P4C
The P4 Compiler
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#include <instruction_adjustment.h>
Public Member Functions | |
AdjustShiftInstructions (const PhvInfo &p) | |
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 | end_apply (const IR::Node *root) |
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 |
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 Attributes inherited from P4::Transform | |
bool | forceClone = false |
Protected Attributes inherited from P4::Visitor | |
bool | dontForwardChildrenBeforePreorder = false |
bool | joinFlows = false |
bool | visitDagOnce = true |
The purpose of this pass is to adjust shift instruction that only write to a single slice but sourced from multiple containers. This is only seen with signed shifted right operation currently since all of the unsigned shift operation are either sliced or splitted. This pass have to adjust the operation, shift value and slice boundary to match the expected result. For example these P4_14 lines: header_type my_header_t { fields { a: 32; } } header my_header_t my_header; header_type my_md_t { fields { a: 32 (signed); } } ... modify_field_with_shift(my_header.a, my_md.a, 9, 0xff);
Will be translated by the compiler to this operation: instruction:shrs(ingress::my_header.a[7:0], ingress::my_md.a[7:0], 9);
As we can see, this operation does not make any sense but the compiler does not decode the shift value to adjust the slice so the source and destination slice will always be at the same position regardless of the shift value. This pass will translate such instructions using shrs, set or funnel-shift depending on the situation. The example above will get translated to: instruction:funnel-shift(ingress::my_header.a[7:0], ingress::my_md.a[23:16], ingress::my_md.a[15:8], 1)