vrp: Improve register_edge_assert_for [PR95757]

The Wstringop-overflow-25.c testcase doesn't emit one of the expected
warnings on targets that don't do short curcuiting due to target costs
(or e.g. with --param=logical-op-non-short-circuit=0 on all targets).

The problem is that only reassoc2 optimizes:
  _49 ={v} unsigned_value_source;
  if (_49 == 0)
    goto <bb 7>; [50.00%]
  else
    goto <bb 5>; [50.00%]

  <bb 5> [local count: 536870913]:
  if (_49 > 2)
    goto <bb 7>; [50.00%]
  else
    goto <bb 6>; [50.00%]

  <bb 6> [local count: 268435457]:
  _53 = _49 + 1;
into:
  _49 ={v} unsigned_value_source;
  _48 = _49 + 18446744073709551615;
  _1 = _48 > 1;
  if (_1 != 0)
    goto <bb 6>; [50.00%]
  else
    goto <bb 5>; [50.00%]

  <bb 5> [local count: 268435457]:
  _53 = _49 + 1;
(but, note the _1 = _48 > 1; if (_1 != 0)),
then dom3 is run and because of that if (_1 != 0) vs. if (_48 > 1) doesn't
register edge asserts for _48 and _49) and so we don't get
SSA_NAME_RANGE_INFO for _53 (and ditto for vrp2) and only afterwards comes
forwprop4 that canonicalizes it to if (_48 > 1).  While with
--param=logical-op-non-short-circuit=1 it is already reassoc1 that optimizes
it and forwprop3 that propagates it, so we have on the SSA_NAME
corresponding to _53 above SSA_NAME_RANGE_INFO and during expansion we warn.

The following patch fixes it by handling those not yet propagated
comparisons into GIMPLE_COND in register_edge_assert_for.  We already
have all the infrastructure there to handle the --param=logical-op-non-short-circuit=1
| and &s.

2021-03-02  Jakub Jelinek  <jakub@redhat.com>

	PR middle-end/95757
	* tree-vrp.c (register_edge_assert_for): Remove superfluous ()s around
	condition.  Call register_edge_assert_for_1 for == 0, != 0, == 1 and
	!= 1 comparisons if name is lhs of a comparison.

diff --git a/gcc/tree-vrp.c b/gcc/tree-vrp.c
index 8d638ae..62b9007 100644 (file)
--- a/gcc/tree-vrp.c
+++ b/gcc/tree-vrp.c
@@ -2180,8 +2180,8 @@ register_edge_assert_for (tree name, edge e,
   /* In the case of NAME == 1 or NAME != 0, for BIT_AND_EXPR defining
      statement of NAME we can assert both operands of the BIT_AND_EXPR
      have nonzero value.  */
-  if (((comp_code == EQ_EXPR && integer_onep (val))
-       || (comp_code == NE_EXPR && integer_zerop (val))))
+  if ((comp_code == EQ_EXPR && integer_onep (val))
+      || (comp_code == NE_EXPR && integer_zerop (val)))
     {
       gimple *def_stmt = SSA_NAME_DEF_STMT (name);
 
@@ -2193,28 +2193,36 @@ register_edge_assert_for (tree name, edge e,
          register_edge_assert_for_1 (op0, NE_EXPR, e, asserts);
          register_edge_assert_for_1 (op1, NE_EXPR, e, asserts);
        }
+      else if (is_gimple_assign (def_stmt)
+              && (TREE_CODE_CLASS (gimple_assign_rhs_code (def_stmt))
+                  == tcc_comparison))
+       register_edge_assert_for_1 (name, NE_EXPR, e, asserts);
     }
 
   /* In the case of NAME == 0 or NAME != 1, for BIT_IOR_EXPR defining
      statement of NAME we can assert both operands of the BIT_IOR_EXPR
      have zero value.  */
-  if (((comp_code == EQ_EXPR && integer_zerop (val))
-       || (comp_code == NE_EXPR && integer_onep (val))))
+  if ((comp_code == EQ_EXPR && integer_zerop (val))
+      || (comp_code == NE_EXPR
+         && integer_onep (val)
+         && TYPE_PRECISION (TREE_TYPE (name)) == 1))
     {
       gimple *def_stmt = SSA_NAME_DEF_STMT (name);
 
       /* For BIT_IOR_EXPR only if NAME == 0 both operands have
         necessarily zero value, or if type-precision is one.  */
       if (is_gimple_assign (def_stmt)
-         && (gimple_assign_rhs_code (def_stmt) == BIT_IOR_EXPR
-             && (TYPE_PRECISION (TREE_TYPE (name)) == 1
-                 || comp_code == EQ_EXPR)))
+         && gimple_assign_rhs_code (def_stmt) == BIT_IOR_EXPR)
        {
          tree op0 = gimple_assign_rhs1 (def_stmt);
          tree op1 = gimple_assign_rhs2 (def_stmt);
          register_edge_assert_for_1 (op0, EQ_EXPR, e, asserts);
          register_edge_assert_for_1 (op1, EQ_EXPR, e, asserts);
        }
+      else if (is_gimple_assign (def_stmt)
+              && (TREE_CODE_CLASS (gimple_assign_rhs_code (def_stmt))
+                  == tcc_comparison))
+       register_edge_assert_for_1 (name, EQ_EXPR, e, asserts);
     }
 
   /* Sometimes we can infer ranges from (NAME & MASK) == VALUE.  */