[analyzer] Left shifting a negative value is undefined

The analyzer did not return an UndefVal in case a negative value was left
shifted. I also altered the UndefResultChecker to emit a clear warning in this
case.

Differential Revision: https://reviews.llvm.org/D39423

llvm-svn: 316924

1 files changed, 7 insertions, 0 deletions

diff --git a/clang/test/Analysis/bitwise-ops.c b/clang/test/Analysis/bitwise-ops.c
index acef6681d89..fe546580be3 100644
--- a/clang/test/Analysis/bitwise-ops.c
+++ b/clang/test/Analysis/bitwise-ops.c
@@ -44,3 +44,10 @@ int testNegativeShift(int a) {
   }
   return 0;
 }
+
+int testNegativeLeftShift(int a) {
+  if (a == -3) {
+    return a << 1; // expected-warning{{The result of the left shift is undefined because the left operand is negative}}
+  }
+  return 0;
+}