[PATCH] sccvn: Punt on ref->size not multiple of 8 for memset (, 123, ) in 9.x [PR93945]

[Jakub Jelinek]

Hi!

And here is the corresponding 9.x change where we the patch just punts if
ref->size is not whole bytes, like we already punt if offseti is not byte
aligned.

Tested on x86_64-linux and powerpc64-linux, ok for 9.3?

2020-02-27  Jakub Jelinek  <ja...@redhat.com>

        PR tree-optimization/93945
        * tree-ssa-sccvn.c (vn_reference_lookup_3): For memset with non-zero
        second operand, require ref->size to be a multiple of BITS_PER_UNIT.

        * gcc.c-torture/execute/pr93945.c: New test.

--- gcc/tree-ssa-sccvn.c.jj     2020-01-12 12:17:01.031158921 +0100
+++ gcc/tree-ssa-sccvn.c        2020-02-27 10:55:16.226236453 +0100
@@ -2113,7 +2113,8 @@ vn_reference_lookup_3 (ao_ref *ref, tree
               || (INTEGRAL_TYPE_P (vr->type) && known_eq (ref->size, 8)))
              && CHAR_BIT == 8 && BITS_PER_UNIT == 8
              && offset.is_constant (&offseti)
-             && offseti % BITS_PER_UNIT == 0))
+             && offseti % BITS_PER_UNIT == 0
+             && multiple_p (ref->size, BITS_PER_UNIT)))
       && poly_int_tree_p (gimple_call_arg (def_stmt, 2))
       && (TREE_CODE (gimple_call_arg (def_stmt, 0)) == ADDR_EXPR
          || TREE_CODE (gimple_call_arg (def_stmt, 0)) == SSA_NAME))
--- gcc/testsuite/gcc.c-torture/execute/pr93945.c.jj    2020-02-27 
10:54:21.234060635 +0100
+++ gcc/testsuite/gcc.c-torture/execute/pr93945.c       2020-02-27 
10:54:21.234060635 +0100
@@ -0,0 +1,45 @@
+/* PR tree-optimization/93945 */
+
+union U { char a[8]; struct S { unsigned int b : 8, c : 13, d : 11; } e; } u;
+
+__attribute__((noipa)) int
+foo (void)
+{
+  __builtin_memset (&u.a, 0xf4, sizeof (u.a));
+  return u.e.c;
+}
+
+__attribute__((noipa)) int
+bar (void)
+{
+  asm volatile ("" : : "g" (&u) : "memory");
+  return u.e.c;
+}
+
+__attribute__((noipa)) int
+baz (void)
+{
+  __builtin_memset (&u.a, 0xf4, sizeof (u.a));
+  return u.e.d;
+}
+
+__attribute__((noipa)) int
+qux (void)
+{
+  asm volatile ("" : : "g" (&u) : "memory");
+  return u.e.d;
+}
+
+int
+main ()
+{
+  int a = foo ();
+  int b = bar ();
+  if (a != b)
+    __builtin_abort ();
+  a = baz ();
+  b = qux ();
+  if (a != b)
+    __builtin_abort ();
+  return 0;
+}

        Jakub