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dpdk: Eliminate unused metadata fields #3096

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Feb 26, 2022
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dpdk: Eliminate unused metadata fields #3096

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4 changes: 3 additions & 1 deletion backends/dpdk/backend.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -108,13 +108,15 @@ void DpdkBackend::convert(const IR::ToplevelBlock *tlb) {
};
simplify.addDebugHook(hook, true);
program = program->apply(simplify);

ordered_set<cstring> used_fields;
dpdk_program = convertToDpdk->getDpdkProgram();
if (!dpdk_program)
return;
PassManager post_code_gen = {
new EliminateUnusedAction(),
new DpdkAsmOptimization,
new CollectUsedMetadataField(used_fields),
new RemoveUnusedMetadataFields(used_fields),
};

dpdk_program = dpdk_program->apply(post_code_gen)->to<IR::DpdkAsmProgram>();
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31 changes: 31 additions & 0 deletions backends/dpdk/dpdkAsmOpt.cpp
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Expand Up @@ -163,4 +163,35 @@ const IR::IndexedVector<IR::DpdkAsmStatement> *RemoveLabelAfterLabel::removeLabe
}
return new_l;
}

const IR::Node* RemoveUnusedMetadataFields::preorder(IR::DpdkAsmProgram *p) {
IR::IndexedVector<IR::DpdkStructType> usedStruct;
bool isMetadataStruct = false;
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I would call this "foundMetadataStruct".
Perhaps you can change it in a future PR.

for (auto st : p->structType) {
if (!isMetadataStruct) {
for (auto anno : st->annotations->annotations) {
if (anno->name == "__metadata__") {
isMetadataStruct = true;
IR::IndexedVector<IR::StructField> usedMetadataFields;
for (auto field : st->fields) {
if (used_fields.count(field->name.name)) {
usedMetadataFields.push_back(field);
}
}
auto newSt = new IR::DpdkStructType(st->srcInfo, st->name,
st->annotations, usedMetadataFields);
usedStruct.push_back(newSt);
}
}
if (!isMetadataStruct) {
usedStruct.push_back(st);
}
} else {
usedStruct.push_back(st);
}
}
p->structType = usedStruct;
return p;
}

} // namespace DPDK
24 changes: 24 additions & 0 deletions backends/dpdk/dpdkAsmOpt.h
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Expand Up @@ -135,6 +135,30 @@ class RemoveLabelAfterLabel : public Transform {
}
};


// This pass Collects all metadata struct member used in program
class CollectUsedMetadataField : public Inspector {
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Alternatively, if this pass is used only within dpdkAsmOpt.cpp, it does not need to have a declaration in the header, it can be local to the file (within an empty namespace to avoid name clashes).

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Now it's used in backend.cpp

ordered_set<cstring>& used_fields;
public:
explicit CollectUsedMetadataField(ordered_set<cstring>& used_fields)
: used_fields(used_fields) {}
bool preorder(const IR::Member *m) override {
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This is not necessarily a field of the metadata structure, but I guess it will include all the fields. So you may keep some extra fields here if they happen to show up in other structures.

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Now only insert if it's metadata's member.

// metadata struct field used like m.<field_name> in expressions
if (m->expr->toString() == "m")
used_fields.insert(m->member.toString());
return true;
}
};

// This pass removes all unused fields from metadata struct
class RemoveUnusedMetadataFields : public Transform {
ordered_set<cstring>& used_fields;
public:
explicit RemoveUnusedMetadataFields(ordered_set<cstring>& used_fields)
: used_fields(used_fields) {}
const IR::Node* preorder(IR::DpdkAsmProgram *p) override;
};

// Instructions can only appear in actions and apply block of .spec file.
// All these individual passes work on the actions and apply block of .spec file.
class DpdkAsmOptimization : public PassRepeated {
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13 changes: 2 additions & 11 deletions backends/dpdk/dpdkProgram.cpp
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Expand Up @@ -24,8 +24,7 @@ limitations under the License.

