[PATCH] Don't assert on a negative shift.

[Andrew MacLeod via Gcc-patches]

We were asserting that the shifts should not be negative, instead, just 
return false indicating we can't tell anything about operand1 from the 
result.

Bootstrapped on x86_64-pc-linux-gnu,  no regressions, pushed.
Andrew


2020-10-16  Andrew Macleod  <amacl:x...@redhat.com>

	PR tree-optimization/97462
	gcc/
	* range-op.cc (operator_lshift::op1_range): Don't trap on negative
	shifts.
	gcc/testsuite/
	 * gcc.dg/pr97462.c: New file.


diff --git a/gcc/range-op.cc b/gcc/range-op.cc
index 6108de367ad..0efa00186e8 100644
--- a/gcc/range-op.cc
+++ b/gcc/range-op.cc
@@ -1577,7 +1577,8 @@ operator_lshift::op1_range (irange &r,
   if (op2.singleton_p (&shift_amount))
     {
       wide_int shift = wi::to_wide (shift_amount);
-      gcc_checking_assert (wi::gt_p (shift, 0, SIGNED));
+      if (wi::lt_p (shift, 0, SIGNED))
+	return false;
 
       // Work completely in unsigned mode to start.
       tree utype = type;
diff --git a/gcc/testsuite/gcc.dg/pr97462.c b/gcc/testsuite/gcc.dg/pr97462.c
new file mode 100644
index 00000000000..52c0533c98e
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr97462.c
@@ -0,0 +1,10 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -w" } */
+
+int a, b;
+
+void d ()
+{
+  a << ~0 && b;
+  b = a;
+}