inline_edge_p): Return false for ifunc fns.
	* ipa-visibility.c (can_replace_by_local_alias): Likewise.

gcc/c-family/ChangeLog:

2017-06-22  Martin Liska  <mliska@suse.cz>

	* c-attribs.c (handle_alias_ifunc_attribute): Append ifunc alias
	to a function declaration.

gcc/testsuite/ChangeLog:

2017-06-22  Martin Liska  <mliska@suse.cz>

	* gcc.target/i386/pr81128.c: New test.
---
 gcc/c-family/c-attribs.c                | 11 ++++--
 gcc/ipa-inline.c                        |  2 +
 gcc/ipa-visibility.c                    |  3 +-
 gcc/testsuite/gcc.target/i386/pr81128.c | 65 +++++++++++++++++++++++++++++++++
 4 files changed, 77 insertions(+), 4 deletions(-)
 create mode 100644 gcc/testsuite/gcc.target/i386/pr81128.c



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diff --git a/gcc/c-family/c-attribs.c b/gcc/c-family/c-attribs.c
index 2b6845f2cbd..626ffa1cde7 100644
--- a/gcc/c-family/c-attribs.c
+++ b/gcc/c-family/c-attribs.c
@@ -1846,9 +1846,14 @@ handle_alias_ifunc_attribute (bool is_alias, tree *node, tree name, tree args,
 	TREE_STATIC (decl) = 1;
 
       if (!is_alias)
-	/* ifuncs are also aliases, so set that attribute too.  */
-	DECL_ATTRIBUTES (decl)
-	  = tree_cons (get_identifier ("alias"), args, DECL_ATTRIBUTES (decl));
+	{
+	  /* ifuncs are also aliases, so set that attribute too.  */
+	  DECL_ATTRIBUTES (decl)
+	    = tree_cons (get_identifier ("alias"), args,
+			 DECL_ATTRIBUTES (decl));
+	  DECL_ATTRIBUTES (decl) = tree_cons (get_identifier ("ifunc"),
+					      NULL, DECL_ATTRIBUTES (decl));
+	}
     }
   else
     {
diff --git a/gcc/ipa-inline.c b/gcc/ipa-inline.c
index fb20d3723cc..588fa9c41e4 100644
--- a/gcc/ipa-inline.c
+++ b/gcc/ipa-inline.c
@@ -370,6 +370,8 @@ can_inline_edge_p (struct cgraph_edge *e, bool report,
       e->inline_failed = CIF_ATTRIBUTE_MISMATCH;
       inlinable = false;
     }
+  else if (lookup_attribute ("ifunc", DECL_ATTRIBUTES (e->callee->decl)))
+      inlinable = false;
   /* Check if caller growth allows the inlining.  */
   else if (!DECL_DISREGARD_INLINE_LIMITS (callee->decl)
 	   && !disregard_limits
diff --git a/gcc/ipa-visibility.c b/gcc/ipa-visibility.c
index d5a3ae56c46..79d05b41085 100644
--- a/gcc/ipa-visibility.c
+++ b/gcc/ipa-visibility.c
@@ -345,7 +345,8 @@ can_replace_by_local_alias (symtab_node *node)
   
   return (node->get_availability () > AVAIL_INTERPOSABLE
 	  && !decl_binds_to_current_def_p (node->decl)
-	  && !node->can_be_discarded_p ());
+	  && !node->can_be_discarded_p ()
+	  && !lookup_attribute ("ifunc", DECL_ATTRIBUTES (node->decl)));
 }
 
 /* Return true if we can replace reference to NODE by local alias
diff --git a/gcc/testsuite/gcc.target/i386/pr81128.c b/gcc/testsuite/gcc.target/i386/pr81128.c
new file mode 100644
index 00000000000..90a567ad690
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr81128.c
@@ -0,0 +1,65 @@
+/* PR ipa/81128 */
+/* { dg-do run } */
+/* { dg-options "-O3" } */
+/* { dg-require-ifunc "" } */
+
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+
+int resolver_fn = 0;
+int resolved_fn = 0;
+
+static inline void
+do_it_right_at_runtime_A ()
+{
+  resolved_fn++;
+}
+
+static inline void
+do_it_right_at_runtime_B ()
+{
+  resolved_fn++;
+}
+
+static inline void do_it_right_at_runtime (void);
+
+void do_it_right_at_runtime (void)
+  __attribute__ ((ifunc ("resolve_do_it_right_at_runtime")));
+
+static void (*resolve_do_it_right_at_runtime (void)) (void)
+{
+  srand (time (NULL));
+  int r = rand ();
+  resolver_fn++;
+
+  /* Use intermediate variable to get a warning for non-matching
+   * prototype. */
+  typeof(do_it_right_at_runtime) *func;
+  if (r & 1)
+    func = do_it_right_at_runtime_A;
+  else
+    func = do_it_right_at_runtime_B;
+
+  return (void *) func;
+}
+
+int
+main (void)
+{
+  const unsigned int ITERS = 10;
+
+  for (int i = ITERS; i > 0; i--)
+    {
+      do_it_right_at_runtime ();
+    }
+
+  if (resolver_fn != 1)
+    __builtin_abort ();
+
+  if (resolved_fn != 10)
+    __builtin_abort ();
+
+  return 0;
+}