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Differential Revision: https://reviews.llvm.org/D159128
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Original commit message:
"
This patch enabled code completion for ClangREPL. The feature was built upon
three existing Clang components: a list completer for LineEditor, a
CompletionConsumer from SemaCodeCompletion, and the ASTUnit::codeComplete method.
The first component serves as the main entry point of handling interactive inputs.
Because a completion point for a compiler instance has to be unchanged once it
is set, an incremental compiler instance is created for each code
completion. Such a compiler instance carries over AST context source from the
main interpreter compiler in order to obtain declarations or bindings from
previous input in the same REPL session.
The most important API codeComplete in Interpreter/CodeCompletion is a thin
wrapper that calls with ASTUnit::codeComplete with necessary arguments, such as
a code completion point and a ReplCompletionConsumer, which communicates
completion results from SemaCodeCompletion back to the list completer for the
REPL.
In addition, PCC_TopLevelOrExpression and CCC_TopLevelOrExpression` top levels
were added so that SemaCodeCompletion can treat top level statements like
expression statements at the REPL. For example,
clang-repl> int foo = 42;
clang-repl> f<tab>
From a parser's persective, the cursor is at a top level. If we used code
completion without any changes, PCC_Namespace would be supplied to
Sema::CodeCompleteOrdinaryName, and thus the completion results would not
include foo.
Currently, the way we use PCC_TopLevelOrExpression and
CCC_TopLevelOrExpression is no different from the way we use PCC_Statement
and CCC_Statement respectively.
Differential revision: https://reviews.llvm.org/D154382
"
The new patch also fixes clangd and several memory issues that the bots reported
and upload the missing files.
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This reverts commit 5ab25a42ba70c4b50214b0e78eaaccd30696fa09 due to forgotten
files.
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Original commit message:
"
This patch enabled code completion for ClangREPL. The feature was built upon
three existing Clang components: a list completer for LineEditor, a
CompletionConsumer from SemaCodeCompletion, and the ASTUnit::codeComplete method.
The first component serves as the main entry point of handling interactive inputs.
Because a completion point for a compiler instance has to be unchanged once it
is set, an incremental compiler instance is created for each code
completion. Such a compiler instance carries over AST context source from the
main interpreter compiler in order to obtain declarations or bindings from
previous input in the same REPL session.
The most important API codeComplete in Interpreter/CodeCompletion is a thin
wrapper that calls with ASTUnit::codeComplete with necessary arguments, such as
a code completion point and a ReplCompletionConsumer, which communicates
completion results from SemaCodeCompletion back to the list completer for the
REPL.
In addition, PCC_TopLevelOrExpression and CCC_TopLevelOrExpression` top levels
were added so that SemaCodeCompletion can treat top level statements like
expression statements at the REPL. For example,
clang-repl> int foo = 42;
clang-repl> f<tab>
From a parser's persective, the cursor is at a top level. If we used code
completion without any changes, PCC_Namespace would be supplied to
Sema::CodeCompleteOrdinaryName, and thus the completion results would not
include foo.
Currently, the way we use PCC_TopLevelOrExpression and
CCC_TopLevelOrExpression is no different from the way we use PCC_Statement
and CCC_Statement respectively.
Differential revision: https://reviews.llvm.org/D154382
"
The new patch also fixes clangd and several memory issues that the bots reported.
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This reverts commit eb0e6c3134ef6deafe0a4958e9e1a1214b3c2f14 due to failures in
clangd such as https://lab.llvm.org/buildbot/#/builders/57/builds/29377
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This patch enabled code completion for ClangREPL. The feature was built upon
three existing Clang components: a list completer for LineEditor, a
CompletionConsumer from SemaCodeCompletion, and the ASTUnit::codeComplete method.
The first component serves as the main entry point of handling interactive inputs.
Because a completion point for a compiler instance has to be unchanged once it
is set, an incremental compiler instance is created for each code
completion. Such a compiler instance carries over AST context source from the
main interpreter compiler in order to obtain declarations or bindings from
previous input in the same REPL session.
The most important API codeComplete in Interpreter/CodeCompletion is a thin
wrapper that calls with ASTUnit::codeComplete with necessary arguments, such as
a code completion point and a ReplCompletionConsumer, which communicates
completion results from SemaCodeCompletion back to the list completer for the
REPL.
In addition, PCC_TopLevelOrExpression and CCC_TopLevelOrExpression` top levels
were added so that SemaCodeCompletion can treat top level statements like
expression statements at the REPL. For example,
clang-repl> int foo = 42;
clang-repl> f<tab>
From a parser's persective, the cursor is at a top level. If we used code
completion without any changes, PCC_Namespace would be supplied to
Sema::CodeCompleteOrdinaryName, and thus the completion results would not
include foo.
