Fix header stack assignment in p4c-dpdk (#4100)

backends/dpdk/dpdkArch.cpp

@@ -1036,6 +1036,8 @@ const IR::Node *ConvertBinaryOperationTo2Params::postorder(IR::AssignmentStateme
     // This pass does not apply to 'bool foo = (a == b)' or 'bool foo = (a > b)' etc.
     if (right->to<IR::Operation_Relation>()) return a;
     if (auto r = right->to<IR::Operation_Binary>()) {
+        // Array Index is replaced with flattened variable for array.
+        if (right->to<IR::ArrayIndex>()) return a;
         if (!isSimpleExpression(r->right) || !isSimpleExpression(r->left))
             BUG("%1%: Statement Unroll pass failed", a);
         if (left->equiv(*r->left)) {

backends/dpdk/dpdkHelpers.cpp

@@ -217,6 +217,8 @@ bool ConvertStatementToDpdk::preorder(const IR::AssignmentStatement *a) {
             add_instr(new IR::DpdkAndStatement(left, src1Op, src2Op));
         } else if (right->is<IR::BXor>()) {
             add_instr(new IR::DpdkXorStatement(left, src1Op, src2Op));
+        } else if (right->is<IR::ArrayIndex>()) {
+            add_instr(new IR::DpdkMovStatement(a->left, a->right));
         } else {
             BUG("%1% not implemented.", right);
         }

