/*
* Copyright 2010, The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef _FRAMEWORKS_COMPILE_SLANG_SLANG_RS_OBJECT_REF_COUNT_H_ // NOLINT
#define _FRAMEWORKS_COMPILE_SLANG_SLANG_RS_OBJECT_REF_COUNT_H_
#include <list>
#include <stack>
#include <vector>
#include "clang/AST/StmtVisitor.h"
#include "slang_assert.h"
#include "slang_rs_export_type.h"
namespace clang {
class Expr;
class Stmt;
}
namespace slang {
// Recursive check
bool HasRSObjectType(const clang::Type *T);
// This class provides the overall reference counting mechanism for handling
// local variables of RS object types (rs_font, rs_allocation, ...). This
// class ensures that appropriate functions (rsSetObject, rsClearObject) are
// called at proper points in the object's lifetime.
// 1) Each local object of appropriate type must be zero-initialized to
// prevent corruption during subsequent rsSetObject()/rsClearObject() calls.
// 2) Assignments using these types must also be converted into the
// appropriate (possibly a series of) rsSetObject() calls.
// 3) Finally, rsClearObject() must be called for each local object when it goes
// out of scope.
class RSObjectRefCount : public clang::StmtVisitor<RSObjectRefCount> {
private:
class Scope {
private:
clang::CompoundStmt *mCS; // Associated compound statement ({ ... })
clang::Stmt *mCurrent; // The statement currently being analyzed
std::list<clang::VarDecl*> mRSO; // Declared RS objects in this scope (but
// not any scopes nested)
public:
explicit Scope(clang::CompoundStmt *CS) : mCS(CS) {
}
bool hasRSObject() const { return !mRSO.empty(); }
inline void addRSObject(clang::VarDecl* VD) {
mRSO.push_back(VD);
}
void ReplaceRSObjectAssignment(clang::BinaryOperator *AS);
void AppendRSObjectInit(clang::VarDecl *VD,
clang::DeclStmt *DS,
DataType DT,
clang::Expr *InitExpr);
// Inserts rsClearObject() calls at the end and at all exiting points of the
// current scope. At each statement that exits the current scope -- e.g.,
// a return, break, or continue statement in the current or a nested scope
// -- rsClearObject() calls are inserted for local variables defined in the
// current scope before that point.
// Note goto statements are not handled. (See the DestructorVisitor class in
// the .cpp file.)
// Also note this function is called for every nested scope. As a result, for a
// return statement, each rsObject declared in all its (nested) enclosing
// scopes would have a rsClearObject() call properly inserted before
// the return statement.
void InsertLocalVarDestructors();
// Sets the current statement being analyzed
void setCurrentStmt(clang::Stmt *S) { mCurrent = S; }
// Inserts a statement before the current statement
void InsertStmt(const clang::ASTContext &C, clang::Stmt *NewStmt);
// Replaces the current statement with NewStmt;
void ReplaceStmt(const clang::ASTContext &C, clang::Stmt *NewStmt);
// Replaces OldExpr with NewExpr in the current statement
void ReplaceExpr(const clang::ASTContext& C, clang::Expr* OldExpr,
clang::Expr* NewExpr);
static clang::Stmt *ClearRSObject(clang::VarDecl *VD,
clang::DeclContext *DC);
};
clang::ASTContext &mCtx;
std::deque<Scope*> mScopeStack; // A deque used as a stack to store scopes, but also
// accessed through its iterator in read-only mode.
clang::DeclContext* mCurrentDC;
bool RSInitFD; // TODO: this should be static, since this flag affects all instances.
unsigned mTempID; // A unique id that can be used to distinguish temporary variables
// RSSetObjectFD and RSClearObjectFD holds FunctionDecl of rsSetObject()
// and rsClearObject() in the current ASTContext.
static clang::FunctionDecl *RSSetObjectFD[];
static clang::FunctionDecl *RSClearObjectFD[];
inline bool emptyScope() const { return mScopeStack.empty(); }
inline Scope *getCurrentScope() {
return mScopeStack.back();
}
// Returns the next available unique id for temporary variables
unsigned getNextID() { return mTempID++; }
// Initialize RSSetObjectFD and RSClearObjectFD.
static void GetRSRefCountingFunctions(clang::ASTContext &C);
// Return false if the type of variable declared in VD does not contain
// an RS object type.
static bool InitializeRSObject(clang::VarDecl *VD,
DataType *DT,
clang::Expr **InitExpr);
// Return an empty list initializer expression at the appropriate location.
// This construct can then be used to cheaply construct a zero-initializer
// for any RenderScript objects (like rs_allocation) or rs_matrix* types
// (possibly even embedded within other types). These types are expected to
// be zero-initialized always, and so we can use this helper to ensure that
// they at least have an empty initializer.
static clang::Expr *CreateEmptyInitListExpr(
clang::ASTContext &C,
const clang::SourceLocation &Loc);
// Given a return statement RS that returns an rsObject, creates a temporary
// variable, and sets it to the original return expression using rsSetObject().
// Creates a new return statement that returns the temporary variable.
