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Reduce the number of memory allocations in def-use #4904

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merged 16 commits into from
Sep 11, 2024
Merged

Reduce the number of memory allocations in def-use #4904

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4d0f982
Explicitly track lifetime of AllDefinitions
asl Sep 5, 2024
6c0efd0
Pass non-null objects by reference
asl Sep 5, 2024
f1f182f
Reduce amount of memory allocations by using sane data structures
asl Sep 5, 2024
28da061
Switch to flat_map with inline storage for fieldLocations
asl Sep 5, 2024
9b9b724
Ensure only StorageFactory could access StorageLocation internals, the
asl Sep 5, 2024
13cfd18
Reduce the size of StorageLocation by 8 bytes via removing the debug …
asl Sep 5, 2024
18f9671
Ensure StorageLocations are immutable
asl Sep 6, 2024
b90f7ca
Ensure AllDefinitions own StorageMap
asl Sep 6, 2024
fb671d7
Make StorageFactory own StorageLocation's
asl Sep 9, 2024
feacfa9
Simplify
asl Sep 9, 2024
8316736
Ensure we can iterate over canonical locations w/o memory allocation
asl Sep 9, 2024
91eb2b8
Reduce number of memory allocations
asl Sep 9, 2024
31c4540
Leak less
asl Sep 9, 2024
d01998e
Improve const-correctness
asl Sep 9, 2024
023d0ae
Further reduce amount of memory allocations and leaks
asl Sep 9, 2024
5a5705d
Get rid of immortal data structures holding things forever
asl Sep 10, 2024
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Ensure only StorageFactory could access StorageLocation internals, the 
locations are immutable otherwise

Signed-off-by: Anton Korobeynikov <anton@korobeynikov.info>
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@asl
asl committed Sep 10, 2024
commit 9b9b72469f754d42f185846e206d8f52a5d4179b
9 changes: 6 additions & 3 deletions frontends/p4/def_use.h
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Expand Up @@ -110,17 +110,19 @@ class WithFieldsLocation : public StorageLocation {
absl::InlinedVector<std::pair<cstring, const StorageLocation *>, 4>>
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I'm very surprised that a flat_map is faster than an hvec_map here -- for that to be true, almost all the structs/headers in the program have no more than 2-3 fields?

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@asl asl Sep 11, 2024 •
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It is not about "fast". It is about memory consumption. Here we do not allocate memory at all for any structs with 4 or less fields. And we resort to memory allocation for anything more. But yes, normally small flat maps have comparable speed to hash maps and, as far as I can see, most structs are small. There are certainly large ones but they are much rare. And we normally do not have struct larger than, say, 16 fields.

fieldLocations;

friend class StorageFactory;
WithFieldsLocation(const IR::Type *type, cstring name) : StorageLocation(type, name) {}

public:
void createField(cstring name, StorageLocation *field) {
fieldLocations.emplace(name, field);
CHECK_NULL(field);
}
void replaceField(cstring field, StorageLocation *replacement) {
fieldLocations[field] = replacement;
}

friend class StorageFactory;

public:
auto fields() const { return Values(fieldLocations); }
void dbprint(std::ostream &out) const override {
for (auto f : fieldLocations) out << *f.second << " ";
Expand Down Expand Up @@ -150,13 +152,14 @@ class StructLocation : public WithFieldsLocation {
class IndexedLocation : public StorageLocation {
protected:
absl::InlinedVector<const StorageLocation *, 8> elements;
friend class StorageFactory;

void createElement(unsigned index, StorageLocation *element) {
elements[index] = element;
CHECK_NULL(element);
}

friend class StorageFactory;

public:
IndexedLocation(const IR::Type *type, cstring name) : StorageLocation(type, name) {
CHECK_NULL(type);
Expand Down