[clang-tidy] Misc redundant expression checker updated for ineffective bitwise operator expressions

Examples:
* Always evaluates to 0:

```
  int X;
  if (0 & X) return;
```

* Always evaluates to ~0:

```
  int Y;
  if (Y | ~0) return;
```

* The symbol is unmodified:

```
  int Z;
  Z &= ~0;
```

Patch by: Lilla Barancsuk!

Differential Revision: https://reviews.llvm.org/D39285

llvm-svn: 321168

1 files changed, 9 insertions, 0 deletions

diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index b8901785b57..bc2ba1d305a 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -268,6 +268,15 @@ Improvements to clang-tidy
 
 - Added the ability to suppress specific checks (or all checks) in a ``NOLINT`` or ``NOLINTNEXTLINE`` comment.
 
+- Added new functionality to `misc-redundant-expression
+  http://clang.llvm.org/extra/clang-tidy/checks/misc-redundant-expression.html`_ check
+
+  Finds redundant binary operator expressions where the operators are overloaded,
+  and ones that contain the same macros twice.
+  Also checks for assignment expressions that do not change the value of the
+  assigned variable, and expressions that always evaluate to the same value
+  because of possible operator confusion.
+
 Improvements to include-fixer
 -----------------------------