[analyzer] Model correct dispatch_once() 'done' value in BodyFarm
The analyzer's BodyFarm models dispatch_once() by comparing the passed-in
predicate against a known 'done' value. If the predicate does not have that
value, the model updates the predicate to have that value and executes the
passed in block.
Unfortunately, the current model uses the wrong 'done' value: 1 instead of ~0.
This interferes with libdispatch's static inline function _dispatch_once(),
which enables a fast path if the block has already been executed. That function
uses __builtin_assume() to tell the compiler that the done flag is set to ~0 on
exit. When r302880 added modeling of __builtin_assume(), this caused the
analyzer to assume 1 == ~0. This in turn caused the analyzer to never explore any code after a call to dispatch_once().
This patch regains the missing coverage by updating BodyFarm to use the correct
'done' value.
rdar://problem/34413048
Differential Revision: https://reviews.llvm.org/D39691
llvm-svn: 317516
diff --git a/clang/lib/Analysis/BodyFarm.cpp b/clang/lib/Analysis/BodyFarm.cpp
index 3e62ae5..e5d3c5c 100644
--- a/clang/lib/Analysis/BodyFarm.cpp
+++ b/clang/lib/Analysis/BodyFarm.cpp
@@ -96,8 +96,8 @@
/// Create a Return statement.
ReturnStmt *makeReturn(const Expr *RetVal);
- /// Create an integer literal.
- IntegerLiteral *makeIntegerLiteral(uint64_t value);
+ /// Create an integer literal expression of the given type.
+ IntegerLiteral *makeIntegerLiteral(uint64_t Value, QualType Ty);
/// Create a member expression.
MemberExpr *makeMemberExpression(Expr *base, ValueDecl *MemberDecl,
@@ -206,11 +206,9 @@
nullptr);
}
-IntegerLiteral *ASTMaker::makeIntegerLiteral(uint64_t value) {
- return IntegerLiteral::Create(C,
- llvm::APInt(
- /*numBits=*/C.getTypeSize(C.IntTy), value),
- /*QualType=*/C.IntTy, SourceLocation());
+IntegerLiteral *ASTMaker::makeIntegerLiteral(uint64_t Value, QualType Ty) {
+ llvm::APInt APValue = llvm::APInt(C.getTypeSize(Ty), Value);
+ return IntegerLiteral::Create(C, APValue, Ty, SourceLocation());
}
MemberExpr *ASTMaker::makeMemberExpression(Expr *base, ValueDecl *MemberDecl,
@@ -447,7 +445,8 @@
// Create assignment.
BinaryOperator *FlagAssignment = M.makeAssignment(
- Deref, M.makeIntegralCast(M.makeIntegerLiteral(1), DerefType), DerefType);
+ Deref, M.makeIntegralCast(M.makeIntegerLiteral(1, C.IntTy), DerefType),
+ DerefType);
IfStmt *Out = new (C)
IfStmt(C, SourceLocation(),
@@ -486,8 +485,8 @@
// sets it, and calls the block. Basically, an AST dump of:
//
// void dispatch_once(dispatch_once_t *predicate, dispatch_block_t block) {
- // if (!*predicate) {
- // *predicate = 1;
+ // if (*predicate != ~0l) {
+ // *predicate = ~0l;
// block();
// }
// }
@@ -504,7 +503,9 @@
/*SourceLocation=*/SourceLocation());
// (2) Create the assignment to the predicate.
- IntegerLiteral *IL = M.makeIntegerLiteral(1);
+ Expr *DoneValue =
+ new (C) UnaryOperator(M.makeIntegerLiteral(0, C.LongTy), UO_Not, C.LongTy,
+ VK_RValue, OK_Ordinary, SourceLocation());
BinaryOperator *B =
M.makeAssignment(
@@ -512,7 +513,7 @@
M.makeLvalueToRvalue(
M.makeDeclRefExpr(Predicate), PredicateQPtrTy),
PredicateTy),
- M.makeIntegralCast(IL, PredicateTy),
+ M.makeIntegralCast(DoneValue, PredicateTy),
PredicateTy);
// (3) Create the compound statement.
@@ -528,20 +529,14 @@
PredicateQPtrTy),
PredicateTy),
PredicateTy);
-
- UnaryOperator *UO = new (C) UnaryOperator(
- /* input=*/ LValToRval,
- /* opc=*/ UO_LNot,
- /* QualType=*/ C.IntTy,
- /* ExprValueKind=*/ VK_RValue,
- /* ExprObjectKind=*/ OK_Ordinary, SourceLocation());
-
+
+ Expr *GuardCondition = M.makeComparison(LValToRval, DoneValue, BO_NE);
// (5) Create the 'if' statement.
IfStmt *If = new (C) IfStmt(C, SourceLocation(),
/* IsConstexpr=*/ false,
/* init=*/ nullptr,
/* var=*/ nullptr,
- /* cond=*/ UO,
+ /* cond=*/ GuardCondition,
/* then=*/ CS);
return If;
}