[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, 58 insertions, 0 deletions

diff --git a/clang-tools-extra/test/clang-tidy/misc-redundant-expression.cpp b/clang-tools-extra/test/clang-tidy/misc-redundant-expression.cpp
index d4644f2f363..36ffbbdd52f 100644
--- a/clang-tools-extra/test/clang-tidy/misc-redundant-expression.cpp
+++ b/clang-tools-extra/test/clang-tidy/misc-redundant-expression.cpp
@@ -154,6 +154,8 @@ bool TestOverloadedOperator(MyStruct& S) {
   // CHECK-MESSAGES: :[[@LINE-1]]:9: warning: both sides of overloaded operator are equivalent
   if (S >= S) return true;
   // CHECK-MESSAGES: :[[@LINE-1]]:9: warning: both sides of overloaded operator are equivalent
+
+  return true;
 }
 
 #define LT(x, y) (void)((x) < (y))
@@ -662,3 +664,59 @@ int TestWithMinMaxInt(int X) {
 
   return 0;
 }
+
+#define FLAG1 1
+#define FLAG2 2
+#define FLAG3 4
+#define FLAGS (FLAG1 | FLAG2 | FLAG3)
+#define NOTFLAGS !(FLAG1 | FLAG2 | FLAG3)
+int operatorConfusion(int X, int Y, long Z)
+{
+  // Ineffective & expressions.
+  Y = (Y << 8) & 0xff;
+  // CHECK-MESSAGES: :[[@LINE-1]]:16: warning: ineffective bitwise and operation.
+  Y = (Y << 12) & 0xfff;
+  // CHECK-MESSAGES: :[[@LINE-1]]:17: warning: ineffective bitwise and
+  Y = (Y << 12) & 0xff;
+  // CHECK-MESSAGES: :[[@LINE-1]]:17: warning: ineffective bitwise and
+  Y = (Y << 8) & 0x77;
+  // CHECK-MESSAGES: :[[@LINE-1]]:16: warning: ineffective bitwise and
+  Y = (Y << 5) & 0x11;
+  // CHECK-MESSAGES: :[[@LINE-1]]:16: warning: ineffective bitwise and
+
+  // Tests for unmatched types
+  Z = (Z << 8) & 0xff;
+  // CHECK-MESSAGES: :[[@LINE-1]]:16: warning: ineffective bitwise and operation.
+  Y = (Y << 12) & 0xfffL;
+  // CHECK-MESSAGES: :[[@LINE-1]]:17: warning: ineffective bitwise and
+  Z = (Y << 12) & 0xffLL;
+  // CHECK-MESSAGES: :[[@LINE-1]]:17: warning: ineffective bitwise and
+  Y = (Z << 8L) & 0x77L;
+  // CHECK-MESSAGES: :[[@LINE-1]]:17: warning: ineffective bitwise and
+
+  // Effective expressions. Do not check.
+  Y = (Y << 4) & 0x15;
+  Y = (Y << 3) & 0x250;
+  Y = (Y << 9) & 0xF33;
+
+  int K = !(1 | 2 | 4);
+  // CHECK-MESSAGES: :[[@LINE-1]]:11: warning: ineffective logical negation operator used; did you mean '~'?
+  // CHECK-FIXES: {{^}}  int K = ~(1 | 2 | 4);{{$}}
+  K = !(FLAG1 & FLAG2 & FLAG3);
+  // CHECK-MESSAGES: :[[@LINE-1]]:7: warning: ineffective logical negation operator
+  // CHECK-FIXES: {{^}}  K = ~(FLAG1 & FLAG2 & FLAG3);{{$}}
+  K = !(3 | 4);
+  // CHECK-MESSAGES: :[[@LINE-1]]:7: warning: ineffective logical negation operator
+  // CHECK-FIXES: {{^}}  K = ~(3 | 4);{{$}}
+  int NotFlags = !FLAGS;
+  // CHECK-MESSAGES: :[[@LINE-1]]:18: warning: ineffective logical negation operator
+  // CHECK-FIXES: {{^}}  int NotFlags = ~FLAGS;{{$}}
+  NotFlags = NOTFLAGS;
+  // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: ineffective logical negation operator
+  return !(1 | 2 | 4);
+  // CHECK-MESSAGES: :[[@LINE-1]]:10: warning: ineffective logical negation operator
+  // CHECK-FIXES: {{^}}  return ~(1 | 2 | 4);{{$}}
+}
+#undef FLAG1
+#undef FLAG2
+#undef FLAG3