From f0c0f124ebe28b71abccbd7247678c9ac608b649 Mon Sep 17 00:00:00 2001
From: Aldy Hernandez <aldyh@redhat.com>
Date: Tue, 20 Oct 2020 08:53:21 +0200
Subject: [PATCH] Special case shifting by zero in operator_rshift::op1_range.

gcc/ChangeLog:

	* range-op.cc (operator_rshift::op1_range): Special case
	shifting by zero.
---
 gcc/range-op.cc | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/gcc/range-op.cc b/gcc/range-op.cc
index 21d98de22406..ee62f103598a 100644
--- a/gcc/range-op.cc
+++ b/gcc/range-op.cc
@@ -1642,6 +1642,11 @@ operator_rshift::op1_range (irange &r,
 		    wi::uhwi (prec, TYPE_PRECISION (TREE_TYPE (shift))),
 		    UNSIGNED))
 	return false;
+      if (wi::to_wide (shift) == 0)
+	{
+	  r = lhs;
+	  return true;
+	}
 
       // Folding the original operation may discard some impossible
       // ranges from the LHS.