Framework for copy-on-write visitors (WIP)

- COWptr/COWref objects that support cloning on demand to allow writes
- Lots of autogenerated code for IR classes to make things work
  transparently
- specialization for vectors/maps etc
- rename IR::MAU::Primitive -> IR::MAU::MauPrimitive to avoid name
  ambiguity with IR::Primitive

Signed-off-by: Chris Dodd <cdodd@nvidia.com>

Author: ChrisDodd

backends/tofino/bf-p4c/common/check_for_unimplemented_features.cpp

@@ -21,15 +21,15 @@
 #include "lib/error_reporter.h"
 
 std::optional<const IR::Operation_Binary *> CheckOperations::getSrcBinop(
-    const IR::MAU::Primitive *prim) const {
+    const IR::MAU::MauPrimitive *prim) const {
     prim = prim->apply(RemoveCasts());
     if (prim->name != "modify_field") return std::nullopt;
     if (prim->operands.size() < 2) return std::nullopt;
     if (auto *binop = prim->operands[1]->to<IR::Operation_Binary>()) return binop;
     return std::nullopt;
 }
 
-bool CheckOperations::isModBitMask(const IR::MAU::Primitive *prim) const {
+bool CheckOperations::isModBitMask(const IR::MAU::MauPrimitive *prim) const {
     auto *binop = getSrcBinop(prim).value_or(nullptr);
     if (!binop || binop->getStringOp() != "|") return false;
     auto leftBinop = binop->left->to<IR::Operation_Binary>();
@@ -38,7 +38,7 @@ bool CheckOperations::isModBitMask(const IR::MAU::Primitive *prim) const {
     return leftBinop->getStringOp() == "&" && rightBinop->getStringOp() == "&";
 }
 
-bool CheckOperations::preorder(const IR::MAU::Primitive *prim) {
+bool CheckOperations::preorder(const IR::MAU::MauPrimitive *prim) {
     if (isModBitMask(prim))
         error("The following operation is not yet supported: %1%", prim->srcInfo);
     return true;

backends/tofino/bf-p4c/common/check_for_unimplemented_features.h

@@ -41,17 +41,17 @@ class CheckOperations : public Inspector {
 
     /// @returns BOP in modify_field(x, BOP), if BOP is a binary operation
     /// expression.
-    std::optional<const IR::Operation_Binary *> getSrcBinop(const IR::MAU::Primitive *p) const;
+    std::optional<const IR::Operation_Binary *> getSrcBinop(const IR::MAU::MauPrimitive *p) const;
 
     /// @returns true if @p is a P4_16 encoding of a P4_14 funnel shift
     /// operation, eg. modify_field(x, (y ++ z) >> n).
-    bool isFunnelShift(const IR::MAU::Primitive *p) const;
+    bool isFunnelShift(const IR::MAU::MauPrimitive *p) const;
 
     /// @returns true if @p is a P4_16 encoding of a P4_14 bitmasked modify_field
     /// operation, eg. modify_field(x, val, 0xAA).
-    bool isModBitMask(const IR::MAU::Primitive *p) const;
+    bool isModBitMask(const IR::MAU::MauPrimitive *p) const;
 
-    bool preorder(const IR::MAU::Primitive *) override;
+    bool preorder(const IR::MAU::MauPrimitive *) override;
 };
 
 class CheckForUnimplementedFeatures : public PassManager {

backends/tofino/bf-p4c/common/extract_maupipe.cpp

@@ -242,10 +242,10 @@ class ConvertMethodCalls : public MauTransform {
         return prim;
     }
 
