Alternate strength reduction and constant folding to eliminate constants

backends/bmv2/common/lower.cpp

@@ -31,7 +31,7 @@ const IR::Expression* LowerExpressions::shift(const IR::Operation_Binary* expres
     auto rhs = expression->right;
     auto rhstype = typeMap->getType(rhs, true);
     if (rhstype->is<IR::Type_InfInt>()) {
-        auto cst = rhs->to<IR::Constant>();
+        auto cst = rhs->checkedTo<IR::Constant>();
         big_int maxShift = Util::shift_left(1, LowerExpressions::maxShiftWidth);
         if (cst->value > maxShift)
             ::error(ErrorType::ERR_OVERLIMIT, "%1%: shift amount limited to %2% on this target",

backends/bmv2/psa_switch/midend.cpp

@@ -140,8 +140,8 @@ PsaSwitchMidEnd::PsaSwitchMidEnd(CompilerOptions& options, std::ostream* outStre
             new P4::MoveDeclarations(),  // more may have been introduced
             new P4::ConstantFolding(&refMap, &typeMap),
             new P4::LocalCopyPropagation(&refMap, &typeMap, nullptr, policy),
-            new P4::ConstantFolding(&refMap, &typeMap),
-            new P4::StrengthReduction(&refMap, &typeMap),
+            new PassRepeated({new P4::ConstantFolding(&refMap, &typeMap),
+                              new P4::StrengthReduction(&refMap, &typeMap)}),
             new P4::MoveDeclarations(),
             new P4::ValidateTableProperties({"psa_implementation", "psa_direct_counter",
                                              "psa_direct_meter", "psa_idle_timeout", "size"}),

backends/bmv2/psa_switch/psaSwitch.cpp

@@ -275,7 +275,8 @@ void PsaSwitchBackend::convert(const IR::ToplevelBlock* tlb) {
         new P4::TypeChecking(refMap, typeMap),
         new P4::SimplifyControlFlow(refMap, typeMap),
         new LowerExpressions(typeMap),
-        new P4::ConstantFolding(refMap, typeMap, false),
+        new PassRepeated(
+            {new P4::ConstantFolding(refMap, typeMap), new P4::StrengthReduction(refMap, typeMap)}),
         new P4::TypeChecking(refMap, typeMap),
         new P4::RemoveComplexExpressions(refMap, typeMap,
                                          new ProcessControls(&structure.pipeline_controls)),

backends/bmv2/simple_switch/midend.cpp

@@ -98,8 +98,8 @@ SimpleSwitchMidEnd::SimpleSwitchMidEnd(CompilerOptions& options, std::ostream* o
              new P4::MoveDeclarations(),  // more may have been introduced
              new P4::ConstantFolding(&refMap, &typeMap),
              new P4::LocalCopyPropagation(&refMap, &typeMap),
-             new P4::ConstantFolding(&refMap, &typeMap),
-             new P4::StrengthReduction(&refMap, &typeMap),
+             new PassRepeated({new P4::ConstantFolding(&refMap, &typeMap),
+                               new P4::StrengthReduction(&refMap, &typeMap)}),
              new P4::SimplifyKey(
                  &refMap, &typeMap,
                  new P4::OrPolicy(new P4::IsValid(&refMap, &typeMap), new P4::IsMask())),

backends/dpdk/midend.cpp

@@ -212,7 +212,8 @@ DpdkMidEnd::DpdkMidEnd(CompilerOptions& options, std::ostream* outStream) {
             new P4::MoveDeclarations(),  // more may have been introduced
             new P4::ConstantFolding(&refMap, &typeMap),
             new P4::LocalCopyPropagation(&refMap, &typeMap, nullptr, policy),
-            new P4::ConstantFolding(&refMap, &typeMap),
+            new PassRepeated({new P4::ConstantFolding(&refMap, &typeMap),
+                              new P4::StrengthReduction(&refMap, &typeMap)}),
             new P4::MoveDeclarations(),
             validateTableProperties(options.arch),
             new P4::SimplifyControlFlow(&refMap, &typeMap),

backends/ebpf/midend.cpp

@@ -92,7 +92,8 @@ const IR::ToplevelBlock* MidEnd::run(EbpfOptions& options, const IR::P4Program*
              new P4::ExpandEmit(&refMap, &typeMap),
              new P4::HandleNoMatch(&refMap),
              new P4::SimplifyParsers(&refMap),
-             new P4::StrengthReduction(&refMap, &typeMap),
+             new PassRepeated({new P4::ConstantFolding(&refMap, &typeMap),
+                               new P4::StrengthReduction(&refMap, &typeMap)}),
              new P4::SimplifyComparisons(&refMap, &typeMap),
              new P4::EliminateTuples(&refMap, &typeMap),
              new P4::SimplifySelectList(&refMap, &typeMap),

