Re: -fstrict-aliasing fixes 1/5: propagate -fno-strict-aliasing in the inliner

[Bernhard Reutner-Fischer <rep dot dot dot nop at gmail dot com>]

On December 1, 2015 12:05:39 AM GMT+01:00, Jan Hubicka <hubicka@ucw.cz> wrote:
>Hi,
>this is first patch in the broken up series.  It adds the logic into
>ipa-inline-transform to drop the flag when inlining.  I do it always
>until
>we find a way to make early optimizations safe WRT this transform.
>
>The testcase triggers with GCC 5.0/4.9 too, older compilers passes if
>-fstrict-aliasing is used at linktime and fails otherwise.
>
>Bootstrapped/regtested x86_64-linux, will commit it after re-testing on
>Firefox.
>
>Honza
>
>	* ipa-inline-transform.c (inline_call): Drop -fstrict-aliasing when
>	inlining -fno-strict-aliasing into -fstrict-aliasing body.
>	* gcc.dg/lto/alias-1_0.c: New testcase.
>	* gcc.dg/lto/alias-1_1.c: New testcase.
>Index: ipa-inline-transform.c
>===================================================================
>--- ipa-inline-transform.c	(revision 231081)
>+++ ipa-inline-transform.c	(working copy)
>@@ -322,6 +322,21 @@ inline_call (struct cgraph_edge *e, bool
>   if (DECL_FUNCTION_PERSONALITY (callee->decl))
>     DECL_FUNCTION_PERSONALITY (to->decl)
>       = DECL_FUNCTION_PERSONALITY (callee->decl);
>+  if (!opt_for_fn (callee->decl, flag_strict_aliasing)
>+      && opt_for_fn (to->decl, flag_strict_aliasing))

Just curious why you don't handle the other way round?

>+    {
>+      struct gcc_options opts = global_options;
>+
>+      cl_optimization_restore (&opts,
>+	 TREE_OPTIMIZATION (DECL_FUNCTION_SPECIFIC_OPTIMIZATION (to->decl)));
>+      opts.x_flag_strict_aliasing = false;
>+      if (dump_file)
>+	fprintf (dump_file, "Dropping flag_strict_aliasing on %s:%i\n",
>+		 to->name (), to->order);

ISTR to have seen %s/%i for printing name and order in IPA, no?

>+      build_optimization_node (&opts);
>+      DECL_FUNCTION_SPECIFIC_OPTIMIZATION (to->decl)
>+	 = build_optimization_node (&opts);
>+    }
> 
>/* If aliases are involved, redirect edge to the actual destination and
>      possibly remove the aliases.  */
>Index: testsuite/gcc.dg/lto/alias-1_0.c
>===================================================================
>--- testsuite/gcc.dg/lto/alias-1_0.c	(revision 0)
>+++ testsuite/gcc.dg/lto/alias-1_0.c	(revision 0)
>@@ -0,0 +1,23 @@
>+/* { dg-lto-do run } */
>+/* { dg-lto-options { { -O2 -flto } } } */
>+int val;
>+
>+__attribute__ ((used))
>+int *ptr = &val;
>+__attribute__ ((used))
>+float *ptr2 = (void *)&val;
>+
>+extern void typefun(float val);
>+
>+void link_error (void);

Unused and unneeded forward decl?

Thanks,
>+
>+int
>+main()
>+{ 
>+  *ptr=1;
>+  typefun (0);
>+  if (*ptr)
>+    __builtin_abort ();
>+  return 0;
>+}
>+
>Index: testsuite/gcc.dg/lto/alias-1_1.c
>===================================================================
>--- testsuite/gcc.dg/lto/alias-1_1.c	(revision 0)
>+++ testsuite/gcc.dg/lto/alias-1_1.c	(revision 0)
>@@ -0,0 +1,7 @@
>+/* { dg-options "-fno-strict-aliasing" } */
>+extern float *ptr2;
>+void
>+typefun (float val)
>+{ 
>+  *ptr2=val;
>+}