From 72739a6fde0020b98cdabad7218c6d4f5ce36bce Mon Sep 17 00:00:00 2001
From: Aldy Hernandez <aldyh@redhat.com>
Date: Sat, 2 Oct 2021 16:59:26 +0200
Subject: [PATCH] [PR102563] Do not clobber range in
 operator_lshift::op1_range.

We're clobbering the final range before we're done calculating it.

Tested on x86-64 Linux.

gcc/ChangeLog:

	* range-op.cc (operator_lshift::op1_range): Do not clobber
	range.

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/pr102563.c: New test.
---
 gcc/range-op.cc                          | 12 ++++++------
 gcc/testsuite/gcc.dg/tree-ssa/pr102563.c | 16 ++++++++++++++++
 2 files changed, 22 insertions(+), 6 deletions(-)
 create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr102563.c

diff --git a/gcc/range-op.cc b/gcc/range-op.cc
index 2baca4a197f..bbf2924f815 100644
--- a/gcc/range-op.cc
+++ b/gcc/range-op.cc
@@ -2112,8 +2112,6 @@ operator_lshift::op1_range (irange &r,
       else
 	op_rshift.fold_range (tmp_range, utype, lhs, op2);
 
-      r.intersect (tmp_range);
-
       // Start with ranges which can produce the LHS by right shifting the
       // result by the shift amount.
       // ie   [0x08, 0xF0] = op1 << 2 will start with
@@ -2128,13 +2126,15 @@ operator_lshift::op1_range (irange &r,
       unsigned low_bits = TYPE_PRECISION (utype)
 			  - TREE_INT_CST_LOW (shift_amount);
       wide_int up_mask = wi::mask (low_bits, true, TYPE_PRECISION (utype));
-      wide_int new_ub = wi::bit_or (up_mask, r.upper_bound ());
-      wide_int new_lb = wi::set_bit (r.lower_bound (), low_bits);
+      wide_int new_ub = wi::bit_or (up_mask, tmp_range.upper_bound ());
+      wide_int new_lb = wi::set_bit (tmp_range.lower_bound (), low_bits);
       int_range<2> fill_range (utype, new_lb, new_ub);
-      r.union_ (fill_range);
+      tmp_range.union_ (fill_range);
 
       if (utype != type)
-	range_cast (r, type);
+	range_cast (tmp_range, type);
+
+      r.intersect (tmp_range);
       return true;
     }
 
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr102563.c b/gcc/testsuite/gcc.dg/tree-ssa/pr102563.c
new file mode 100644
index 00000000000..8871dffe24a
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr102563.c
@@ -0,0 +1,16 @@
+// { dg-do compile }
+// { dg-options "-O2 -w" }
+
+int _bdf_parse_glyphs_bp;
+long _bdf_parse_glyphs_nibbles;
+
+void _bdf_parse_glyphs_p() 
+{
+  long p_2;
+
+  _bdf_parse_glyphs_nibbles = p_2 << 1;
+
+  for (; 0 < _bdf_parse_glyphs_nibbles;)
+    if (1 < _bdf_parse_glyphs_nibbles)
+      _bdf_parse_glyphs_bp = _bdf_parse_glyphs_p;
+}
-- 
2.31.1