Recent changes caused VRP to create [-2147483646, +INF] from
merging ~[0, 0] and [-2147483646, +INF]. This causes i386 specific
folding of lznct to no longer trigger. The following extends the
existing special-casing of ~[0, 0] from pointer-like types to
pointer types and integer types > int (covering integral arguments).
Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk.
Richard.
2017-11-28 Richard Biener <rguent...@suse.de>
PR tree-optimization/83158
* tree-vrp.c (intersect_ranges): Prefer ~[0, 0] in a few more
cases.
Index: gcc/tree-vrp.c
===================================================================
--- gcc/tree-vrp.c (revision 255173)
+++ gcc/tree-vrp.c (working copy)
@@ -6021,11 +6021,14 @@ intersect_ranges (enum value_range_type
&& vrp_val_is_max (vr1max))
;
/* Choose the anti-range if it is ~[0,0], that range is special
- enough to special case when vr1's range is relatively wide. */
+ enough to special case when vr1's range is relatively wide.
+ At least for types bigger than int - this covers pointers
+ and arguments to functions like ctz. */
else if (*vr0min == *vr0max
&& integer_zerop (*vr0min)
- && (TYPE_PRECISION (TREE_TYPE (*vr0min))
- == TYPE_PRECISION (ptr_type_node))
+ && ((TYPE_PRECISION (TREE_TYPE (*vr0min))
+ >= TYPE_PRECISION (integer_type_node))
+ || POINTER_TYPE_P (TREE_TYPE (*vr0min)))
&& TREE_CODE (vr1max) == INTEGER_CST
&& TREE_CODE (vr1min) == INTEGER_CST
&& (wi::clz (wi::to_wide (vr1max) - wi::to_wide (vr1min))
