[PR 68064] Do not create jump functions with zero alignment

[Martin Jambor]

Hi,

in PR 68064, IPA-CP hits an assert upon encountering a jump function
claiming that a pointer has known alignment of zero.  That is actually
what get_pointer_alignment_1 returns when asked what is the alignment
of iftmp.0_1 in:

  <bb 4>:
  # iftmp.0_1 = PHI <0B(2), 2147483648B(3)>
  {anonymous}::fn1 (iftmp.0_1);

I suppose that given the circumstances, it is more-or-less reasonable
answer, even if very weird, so we should check for that possibility.
That is what the patch below does.  Bootstrapped and tested on
x86_64-linux.  OK for trunk?

Thanks,

Martin



2015-10-29  Martin Jambor  <mjam...@suse.cz>

        PR ipa/68064
        * ipa-prop.c (ipa_compute_jump_functions_for_edge): Check that
        alignment iz not zero.

testsuite/
        * g++.dg/torture/pr68064.C: New.

diff --git a/gcc/ipa-prop.c b/gcc/ipa-prop.c
index 19846a8..f36e2fd 100644
--- a/gcc/ipa-prop.c
+++ b/gcc/ipa-prop.c
@@ -1651,6 +1651,7 @@ ipa_compute_jump_functions_for_edge (struct 
ipa_func_body_info *fbi,
          unsigned align;
 
          if (get_pointer_alignment_1 (arg, &align, &hwi_bitpos)
+             && align != 0
              && align % BITS_PER_UNIT == 0
              && hwi_bitpos % BITS_PER_UNIT == 0)
            {
diff --git a/gcc/testsuite/g++.dg/torture/pr68064.C 
b/gcc/testsuite/g++.dg/torture/pr68064.C
new file mode 100644
index 0000000..59b6897
--- /dev/null
+++ b/gcc/testsuite/g++.dg/torture/pr68064.C
@@ -0,0 +1,35 @@
+// { dg-do compile }
+
+template <class Config> class A {
+public:
+  class B;
+  typedef typename Config::template D<A>::type TypeHandle;
+  static A *Tagged() { return B::New(B::kTagged); }
+  static TypeHandle Union(TypeHandle);
+  static TypeHandle Representation(TypeHandle, typename Config::Region *);
+  bool Is();
+};
+
+template <class Config> class A<Config>::B {
+  friend A;
+  enum { kTaggedPointer = 1 << 31, kTagged = kTaggedPointer };
+  static A *New(int p1) { return Config::from_bitset(p1); }
+};
+
+struct C {
+  typedef int Region;
+  template <class> struct D { typedef A<C> *type; };
+  static A<C> *from_bitset(unsigned);
+};
+A<C> *C::from_bitset(unsigned p1) { return reinterpret_cast<A<C> *>(p1); }
+
+namespace {
+int *a;
+void fn1(A<C> *p1) { A<C>::Union(A<C>::Representation(p1, a)); }
+}
+
+void fn2() {
+  A<C> b;
+  A<C> *c = b.Is() ? 0 : A<C>::Tagged();
+  fn1(c);
+}