simplify_key_policy.h

 
#ifndef BF_P4C_MIDEND_SIMPLIFY_KEY_POLICY_H_
#define BF_P4C_MIDEND_SIMPLIFY_KEY_POLICY_H_
 
#include "midend/simplifyKey.h"
 
namespace BFN {
 
class IsPhase0 : public P4::KeyIsSimple {
 public:
    IsPhase0() {}
 
    bool isSimple(const IR::Expression *, const Visitor::Context *ctxt) override {
        while (true) {
            if (ctxt == nullptr) return false;
            auto *n = ctxt->node;
            if (n->is<IR::P4Program>()) return false;
            if (auto table = n->to<IR::P4Table>()) {
                return table->hasAnnotation("phase0"_cs);
            }
            ctxt = ctxt->parent;
        }
        return false;
    }
};
 
class IsSlice : public P4::KeyIsSimple {
 public:
    IsSlice() {}
 
    bool isSimple(const IR::Expression *expr, const Visitor::Context *) override {
        auto slice = expr->to<IR::Slice>();
        if (!slice) return false;
        auto *e = slice->e0;
        while (e->is<IR::Member>()) e = e->to<IR::Member>()->expr;
        return e->to<IR::PathExpression>() != nullptr;
    }
};
 
// Extend P4::IsMask to handle Slices
// E.g. hdr.ethernet.smac[15:0] & 0x1f1f
// This is a valid key which contains a field slice and a mask
// Frontend IsMask only handles non sliced fields on masks.
class IsSliceMask : public P4::IsMask {
    void postorder(const IR::Slice *) override {}
    void postorder(const IR::Constant *) override {
        // Only skip constants under a Slice
        if (!getParent<IR::Slice>()) simple = false;
    }
 
 public:
    IsSliceMask() { setName("IsSlicMask"); }
 
    bool isSimple(const IR::Expression *expr, const Visitor::Context *ctxt) override {
        return P4::IsMask::isSimple(expr, ctxt);
    }
};
 
class KeyIsSimple {
 public:
    static P4::KeyIsSimple *getPolicy(P4::TypeMap &typeMap) {
        return new P4::OrPolicy(
            new P4::OrPolicy(new P4::OrPolicy(new P4::IsValid(&typeMap), new P4::IsMask()),
                             new BFN::IsPhase0()),
            new P4::OrPolicy(new BFN::IsSlice(), new BFN::IsSliceMask()));
    }
};
 
}  // namespace BFN
 
#endif /* BF_P4C_MIDEND_SIMPLIFY_KEY_POLICY_H_ */