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

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This catches issues like:

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

Patch by Anders Rönnholm!

llvm-svn: 209221
This commit is contained in:
Jordan Rose
2014-05-20 17:31:11 +00:00
parent d2402470ee
commit 7afd71e4ff
5 changed files with 77 additions and 8 deletions
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43
clang/lib/Analysis/CFG.cpp
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@@ -534,9 +534,10 @@ private:
}
}
/// Find a equality comparison with an expression evaluating to a boolean and
/// a constant other than 0 and 1.
/// e.g. if (!x == 10)
/// Find an incorrect equality comparison. Either with an expression
/// evaluating to a boolean and a constant other than 0 and 1.
/// e.g. if (!x == 10) or a bitwise and/or operation that always evaluates to
/// true/false e.q. (x & 8) == 4.
TryResult checkIncorrectEqualityOperator(const BinaryOperator *B) {
const Expr *LHSExpr = B->getLHS()->IgnoreParens();
const Expr *RHSExpr = B->getRHS()->IgnoreParens();
@@ -549,15 +550,41 @@ private:
BoolExpr = LHSExpr;
}
if (!IntLiteral || !BoolExpr->isKnownToHaveBooleanValue())
if (!IntLiteral)
return TryResult();
llvm::APInt IntValue = IntLiteral->getValue();
if ((IntValue == 1) || (IntValue == 0)) {
return TryResult();
const BinaryOperator *BitOp = dyn_cast<BinaryOperator>(BoolExpr);
if (BitOp && (BitOp->getOpcode() == BO_And ||
BitOp->getOpcode() == BO_Or)) {
const Expr *LHSExpr2 = BitOp->getLHS()->IgnoreParens();
const Expr *RHSExpr2 = BitOp->getRHS()->IgnoreParens();
const IntegerLiteral *IntLiteral2 = dyn_cast<IntegerLiteral>(LHSExpr2);
if (!IntLiteral2)
IntLiteral2 = dyn_cast<IntegerLiteral>(RHSExpr2);
if (!IntLiteral2)
return TryResult();
llvm::APInt L1 = IntLiteral->getValue();
llvm::APInt L2 = IntLiteral2->getValue();
if ((BitOp->getOpcode() == BO_And && (L2 & L1) != L1) ||
(BitOp->getOpcode() == BO_Or && (L2 | L1) != L1)) {
if (BuildOpts.Observer)
BuildOpts.Observer->compareBitwiseEquality(B,
B->getOpcode() != BO_EQ);
TryResult(B->getOpcode() != BO_EQ);
}
} else if (BoolExpr->isKnownToHaveBooleanValue()) {
llvm::APInt IntValue = IntLiteral->getValue();
if ((IntValue == 1) || (IntValue == 0)) {
return TryResult();
}
return TryResult(B->getOpcode() != BO_EQ);
}
return TryResult(B->getOpcode() != BO_EQ);
return TryResult();
}
TryResult analyzeLogicOperatorCondition(BinaryOperatorKind Relation,