testdata/p4_16_samples/pna-dpdk-header-stack-assignment.p4

@@ -0,0 +1,212 @@
+/* Issue #4087 p4c-dpdk back end gives error for assignment between elements of a header stack */
+#include <core.p4>
+#include <pna.p4>
+
+header eth_t {
+    bit<48> da;
+    bit<48> sa;
+    bit<16> type;
+}
+
+const bit<16> ETYPE_IPV4 = 0x800;
+
+header ipv4_t {
+    bit<4>  version;
+    bit<4>  ihl;
+    bit<6>  dscp;
+    bit<2>  ecn;
+    bit<16> length;
+    bit<16> identification;
+    bit<1>  rsvd;
+    bit<1>  df;
+    bit<1>  mf;
+    bit<13> frag_off;
+    bit<8>  ttl;
+    bit<8>  protocol;
+    bit<16> csum;
+    bit<32> src_ip;
+    bit<32> dst_ip;
+}
+
+const bit<8> IP_PROTO_IPV4 = 4;
+const bit<8> IP_PROTO_TCP = 6;
+const bit<8> IP_PROTO_UDP = 17;
+
+header udp_t {
+    bit<16> sport;
+    bit<16> dport;
+    bit<16> length;
+    bit<16> csum;
+}
+
+header tcp_t {
+    bit<16> sport;
+    bit<16> dport;
+    bit<32> seqno;
+    bit<32> ackno;
+    bit<4>  offset;
+    bit<6>  reserved;
+    bit<1>  urg;
+    bit<1>  ack;
+    bit<1>  psh;
+    bit<1>  rst;
+    bit<1>  syn;
+    bit<1>  fin;
+    bit<16> window;
+    bit<16> csum;
+    bit<16> urgptr;
+}
+
+struct parsed_headers_t {
+    eth_t         mac;
+    ipv4_t[3 + 1] ipv4;
+    udp_t         udp;
+    tcp_t         tcp;
+}
+
+struct user_meta_t {
+    bit<16> L2_packet_len_bytes;
+}
+
+control PreControlImpl(
+    in parsed_headers_t hdrs,
+    inout user_meta_t umeta,
+    in pna_pre_input_metadata_t istd,
+    inout pna_pre_output_metadata_t ostd)
+{
+    apply {
+    }
+}
+
+parser MainParserImpl(
+    packet_in pkt,
+    out parsed_headers_t hdrs,
+    inout user_meta_t umeta,
+    in pna_main_parser_input_metadata_t istd)
+{
+    state start {
+        pkt.extract(hdrs.mac);
+        transition select(hdrs.mac.type) {
+            ETYPE_IPV4: Parse_IPv4_Depth0;
+            default: accept;
+        }
+    }
+    state Parse_IPv4_Depth0 {
+        pkt.extract(hdrs.ipv4[0]);
+        transition select(hdrs.ipv4[0].protocol) {
+            IP_PROTO_IPV4: Parse_IPv4_Depth1;
+            IP_PROTO_UDP: Parse_UDP;
+            IP_PROTO_TCP: Parse_TCP;
+            default: accept;
+        }
+    }
+    state Parse_IPv4_Depth1 {
+        pkt.extract(hdrs.ipv4[1]);
+        transition select(hdrs.ipv4[1].protocol) {
+            IP_PROTO_IPV4: Parse_IPv4_Depth2;
+            IP_PROTO_UDP: Parse_UDP;
+            IP_PROTO_TCP: Parse_TCP;
+            default: accept;
+        }
+    }
+    state Parse_IPv4_Depth2 {
+        pkt.extract(hdrs.ipv4[2]);
+        transition select(hdrs.ipv4[2].protocol) {
+            IP_PROTO_UDP: Parse_UDP;
+            IP_PROTO_TCP: Parse_TCP;
+            default: accept;
+        }
+    }
+    state Parse_TCP {
+        pkt.extract(hdrs.tcp);
+        transition accept;
+    }
+    state Parse_UDP {
+        pkt.extract(hdrs.udp);
+        transition accept;
+    }
+}
+
+control MainControlImpl(
+    inout parsed_headers_t hdrs,
+    inout user_meta_t umeta,
+    in pna_main_input_metadata_t istd,
+    inout pna_main_output_metadata_t ostd)
+{
+    action encap_one_tunnel_layer_ipv4(
+        bit<48> mac_da,
+        bit<48> mac_sa,
+        bit<32> ipv4_sa,
+        bit<32> ipv4_da)
+    {
+        hdrs.ipv4[3] = hdrs.ipv4[2];
+        hdrs.ipv4[2] = hdrs.ipv4[1];
+        hdrs.ipv4[1] = hdrs.ipv4[0];
+        hdrs.ipv4[0].setInvalid();
+        hdrs.mac.da = mac_da;
+        hdrs.mac.sa = mac_sa;
+        hdrs.mac.type = ETYPE_IPV4;
+        hdrs.ipv4[0].setValid();
+        hdrs.ipv4[0].version = 4;
+        hdrs.ipv4[0].ihl = 5;
+        hdrs.ipv4[0].dscp = 5;
+        hdrs.ipv4[0].ecn = 0;
+        hdrs.ipv4[0].length = (hdrs.ipv4[0].maxSizeInBytes() +
+            umeta.L2_packet_len_bytes);
+        hdrs.ipv4[0].identification = 0;
+        hdrs.ipv4[0].rsvd = 0;
+        hdrs.ipv4[0].df = 0;
+        hdrs.ipv4[0].mf = 0;
+        hdrs.ipv4[0].frag_off = 0;
+        hdrs.ipv4[0].ttl = 64;
+        hdrs.ipv4[0].protocol = IP_PROTO_IPV4;
+        hdrs.ipv4[0].csum = 0;
+        hdrs.ipv4[0].src_ip = ipv4_sa;
+        hdrs.ipv4[0].dst_ip = ipv4_da;
+    }
+    action decap_one_tunnel_layer_just_before_eth() {
+        // Uncomment below statement when  pop_front is supported.
+        // hdrs.ipv4.pop_front(1);
+    }
+    table header_mod {
+        key = {
+            hdrs.mac.da: exact;
+        }
+        actions = {
+            @tableonly encap_one_tunnel_layer_ipv4;
+            @tableonly decap_one_tunnel_layer_just_before_eth;
+            NoAction;
+        }
+        const default_action = NoAction;
+    }
+    apply {
+        if (hdrs.mac.isValid()) {
+            header_mod.apply();
+        }
+        send_to_port((PortId_t)1);
+    }
+}
+
+control MainDeparserImpl(
+    packet_out pkt,
+    in parsed_headers_t hdrs,
+    in user_meta_t umeta,
+    in pna_main_output_metadata_t ostd)
+{
+    apply {
+        pkt.emit(hdrs.mac);
+        pkt.emit(hdrs.ipv4[0]);
+        pkt.emit(hdrs.ipv4[1]);
+        pkt.emit(hdrs.ipv4[2]);
+        pkt.emit(hdrs.ipv4[3]);
+        pkt.emit(hdrs.tcp);
+        pkt.emit(hdrs.udp);
+    }
+}
+
+PNA_NIC(
+    MainParserImpl(),
+    PreControlImpl(),
+    MainControlImpl(),
+    MainDeparserImpl()) main;
+