On November 23, 2015 5:31:11 PM GMT+01:00, Marek Polacek <pola...@redhat.com>
wrote:
>We blow up on the following testcase because we find ourselves passing
>[_13 + 1, INT_MAX] as a vr1 to extract_range_from_multiplicative_op_1;
>that's bad because this function immediately calls vrp_int_const_binop
>which just doesn't work for symbolic ranges, it only wants int_csts.
>
>This started with Richards S.'s changes in r228614 -- we're now since
>able to recurse into SSA names, thus get better info about ranges.
>That means that range_includes_zero_p in
>extract_range_from_binary_expr_1
>for the *_DIV_EXPR cases was able to determine that the range doesn't
>include zero, so we went through a different code path and ended up
>calling extract_range_from_multiplicative_op_1 even with symbolic
>ranges.
>
>I couldn't come up with anything better than checking that we're
>dealing
>with nonsymbolic ranges for such a case.
>
>Bootstrapped/regtested on x86_64-linux, ok for trunk?
Hmm. I think we can do better if vr0 is symbolical - use min, max for it.
I suppose it would be best to implement a get_integer_range () function doing
that or also looking at equivalences if we are getting a symbolic range.
Anyway, those are future enhancements that shouldn't block this patch.
Thus OK.
Richard.
>2015-11-23 Marek Polacek <pola...@redhat.com>
>
> PR tree-optimization/68455
> * tree-vrp.c (extract_range_from_binary_expr_1): Don't call
> extract_range_from_multiplicative_op_1 on symbolic ranges.
>
> * gcc.dg/tree-ssa/pr68455.c: New test.
>
>diff --git gcc/testsuite/gcc.dg/tree-ssa/pr68455.c
>gcc/testsuite/gcc.dg/tree-ssa/pr68455.c
>index e69de29..6b46b30 100644
>--- gcc/testsuite/gcc.dg/tree-ssa/pr68455.c
>+++ gcc/testsuite/gcc.dg/tree-ssa/pr68455.c
>@@ -0,0 +1,19 @@
>+/* PR tree-optimization/68455 */
>+/* { dg-do compile } */
>+/* { dg-options "-O2" } */
>+
>+int r;
>+int n;
>+
>+void
>+fn1 (void)
>+{
>+ int i;
>+
>+ for (i = 0; i < 1; ++i)
>+ {
>+ unsigned short int u;
>+ if (u < n)
>+ r = 1 / n;
>+ }
>+}
>diff --git gcc/tree-vrp.c gcc/tree-vrp.c
>index 7001190..acbb70b 100644
>--- gcc/tree-vrp.c
>+++ gcc/tree-vrp.c
>@@ -3015,7 +3015,7 @@ extract_range_from_binary_expr_1 (value_range
>*vr,
> return;
> }
> }
>- else
>+ else if (!symbolic_range_p (&vr0) && !symbolic_range_p (&vr1))
> {
> extract_range_from_multiplicative_op_1 (vr, code, &vr0, &vr1);
> return;
>
> Marek
