Add a check for tautological bitwise comparisons to -Wtautological-compare.

This catches issues like:

if ((x & 8) == 4) { ... }
if ((x | 4) != 3) { ... }

Patch by Anders Rönnholm!

llvm-svn: 209221

1 files changed, 9 insertions, 0 deletions

diff --git a/clang/lib/Sema/AnalysisBasedWarnings.cpp b/clang/lib/Sema/AnalysisBasedWarnings.cpp
index d10b5a8..048019f 100644
--- a/clang/lib/Sema/AnalysisBasedWarnings.cpp
+++ b/clang/lib/Sema/AnalysisBasedWarnings.cpp
@@ -146,6 +146,15 @@ public:
     S.Diag(B->getExprLoc(), diag::warn_tautological_overlap_comparison)
         << DiagRange << isAlwaysTrue;
   }
+
+  void compareBitwiseEquality(const BinaryOperator *B, bool isAlwaysTrue) {
+    if (HasMacroID(B))
+      return;
+
+    SourceRange DiagRange = B->getSourceRange();
+    S.Diag(B->getExprLoc(), diag::warn_comparison_bitwise_always)
+        << DiagRange << isAlwaysTrue;
+  }
 };