Improvements to IdempotentOperationChecker and its use of PseudoConstantAnalysis
- Added wasReferenced function to PseudoConstantAnalysis to determine if a variable was ever referenced in a function (outside of a self-assignment)
- BlockDeclRefExpr referenced variables are now explicitly added to the non-constant list
- Remove unnecessary ignore of implicit casts
- Generalized parameter self-assign detection to detect deliberate self-assigns of variables to avoid unused variable warnings
- Updated test cases with deliberate self-assignments
- Fixed bug with C++ references and pseudoconstants
- Added test case for C++ references and pseudoconstants
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@111965 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/PseudoConstantAnalysis.cpp b/lib/Analysis/PseudoConstantAnalysis.cpp
index 7a2fa8a..5deabac 100644
--- a/lib/Analysis/PseudoConstantAnalysis.cpp
+++ b/lib/Analysis/PseudoConstantAnalysis.cpp
@@ -28,10 +28,12 @@
PseudoConstantAnalysis::PseudoConstantAnalysis(const Stmt *DeclBody) :
DeclBody(DeclBody), Analyzed(false) {
NonConstantsImpl = new VarDeclSet;
+ UsedVarsImpl = new VarDeclSet;
}
PseudoConstantAnalysis::~PseudoConstantAnalysis() {
delete (VarDeclSet*)NonConstantsImpl;
+ delete (VarDeclSet*)UsedVarsImpl;
}
// Returns true if the given ValueDecl is never written to in the given DeclBody
@@ -50,9 +52,22 @@
return !NonConstants->count(VD);
}
+// Returns true if the variable was used (self assignments don't count)
+bool PseudoConstantAnalysis::wasReferenced(const VarDecl *VD) {
+ if (!Analyzed) {
+ RunAnalysis();
+ Analyzed = true;
+ }
+
+ VarDeclSet *UsedVars = (VarDeclSet*)UsedVarsImpl;
+
+ return UsedVars->count(VD);
+}
+
void PseudoConstantAnalysis::RunAnalysis() {
std::deque<const Stmt *> WorkList;
VarDeclSet *NonConstants = (VarDeclSet*)NonConstantsImpl;
+ VarDeclSet *UsedVars = (VarDeclSet*)UsedVarsImpl;
// Start with the top level statement of the function
WorkList.push_back(DeclBody);
@@ -65,7 +80,7 @@
// Case 1: Assignment operators modifying ValueDecl
case Stmt::BinaryOperatorClass: {
const BinaryOperator *BO = cast<BinaryOperator>(Head);
- const Expr *LHS = BO->getLHS()->IgnoreParenImpCasts();
+ const Expr *LHS = BO->getLHS()->IgnoreParenCasts();
const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(LHS);
// We only care about DeclRefExprs on the LHS
@@ -76,7 +91,16 @@
// for any of the assignment operators, implying that this Decl is being
// written to.
