[bmv2] conditional execution + negation

[smolkaj]

Invoking a table inside the condition of a if-then statement leads to the following error:

terminate called after throwing an instance of 'Util::CompilerBug'
  what():  COMPILER BUG: ../backends/bmv2/jsonconverter.cpp:202
multicast.p4(397): do_process_multicast_do_process_ipv4_multicast_ipv4_multicast_bridge;: could not convert to Json
            if(!ipv4_multicast_bridge.apply().hit) {
                ^^^^^^^^^^^^^^^^^^^^^

Here is a minimal example:

#include <core.p4>
#include <v1model.p4>

struct H { };
struct M { };

parser ParserI(packet_in pk, out H hdr, inout M meta, inout standard_metadata_t smeta) {
    state start { transition accept; }
}

control IngressI(inout H hdr, inout M meta, inout standard_metadata_t smeta) {
    
    table t {
        key = {}
        actions = { NoAction; }
    }
    apply {
        // works when removing the `!`
        if(!t.apply().hit) {

        }
    }
}

control EgressI(inout H hdr, inout M meta, inout standard_metadata_t smeta) {
    apply { }
}

control DeparserI(packet_out pk, in H hdr) {
    apply { }
}

control VerifyChecksumI(in H hdr, inout M meta) {
    apply { }
}

control ComputeChecksumI(inout H hdr, inout M meta) {
    apply { }
}


V1Switch(ParserI(), VerifyChecksumI(), IngressI(), EgressI(),
         ComputeChecksumI(), DeparserI()) main;

Interestingly, there is no problem when removing the logical negation !.

[smolkaj]

fixed