-    const IR::MAU::Primitive *postorder(IR::MAU::Primitive *prim) {
+    const IR::MAU::MauPrimitive *postorder(IR::MAU::MauPrimitive *prim) {
         if (prim->name == "method_call_init") {
             BUG_CHECK(prim->operands.size() == 1, "method call initialization failed");
-            if (auto *p = prim->operands.at(0)->to<IR::MAU::Primitive>())
+            if (auto *p = prim->operands.at(0)->to<IR::MAU::MauPrimitive>())
                 return p;
             else if (prim->operands.at(0)->is<IR::Member>())
                 // comes from a bare "isValid" call -- is a noop
@@ -379,7 +379,8 @@ class ActionBodySetup : public Inspector {
         if (!af->exitAction) {
             cstring pname = "modify_field"_cs;
             if (assign->left->type->is<IR::Type_Header>()) pname = "copy_header"_cs;
-            auto prim = new IR::MAU::Primitive(assign->srcInfo, pname, assign->left, assign->right);
+            auto prim =
+                new IR::MAU::MauPrimitive(assign->srcInfo, pname, assign->left, assign->right);
             prim->in_hash = InHashAnnot();
             af->action.push_back(prim);
         }
@@ -388,7 +389,7 @@ class ActionBodySetup : public Inspector {
     bool preorder(const IR::MethodCallStatement *mc) override {
         if (!af->exitAction) {
             auto mc_init =
-                new IR::MAU::Primitive(mc->srcInfo, "method_call_init"_cs, mc->methodCall);
+                new IR::MAU::MauPrimitive(mc->srcInfo, "method_call_init"_cs, mc->methodCall);
             af->action.push_back(mc_init);
         }
         return false;
@@ -1293,7 +1294,7 @@ void AttachTables::InitializeStatefulAlus ::updateAttachedSalu(const IR::Declara
     }
     if (ext->type->toString().startsWith("LearnAction")) salu->learn_action = true;
 
-    auto prim = findContext<IR::MAU::Primitive>();
+    auto prim = findContext<IR::MAU::MauPrimitive>();
     LOG6("  - " << (prim ? prim->name.c_str() : "<no primitive>"));
     if (prim && prim->name.endsWith(".address")) {
         salu->chain_vpn = true;
@@ -1340,7 +1341,7 @@ void AttachTables::InitializeStatefulAlus::postorder(const IR::GlobalRef *gref)
  * Gathers information about register params and checks
  * that they are used in a single stateful ALU.
  */
-bool AttachTables::InitializeRegisterParams::preorder(const IR::MAU::Primitive *prim) {
+bool AttachTables::InitializeRegisterParams::preorder(const IR::MAU::MauPrimitive *prim) {
     if (prim->name != "RegisterParam.read") return true;
     const IR::Declaration_Instance *reg_param_decl = nullptr;
     if (auto *gr = prim->operands.at(0)->to<IR::GlobalRef>())

backends/tofino/bf-p4c/common/extract_maupipe.h

@@ -126,7 +126,7 @@ class AttachTables : public PassManager {
         ordered_map<const IR::Declaration_Instance *,
                     IR::MAU::StatefulAlu *>
             param_salus;  // RegisterParam -> StatefulAlu
-        bool preorder(const IR::MAU::Primitive *prim) override;
+        bool preorder(const IR::MAU::MauPrimitive *prim) override;
         void end_apply() override;
 
      public:

backends/tofino/bf-p4c/common/field_defuse.cpp

@@ -384,13 +384,13 @@ bool FieldDefUse::preorder(const IR::MAU::Action *act) {
     return false;
 }
 
-bool FieldDefUse::preorder(const IR::MAU::Primitive *prim) {
+bool FieldDefUse::preorder(const IR::MAU::MauPrimitive *prim) {
     // TODO: consider h.f1 = h.f1 + 1; When we visit it,
     // we should first visit the source on the RHS, as how hardware does.
     // The h.f1 on RHS is an use of previous def, and the one on LHS is a
     // write that clears the previous defs from this point.
     // TODO: The long-term fix for this is to change the order of visiting when
-    // visiting IR::MAU::Primitive to the evaluation order defined in spec,
+    // visiting IR::MAU::MauPrimitive to the evaluation order defined in spec,
     // to make control flow visit correct.
     LOG6("FieldDefUse preorder Primitive : " << prim << IndentCtl::indent);
     if (prim->operands.size() > 0) {