namespace DPDK {
/* Insert the metadata structure updated with tmp variables created during parser conversion
Add annotations to metadata and header structures and add all the structures to DPDK
structtype.
Add all the structures to DPDK structtype.
*/
IR::IndexedVector<IR::DpdkStructType> ConvertToDpdkProgram::UpdateHeaderMetadata
(IR::P4Program *prog, IR::Type_Struct *metadata) {
Expand All @@ -34,13 +33,9 @@ IR::IndexedVector<IR::DpdkStructType> ConvertToDpdkProgram::UpdateHeaderMetadata
for (auto obj : prog->objects) {
if (auto s = obj->to<IR::Type_Struct>()) {
if (s->name.name == structure->local_metadata_type) {
auto *annotations = new IR::Annotations(
{new IR::Annotation(IR::ID("__metadata__"), {})});
for (auto anno : s->annotations->annotations)
annotations->add(anno);
new_objs->push_back(metadata);
auto st = new IR::DpdkStructType(s->srcInfo, s->name,
annotations, metadata->fields);
s->annotations, metadata->fields);
structType.push_back(st);
} else {
if (structure->args_struct_map.find(s->name.name) !=
Expand All @@ -49,10 +44,6 @@ IR::IndexedVector<IR::DpdkStructType> ConvertToDpdkProgram::UpdateHeaderMetadata
s->annotations, s->fields);
structType.push_back(st);
} else if (s->name.name == structure->header_type) {
auto *annotations = new IR::Annotations(
{new IR::Annotation(IR::ID("__packet_data__"), {})});
for (auto anno : s->annotations->annotations)
annotations->add(anno);
auto st = new IR::DpdkStructType(s->srcInfo, s->name,
s->annotations, s->fields);
structType.push_back(st);
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19 changes: 0 additions & 19 deletions testdata/p4_16_samples_outputs/pna-action-selector.p4.spec
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Expand Up @@ -34,26 +34,7 @@ struct tbl_set_group_id_arg_t {
}

struct main_metadata_t {
bit<32> pna_pre_input_metadata_input_port
bit<16> pna_pre_input_metadata_parser_error
bit<32> pna_pre_input_metadata_direction
bit<3> pna_pre_input_metadata_pass
bit<8> pna_pre_input_metadata_loopedback
bit<8> pna_pre_output_metadata_decrypt
bit<32> pna_pre_output_metadata_said
bit<16> pna_pre_output_metadata_decrypt_start_offset
bit<32> pna_main_parser_input_metadata_direction
bit<3> pna_main_parser_input_metadata_pass
bit<8> pna_main_parser_input_metadata_loopedback
bit<32> pna_main_parser_input_metadata_input_port
bit<32> pna_main_input_metadata_direction
bit<3> pna_main_input_metadata_pass
bit<8> pna_main_input_metadata_loopedback
bit<64> pna_main_input_metadata_timestamp
bit<16> pna_main_input_metadata_parser_error
bit<8> pna_main_input_metadata_class_of_service
bit<32> pna_main_input_metadata_input_port
bit<8> pna_main_output_metadata_class_of_service
bit<16> local_metadata_data
bit<32> pna_main_output_metadata_output_port
bit<32> MainControlT_as_group_id
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19 changes: 0 additions & 19 deletions testdata/p4_16_samples_outputs/pna-add-on-miss.p4.spec
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Expand Up @@ -30,26 +30,7 @@ struct next_hop_arg_t {
}

