[PATCH] Fix tail recursion (PR tree-optimization/84739)

[Jakub Jelinek]

Hi!

Before Honza introduced recursive_call_p, this tree-tailcall.c snipped
has been guarded with if (func == current_function_decl), so what we used
for DECL_ARGUMENTS didn't really matter.  But as it can now be some alias
to it, we really want to check that the current function's arguments
match the arguments of the call, rather than just that the call's arguments
match its function type.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2018-03-07  Jakub Jelinek  <ja...@redhat.com>

        PR tree-optimization/84739
        * tree-tailcall.c (find_tail_calls): Check call arguments against
        DECL_ARGUMENTS (current_function_decl) rather than
        DECL_ARGUMENTS (func) when checking for tail recursion.

        * gcc.dg/pr84739.c: New test.

--- gcc/tree-tailcall.c.jj      2018-01-12 11:35:51.470222838 +0100
+++ gcc/tree-tailcall.c 2018-03-06 23:05:39.779048759 +0100
@@ -481,7 +481,7 @@ find_tail_calls (basic_block bb, struct
     {
       tree arg;
 
-      for (param = DECL_ARGUMENTS (func), idx = 0;
+      for (param = DECL_ARGUMENTS (current_function_decl), idx = 0;
           param && idx < gimple_call_num_args (call);
           param = DECL_CHAIN (param), idx ++)
        {
--- gcc/testsuite/gcc.dg/pr84739.c.jj   2018-03-07 09:43:13.961110879 +0100
+++ gcc/testsuite/gcc.dg/pr84739.c      2018-03-07 09:43:19.856109830 +0100
@@ -0,0 +1,26 @@
+/* PR tree-optimization/84739 */
+/* { dg-do compile } */
+/* { dg-require-weak "" } */
+/* { dg-options "-O2" } */
+
+static void baz (void) __attribute__((weakref("bar")));        /* { dg-warning 
"alias between functions of incompatible types" } */
+
+int
+foo (int x, int y)
+{
+  if (x)
+    y = 0;
+  if (y)
+    goto lab;
+  y = 0;
+lab:
+  return y;
+}
+
+void
+bar (int x, int y)     /* { dg-message "aliased declaration here" } */
+{
+  y = foo (x, y);
+  if (y != 0)
+    baz ();
+}

        Jakub