backends/tofino/bf-p4c/common/field_defuse.h

@@ -155,7 +155,7 @@ class FieldDefUse : public BFN::ControlFlowVisitor, public Inspector, TofinoWrit
     bool preorder(const IR::BFN::LoweredParser *p) override;
     bool preorder(const IR::MAU::Table *t) override;
     void postorder(const IR::MAU::Table *t) override;
-    bool preorder(const IR::MAU::Primitive *prim) override;
+    bool preorder(const IR::MAU::MauPrimitive *prim) override;
     bool preorder(const IR::MAU::Action *p) override;
     bool preorder(const IR::MAU::StatefulAlu *prim) override;
     bool preorder(const IR::Expression *e) override;

backends/tofino/bf-p4c/common/header_stack.cpp

@@ -51,7 +51,7 @@ void CollectHeaderStackInfo::postorder(IR::HeaderStack *hs) {
         i.inThread[INGRESS] = false;
 }
 
-void CollectHeaderStackInfo::postorder(IR::MAU::Primitive *prim) {
+void CollectHeaderStackInfo::postorder(IR::MAU::MauPrimitive *prim) {
     if (prim->name == "push_front" || prim->name == "pop_front") {
         LOG3("CollectHeaderStackInfo: visiting " << prim);
         BUG_CHECK(prim->operands.size() == 2, "wrong number of operands to %s", prim);
@@ -147,8 +147,8 @@ IR::Node *RemovePushInitialization::preorder(IR::MAU::Action *act) {
     // then cleared when an initialization is found.
     ordered_map<cstring, bitvec> pushed_inits;
 
-    ordered_map<cstring, const IR::MAU::Primitive *> push_prims;
-    IR::Vector<IR::MAU::Primitive> to_keep;
+    ordered_map<cstring, const IR::MAU::MauPrimitive *> push_prims;
+    IR::Vector<IR::MAU::MauPrimitive> to_keep;
 
     for (auto *prim : act->action) {
         to_keep.push_back(prim);

backends/tofino/bf-p4c/common/header_stack.h

@@ -39,7 +39,7 @@ struct CollectHeaderStackInfo : public Modifier {
  private:
     Visitor::profile_t init_apply(const IR::Node *root) override;
     void postorder(IR::HeaderStack *stack) override;
-    void postorder(IR::MAU::Primitive *primitive) override;
+    void postorder(IR::MAU::MauPrimitive *primitive) override;
     void postorder(IR::BFN::Pipe *pipe) override;
 
     BFN::HeaderStackInfo *stacks;

backends/tofino/bf-p4c/ir/gateway_control_flow.h

@@ -56,6 +56,9 @@ class GatewayControlFlow : public virtual ControlFlowVisitor {
 
  public:
     virtual void pre_visit_table_next(const IR::MAU::Table *tbl, cstring tags) = 0;
+    void pre_visit_table_next(IR::COWptr<IR::MAU::Table> tbl, cstring tags) {
+        pre_visit_table_next(tbl.get(), tags);
+    }
 };
 
 }  // end namespace BFN

backends/tofino/bf-p4c/ir/mau.cpp

@@ -37,6 +37,7 @@ namespace MAU {
 // function templates to be in the same compilation unit.
 void Table::visit_children(Visitor &v, const char *n) { visit_children(this, v, n); }
 void Table::visit_children(Visitor &v, const char *n) const { visit_children(this, v, n); }
+void Table::COWref::visit_children(Visitor &v, const char *n) { Table::visit_children(this, v, n); }
 
 /**
  * The potential control flow(s) through an IR::MAU::Table object are quite complex, which
@@ -167,7 +168,7 @@ void Table::visit_gateway_inhibited(THIS *self, Visitor &v, const char *,
     std::set<cstring> gw_tags_seen;
     bool fallen_through = false;
     for (auto &gw : self->gateway_rows) {
-        auto tag = gw.second;
+        cstring tag = gw.second;
         if (!tag || gw_tags_seen.count(tag)) continue;
 
         gw_tags_seen.emplace(tag);