Changes in LRTable.cpp

9fbf1107 - [pseudo] Eliminate LRTable::Action. NFC

Mon, 04 Jul 2022 18:35:40 +0000

[pseudo] Eliminate LRTable::Action. NFCThe last remaining uses are in tests/test builders.Replace with a builder struct.Differential Revision: https://reviews.llvm.org/D129093 List of files: /llvm-project-15.0.7/clang-tools-extra/pseudo/lib/grammar/LRTable.cpp

b37dafd5 - [pseudo] Store shift and goto actions in a compact structure with faster lookup.

Fri, 24 Jun 2022 01:01:45 +0000

[pseudo] Store shift and goto actions in a compact structure with faster lookup.The actions table is very compact but the binary search to find thecorrect action is relatively expensive.A hashtable is faster but pretty large (64 bits per value, plus emptyslots, and lookup is constant time but not trivial due to collisions).The structure in this patch uses 1.25 bits per entry (whether present or absent)plus the size of the values, and lookup is trivial.The Shift table is 119KB = 27KB values + 92KB keys.The Goto table is 86KB = 30KB values + 57KB keys.(Goto has a smaller keyspace as #nonterminals < #terminals, and more entries).This patch improves glrParse speed by 28%: 4.69 => 5.99 MB/sOverall the table grows by 60%: 142 => 228KB.By comparison, DenseMap is "only" 16% faster (5.43 MB/s),and results in a 285% larger table (547 KB) vs the baseline.Differential Revision: https://reviews.llvm.org/D128485 List of files: /llvm-project-15.0.7/clang-tools-extra/pseudo/lib/grammar/LRTable.cpp

85eaecbe - [pseudo] Check follow-sets instead of tying reduce actions to lookahead tokens.

Thu, 23 Jun 2022 21:55:41 +0000

[pseudo] Check follow-sets instead of tying reduce actions to lookahead tokens.Previously, the action table stores a reduce action for each lookaheadtoken it should allow. These tokens are the followSet(action.rule.target).In practice, the follow sets are large, so we spend a bunch of time binarysearching around all these essentially-duplicates to check whether our lookaheadtoken is there.However the number of reduces for a given state is very small, so we'remuch better off linear scanning over them and performing a fast check for each.D128318 was an attempt at this, storing a bitmap for each reduce.However it's even more compact just to use the follow sets directly, asthere are fewer nonterminals than (state, rule) pairs. It's also faster.This specialized approach means unbundling Reduce from other actions inLRTable, so it's no longer useful to support it in Action. I suspectAction will soon go away, as we store each kind of action separately.This improves glrParse speed by 42% (3.30 -> 4.69 MB/s).It also reduces LR table size by 59% (343 -> 142kB).Differential Revision: https://reviews.llvm.org/D128472 List of files: /llvm-project-15.0.7/clang-tools-extra/pseudo/lib/grammar/LRTable.cpp

b70ee9d9 - Reland "[pseudo] Track heads as GSS nodes, rather than as "pending actions"."

Thu, 23 Jun 2022 16:16:49 +0000

Reland "[pseudo] Track heads as GSS nodes, rather than as "pending actions"."This reverts commit 2c80b5319870b57fbdbb6c9cef9c86c26c65371d.Fixes LRTable::buildForTest to create states that are referenced buthave no actions. List of files: /llvm-project-15.0.7/clang-tools-extra/pseudo/lib/grammar/LRTable.cpp

2c80b531 - Revert "[pseudo] Track heads as GSS nodes, rather than as "pending actions"."

Thu, 23 Jun 2022 16:16:03 +0000

Revert "[pseudo] Track heads as GSS nodes, rather than as "pending actions"."This reverts commit e3ec054dfdf48f19cb6726cb3f4965b9ab320ed9.Tests fail in asserts mode: https://lab.llvm.org/buildbot/#/builders/109/builds/41217 List of files: /llvm-project-15.0.7/clang-tools-extra/pseudo/lib/grammar/LRTable.cpp

e3ec054d - [pseudo] Track heads as GSS nodes, rather than as "pending actions".