struct main_metadata_t {
bit<32> pna_pre_input_metadata_input_port
bit<16> pna_pre_input_metadata_parser_error
bit<32> pna_pre_input_metadata_direction
bit<3> pna_pre_input_metadata_pass
bit<8> pna_pre_input_metadata_loopedback
bit<8> pna_pre_output_metadata_decrypt
bit<32> pna_pre_output_metadata_said
bit<16> pna_pre_output_metadata_decrypt_start_offset
bit<32> pna_main_parser_input_metadata_direction
bit<3> pna_main_parser_input_metadata_pass
bit<8> pna_main_parser_input_metadata_loopedback
bit<32> pna_main_parser_input_metadata_input_port
bit<32> pna_main_input_metadata_direction
bit<3> pna_main_input_metadata_pass
bit<8> pna_main_input_metadata_loopedback
bit<64> pna_main_input_metadata_timestamp
bit<16> pna_main_input_metadata_parser_error
bit<8> pna_main_input_metadata_class_of_service
bit<32> pna_main_input_metadata_input_port
bit<8> pna_main_output_metadata_class_of_service
bit<32> pna_main_output_metadata_output_port
bit<32> MainControlT_tmp
bit<32> MainControlT_tmp_0
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18 changes: 0 additions & 18 deletions testdata/p4_16_samples_outputs/pna-example-SelectByDirection.p4.spec
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Expand Up @@ -25,26 +25,8 @@ struct next_hop_arg_t {
}

struct main_metadata_t {
bit<32> pna_pre_input_metadata_input_port
bit<16> pna_pre_input_metadata_parser_error
bit<32> pna_pre_input_metadata_direction
bit<3> pna_pre_input_metadata_pass
bit<8> pna_pre_input_metadata_loopedback
bit<8> pna_pre_output_metadata_decrypt
bit<32> pna_pre_output_metadata_said
bit<16> pna_pre_output_metadata_decrypt_start_offset
bit<32> pna_main_parser_input_metadata_direction
bit<3> pna_main_parser_input_metadata_pass
bit<8> pna_main_parser_input_metadata_loopedback
bit<32> pna_main_parser_input_metadata_input_port
bit<32> pna_main_input_metadata_direction
bit<3> pna_main_input_metadata_pass
bit<8> pna_main_input_metadata_loopedback
bit<64> pna_main_input_metadata_timestamp
bit<16> pna_main_input_metadata_parser_error
bit<8> pna_main_input_metadata_class_of_service
bit<32> pna_main_input_metadata_input_port
bit<8> pna_main_output_metadata_class_of_service
bit<32> pna_main_output_metadata_output_port
bit<32> MainControlT_key
}
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18 changes: 0 additions & 18 deletions testdata/p4_16_samples_outputs/pna-example-SelectByDirection1.p4.spec
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Expand Up @@ -25,26 +25,8 @@ struct next_hop_arg_t {
}

struct main_metadata_t {
bit<32> pna_pre_input_metadata_input_port
bit<16> pna_pre_input_metadata_parser_error
bit<32> pna_pre_input_metadata_direction
bit<3> pna_pre_input_metadata_pass
bit<8> pna_pre_input_metadata_loopedback
bit<8> pna_pre_output_metadata_decrypt
bit<32> pna_pre_output_metadata_said
bit<16> pna_pre_output_metadata_decrypt_start_offset
bit<32> pna_main_parser_input_metadata_direction
bit<3> pna_main_parser_input_metadata_pass
bit<8> pna_main_parser_input_metadata_loopedback
bit<32> pna_main_parser_input_metadata_input_port
bit<32> pna_main_input_metadata_direction
bit<3> pna_main_input_metadata_pass
bit<8> pna_main_input_metadata_loopedback
bit<64> pna_main_input_metadata_timestamp
bit<16> pna_main_input_metadata_parser_error
bit<8> pna_main_input_metadata_class_of_service
bit<32> pna_main_input_metadata_input_port
bit<8> pna_main_output_metadata_class_of_service
bit<32> pna_main_output_metadata_output_port
bit<32> MainControlT_tmp
}
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18 changes: 0 additions & 18 deletions testdata/p4_16_samples_outputs/pna-example-SelectByDirection2.p4.spec
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Expand Up @@ -25,26 +25,8 @@ struct forward_arg_t {
}