backends/ubpf/midend.cpp

@@ -86,7 +86,9 @@ const IR::ToplevelBlock* MidEnd::run(EbpfOptions& options, const IR::P4Program*
              new P4::ConstantFolding(&refMap, &typeMap),
              // accept non-constant keysets
              new P4::SimplifySelectCases(&refMap, &typeMap, false), new P4::HandleNoMatch(&refMap),
-             new P4::SimplifyParsers(&refMap), new P4::StrengthReduction(&refMap, &typeMap),
+             new P4::SimplifyParsers(&refMap),
+             new PassRepeated({new P4::ConstantFolding(&refMap, &typeMap),
+                               new P4::StrengthReduction(&refMap, &typeMap)}),
              new P4::SimplifyComparisons(&refMap, &typeMap),
              new P4::CopyStructures(&refMap, &typeMap),
              new P4::LocalCopyPropagation(&refMap, &typeMap),

testdata/p4_16_samples/issue3702-bmv2.p4

@@ -0,0 +1,105 @@
+//#include "third_party/p4lang_p4c/p4include/core.p4"
+//#include "third_party/p4lang_p4c/p4include/v1model.p4"
+#include "core.p4"
+#include "v1model.p4"
+
+typedef bit<48> ethernet_addr_t;
+typedef bit<32> ipv4_addr_t;
+
+// Enums
+enum bit <16> EtherType {
+ETYPE_IPV4 = 0x0800
+};
+
+// Header definitions
+header ethernet_t {
+ethernet_addr_t da; // destination address
+ethernet_addr_t sa; // source address
+bit<16> type; // First (mandatory) Ethertype field
+}
+
+header ipv4_t {
+bit<4> version;
+bit<4> ihl;
+bit<6> dscp; // The 6 most significant bits of the diff_serv field.
+bit<2> ecn; // The 2 least significant bits of the diff_serv field.
+bit<16> total_len;
+bit<16> identification;
+bit<1> reserved;
+bit<1> do_not_fragment;
+bit<1> more_fragments;
+bit<13> frag_offset;
+bit<8> ttl;
+bit<8> protocol;
+bit<16> header_checksum;
+ipv4_addr_t src_addr;
+ipv4_addr_t dst_addr;
+}
+
+header ipv4_options_t {
+varbit<480> options;
+}
+
+// Set of extracted headers.
+struct headers_t {
+ethernet_t mac; // mac header
+ipv4_options_t ip; // v4/v6 union
+}
+
+// Required metadata structure.
+struct local_metadata_t {
+
+}
+
+// Signature is governed by the architecture (PNA)
+parser v1model_parser(packet_in pkt, out headers_t hdrs,
+inout local_metadata_t local_meta,
+inout standard_metadata_t standard_meta) {
+state start {
+pkt.extract(hdrs.mac);
+transition select(hdrs.mac.type) {
+EtherType.ETYPE_IPV4 : parse_ipv4;
+default: accept;
+}
+}
+
+state parse_ipv4 {
+ipv4_t ipv4 = pkt.lookahead<ipv4_t>();
+bit<32> byte_len = ((bit<32>)(ipv4.ihl & 0xF)) << 2;
+pkt.extract(hdrs.ip, byte_len << 3);
+transition accept;
+}
+
+}
+
+control compute_ip_checksum(inout headers_t headers,
+inout local_metadata_t local_metadata) {
+apply {
+}
+}
+control verify_ip_checksum(inout headers_t headers,
+inout local_metadata_t local_metadata) {
+apply {
+}
+}
+
+control egress(inout headers_t headers,
+inout local_metadata_t local_metadata,
+inout standard_metadata_t standard_metadata) {
+apply {
+}
+}
+control ingress(inout headers_t headers,
+inout local_metadata_t local_metadata,
+inout standard_metadata_t standard_metadata) {
+apply {
+}
+}
+
+control deparser(packet_out packet, in headers_t headers) {
+apply {
+}
+}
+
+// Main invocation
+V1Switch(v1model_parser(), verify_ip_checksum(), ingress(), egress(), compute_ip_checksum(), deparser()) main;