Tue, 21 Jun 2022 19:22:22 +0000

[pseudo] Track heads as GSS nodes, rather than as "pending actions".IMO this model is simpler to understand (borrowed from the LR0 patch D127357).It also makes error recovery easier to implement, as we have a simple list ofhead nodes lying around to recover from when needed.(It's not quite as nice as LR0 in this respect though).It's slightly slower (2.24 -> 2.12 MB/S on my machine = 5%) but nothing closeto as bad as LR0.However - I think we'd have to eat a litle performance loss otherwise to implement error recovery. - this frees up some complexity budget for optimizations like fastpath push/pop (this + fastpath is already faster than head) - I haven't changed the data structure here and it's now pretty dumb, we can make it fasterDifferential Revision: https://reviews.llvm.org/D128297 List of files: /llvm-project-15.0.7/clang-tools-extra/pseudo/lib/grammar/LRTable.cpp

c70aeaad - [pseudo] Move grammar-related headers to a separate dir, NFC.

Thu, 09 Jun 2022 10:16:14 +0000

[pseudo] Move grammar-related headers to a separate dir, NFC.We did that for .cpp, but forgot the headers.Differential Revision: https://reviews.llvm.org/D127388 List of files: /llvm-project-15.0.7/clang-tools-extra/pseudo/lib/grammar/LRTable.cpp

7a05942d - [pseudo] Remove the explicit Accept actions.

Wed, 08 Jun 2022 11:26:53 +0000

[pseudo] Remove the explicit Accept actions.As pointed out in the previous review section, having a dedicated acceptaction doesn't seem to be necessary. This patch implements the the same behaviorwithout accept acction, which will save some code complexity.Reviewed By: sammccallDifferential Revision: https://reviews.llvm.org/D125677 List of files: /llvm-project-15.0.7/clang-tools-extra/pseudo/lib/grammar/LRTable.cpp

075449da - [pseudo] Fix a sign-compare warning in debug build, NFC.

Thu, 09 Jun 2022 09:18:03 +0000

[pseudo] Fix a sign-compare warning in debug build, NFC. List of files: /llvm-project-15.0.7/clang-tools-extra/pseudo/lib/grammar/LRTable.cpp

bbc58c5e - [pseudo] Restore accidentally removed debug print

Wed, 08 Jun 2022 21:39:34 +0000

[pseudo] Restore accidentally removed debug print List of files: /llvm-project-15.0.7/clang-tools-extra/pseudo/lib/grammar/LRTable.cpp

93bcff8a - [pseudo] Invert rows/columns of LRTable storage for speedup. NFC

Fri, 03 Jun 2022 21:48:41 +0000

[pseudo] Invert rows/columns of LRTable storage for speedup. NFCThere are more states than symbols.This means first partioning the action list by state leaves us with a smallerrange to binary search over. This improves find() a lot and glrParse() by 7%.The tradeoff is storing more smaller ranges increases the size of the offsetsarray, overall grammar memory is +1% (337->340KB).Before:glrParse 188795975 ns 188778003 ns 77 bytes_per_second=1.98068M/sAfter:glrParse 175936203 ns 175916873 ns 81 bytes_per_second=2.12548M/sDifferential Revision: https://reviews.llvm.org/D127006 List of files: /llvm-project-15.0.7/clang-tools-extra/pseudo/lib/grammar/LRTable.cpp

cd2292ef - [pseudo] A basic implementation of compiling cxx grammar at build time.

Tue, 24 May 2022 18:21:45 +0000

[pseudo] A basic implementation of compiling cxx grammar at build time.The main idea is to compile the cxx grammar at build time, and constructthe core pieces (Grammar, LRTable) of the pseudoparse based on the compileddata sources.This is a tiny implementation, which is good for start:- defines how the public API should look like;- integrates the cxx grammar compilation workflow with the cmake system.- onlynonterminal symbols of the C++ grammar are compiled, anything else are still doing the real compilation work at runtime, we can opt-in more bits in the future;- splits the monolithic clangPsuedo library for better layering;Reviewed By: sammccallDifferential Revision: https://reviews.llvm.org/D125667 List of files: /llvm-project-15.0.7/clang-tools-extra/pseudo/lib/grammar/LRTable.cpp