Convert expressions so that each expression contains at most one side effect. More...

#include <sideEffects.h>

Inheritance diagram for P4::DoSimplifyExpressions:

Public Member Functions
	DoSimplifyExpressions (TypeMap typeMap, std::set< const IR::Expression > *added)

void	end_apply (const IR::Node *) override

profile_t	init_apply (const IR::Node *node) override

const IR::Node *	postorder (IR::AssignmentStatement *statement) override

const IR::Node *	postorder (IR::Expression *expression) override

const IR::Node *	postorder (IR::Function *function) override

const IR::Node *	postorder (IR::MethodCallStatement *statement) override

const IR::Node *	postorder (IR::P4Action *action) override

const IR::Node *	postorder (IR::P4Control *control) override

const IR::Node *	postorder (IR::P4Parser *parser) override

const IR::Node *	postorder (IR::ParserState *state) override

const IR::Node *	postorder (IR::ReturnStatement *statement) override

const IR::Node *	preorder (IR::Annotation *anno) override

const IR::Node *	preorder (IR::ArrayIndex *expression) override

const IR::Node *	preorder (IR::ConstructorCallExpression *cce) override

const IR::Node *	preorder (IR::ForInStatement *statement) override

const IR::Node *	preorder (IR::ForStatement *statement) override

const IR::Node *	preorder (IR::IfStatement *statement) override

const IR::Node *	preorder (IR::LAnd *expression) override

const IR::Node *	preorder (IR::ListExpression *expression) override

const IR::Node *	preorder (IR::Literal *expression) override

const IR::Node *	preorder (IR::LOr *expression) override

const IR::Node *	preorder (IR::Member *expression) override

const IR::Node *	preorder (IR::MethodCallExpression *mce) override

const IR::Node *	preorder (IR::Mux *expression) override

const IR::Node *	preorder (IR::Operation_Binary *expression) override

const IR::Node *	preorder (IR::Operation_Unary *expression) override

const IR::Node *	preorder (IR::Property *prop) override

const IR::Node *	preorder (IR::SelectExpression *expression) override

const IR::Node *	preorder (IR::StructExpression *expression) override

const IR::Node *	preorder (IR::SwitchStatement *statement) override

const IR::Node *	shortCircuit (IR::Operation_Binary *expression)

Public Member Functions inherited from P4::Transform
const IR::Node *	apply_visitor (const IR::Node , const char name=0) override

profile_t	init_apply (const IR::Node *root) override

virtual void	loop_revisit (const IR::Node *)

virtual const IR::Node *	postorder (IR::Node *n)

virtual const IR::Node *	preorder (IR::Node *n)

void	prune ()

virtual void	revisit (const IR::Node , const IR::Node )

void	revisit_visited ()

bool	visit_in_progress (const IR::Node *) const

void	visitAgain () const override

void	visitOnce () const override

Public Member Functions inherited from P4::Visitor
virtual bool	check_global (cstring)

virtual void	clear_globals ()

virtual Visitor *	clone () const

virtual ControlFlowVisitor *	controlFlowVisitor ()

virtual void	end_apply ()

virtual void	erase_global (cstring)

template<class T >
const T *	findContext () const

template<class T >
const T *	findContext (const Context *&c) const

template<class T >
const T *	findOrigCtxt () const

template<class T >
const T *	findOrigCtxt (const Context *&c) const

virtual Visitor &	flow_clone ()

virtual void	flow_merge (Visitor &)

virtual bool	flow_merge_closure (Visitor &)

virtual void	flow_merge_global_from (cstring)

virtual void	flow_merge_global_to (cstring)

const Context *	getChildContext () const

int	getChildrenVisited () const

const Context *	getContext () const

int	getContextDepth () const

const IR::Node *	getCurrentNode () const

template<class T >
const T *	getCurrentNode () const

const IR::Node *	getOriginal () const

template<class T >
const T *	getOriginal () const

template<class T >
const T *	getParent () const

virtual bool	has_flow_joins () const

profile_t	init_apply (const IR::Node root, const Context parent_context)

bool	isInContext (const IR::Node *n) const

virtual const char *	name () const

template<class T >
void	parallel_visit (const IR::Vector< T > &v, const char *name, int cidx)

template<class T >
void	parallel_visit (const IR::Vector< T > &v, const char *name=0)

template<class T >
void	parallel_visit (IR::Vector< T > &v, const char *name, int cidx)

template<class T >
void	parallel_visit (IR::Vector< T > &v, const char *name=0)

void	print_context () const

const Visitor &	setCalledBy (const Visitor *visitor)

void	setName (const char *name)

void	visit (const IR::Node &n, const char *name, int cidx)

void	visit (const IR::Node &n, const char *name=0)

void	visit (const IR::Node &n, const char name, int cidx)

void	visit (const IR::Node &n, const char name=0)

void	visit (const IR::Node const &n, const char name, int cidx)

void	visit (const IR::Node const &n, const char name=0)

void	visit (IR::Node &n, const char *name, int cidx)

void	visit (IR::Node &n, const char *name=0)

void	visit (IR::Node &, const char =0, int=0)

template<class T , typename = std::enable_if_t<Util::has_SourceInfo_v<T> && !std::is_pointer_v<T>>, class... Args>
void	warn (const int kind, const char *format, const T &node, Args &&...args)
	The const ref variant of the above.

