[gcc(refs/users/aoliva/heads/testme)] [ifcombine] check for more zero-extension cases [PR118572]

[Alexandre Oliva via Gcc-cvs]

https://gcc.gnu.org/g:c3226db63fa8e694d1edd064c4634a3514e69878

commit c3226db63fa8e694d1edd064c4634a3514e69878
Author: Alexandre Oliva <ol...@gnu.org>
Date:   Thu Jan 23 02:51:41 2025 -0300

    [ifcombine] check for more zero-extension cases [PR118572]

Diff:
---
 gcc/gimple-fold.cc | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/gcc/gimple-fold.cc b/gcc/gimple-fold.cc
index cd9d35034918..53bbf6cf70aa 100644
--- a/gcc/gimple-fold.cc
+++ b/gcc/gimple-fold.cc
@@ -8552,12 +8552,20 @@ fold_truth_andor_for_ifcombine (enum tree_code code, 
tree truth_type,
     {
       /* Before clipping upper bits of the right-hand operand of the compare,
         check that they're sign or zero extensions, depending on how the
-        left-hand operand would be extended.  */
+        left-hand operand would be extended.  If it is unsigned, or if there's
+        a mask that zeroes out extension bits, whether because we've checked
+        for upper bits in the mask and did not set ll_signbit, or because the
+        sign bit itself is masked out, check that the right-hand operand is
+        zero-extended.  */
       bool l_non_ext_bits = false;
       if (ll_bitsize < lr_bitsize)
        {
          wide_int zext = wi::zext (l_const, ll_bitsize);
-         if ((ll_unsignedp ? zext : wi::sext (l_const, ll_bitsize)) == l_const)
+         if ((ll_unsignedp
+              || (ll_and_mask.get_precision ()
+                  && (!ll_signbit
+                      || !(ll_and_mask & wi::mask (ll_bitsize - 1, true, 
ll_bitsize)))))
+              ? zext : wi::sext (l_const, ll_bitsize)) == l_const)
            l_const = zext;
          else
            l_non_ext_bits = true;
@@ -8583,7 +8591,11 @@ fold_truth_andor_for_ifcombine (enum tree_code code, 
tree truth_type,
       if (rl_bitsize < rr_bitsize)
        {
          wide_int zext = wi::zext (r_const, rl_bitsize);
-         if ((rl_unsignedp ? zext : wi::sext (r_const, rl_bitsize)) == r_const)
+         if ((rl_unsignedp
+              || (rl_and_mask.get_precision ()
+                  && (!rl_signbit
+                      || !(rl_and_mask & wi::mask (rl_bitsize - 1, true, 
rl_bitsize))))
+              ? zext : wi::sext (r_const, rl_bitsize)) == r_const)
            r_const = zext;
          else
            r_non_ext_bits = true;