Currently, the way we use PCC_TopLevelOrExpression and
CCC_TopLevelOrExpression is no different from the way we use PCC_Statement
and CCC_Statement respectively.
Differential revision: https://reviews.llvm.org/D154382
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This patch uses castAs instead of getAs which will assert if the type doesn't match in SetValueDataBasedOnQualType(clang::Value &, unsigned long long).
Reviewed By: erichkeane
Differential Revision: https://reviews.llvm.org/D151770
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CUDA support can be enabled in clang-repl with --cuda flag.
Device code linking is not yet supported. inline must be used with all
__device__ functions.
Differential Revision: https://reviews.llvm.org/D146389
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This reverts commit 094ab4781262b6cb49d57b0ecdf84b047c879295.
Reland with changing `ParseAndExecute` to `Parse` in
`Interpreter::create`. This avoid creating JIT instance everytime even
if we don't really need them.
This should fixes failures like https://lab.llvm.org/buildbot/#/builders/38/builds/11955
The original reverted patch also causes GN bot fails on M1. (https://lab.llvm.org/buildbot/#/builders/38/builds/11955)
However, we can't reproduce it so let's reland it and see what happens.
See discussions here: https://reviews.llvm.org/rGd71a4e02277a64a9dece591cdf2b34f15c3b19a0
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This reverts commit 80e7eed6a610ab3c7289e6f9b7ec006bc7d7ae31.
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CUDA support can be enabled in clang-repl with --cuda flag.
Device code linking is not yet supported. inline must be used with all
__device__ functions.
Differential Revision: https://reviews.llvm.org/D146389
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This reverts commit d71a4e02277a64a9dece591cdf2b34f15c3b19a0.
See http://45.33.8.238/macm1/61024/step_7.txt
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This reverts commit 7158fd381a0bc0222195d6a07ebb42ea57957bda.
* Fixes endianness issue on big endian machines like PowerPC-bl
* Disable tests on platforms that having trouble to support JIT
Signed-off-by: Jun Zhang <jun@junz.org>
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This reverts commit a423b7f1d7ca8b263af85944f57a69aa08fc942c.
See https://lab.llvm.org/buildbot/#/changes/95083
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This is the second part of the below RFC:
https://discourse.llvm.org/t/rfc-handle-execution-results-in-clang-repl/68493
This patch implements a Value class that can be used to carry expression
results in clang-repl. In other words, when we see a top expression
without semi, it will be captured and stored to a Value object. You can
explicitly specify where you want to store the object, like:
```
Value V;
llvm::cantFail(Interp->ParseAndExecute("int x = 42;"));
llvm::cantFail(Interp->ParseAndExecute("x", &V));
```
`V` now stores some useful infomation about `x`, you can get its real
value (42), it's `clang::QualType` or anything interesting.
However, if you don't specify the optional argument, it will be captured
to a local variable, and automatically called `Value::dump`, which is
not implemented yet in this patch.
Signed-off-by: Jun Zhang <jun@junz.org>
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Most of Orc and JITLink are movinng away from JITTargetAddress and
use ExecutorAddr instead.
Signed-off-by: Jun Zhang <jun@junz.org>
Differential Revision: https://reviews.llvm.org/D148434
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This commit adds the %lib <file> command to load a dynamic library to be
used by the currently running interpreted code.
For example `%lib libSDL2.so`.
Differential Revision: https://reviews.llvm.org/D141824
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The forwarding header is left in place because of its use in
`polly/lib/External/isl/interface/extract_interface.cc`, but I have
added a GCC warning about the fact it is deprecated, because it is used
in `isl` from where it is included by Polly.
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This is a follow-up to https://reviews.llvm.org/D140896, split into
several parts as it touches a lot of files.
Differential Revision: https://reviews.llvm.org/D141139
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This patch teaches clang to parse statements on the global scope to allow:
```
./bin/clang-repl
clang-repl> int i = 12;
clang-repl> ++i;
clang-repl> extern "C" int printf(const char*,...);
clang-repl> printf("%d\n", i);
13
clang-repl> %quit
```
Generally, disambiguating between statements and declarations is a non-trivial
task for a C++ parser. The challenge is to allow both standard C++ to be
translated as if this patch does not exist and in the cases where the user typed
a statement to be executed as if it were in a function body.
