From: Aldy Hernandez <aldyh@redhat.com>
Date: Mon, 19 Oct 2020 10:18:46 +0000 (-0400)
Subject: Gracefully handle right shifts larger than the precision.
X-Git-Tag: basepoints/gcc-12~4187
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=2d2f4ffc97a8510e72a99ee106159aeae2627a42;p=thirdparty%2Fgcc.git

Gracefully handle right shifts larger than the precision.

gcc/ChangeLog:

	PR tree-optimization/97488
	* range-op.cc (operator_lshift::op1_range): Handle large right shifts.

gcc/testsuite/ChangeLog:

	* gcc.dg/pr97488.c: New test.
---

diff --git a/gcc/range-op.cc b/gcc/range-op.cc
index 30d2a4d3987e..21d98de22406 100644
--- a/gcc/range-op.cc
+++ b/gcc/range-op.cc
@@ -1579,6 +1579,10 @@ operator_lshift::op1_range (irange &r,
       wide_int shift = wi::to_wide (shift_amount);
       if (wi::lt_p (shift, 0, SIGNED))
 	return false;
+      if (wi::ge_p (shift, wi::uhwi (TYPE_PRECISION (type),
+				     TYPE_PRECISION (op2.type ())),
+		    UNSIGNED))
+	return false;
       if (shift == 0)
 	{
 	  r = lhs;
diff --git a/gcc/testsuite/gcc.dg/pr97488.c b/gcc/testsuite/gcc.dg/pr97488.c
new file mode 100644
index 000000000000..96dc33cf2589
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr97488.c
@@ -0,0 +1,11 @@
+// { dg-do compile }
+// { dg-options "-O1 -ftree-vrp" }
+
+__int128
+ef (__int128 ms)
+{
+  int dh = 129;
+  int *hj = &dh;
+
+  return ms << *hj ? ms : 0;
+}