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, 28 insertions, 0 deletions

diff --git a/clang/test/Sema/warn-bitwise-compare.c b/clang/test/Sema/warn-bitwise-compare.c
new file mode 100644
index 00000000000..175f8f5367f
--- /dev/null
+++ b/clang/test/Sema/warn-bitwise-compare.c
@@ -0,0 +1,28 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -Wtautological-compare %s
+
+#define mydefine 2
+
+void f(int x) {
+  if ((8 & x) == 3) {}  // expected-warning {{bitwise comparison always evaluates to false}}
+  if ((x & 8) == 4) {}  // expected-warning {{bitwise comparison always evaluates to false}}
+  if ((x & 8) != 4) {}  // expected-warning {{bitwise comparison always evaluates to true}}
+  if ((2 & x) != 4) {}  // expected-warning {{bitwise comparison always evaluates to true}}
+  if ((x | 4) == 3) {}  // expected-warning {{bitwise comparison always evaluates to false}}
+  if ((x | 3) != 4) {}  // expected-warning {{bitwise comparison always evaluates to true}}
+  if ((5 | x) != 3) {}  // expected-warning {{bitwise comparison always evaluates to true}}
+  if ((x & 0x15) == 0x13) {} // expected-warning {{bitwise comparison always evaluates to false}}
+  if ((0x23 | x) == 0x155){} // expected-warning {{bitwise comparison always evaluates to false}}
+
+  if ((x & 8) == 8) {}
+  if ((x & 8) != 8) {}
+  if ((x | 4) == 4) {}
+  if ((x | 4) != 4) {}
+
+  if ((x & 9) == 8) {}
+  if ((x & 9) != 8) {}
+  if ((x | 4) == 5) {}
+  if ((x | 4) != 5) {}
+
+  if ((x & mydefine) == 8) {}
+  if ((x | mydefine) == 4) {}
+}