testdata/p4_16_samples_outputs/issue3702-bmv2-first.p4

@@ -0,0 +1,88 @@
+#include <core.p4>
+#define V1MODEL_VERSION 20180101
+#include <v1model.p4>
+
+typedef bit<48> ethernet_addr_t;
+typedef bit<32> ipv4_addr_t;
+enum bit<16> EtherType {
+    ETYPE_IPV4 = 16w0x800
+}
+
+header ethernet_t {
+    ethernet_addr_t da;
+    ethernet_addr_t sa;
+    bit<16>         type;
+}
+
+header ipv4_t {
+    bit<4>      version;
+    bit<4>      ihl;
+    bit<6>      dscp;
+    bit<2>      ecn;
+    bit<16>     total_len;
+    bit<16>     identification;
+    bit<1>      reserved;
+    bit<1>      do_not_fragment;
+    bit<1>      more_fragments;
+    bit<13>     frag_offset;
+    bit<8>      ttl;
+    bit<8>      protocol;
+    bit<16>     header_checksum;
+    ipv4_addr_t src_addr;
+    ipv4_addr_t dst_addr;
+}
+
+header ipv4_options_t {
+    varbit<480> options;
+}
+
+struct headers_t {
+    ethernet_t     mac;
+    ipv4_options_t ip;
+}
+
+struct local_metadata_t {
+}
+
+parser v1model_parser(packet_in pkt, out headers_t hdrs, inout local_metadata_t local_meta, inout standard_metadata_t standard_meta) {
+    state start {
+        pkt.extract<ethernet_t>(hdrs.mac);
+        transition select(hdrs.mac.type) {
+            EtherType.ETYPE_IPV4: parse_ipv4;
+            default: accept;
+        }
+    }
+    state parse_ipv4 {
+        ipv4_t ipv4 = pkt.lookahead<ipv4_t>();
+        bit<32> byte_len = (bit<32>)ipv4.ihl << 2;
+        pkt.extract<ipv4_options_t>(hdrs.ip, byte_len << 3);
+        transition accept;
+    }
+}
+
+control compute_ip_checksum(inout headers_t headers, inout local_metadata_t local_metadata) {
+    apply {
+    }
+}
+
+control verify_ip_checksum(inout headers_t headers, inout local_metadata_t local_metadata) {
+    apply {
+    }
+}
+
+control egress(inout headers_t headers, inout local_metadata_t local_metadata, inout standard_metadata_t standard_metadata) {
+    apply {
+    }
+}
+
+control ingress(inout headers_t headers, inout local_metadata_t local_metadata, inout standard_metadata_t standard_metadata) {
+    apply {
+    }
+}
+
+control deparser(packet_out packet, in headers_t headers) {
+    apply {
+    }
+}
+
+V1Switch<headers_t, local_metadata_t>(v1model_parser(), verify_ip_checksum(), ingress(), egress(), compute_ip_checksum(), deparser()) main;

testdata/p4_16_samples_outputs/issue3702-bmv2-frontend.p4

@@ -0,0 +1,90 @@
+#include <core.p4>
+#define V1MODEL_VERSION 20180101
+#include <v1model.p4>
+
+typedef bit<48> ethernet_addr_t;
+typedef bit<32> ipv4_addr_t;
+enum bit<16> EtherType {
+    ETYPE_IPV4 = 16w0x800
+}
+
+header ethernet_t {
+    ethernet_addr_t da;
+    ethernet_addr_t sa;
+    bit<16>         type;
+}
+
+header ipv4_t {
+    bit<4>      version;
+    bit<4>      ihl;
+    bit<6>      dscp;
+    bit<2>      ecn;
+    bit<16>     total_len;
+    bit<16>     identification;
+    bit<1>      reserved;
+    bit<1>      do_not_fragment;
+    bit<1>      more_fragments;
+    bit<13>     frag_offset;
+    bit<8>      ttl;
+    bit<8>      protocol;
+    bit<16>     header_checksum;
+    ipv4_addr_t src_addr;
+    ipv4_addr_t dst_addr;
+}
+
+header ipv4_options_t {
+    varbit<480> options;
+}
+
+struct headers_t {
+    ethernet_t     mac;
+    ipv4_options_t ip;
+}
+
+struct local_metadata_t {
+}
+
+parser v1model_parser(packet_in pkt, out headers_t hdrs, inout local_metadata_t local_meta, inout standard_metadata_t standard_meta) {
+    @name("v1model_parser.ipv4") ipv4_t ipv4_0;
+    @name("v1model_parser.byte_len") bit<32> byte_len_0;
+    state start {
+        pkt.extract<ethernet_t>(hdrs.mac);
+        transition select(hdrs.mac.type) {
+            EtherType.ETYPE_IPV4: parse_ipv4;
+            default: accept;
+        }
+    }
+    state parse_ipv4 {
+        ipv4_0 = pkt.lookahead<ipv4_t>();
+        byte_len_0 = (bit<32>)ipv4_0.ihl << 2;
+        pkt.extract<ipv4_options_t>(hdrs.ip, byte_len_0 << 3);
+        transition accept;
+    }
+}
+
+control compute_ip_checksum(inout headers_t headers, inout local_metadata_t local_metadata) {
+    apply {
+    }
+}
+
+control verify_ip_checksum(inout headers_t headers, inout local_metadata_t local_metadata) {
+    apply {
+    }
+}
+
+control egress(inout headers_t headers, inout local_metadata_t local_metadata, inout standard_metadata_t standard_metadata) {
+    apply {
+    }
+}
+
+control ingress(inout headers_t headers, inout local_metadata_t local_metadata, inout standard_metadata_t standard_metadata) {
+    apply {
+    }
+}
+
+control deparser(packet_out packet, in headers_t headers) {
+    apply {
+    }
+}
+
+V1Switch<headers_t, local_metadata_t>(v1model_parser(), verify_ip_checksum(), ingress(), egress(), compute_ip_checksum(), deparser()) main;