Fix -Wshift-count-negative. It didn't work if the right hand side

of the shift wasn't a constant integer expression, now it (hopefully)
does.

PR:		22059


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@233320 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Sema/SemaExpr.cpp

@@ -7769,7 +7769,7 @@ static void DiagnoseBadShiftValues(Sema& S, ExprResult &LHS, ExprResult &RHS,
   llvm::APSInt Right;
   // Check right/shifter operand
   if (RHS.get()->isValueDependent() ||
-      !RHS.get()->isIntegerConstantExpr(Right, S.Context))
+      !RHS.get()->EvaluateAsInt(Right, S.Context))
     return;
 
   if (Right.isNegative()) {

test/Sema/warn-shift-negative.c

@@ -0,0 +1,6 @@
+// RUN: %clang_cc1 -fsyntax-only -Wshift-count-negative -fblocks -verify %s
+
+int f(int a) {
+  const int i = -1;
+  return a << i; // expected-warning{{shift count is negative}}
+}