The actions table is very compact but the binary search to find the
correct action is relatively expensive.
A hashtable is faster but pretty large (64 bits per value, plus empty
slots, 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/s
Overall the table grows by 60%: 142 => 228KB.
By comparison, DenseMap<unsigned, StateID> 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
Previously, the action table stores a reduce action for each lookahead
token 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 binary
searching around all these essentially-duplicates to check whether our lookahead
token is there.
However the number of reduces for a given state is very small, so we're
much 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, as
there are fewer nonterminals than (state, rule) pairs. It's also faster.
This specialized approach means unbundling Reduce from other actions in
LRTable, so it's no longer useful to support it in Action. I suspect
Action 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
As pointed out in the previous review section, having a dedicated accept
action doesn't seem to be necessary. This patch implements the the same behavior
without accept acction, which will save some code complexity.
Reviewed By: sammccall
Differential Revision: https://reviews.llvm.org/D125677
This reverts commit 049f4e4eab.
The problem was a stray dependency in CLANG_TEST_DEPS which caused cmake
to fail if clang-pseudo wasn't built. This is now removed.
This should make clearer that:
- it's not part of clang proper
- there's no expectation to update it along with clang (beyond green tests)
- clang should not depend on it
This is intended to be expose a library, so unlike other tools has a split
between include/ and lib/.
The main renames are:
clang/lib/Tooling/Syntax/Pseudo/* => clang-tools-extra/pseudo/lib/*
clang/include/clang/Tooling/Syntax/Pseudo/* => clang-tools-extra/pseudo/include/clang-pseudo/*
clang/tools/clang/pseudo/* => clang-tools-extra/pseudo/tool/*
clang/test/Syntax/* => clang-tools-extra/pseudo/test/*
clang/unittests/Tooling/Syntax/Pseudo/* => clang-tools-extra/pseudo/unittests/*
#include "clang/Tooling/Syntax/Pseudo/*" => #include "clang-pseudo/*"
namespace clang::syntax::pseudo => namespace clang::pseudo
check-clang => check-clang-pseudo
clangToolingSyntaxPseudo => clangPseudo
The clang-pseudo and ClangPseudoTests binaries are not renamed.
See discussion around:
https://discourse.llvm.org/t/rfc-a-c-pseudo-parser-for-tooling/59217/50
Differential Revision: https://reviews.llvm.org/D121233
Sam McCall