[gcc r16-661] Check for casts becoming UNDEFINED.

[Andrew Macleod via Gcc-cvs]

https://gcc.gnu.org/g:4291071a6aa3b50800ad5fc70b5fb83cb9398237

commit r16-661-g4291071a6aa3b50800ad5fc70b5fb83cb9398237
Author: Andrew MacLeod <amacl...@redhat.com>
Date:   Thu May 15 11:06:05 2025 -0400

    Check for casts becoming UNDEFINED.
    
    In various situations a cast that is ultimately unreahcable may produce
    an UNDEFINED result, and we can't check the bounds in this case.
    
            PR tree-optimization/120277
            gcc/
            * range-op-ptr.cc (operator_cast::fold_range): Check if the cast
            if UNDEFINED before setting bounds.
    
            gcc/testsuite/
            * gcc.dg/pr120277.c: New.

Diff:
---
 gcc/range-op-ptr.cc             | 10 ++++++++--
 gcc/testsuite/gcc.dg/pr120277.c | 21 +++++++++++++++++++++
 2 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/gcc/range-op-ptr.cc b/gcc/range-op-ptr.cc
index 36e9dfc20baf..6aadc9cf2c95 100644
--- a/gcc/range-op-ptr.cc
+++ b/gcc/range-op-ptr.cc
@@ -602,8 +602,14 @@ operator_cast::fold_range (prange &r, tree type,
   int_range<2> tmp = inner;
   tree pointer_uint_type = make_unsigned_type (TYPE_PRECISION (type));
   range_cast (tmp, pointer_uint_type);
-  r.set (type, tmp.lower_bound (), tmp.upper_bound ());
-  r.update_bitmask (tmp.get_bitmask ());
+  // Casts may cause ranges to become UNDEFINED based on bitmasks.
+  if (tmp.undefined_p ())
+    r.set_varying (type);
+  else
+    {
+      r.set (type, tmp.lower_bound (), tmp.upper_bound ());
+      r.update_bitmask (tmp.get_bitmask ());
+    }
   return true;
 }
 
diff --git a/gcc/testsuite/gcc.dg/pr120277.c b/gcc/testsuite/gcc.dg/pr120277.c
new file mode 100644
index 000000000000..f291e920db16
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr120277.c
@@ -0,0 +1,21 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+int a, b;
+int c(int d, long e) {
+  switch (d) {
+  case 129:
+    a = 1;
+  case 128:
+    break;
+  default:
+    return 1;
+  }
+  *(int *)e = 0;
+}
+void f(int d, long e) { c(d, e); }
+void g() {
+  int h = b * sizeof(int);
+  f(h + 7, h);
+}
+void main() {}