[lldb][Type Completion] Load C++ methods lazily from DWARF #8579
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
|
@swift-ci test |
Michael137
force-pushed
the
lldb/type-completion-rework/lazy-method-loading
branch
2 times, most recently
from
f262b1f to
073b109
Compare
|
@swift-ci test |
| TypeSystemClang &ts) { | ||
| auto CDC1 = candidate_decl_ctx.GetTypeSystem()->DeclContextGetCompilerContext( | ||
| candidate_decl_ctx.GetOpaqueDeclContext()); | ||
| assert(CDC1.size() > 1); // Member functions have at least 2 entries (1 |
There was a problem hiding this comment.
Nit: If a comment is > 1 line, I'd rather put it on top.
| auto CDC1 = candidate_decl_ctx.GetTypeSystem()->DeclContextGetCompilerContext( | ||
| candidate_decl_ctx.GetOpaqueDeclContext()); | ||
| assert(CDC1.size() > 1); // Member functions have at least 2 entries (1 | ||
| // for method name, 1 for partent class) |
| function_options, sc_list); | ||
|
|
||
| auto num_matches = sc_list.GetSize(); | ||
| if (num_matches > 0) { |
There was a problem hiding this comment.
Suggested change
| if (num_matches > 0) { | |
| if (!num_matches) | |
| return;``` |
| DW_AT_virtuality, DW_VIRTUALITY_none) > DW_VIRTUALITY_none; | ||
| const bool is_operator = mem_name.GetStringRef().starts_with("operator"); | ||
|
|
||
| if (is_ctor || is_operator || is_virtual_method) |
There was a problem hiding this comment.
Can you comment here, why only these three in partiuclar?
Michael137
force-pushed
the
lldb/type-completion-rework/lazy-method-loading
branch
from
073b109 to
e56bbcc
Compare
|
@swift-ci test |
|
@swift-ci test Windows |
Note, this is a no-op when the LLDB setting `plugin.typesystem.clang.experimental-redecl-completion` is not set (which is currently the default). So this patch has no affect unless the user explicitly opts into it. The type-completion rework (aka redecl-completion) implemented in swiftlang#8222 comes with a large performance penalty, since we now eagerly complete `RecordType`s. Completing a `RecordType` previously unconditionally resolved all member function of said type. With redecl-completion completion, however, this meant we were now pulling in many more definitions than needed. Without redecl-completion, this isn't a problem, since importing method parameters is cheap (they are imported minimally), so we wouldn't notice that we always resolved all member functions. This patch tries to load methods lazily when in redecl-completion mode. We do this by introducing a new `ExternalASTSource::FindExternalVisibleMethods` API which Clang parses a member access expression. The callback into LLDB will do a `FindFunctions` call for all methods with the method name we're looking for, filters out any mismatches, and lets Clang continue with it's parsing. We still load following methods eagerly: 1. virtual functions: currently overrides are resolved in `CompleteRecordType` 2. operators: currently I couldn't find a point at which Clang can call into LLDB here to facilitate lazy loading 3. ctors/dtors: same reason as (2) In our benchmark harness, we saw this patch bring down redecl-completion expression evaluation on-par with top-of-tree expression evaluation.
…lazy method loading
Michael137
force-pushed
the
lldb/type-completion-rework/lazy-method-loading
branch
from
bb452ec to
4397f63
Compare
|
@swift-ci test |
|
@swift-ci test Windows |
1 similar comment
|
@swift-ci test Windows |
Michael137
added a commit
to Michael137/llvm-project
that referenced
this pull request
May 3, 2024
Expected failures due to lazy method loading (swiftlang#8579)
Michael137
added a commit
to Michael137/llvm-project
that referenced
this pull request
May 3, 2024
Expected failures due to lazy method loading (swiftlang#8579)
Michael137
added a commit
to Michael137/llvm-project
that referenced
this pull request
May 6, 2024
Expected failures due to lazy method loading (swiftlang#8579) (cherry picked from commit 9507b8b)
Michael137
added a commit
to Michael137/llvm-project
that referenced
this pull request
May 8, 2024
Expected failures due to lazy method loading (swiftlang#8579) (cherry picked from commit 9507b8b)
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Note, this is a no-op when the LLDB setting
plugin.typesystem.clang.experimental-redecl-completionis not set (which is currently the default). So this patch has no effect unless the user explicitly opts into it.The type-completion rework (aka redecl-completion) implemented in #8222 comes with a large performance penalty, since we now eagerly complete
RecordTypes. Completing aRecordTypepreviously unconditionally resolved all member functions of said type. With redecl-completion completion, however, this meant we were now pulling in many more definitions than needed. Without redecl-completion, this isn't a problem, since importing method parameters is cheap (they are imported minimally), so we wouldn't notice that we always resolved all member functions.This patch tries to load methods lazily when in redecl-completion mode. We do this by introducing a new
ExternalASTSource::FindExternalVisibleMethodsAPI which Clang calls when parsing a member access expression. The callback into LLDB will do aFindFunctionscall for all methods with the method name we're looking for, filters out any mismatches, and lets Clang continue with its parsing. We still load following methods eagerly:CompleteRecordTypeIn our benchmark harness, we saw this patch bring down redecl-completion expression evaluation performance on-par with top-of-tree expression evaluation.