Re: [PATCH, PR 63551] Use proper type in evaluate_conditions_for_known_args

[Richard Biener <richard dot guenther at gmail dot com>]

On November 21, 2014 9:07:50 PM CET, Martin Jambor <mjambor@suse.cz> wrote:
>Hi,
>
>the testcase of PR 63551 passes a union between a signed and an
>unsigned integer between two functions as a parameter.  The caller
>initializes to an unsigned integer with the highest order bit set, the
>callee loads the data through the signed field and compares with zero.
>evaluate_conditions_for_known_args then wrongly evaluated the
>condition in these circumstances, which later on lead to insertion of
>builtin_unreachable and miscompilation.
>
>Fixed by fold_converting the known value first.  I use the type of the
>value in the condition which should do exactly the right thing because
>the value is taken from the corresponding gimple_cond statement in
>which types must match.
>
>Bootstrapped and tested on x86_64-linux.  OK for trunk?

I think you want to use fold_unary (VIEW_CONVERT,...) Here if you consider the case with
Int and float.  And "fail" if that returns NULL or not a constant.

Thanks,
Richard.

>Thanks,
>
>Martin
>
>
>2014-11-21  Martin Jambor  <mjambor@suse.cz>
>
>	PR ipa/63551
>	* ipa-inline-analysis.c (evaluate_conditions_for_known_args): Convert
>	value of the argument to the type of the value in the condition.
>
>testsuite/
>	* gcc.dg/ipa/pr63551.c: New test.
>
>
>Index: src/gcc/ipa-inline-analysis.c
>===================================================================
>--- src.orig/gcc/ipa-inline-analysis.c
>+++ src/gcc/ipa-inline-analysis.c
>@@ -880,6 +880,7 @@ evaluate_conditions_for_known_args (stru
> 	}
>       if (c->code == IS_NOT_CONSTANT || c->code == CHANGED)
> 	continue;
>+      val = fold_convert (TREE_TYPE (c->val), val);
>res = fold_binary_to_constant (c->code, boolean_type_node, val,
>c->val);
>       if (res && integer_zerop (res))
> 	continue;
>Index: src/gcc/testsuite/gcc.dg/ipa/pr63551.c
>===================================================================
>--- /dev/null
>+++ src/gcc/testsuite/gcc.dg/ipa/pr63551.c
>@@ -0,0 +1,33 @@
>+/* { dg-do run } */
>+/* { dg-options "-Os" } */
>+
>+union U
>+{
>+  unsigned int f0;
>+  int f1;
>+};
>+
>+int a, d;
>+
>+void
>+fn1 (union U p)
>+{
>+  if (p.f1 <= 0)
>+    if (a)
>+      d = 0;
>+}
>+
>+void
>+fn2 ()
>+{
>+  d = 0;
>+  union U b = { 4294967286 };
>+  fn1 (b);
>+}
>+
>+int
>+main ()
>+{
>+  fn2 ();
>+  return 0;
>+}