Clang's Parser does pretty well in disambiguating between declarations and
expressions. We have added DisambiguatingWithExpression flag which allows us to
preserve the existing and optimized behavior where needed and implement the
extra rules for disambiguating. Only few cases require additional attention:
* Constructors/destructors -- Parser::isConstructorDeclarator was used in to
disambiguate between ctor-looking declarations and statements on the global
scope(eg. `Ns::f()`).
* The template keyword -- the template keyword can appear in both declarations
and statements. This patch considers the template keyword to be a declaration
starter which breaks a few cases in incremental mode which will be tackled
later.
* The inline (and similar) keyword -- looking at the first token in many cases
allows us to classify what is a declaration.
* Other language keywords and specifiers -- ObjC/ObjC++/OpenCL/OpenMP rely on
pragmas or special tokens which will be handled in subsequent patches.
The patch conceptually models a "top-level" statement into a TopLevelStmtDecl.
The TopLevelStmtDecl is lowered into a void function with no arguments.
We attach this function to the global initializer list to execute the statement
blocks in the correct order.
Differential revision: https://reviews.llvm.org/D127284
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Supports destructors of global objects by properly calling jitdylib deinitialize which calls the global dtors of ir modules.
This supersedes https://reviews.llvm.org/D127945. There was an issue when calling deinitialize on windows but it got fixed by https://reviews.llvm.org/D128037.
Reviewed By: v.g.vassilev
Differential Revision: https://reviews.llvm.org/D128589
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This is required to support RISC-V where the '+d' target feature
indicates the presence of the D instruction set extension, which
changes to the Hard-float 'd' ABI.
Differential Revision: https://reviews.llvm.org/D128853
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This reverts commit 9de8b05bfe0de2915d2443d06159396c5f9d389f.
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In interactive C++ it is convenient to roll back to a previous state of the
compiler. For example:
clang-repl> int x = 42;
clang-repl> %undo
clang-repl> float x = 24 // not an error
To support this, the patch extends the functionality used to recover from
errors and adds functionality to recover the low-level execution infrastructure.
The current implementation is based on watermarks. It exploits the fact that
at each incremental input the underlying compiler infrastructure is in a valid
state. We can only go N incremental inputs back to a previous valid state. We do
not need and do not do any further dependency tracking.
This patch was co-developed with V. Vassilev, relies on the past work of Purva
Chaudhari in clang-repl and is inspired by the past work on the same feature
in the Cling interpreter.
Co-authored-by: Purva-Chaudhari <purva.chaudhari02@gmail.com>
Co-authored-by: Vassil Vassilev <v.g.vassilev@gmail.com>
Signed-off-by: Jun Zhang <jun@junz.org>
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Supports destructors of global objects by properly calling jitdylib deinitialize which calls the global dtors of ir modules.
This supersedes https://reviews.llvm.org/D127945. There was an issue when calling deinitialize on windows but it got fixed by https://reviews.llvm.org/D128037.
Reviewed By: v.g.vassilev
Differential Revision: https://reviews.llvm.org/D128589
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Removes memory leak of ASTContext and TargetMachine. When DisableFree is turned on, it intentionally leaks these instances as they can be trivially deallocated. This patch turns this off and delete Parser instance early so that they will not reference dangling pargma headers.
Asan shouldn't detect these as leaks normally, since burypointer is called for them. But, every invocation of incremental parser createa an additional leak of TargetMachine. If there are many invocations within a single test case, we easily reach number of leaks exceeding kGraveYardMaxSize (which is 12) and leaks start to get reported by asan buildbots.
Reviewed By: v.g.vassilev
Differential Revision: https://reviews.llvm.org/D127991
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This patch will allow better incremental adoption of these changes in downstream
cling and other users which want to experiment by customizing the execution
engine.
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Original commit message: "
Original commit message: "
Original commit message: "
Original commit message:"
The current infrastructure in lib/Interpreter has a tool, clang-repl, very
similar to clang-interpreter which also allows incremental compilation.
This patch moves clang-interpreter as a test case and drops it as conditionally
built example as we already have clang-repl in place.
"
This patch also ignores ppc due to missing weak symbol for __gxx_personality_v0
which may be a feature request for the jit infrastructure. Also, adds a missing
build system dependency to the orc jit.
"
Additionally, this patch defines a custom exception type and thus avoids the
requirement to include header <exception>, making it easier to deploy across
systems without standard location of the c++ headers.
"
This patch also works around PR49692 and finds a way to use llvm::consumeError
in rtti mode.
"
This patch also checks if stl is built with rtti.