template<class T , typename = std::enable_if_t<Util::has_SourceInfo_v<T>>, class... Args>
void	warn (const int kind, const char format, const T node, Args &&...args)

bool	warning_enabled (int warning_kind) const

Public Member Functions inherited from P4::ResolutionContext
const IR::IDeclaration *	getDeclaration (const IR::Path *path, bool notNull=false) const

const IR::IDeclaration *	getDeclaration (const IR::This *, bool notNull=false) const

auto	getDeclarations (const IR::INamespace *ns) const
	Returns the set of decls that exist in the given namespace.

auto	getDeclsByName (const IR::INamespace *ns, cstring name) const
	Returns the set of decls with the given name that exist in the given namespace.

std::vector< const IR::IDeclaration * >	resolve (const IR::ID &name, ResolutionType type) const
	Resolve references for `name`, restricted to `type` declarations.

virtual const IR::IDeclaration *	resolvePath (const IR::Path *path, bool isType) const

const IR::Type *	resolveType (const IR::Type *type) const
	Resolve a refrence to a type `type`.

const IR::IDeclaration *	resolveUnique (const IR::ID &name, ResolutionType type, const IR::INamespace *=nullptr) const
	Resolve reference for `name`, restricted to `type` declarations, and expect one result.

Public Member Functions inherited from P4::DeclarationLookup

Additional Inherited Members
Public Types inherited from P4::Visitor
typedef Visitor_Context	Context

Static Public Member Functions inherited from P4::Visitor
static cstring	demangle (const char *)

static bool	warning_enabled (const Visitor *visitor, int warning_kind)

Public Attributes inherited from P4::Visitor
const Visitor *	called_by = nullptr

cstring	internalName

SplitFlowVisit_base *&	split_link

SplitFlowVisit_base *	split_link_mem = nullptr

Protected Member Functions inherited from P4::Transform
const IR::Node *	transform_child (const IR::Node *child)

Protected Member Functions inherited from P4::Visitor
virtual void	init_join_flows (const IR::Node *)

virtual bool	join_flows (const IR::Node *)

virtual void	post_join_flows (const IR::Node , const IR::Node )

void	visit_children (const IR::Node *, std::function< void()> fn)

Protected Member Functions inherited from P4::ResolutionContext
	ResolutionContext (bool ao)

std::vector< const IR::IDeclaration * >	lookup (const IR::INamespace *ns, const IR::ID &name, ResolutionType type) const

std::vector< const IR::IDeclaration * >	lookupMatchKind (const IR::ID &name) const

const IR::Vector< IR::Argument > *	methodArguments (cstring name) const
	We are resolving a method call. Find the arguments from the context.

Protected Attributes inherited from P4::Transform
bool	forceClone = false

Protected Attributes inherited from P4::Visitor
bool	dontForwardChildrenBeforePreorder = false

bool	joinFlows = false

bool	visitDagOnce = true

Protected Attributes inherited from P4::ResolutionContext
bool	anyOrder = false

Detailed Description

Convert expressions so that each expression contains at most one side effect.

Left-values are converted to contain no side-effects. An important consequence of this pass is that it converts function calls so that no two parameters (one of which is output) can alias. This makes the job of the inliner simpler. For example:

The expression a[f(x)] = b; is converted to tmp = f(x); a[tmp] = b;
And m(n()) is converted to tmp = n(); m(tmp)

This is especially tricky for handling out and inout arguments. Consider two function prototypes, bit f(inout T a, in T b); T g(inout T c);. The expression a[g(w)].x = f(a[1].x, g(a[1].x)); is translated as

T tmp1 = g(w);           // modifies w
T tmp2 = a[1].x;         // save a[1].x
T tmp3 = g(a[1].x);      // modifies a[1].x
T tmp4 = f(tmp2, tmp3);  // modifies tmp2
a[1].x = tmp2;           // copy tmp2 to a[1].x - out argument
a[tmp1].x = tmp4;        // assign result of call of f to actual left value

Translating function calls proceeds as follows:

arguments are evaluated in order
inout and out arguments produce left-values—these are "saved"
function is called with temporaries for all arguments
out and inout temporaries are copied to the saved left-values in order

For assignment statements e = e1; the left hand side is evaluated first.

Member Function Documentation

◆ end_apply()

void P4::DoSimplifyExpressions::end_apply ( const IR::Node * )

overridevirtual

Reimplemented from P4::Visitor.

◆ init_apply()

Visitor::profile_t P4::DoSimplifyExpressions::init_apply ( const IR::Node * node )