// Returns a new compound statement that contains the new variable declaration,
// the rsSetOjbect() call, and the new return statement.
static clang::CompoundStmt* CreateRetStmtWithTempVar(
clang::ASTContext& C,
clang::DeclContext* DC,
clang::ReturnStmt* RS,
const unsigned id);
public:
explicit RSObjectRefCount(clang::ASTContext &C)
: mCtx(C), RSInitFD(false), mTempID(0) {
}
void Init() {
if (!RSInitFD) {
GetRSRefCountingFunctions(mCtx);
RSInitFD = true;
}
}
// For function parameters and local variables that are or contain RS objects,
// e.g., rs_allocation, this method transforms the function body to correctly
// adjust reference counts of those objects.
void HandleParamsAndLocals(clang::FunctionDecl *FD);
static clang::FunctionDecl *GetRSSetObjectFD(DataType DT) {
slangAssert(RSExportPrimitiveType::IsRSObjectType(DT));
if (DT >= 0 && DT < DataTypeMax) {
return RSSetObjectFD[DT];
} else {
slangAssert(false && "incorrect type");
return nullptr;
}
}
static clang::FunctionDecl *GetRSSetObjectFD(const clang::Type *T) {
return GetRSSetObjectFD(RSExportPrimitiveType::GetRSSpecificType(T));
}
static clang::FunctionDecl *GetRSClearObjectFD(DataType DT) {
slangAssert(RSExportPrimitiveType::IsRSObjectType(DT));
if (DT >= 0 && DT < DataTypeMax) {
return RSClearObjectFD[DT];
} else {
slangAssert(false && "incorrect type");
return nullptr;
}
}
static clang::FunctionDecl *GetRSClearObjectFD(const clang::Type *T) {
return GetRSClearObjectFD(RSExportPrimitiveType::GetRSSpecificType(T));
}
// This method creates a "guard" variable for the expression E that is object-
// typed or object-containing, e.g., a struct with object-type fields.
// It creates one or more rsSetObject() calls to set the value of the guard to E.
// This effectively increases the sysRef count of the objects referenced by E
// by 1, therefore "guarding" the objects, which might otherwise lose a
// reference and get deleted. Statements that declare the new variable and set
// the value of the new variable are added to the vector NewStmts.
//
// Parameters:
// C: The clang AST Context.
// DC: The DeclContext for any new Decl to add
// E: The expression with reference to the objects for which we want to
// increase the sysRef count
// VarName: The name to use for the new guard variable
// NewStmts: The vector for all statements added to create and set the guard.
//
// Returns:
// An expression consisting of the guard variable
//
static clang::DeclRefExpr *CreateGuard(clang::ASTContext &C,
clang::DeclContext *DC,
clang::Expr *E,
const llvm::Twine &VarName,
std::vector<clang::Stmt*> &NewStmts);
// For any function parameter that is object-typed or object-containing, if it
// is overwritten inside the function, a system reference (sysRef) count
// would decrement and may reach 0, leading the object to be deleted. This may
// create a dangling pointer reference after a call to the function.
// For example, the object in parameter a in the function below may be deleted
// before the function returns.
// void foo(rs_allocation a) { // assuming a references obj with sysRef of 1
// rs_allocation b = {};
// a = b; // decrements sysRef of obj and deletes it
// }
//
// To avoid this problem, the sysRef counts of objects contained in parameters
// --directly for object-typed parameters or indirectly as fields for struct-
// typed parameters--are incremented at the beginning of the function, and
// decremented at the end and any exiting point of the function. To achieve
// these effects, the compiler creates a temporary local variable, and calls
// rsSetObject() to set its value to that of the parameter. At the end of the
// function and at any exiting point, the compiler adds calls to
// rsClearObject() on the parameter. Each rsClearObject() call would decrement
// the sysRef count of an incoming object if the parameter is never overwritten
// in the function, or it would properly decrement the sysRef count of the new
// object that the parameter is updated to in the function, since now the
// parameter is going out of scope. For example, the compiler would transform
// the previous code example into the following.
// void foo(rs_allocation a) { // assuming a references obj with sysRef of 1
// rs_allocation .rs.param.a;
// rsSetObject(&.rs.param.a, a); // sysRef of obj becomes 2
// rs_allocation b = {};
// a = b; // sysRef of obj becomes 1
// rsClearObject(&a); // sysRef of obj stays 1. obj stays undeleted.
// }
//
// This method creates the guard variable for a object-type parameter,
// named with the prefix ".rs.param." added to the parameter name. It calls
// CreateGuard() to do this. The rsClearObject() call for the parameter as
// described above is not added by this function, but by the caller of this
// function, i.e., HandleParametersAndLocals().
//
// Parameters:
// C: The clang AST Context.
// DC: The DeclContext for any new Decl to add. It should be the FunctionnDecl
// of the function being transformed.
// PD: The ParmDecl for the parameter.
// NewStmts: The vector for all statements added to create and set the guard.
//
static void CreateParameterGuard(
clang::ASTContext &C,
clang::DeclContext *DC,
clang::ParmVarDecl *PD,
std::vector<clang::Stmt*> &NewStmts);
void SetDeclContext(clang::DeclContext* DC) { mCurrentDC = DC; }
clang::DeclContext* GetDeclContext() const { return mCurrentDC; }
void VisitStmt(clang::Stmt *S);
void VisitCallExpr(clang::CallExpr *CE);
void VisitDeclStmt(clang::DeclStmt *DS);
void VisitCompoundStmt(clang::CompoundStmt *CS);
void VisitBinAssign(clang::BinaryOperator *AS);
void VisitReturnStmt(clang::ReturnStmt *RS);
// We believe that RS objects are never involved in CompoundAssignOperator.
// I.e., rs_allocation foo; foo += bar;
// Emit a global destructor to clean up RS objects.
clang::FunctionDecl *CreateStaticGlobalDtor();
};
} // namespace slang
#endif // _FRAMEWORKS_COMPILE_SLANG_SLANG_RS_OBJECT_REF_COUNT_H_ NOLINT