I am testing the following patch to fix PR79666 - we may not create
a symbolic range with expressions that may introduce (not already present)
undefined overflow.
With a new predicate like operand_not_min_p we can possibly improve
this for symbolic ops with a useful range, but I'm not sure we'd
ever arrive with non-VARYING ops here.
Bootstrap and regtest running on x86_64-unknown-linux-gnu.
Eric - you added these improvements so you might want to double-check
effects on Ada code (and see if the above suggestion is worth
the effort).
Thanks,
Richard.
2017-02-22 Richard Biener <rguent...@suse.de>
PR tree-optimization/79666
* tree-vrp.c (extract_range_from_binary_expr_1): Make sure
to not symbolically negate if that may introduce undefined
overflow.
* gcc.dg/torture/pr79666.c: New testcase.
Index: gcc/tree-vrp.c
===================================================================
--- gcc/tree-vrp.c (revision 245646)
+++ gcc/tree-vrp.c (working copy)
@@ -2631,8 +2631,17 @@ extract_range_from_binary_expr_1 (value_
min = build_symbolic_expr (expr_type, sym_min_op0,
neg_min_op0, min);
else if (sym_min_op1)
- min = build_symbolic_expr (expr_type, sym_min_op1,
- neg_min_op1 ^ minus_p, min);
+ {
+ /* We may not negate if that might introduce
+ undefined overflow. */
+ if (! minus_p
+ || neg_min_op1
+ || TYPE_OVERFLOW_WRAPS (expr_type))
+ min = build_symbolic_expr (expr_type, sym_min_op1,
+ neg_min_op1 ^ minus_p, min);
+ else
+ min = NULL_TREE;
+ }
/* Likewise for the upper bound. */
if (sym_max_op0 == sym_max_op1)
@@ -2641,8 +2650,17 @@ extract_range_from_binary_expr_1 (value_
max = build_symbolic_expr (expr_type, sym_max_op0,
neg_max_op0, max);
else if (sym_max_op1)
- max = build_symbolic_expr (expr_type, sym_max_op1,
- neg_max_op1 ^ minus_p, max);
+ {
+ /* We may not negate if that might introduce
+ undefined overflow. */
+ if (! minus_p
+ || neg_max_op1
+ || TYPE_OVERFLOW_WRAPS (expr_type))
+ max = build_symbolic_expr (expr_type, sym_max_op1,
+ neg_max_op1 ^ minus_p, max);
+ else
+ max = NULL_TREE;
+ }
}
else
{
Index: gcc/testsuite/gcc.dg/torture/pr79666.c
===================================================================
--- gcc/testsuite/gcc.dg/torture/pr79666.c (nonexistent)
+++ gcc/testsuite/gcc.dg/torture/pr79666.c (working copy)
@@ -0,0 +1,30 @@
+/* { dg-do run } */
+
+struct
+{
+ unsigned a:6;
+} b;
+
+int c, e, g = 7;
+signed char d, f = 6, h = -10;
+
+void fn1 ()
+{
+ for (; c < 9; c++)
+ {
+ if (f)
+ g = ~(~0 / (g ^ e));
+ b.a = ~0;
+ d = ~((h ^ b.a) & 132 & (~(f && g) | (d && 1)));
+ e = ~0;
+ if (d < 127 || f < 1)
+ continue;
+ g = 0;
+ }
+}
+
+int main ()
+{
+ fn1 ();
+ return 0;
+}