struct main_metadata_t {
bit<32> pna_pre_input_metadata_input_port
bit<16> pna_pre_input_metadata_parser_error
bit<32> pna_pre_input_metadata_direction
bit<3> pna_pre_input_metadata_pass
bit<8> pna_pre_input_metadata_loopedback
bit<8> pna_pre_output_metadata_decrypt
bit<32> pna_pre_output_metadata_said
bit<16> pna_pre_output_metadata_decrypt_start_offset
bit<32> pna_main_parser_input_metadata_direction
bit<3> pna_main_parser_input_metadata_pass
bit<8> pna_main_parser_input_metadata_loopedback
bit<32> pna_main_parser_input_metadata_input_port
bit<32> pna_main_input_metadata_direction
bit<3> pna_main_input_metadata_pass
bit<8> pna_main_input_metadata_loopedback
bit<64> pna_main_input_metadata_timestamp
bit<16> pna_main_input_metadata_parser_error
bit<8> pna_main_input_metadata_class_of_service
bit<32> pna_main_input_metadata_input_port
bit<8> pna_main_output_metadata_class_of_service
bit<32> local_metadata_meta
bit<32> pna_main_output_metadata_output_port
bit<32> MainControlT_addr
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19 changes: 0 additions & 19 deletions testdata/p4_16_samples_outputs/pna-example-dpdk-varbit.p4.spec
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Expand Up @@ -42,26 +42,7 @@ struct a2_arg_t {
}

struct main_metadata_t {
bit<32> pna_pre_input_metadata_input_port
bit<16> pna_pre_input_metadata_parser_error
bit<32> pna_pre_input_metadata_direction
bit<3> pna_pre_input_metadata_pass
bit<8> pna_pre_input_metadata_loopedback
bit<8> pna_pre_output_metadata_decrypt
bit<32> pna_pre_output_metadata_said
bit<16> pna_pre_output_metadata_decrypt_start_offset
bit<32> pna_main_parser_input_metadata_direction
bit<3> pna_main_parser_input_metadata_pass
bit<8> pna_main_parser_input_metadata_loopedback
bit<32> pna_main_parser_input_metadata_input_port
bit<32> pna_main_input_metadata_direction
bit<3> pna_main_input_metadata_pass
bit<8> pna_main_input_metadata_loopedback
bit<64> pna_main_input_metadata_timestamp
bit<16> pna_main_input_metadata_parser_error
bit<8> pna_main_input_metadata_class_of_service
bit<32> pna_main_input_metadata_input_port
bit<8> pna_main_output_metadata_class_of_service
bit<32> pna_main_output_metadata_output_port
bit<32> MainParserT_parser_tmp
bit<32> MainParserT_parser_tmp_0
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19 changes: 0 additions & 19 deletions testdata/p4_16_samples_outputs/pna-example-template.p4.spec
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Expand Up @@ -25,26 +25,7 @@ struct next_hop_arg_t {
}

struct main_metadata_t {
bit<32> pna_pre_input_metadata_input_port
bit<16> pna_pre_input_metadata_parser_error
bit<32> pna_pre_input_metadata_direction
bit<3> pna_pre_input_metadata_pass
bit<8> pna_pre_input_metadata_loopedback
bit<8> pna_pre_output_metadata_decrypt
bit<32> pna_pre_output_metadata_said
bit<16> pna_pre_output_metadata_decrypt_start_offset
bit<32> pna_main_parser_input_metadata_direction
bit<3> pna_main_parser_input_metadata_pass
bit<8> pna_main_parser_input_metadata_loopedback
bit<32> pna_main_parser_input_metadata_input_port
bit<32> pna_main_input_metadata_direction
bit<3> pna_main_input_metadata_pass
bit<8> pna_main_input_metadata_loopedback
bit<64> pna_main_input_metadata_timestamp
bit<16> pna_main_input_metadata_parser_error
bit<8> pna_main_input_metadata_class_of_service
bit<32> pna_main_input_metadata_input_port
bit<8> pna_main_output_metadata_class_of_service
bit<32> pna_main_output_metadata_output_port
}
metadata instanceof main_metadata_t
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19 changes: 0 additions & 19 deletions testdata/p4_16_samples_outputs/pna-extract-local-header.p4.spec
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Expand Up @@ -6,26 +6,7 @@ struct my_header_t {
}

