[gcc r17-2929] [frange] Convert float_widen_lhs_range to sub-ranges.

https://gcc.gnu.org/g:1e5aaad93d8426a4112873e6ff7266f49153c535

commit r17-2929-g1e5aaad93d8426a4112873e6ff7266f49153c535
Author: Aldy Hernandez <[email protected]>
Date:   Mon Aug 3 11:02:38 2026 +0000

    [frange] Convert float_widen_lhs_range to sub-ranges.
    
    Tested on ppc64le Linux.
    
    gcc/ChangeLog:
    
            * range-op-float.cc (float_widen_lhs_range): Convert to
            sub-ranges.
            (range_op_float_tests): New test.

Diff:
---
 gcc/range-op-float.cc | 27 ++++++++++++++++++++++++---
 1 file changed, 24 insertions(+), 3 deletions(-)

diff --git a/gcc/range-op-float.cc b/gcc/range-op-float.cc
index d5a3a49fb7d7..baf8a6dc098a 100644
--- a/gcc/range-op-float.cc
+++ b/gcc/range-op-float.cc
@@ -2413,14 +2413,22 @@ float_widen_lhs_range (tree type, const frange &lhs)
   frange ret = lhs;
   if (lhs.known_isnan ())
     return ret;
-  REAL_VALUE_TYPE lb = float_widen_bound (type, lhs.lower_bound (), dconstninf);
-  REAL_VALUE_TYPE ub = float_widen_bound (type, lhs.upper_bound (), dconstinf);
   /* Temporarily disable -ffinite-math-only, so that frange::set doesn't
      reduce the range back to real_min_representable (type) as lower bound
      or real_max_representable (type) as upper bound.  */
   bool save_flag_finite_math_only = flag_finite_math_only;
   flag_finite_math_only = false;
-  ret.set (type, lb, ub, lhs.get_nan_state ());
+  ret.set_undefined ();
+  for (unsigned i = 0; i < lhs.num_pairs (); ++i)
+    {
+      REAL_VALUE_TYPE lb = float_widen_bound (type, lhs.lower_bound (i),
+					      dconstninf);
+      REAL_VALUE_TYPE ub = float_widen_bound (type, lhs.upper_bound (i),
+					      dconstinf);
+      frange tmp;
+      tmp.set (type, lb, ub, lhs.get_nan_state ());
+      ret.union_ (tmp);
+    }
   flag_finite_math_only = save_flag_finite_math_only;
   return ret;
 }
@@ -3256,6 +3264,19 @@ range_op_float_tests ()
   plus.fold_range (r, float_type_node, r0, r1);
   if (HONOR_NANS (float_type_node))
     ASSERT_TRUE (r.maybe_isnan ());
+
+  // float_widen_lhs_range widens each sub-range and keeps the gap between
+  // them.
+  r0 = frange_float ("1.0", "2.0");
+  r1 = frange_float ("10.0", "11.0");
+  r0.union_ (r1);
+  r0.clear_nan ();
+  ASSERT_EQ (r0.num_pairs (), 2);
+  r = float_widen_lhs_range (float_type_node, r0);
+  ASSERT_EQ (r.num_pairs (), 2);
+  REAL_VALUE_TYPE five;
+  real_from_string (&five, "5.0");
+  ASSERT_FALSE (r.contains_p (five));
 }
 
 } // namespace selftest