From a87819b8f1b890d36a3f05bd9de80be20e9525dd Mon Sep 17 00:00:00 2001
From: Andrew MacLeod <amacleod@redhat.com>
Date: Tue, 25 Oct 2022 15:16:47 -0400
Subject: [PATCH] Check if varying may also be non-negative.
When using strict enums, we can sometimes turn varying into a better
range.
* gimple-range-fold.cc (fold_using_range::fold_stmt): Check if
stmt is non-negative and adjust the range.
---
gcc/gimple-range-fold.cc | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/gcc/gimple-range-fold.cc b/gcc/gimple-range-fold.cc
index f91923782dca..a899d8260b3d 100644
--- a/gcc/gimple-range-fold.cc
+++ b/gcc/gimple-range-fold.cc
@@ -494,6 +494,14 @@ fold_using_range::fold_stmt (vrange &r, gimple *s, fur_source &src, tree name)
else if (is_a<gassign *> (s) && gimple_assign_rhs_code (s) == COND_EXPR)
res = range_of_cond_expr (r, as_a<gassign *> (s), src);
+ // If the result is varying, check for basic nonnegativeness.
+ // Specifically this helps for now with strict enum in cases like
+ // g++.dg/warn/pr33738.C.
+ bool so_p;
+ if (res && r.varying_p () && INTEGRAL_TYPE_P (r.type ())
+ && gimple_stmt_nonnegative_warnv_p (s, &so_p))
+ r.set_nonnegative (r.type ());
+
if (!res)
{
// If no name specified or range is unsupported, bail.
--
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