[PATCH] c++: Fix ICE with nullptr comparison (GCC 11) [PR101592]

[Marek Polacek via Gcc-patches]

On trunk, PR101592 was fixed by r12-2537, but that change shouldn't be
backported to GCC 11.  In the PR Jakub suggested this fix, so here it
is, after the usual testing.

Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for 11?

        PR c++/101592

gcc/ChangeLog:

        * fold-const.c (make_range_step): Return NULL_TREE for NULLPTR_TYPE.

gcc/testsuite/ChangeLog:

        * g++.dg/warn/Wlogical-op-3.C: New test.

Co-authored-by: Jakub Jelinek <ja...@redhat.com>
---
 gcc/fold-const.c                          |  3 ++-
 gcc/testsuite/g++.dg/warn/Wlogical-op-3.C | 12 ++++++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/warn/Wlogical-op-3.C

diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index 39f120db38c..a1d08c74025 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -5003,7 +5003,8 @@ make_range_step (location_t loc, enum tree_code code, 
tree arg0, tree arg1,
         being not equal to zero; "out" is leaving it alone.  */
       if (low == NULL_TREE || high == NULL_TREE
          || ! integer_zerop (low) || ! integer_zerop (high)
-         || TREE_CODE (arg1) != INTEGER_CST)
+         || TREE_CODE (arg1) != INTEGER_CST
+         || TREE_CODE (arg0_type) == NULLPTR_TYPE)
        return NULL_TREE;
 
       switch (code)
diff --git a/gcc/testsuite/g++.dg/warn/Wlogical-op-3.C 
b/gcc/testsuite/g++.dg/warn/Wlogical-op-3.C
new file mode 100644
index 00000000000..4b0bc22af4d
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wlogical-op-3.C
@@ -0,0 +1,12 @@
+// PR c++/101592
+// { dg-do compile { target c++11 } }
+// { dg-options "-O2 -Wlogical-op" }
+
+decltype(nullptr) foo ();
+
+bool
+bar ()
+{
+  return foo () > nullptr
+    || foo () < nullptr;
+}

base-commit: 051040f0642cfd002d31f655a70aef50e6f44d25
-- 
2.31.1