struct main_metadata_t {
bit<32> pna_pre_input_metadata_input_port
bit<16> pna_pre_input_metadata_parser_error
bit<32> pna_pre_input_metadata_direction
bit<3> pna_pre_input_metadata_pass
bit<8> pna_pre_input_metadata_loopedback
bit<8> pna_pre_output_metadata_decrypt
bit<32> pna_pre_output_metadata_said
bit<16> pna_pre_output_metadata_decrypt_start_offset
bit<32> pna_main_parser_input_metadata_direction
bit<3> pna_main_parser_input_metadata_pass
bit<8> pna_main_parser_input_metadata_loopedback
bit<32> pna_main_parser_input_metadata_input_port
bit<32> pna_main_input_metadata_direction
bit<3> pna_main_input_metadata_pass
bit<8> pna_main_input_metadata_loopedback
bit<64> pna_main_input_metadata_timestamp
bit<16> pna_main_input_metadata_parser_error
bit<8> pna_main_input_metadata_class_of_service
bit<32> pna_main_input_metadata_input_port
bit<8> pna_main_output_metadata_class_of_service
bit<32> pna_main_output_metadata_output_port
}
metadata instanceof main_metadata_t
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19 changes: 0 additions & 19 deletions testdata/p4_16_samples_outputs/pna-issue3041.p4.spec
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Expand Up @@ -40,26 +40,7 @@ struct a2_arg_t {
}

struct main_metadata_t {
bit<32> pna_pre_input_metadata_input_port
bit<16> pna_pre_input_metadata_parser_error
bit<32> pna_pre_input_metadata_direction
bit<3> pna_pre_input_metadata_pass
bit<8> pna_pre_input_metadata_loopedback
bit<8> pna_pre_output_metadata_decrypt
bit<32> pna_pre_output_metadata_said
bit<16> pna_pre_output_metadata_decrypt_start_offset
bit<32> pna_main_parser_input_metadata_direction
bit<3> pna_main_parser_input_metadata_pass
bit<8> pna_main_parser_input_metadata_loopedback
bit<32> pna_main_parser_input_metadata_input_port
bit<32> pna_main_input_metadata_direction
bit<3> pna_main_input_metadata_pass
bit<8> pna_main_input_metadata_loopedback
bit<64> pna_main_input_metadata_timestamp
bit<16> pna_main_input_metadata_parser_error
bit<8> pna_main_input_metadata_class_of_service
bit<32> pna_main_input_metadata_input_port
bit<8> pna_main_output_metadata_class_of_service
bit<32> pna_main_output_metadata_output_port
bit<32> MainParserT_parser_tmp
bit<32> MainParserT_parser_tmp_0
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19 changes: 0 additions & 19 deletions testdata/p4_16_samples_outputs/pna-lookahead-structure-bit-field.p4.spec
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Expand Up @@ -14,26 +14,7 @@ struct lookahead_tmp_hdr {
}

struct main_metadata_t {
bit<32> pna_pre_input_metadata_input_port
bit<16> pna_pre_input_metadata_parser_error
bit<32> pna_pre_input_metadata_direction
bit<3> pna_pre_input_metadata_pass
bit<8> pna_pre_input_metadata_loopedback
bit<8> pna_pre_output_metadata_decrypt
bit<32> pna_pre_output_metadata_said
bit<16> pna_pre_output_metadata_decrypt_start_offset
bit<32> pna_main_parser_input_metadata_direction
bit<3> pna_main_parser_input_metadata_pass
bit<8> pna_main_parser_input_metadata_loopedback
bit<32> pna_main_parser_input_metadata_input_port
bit<32> pna_main_input_metadata_direction
bit<3> pna_main_input_metadata_pass
bit<8> pna_main_input_metadata_loopedback
bit<64> pna_main_input_metadata_timestamp
bit<16> pna_main_input_metadata_parser_error
bit<8> pna_main_input_metadata_class_of_service
bit<32> pna_main_input_metadata_input_port
bit<8> pna_main_output_metadata_class_of_service
bit<8> local_metadata_f1
bit<32> pna_main_output_metadata_output_port
}
Expand Down
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