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