[Bug tree-optimization/114965] [13/14/15 Regression] wrong code generated for Emacs/Gnulib strftime (regression from 13.2)

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114965

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |jakub at gcc dot gnu.org

--- Comment #10 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Untested fix.
If entry_test_needed, earlier code ensures that exp is in [lowi, high] range,
so the optimization is ok.  But without it, we need to ensure that if we lower
lowi we can still do the shifts safely.
r in this case is [43,43][48,48][95,95], so we don't need entry test if we
subtract the low bound (43), but 95 is too high for 64-bit prec.
--- gcc/tree-ssa-reassoc.cc.jj  2023-10-15 23:04:06.181422840 +0200
+++ gcc/tree-ssa-reassoc.cc     2024-05-07 13:46:42.722966813 +0200
@@ -3414,7 +3414,8 @@ optimize_range_tests_to_bit_test (enum t
             We can avoid then subtraction of the minimum value, but the
             mask constant could be perhaps more expensive.  */
          if (compare_tree_int (lowi, 0) > 0
-             && compare_tree_int (high, prec) < 0)
+             && compare_tree_int (high, prec) < 0
+             && (entry_test_needed || wi::ltu_p (r.upper_bound (), prec)))
            {
              int cost_diff;
              HOST_WIDE_INT m = tree_to_uhwi (lowi);