Hi!
maybe_set_nonzero_bits calls set_nonzero_bits which asserts that
var doesn't have pointer type. While we could punt for those
cases, I think we can handle at least some easy cases.
Earlier in maybe_set_nonzero_bits we've checked this is on
(var & cst) == 0
edge and the other edge is __builtin_unreachable, so if cst
is say 3 as in the testcase, we want to turn it into 4 byte alignment
of the pointer.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2023-01-04 Jakub Jelinek <ja...@redhat.com>
PR tree-optimization/108253
* tree-vrp.cc (maybe_set_nonzero_bits): Handle var with pointer
types.
* g++.dg/opt/pr108253.C: New test.
--- gcc/tree-vrp.cc.jj 2023-01-02 09:32:53.634833769 +0100
+++ gcc/tree-vrp.cc 2023-01-03 15:57:51.613239761 +0100
@@ -789,8 +789,22 @@ maybe_set_nonzero_bits (edge e, tree var
return;
}
cst = gimple_assign_rhs2 (stmt);
- set_nonzero_bits (var, wi::bit_and_not (get_nonzero_bits (var),
- wi::to_wide (cst)));
+ if (POINTER_TYPE_P (TREE_TYPE (var)))
+ {
+ struct ptr_info_def *pi = SSA_NAME_PTR_INFO (var);
+ if (pi && pi->misalign)
+ return;
+ wide_int w = wi::bit_not (wi::to_wide (cst));
+ unsigned int bits = wi::ctz (w);
+ if (bits == 0 || bits >= HOST_BITS_PER_INT)
+ return;
+ unsigned int align = 1U << bits;
+ if (pi == NULL || pi->align < align)
+ set_ptr_info_alignment (get_ptr_info (var), align, 0);
+ }
+ else
+ set_nonzero_bits (var, wi::bit_and_not (get_nonzero_bits (var),
+ wi::to_wide (cst)));
}
/* Searches the case label vector VEC for the index *IDX of the CASE_LABEL
--- gcc/testsuite/g++.dg/opt/pr108253.C.jj 2023-01-03 16:02:16.366438488
+0100
+++ gcc/testsuite/g++.dg/opt/pr108253.C 2023-01-03 16:02:33.549191780 +0100
@@ -0,0 +1,48 @@
+// PR tree-optimization/108253
+// { dg-do compile { target c++11 } }
+// { dg-options "-O2" }
+
+struct S
+{
+ int *s;
+ S () : s (new int) {}
+ S (const S &r) noexcept : s (r.s) { __atomic_fetch_add (r.s, 1, 4); }
+};
+struct T
+{
+ explicit T (const S &x) : t (x) {}
+ const S t;
+};
+struct U
+{
+ operator int () const { new T (u); return 0; }
+ S u;
+};
+bool foo (int matcher);
+unsigned long bar (unsigned long pos, unsigned long end_pos);
+struct V
+{
+ alignas (4) char v[4];
+};
+struct W
+{
+ void baz ()
+ {
+ if (!w) __builtin_abort ();
+ if (reinterpret_cast <__UINTPTR_TYPE__> (w->v) % 4 != 0) __builtin_abort
();
+ __builtin_unreachable ();
+ }
+ [[gnu::noinline]] void qux (unsigned long) { if (!w) bar (0, x); }
+ V *w = nullptr;
+ unsigned x = 0;
+};
+
+void
+test ()
+{
+ W w;
+ U t;
+ if (!foo (t))
+ w.baz ();
+ w.qux (0);
+}
Jakub
