2017-03-08 18:59:01 +00:00
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// Copyright (c) 2017 Google Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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2018-08-03 12:05:33 +00:00
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#ifndef SOURCE_EXTENSIONS_H_
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#define SOURCE_EXTENSIONS_H_
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2017-03-08 18:59:01 +00:00
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NFC: rewrite EnumSet to handle larger enums. (#5289)
The current EnumSet implementation is only efficient for enums with
values < than 64. The reason is the first 63 values are stored as a
bitmask in a 64 bit unsigned integer, and the other values are stored
in a std::set.
For small enums, this is fine (most SPIR-V enums have IDs < than 64),
but performance starts to drop with larger enums (Capabilities,
opcodes).
Design considerations:
----------------------
This PR changes the internal behavior of the EnumSet to handle enums
with arbitrary values while staying performant.
The idea is to extend the 64-bits buckets sparsely:
- each bucket can store 64 value, starting from a multiplier of 64.
This could be considered as a hashset with linear probing.
- For small enums, there is a slight memory overhead due to the bucket
storage, but lookup is still constant.
- For linearly distributed values, lookup is constant.
- Worse case for storage are for enums with values which are multiples of 64.
But lookup is constant.
- Worse case for lookup are enums with a lot of small ranges scattered in
the space (requires linear probing).
For enums like capabilities/opcodes, this bucketing is useful as values
are usually scatters in distinct, but almost contiguous blocks.
(vendors usually have allocated ranges, like [5000;5500], while [1000;5000]
is mostly unused).
Benchmarking:
-------------
Benchmarking was done in 2 ways:
- a benchmark built for the occasion, which only measure the EnumSet
performance.
- SPIRV-Tools tests, to measure a more realist scenario.
Running SPIR-V tests with both implementations shows the same
performance (delta < noise). So seems like we have no regressions.
This method is noisy by nature (I/O, etc), but the most representative
of a real-life scenario.
Protocol:
- run spirv-tests with no stdout using perf, multiple times.
Result:
- measure noise is larger than the observed difference.
The custom benchmark was testing EnumSet interfaces using SPIRV enums.
Doing thousand of insertion/deletion/lookup, with 2 kind of scenarios:
- add once, lookup many times.
- add/delete/loopkup many time.
For small enums, results are similar (delta < noise). Seems relevant
with the previously observed results as most SPIRV enums are small, and
SPIRV-Tools is not doing that many intensive operations on EnumSets.
Performance on large enums (opcode/capabilities) shows an improvement:
+-----------------------------+---------+---------+---------+
| Metric | Old | New | Delta % |
+-----------------------------+---------+---------+---------+
| Execution time | 27s | 7s | -72% |
| Instruction count | 174b | 129b | -25% |
| Branch count | 28b | 33b | +17% |
| Branch miss | 490m | 26m | -94% |
| Cache-misses | 149k | 26k | -82% |
+-----------------------------+---------+---------+---------+
Future work
-----------
This was by-design an NFC change to compare apples-to-apples.
The next PR aims to add STL-like iterators to the EnumSet to allow
using it with STL algorithms, and range-based for loops.
Signed-off-by: Nathan Gauër <brioche@google.com>
2023-07-07 14:41:52 +00:00
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#include <cstdint>
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2017-03-08 18:59:01 +00:00
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#include <string>
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2018-08-03 19:06:09 +00:00
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#include "source/enum_set.h"
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2017-03-10 20:58:15 +00:00
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#include "spirv-tools/libspirv.h"
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2017-03-08 18:59:01 +00:00
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2018-07-07 13:38:00 +00:00
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namespace spvtools {
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2017-03-08 18:59:01 +00:00
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// The known SPIR-V extensions.
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NFC: rewrite EnumSet to handle larger enums. (#5289)
The current EnumSet implementation is only efficient for enums with
values < than 64. The reason is the first 63 values are stored as a
bitmask in a 64 bit unsigned integer, and the other values are stored
in a std::set.
For small enums, this is fine (most SPIR-V enums have IDs < than 64),
but performance starts to drop with larger enums (Capabilities,
opcodes).
Design considerations:
----------------------
This PR changes the internal behavior of the EnumSet to handle enums
with arbitrary values while staying performant.
The idea is to extend the 64-bits buckets sparsely:
- each bucket can store 64 value, starting from a multiplier of 64.
This could be considered as a hashset with linear probing.
- For small enums, there is a slight memory overhead due to the bucket
storage, but lookup is still constant.
- For linearly distributed values, lookup is constant.
- Worse case for storage are for enums with values which are multiples of 64.
But lookup is constant.
- Worse case for lookup are enums with a lot of small ranges scattered in
the space (requires linear probing).
For enums like capabilities/opcodes, this bucketing is useful as values
are usually scatters in distinct, but almost contiguous blocks.
(vendors usually have allocated ranges, like [5000;5500], while [1000;5000]
is mostly unused).
Benchmarking:
-------------
Benchmarking was done in 2 ways:
- a benchmark built for the occasion, which only measure the EnumSet
performance.
- SPIRV-Tools tests, to measure a more realist scenario.
Running SPIR-V tests with both implementations shows the same
performance (delta < noise). So seems like we have no regressions.
This method is noisy by nature (I/O, etc), but the most representative
of a real-life scenario.
Protocol:
- run spirv-tests with no stdout using perf, multiple times.
Result:
- measure noise is larger than the observed difference.
The custom benchmark was testing EnumSet interfaces using SPIRV enums.
Doing thousand of insertion/deletion/lookup, with 2 kind of scenarios:
- add once, lookup many times.
- add/delete/loopkup many time.
For small enums, results are similar (delta < noise). Seems relevant
with the previously observed results as most SPIRV enums are small, and
SPIRV-Tools is not doing that many intensive operations on EnumSets.
Performance on large enums (opcode/capabilities) shows an improvement:
+-----------------------------+---------+---------+---------+
| Metric | Old | New | Delta % |
+-----------------------------+---------+---------+---------+
| Execution time | 27s | 7s | -72% |
| Instruction count | 174b | 129b | -25% |
| Branch count | 28b | 33b | +17% |
| Branch miss | 490m | 26m | -94% |
| Cache-misses | 149k | 26k | -82% |
+-----------------------------+---------+---------+---------+
Future work
-----------
This was by-design an NFC change to compare apples-to-apples.
The next PR aims to add STL-like iterators to the EnumSet to allow
using it with STL algorithms, and range-based for loops.
Signed-off-by: Nathan Gauër <brioche@google.com>
2023-07-07 14:41:52 +00:00
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enum Extension : uint32_t {
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2017-03-15 21:28:24 +00:00
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#include "extension_enum.inc"
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2017-03-08 18:59:01 +00:00
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};
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using ExtensionSet = EnumSet<Extension>;
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2017-03-10 20:58:15 +00:00
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// Returns literal string operand of OpExtension instruction.
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std::string GetExtensionString(const spv_parsed_instruction_t* inst);
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// Returns text string listing |extensions| separated by whitespace.
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std::string ExtensionSetToString(const ExtensionSet& extensions);
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2018-07-07 13:38:00 +00:00
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} // namespace spvtools
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2017-03-08 18:59:01 +00:00
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2018-08-03 12:05:33 +00:00
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#endif // SOURCE_EXTENSIONS_H_
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