switch (BO->getOpcode()) {
- case BinaryOperator::Assign:
+ case BinaryOperator::Assign: {
+ const Expr *RHS = BO->getRHS()->IgnoreParenCasts();
+ if (const DeclRefExpr *RHSDecl = dyn_cast<DeclRefExpr>(RHS)) {
+ // Self-assignments don't count as use of a variable
+ if (DR->getDecl() == RHSDecl->getDecl())
+ // Do not visit the children
+ continue;
+ }
+
+ }
case BinaryOperator::AddAssign:
case BinaryOperator::SubAssign:
case BinaryOperator::MulAssign:
@@ -148,16 +172,37 @@
if (!VD->getType().getTypePtr()->isReferenceType())
continue;
- // Ignore VarDecls without a body
- if (!VD->getBody())
- continue;
-
// If the reference is to another var, add the var to the non-constant
// list
- if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(VD->getBody()))
- if (const VarDecl *RefVD = dyn_cast<VarDecl>(DR->getDecl()))
+ if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(VD->getInit()))
+ if (const VarDecl *RefVD = dyn_cast<VarDecl>(DR->getDecl())) {
NonConstants->insert(RefVD);
+ continue;
+ }
}
+ break;
+ }
+
+ // Case 4: Block variable references
+ case Stmt::BlockDeclRefExprClass: {
+ // Any block variables are assumed to be non-constant
+ const BlockDeclRefExpr *BDR = cast<BlockDeclRefExpr>(Head);
+ if (const VarDecl *VD = dyn_cast<VarDecl>(BDR->getDecl())) {
+ NonConstants->insert(VD);
+ UsedVars->insert(VD);
+ continue;
+ }
+ break;
+ }
+
+ // Case 5: Variable references
+ case Stmt::DeclRefExprClass: {
+ const DeclRefExpr *DR = cast<DeclRefExpr>(Head);
+ if (const VarDecl *VD = dyn_cast<VarDecl>(DR->getDecl())) {
+ UsedVars->insert(VD);
+ continue;
+ }
+ break;
}
default:
diff --git a/lib/Checker/IdempotentOperationChecker.cpp b/lib/Checker/IdempotentOperationChecker.cpp
index 2cfcaa4..d893620 100644
--- a/lib/Checker/IdempotentOperationChecker.cpp
+++ b/lib/Checker/IdempotentOperationChecker.cpp
@@ -74,7 +74,9 @@
void UpdateAssumption(Assumption &A, const Assumption &New);
// False positive reduction methods
- static bool isParameterSelfAssign(const Expr *LHS, const Expr *RHS);
+ static bool isUnusedSelfAssign(const Expr *LHS,
+ const Expr *RHS,
+ AnalysisContext *AC);
static bool isTruncationExtensionAssignment(const Expr *LHS,
const Expr *RHS);
static bool PathWasCompletelyAnalyzed(const CFG *C,
@@ -182,12 +184,19 @@
// Fall through intentional
case BinaryOperator::Assign:
- // x Assign x has a few more false positives we can check for
- if (isParameterSelfAssign(RHS, LHS)
- || isTruncationExtensionAssignment(RHS, LHS)) {
+ // x Assign x can be used to silence unused variable warnings intentionally,
+ // and has a slightly different definition for false positives.
+ if (isUnusedSelfAssign(RHS, LHS, AC)
+ || isTruncationExtensionAssignment(RHS, LHS)
+ || containsNonLocalVarDecl(RHS)
+ || containsNonLocalVarDecl(LHS)) {
A = Impossible;
return;
}
+ if (LHSVal != RHSVal)
+ break;
+ UpdateAssumption(A, Equal);
+ return;
case BinaryOperator::SubAssign:
case BinaryOperator::DivAssign:
@@ -397,10 +406,12 @@
}
}
-// Check for a statement were a parameter is self assigned (to avoid an unused
-// variable warning)
-bool IdempotentOperationChecker::isParameterSelfAssign(const Expr *LHS,
- const Expr *RHS) {
+// Check for a statement where a variable is self assigned to avoid an unused
+// variable warning. We still report if the variable is used after the self
+// assignment.
+bool IdempotentOperationChecker::isUnusedSelfAssign(const Expr *LHS,
+ const Expr *RHS,
+ AnalysisContext *AC) {
LHS = LHS->IgnoreParenCasts();
RHS = RHS->IgnoreParenCasts();
@@ -408,15 +419,22 @@
if (!LHS_DR)
return false;
- const ParmVarDecl *PD = dyn_cast<ParmVarDecl>(LHS_DR->getDecl());
- if (!PD)
+ const VarDecl *VD = dyn_cast<VarDecl>(LHS_DR->getDecl());
+ if (!VD)
return false;
const DeclRefExpr *RHS_DR = dyn_cast<DeclRefExpr>(RHS);
if (!RHS_DR)
return false;
- return PD == RHS_DR->getDecl();
+ if (VD != RHS_DR->getDecl())
+ return false;
+
+ // If the var was used outside of a selfassign, then we should still report
+ if (AC->getPseudoConstantAnalysis()->wasReferenced(VD))
+ return false;
+
+ return true;
}
// Check for self casts truncating/extending a variable