[PATCH] D145737: PR60985: Fix merging of lambda closure types across modules.

[Richard Smith - zygoloid via Phabricator via cfe-commits]

rsmith created this revision.
Herald added a subscriber: martong.
Herald added a reviewer: shafik.
Herald added a project: All.
rsmith requested review of this revision.
Herald added a project: clang.
Herald added a subscriber: cfe-commits.

Previously, distinct lambdas would get merged, and multiple definitions
of the same lambda would not get merged, because we attempted to
identify lambdas by their ordinal position within their lexical
DeclContext. This failed for lambdas within namespace-scope variables
and within variable templates, where the lexical position in the context
containing the variable didn't uniquely identify the lambda.

In this patch, we instead identify lambda closure types by index within
their context declaration, which does uniquely identify them in a way
that's consistent across modules.

This change causes a deserialization cycle between the type of a
variable with deduced type and a lambda appearing as the initializer of
the variable -- reading the variable's type requires reading and merging
the lambda, and reading the lambda requires reading and merging the
variable. This is addressed by deferring loading the deduced type of a
variable until after we finish recursive deserialization.

This also exposes a pre-existing subtle issue where loading a
variable declaration would trigger immediate loading of its initializer,
which could recursively refer back to properties of the variable. This
particularly causes problems if the initializer contains a
lambda-expression, but can be problematic in general. That is addressed
by switching to lazily loading the initializers of variables rather than
always loading them with the variable declaration. As well as fixing a
deserialization cycle, that should improve laziness of deserialization
in general.

LambdaDefinitionData had 63 spare bits in it, presumably caused by an
off-by-one-error in some previous change. This change claims 32 of those bits
as a counter for the lambda within its context. We could probably move the
numbering to separate storage, like we do for the device-side mangling number,
to optimize the likely-common case where all three numbers (host-side mangling
number, device-side mangling number, and index within the context declaration)
are zero, but that's not done in this change.

Fixes #60985.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D145737

Files:
  clang/docs/ReleaseNotes.rst
  clang/include/clang/AST/Decl.h
  clang/include/clang/AST/DeclCXX.h
  clang/include/clang/AST/ExternalASTSource.h
  clang/include/clang/AST/MangleNumberingContext.h
  clang/include/clang/AST/Stmt.h
  clang/include/clang/Sema/ExternalSemaSource.h
  clang/include/clang/Sema/MultiplexExternalSemaSource.h
  clang/include/clang/Sema/Sema.h
  clang/include/clang/Serialization/ASTReader.h
  clang/lib/AST/ASTContext.cpp
  clang/lib/AST/ASTImporter.cpp
  clang/lib/AST/Decl.cpp
  clang/lib/AST/DeclCXX.cpp
  clang/lib/AST/ODRDiagsEmitter.cpp
  clang/lib/Sema/MultiplexExternalSemaSource.cpp
  clang/lib/Sema/SemaExprCXX.cpp
  clang/lib/Sema/SemaLambda.cpp
  clang/lib/Sema/TreeTransform.h
  clang/lib/Serialization/ASTReader.cpp
  clang/lib/Serialization/ASTReaderDecl.cpp
  clang/lib/Serialization/ASTReaderStmt.cpp
  clang/lib/Serialization/ASTWriter.cpp
  clang/lib/Serialization/ASTWriterDecl.cpp
  clang/lib/Serialization/ASTWriterStmt.cpp
  clang/test/Modules/lambda-in-variable.cpp
  clang/test/OpenMP/parallel_master_taskloop_simd_codegen.cpp

-------------- next part --------------
A non-text attachment was scrubbed...
Name: D145737.503963.patch
Type: text/x-patch
Size: 66025 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20230310/8acf96ed/attachment-0001.bin>