Differential revision: https://reviews.llvm.org/D107049
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This clears the memory used for the Clang AST before we run LLVM passes.
https://llvm-compile-time-tracker.com/compare.php?from=d0a5f61c4f6fccec87fd5207e3fcd9502dd59854&to=b7437fee79e04464dd968e1a29185495f3590481&stat=max-rss
shows significant memory savings with no slowdown (in fact -O0 slightly speeds up).
For more background, see
https://lists.llvm.org/pipermail/cfe-dev/2021-September/068930.html.
Turn this off for the interpreter since it does codegen multiple times.
Relanding with fix for -print-stats: D111973
Relanding with fix for plugins: D112190
If you'd like to use this even with plugins, consider using the features
introduced in D112096.
This can be turned off with -Xclang -no-clear-ast-before-backend.
Differential Revision: https://reviews.llvm.org/D111270
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This reverts commit 1fb24fe85a19ae71b00875ff6c96ef1831dcf7e3.
This causes clang crash on chromium. See repro at https://bugs.chromium.org/p/chromium/issues/detail?id=1261551#c1.
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This clears the memory used for the Clang AST before we run LLVM passes.
https://llvm-compile-time-tracker.com/compare.php?from=d0a5f61c4f6fccec87fd5207e3fcd9502dd59854&to=b7437fee79e04464dd968e1a29185495f3590481&stat=max-rss
shows significant memory savings with no slowdown (in fact -O0 slightly speeds up).
For more background, see
https://lists.llvm.org/pipermail/cfe-dev/2021-September/068930.html.
Turn this off for the interpreter since it does codegen multiple times.
Relanding with fix for -print-stats: D111973
Differential Revision: https://reviews.llvm.org/D111270
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This reverts commit 47eb99aa44ab1d20327d67a49d6c47163de76387.
This causes crashes with -print-stats: PR52193.
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This clears the memory used for the Clang AST before we run LLVM passes.
https://llvm-compile-time-tracker.com/compare.php?from=d0a5f61c4f6fccec87fd5207e3fcd9502dd59854&to=b7437fee79e04464dd968e1a29185495f3590481&stat=max-rss
shows significant memory savings with no slowdown (in fact -O0 slightly speeds up).
For more background, see
https://lists.llvm.org/pipermail/cfe-dev/2021-September/068930.html.
Turn this off for the interpreter since it does codegen multiple times.
Differential Revision: https://reviews.llvm.org/D111270
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This reverts commit 1dba6b37bdc70210f75a480eff3715ebe1f1d8be.
Reverting because the ClangReplInterpreterExceptionTests test fails on
our builders with this patch.
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Original commit message: "
Original commit message: "
Original commit message:"
The current infrastructure in lib/Interpreter has a tool, clang-repl, very
similar to clang-interpreter which also allows incremental compilation.
This patch moves clang-interpreter as a test case and drops it as conditionally
built example as we already have clang-repl in place.
Differential revision: https://reviews.llvm.org/D107049
"
This patch also ignores ppc due to missing weak symbol for __gxx_personality_v0
which may be a feature request for the jit infrastructure. Also, adds a missing
build system dependency to the orc jit.
"
Additionally, this patch defines a custom exception type and thus avoids the
requirement to include header <exception>, making it easier to deploy across
systems without standard location of the c++ headers.
"
This patch also works around PR49692 and finds a way to use llvm::consumeError
in rtti mode.
Differential revision: https://reviews.llvm.org/D107049
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mingw-g++ does not correctly support the full `std::errc` namespace as
worded in the standard[1]. As such, we cannot reliably use all names
therein. This patch changes the use of
`std::errc::state_not_recoverable`, to use portable error codes from the
`llvm::errc` equivalent.
[1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71444
Reviewed by v.g.vassilev
Differential Revision: https://reviews.llvm.org/D111315
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This reverts commit 6fe2beba7d2a41964af658c8c59dd172683ef739 which fails on
clang-hexagon-elf
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Original commit message: "
Original commit message:"
The current infrastructure in lib/Interpreter has a tool, clang-repl, very
similar to clang-interpreter which also allows incremental compilation.
This patch moves clang-interpreter as a test case and drops it as conditionally
built example as we already have clang-repl in place.
Differential revision: https://reviews.llvm.org/D107049
"
This patch also ignores ppc due to missing weak symbol for __gxx_personality_v0
which may be a feature request for the jit infrastructure. Also, adds a missing
build system dependency to the orc jit.
"
Additionally, this patch defines a custom exception type and thus avoids the
requirement to include header <exception>, making it easier to deploy across
systems without standard location of the c++ headers.
Differential revision: https://reviews.llvm.org/D107049
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The way we parse `DiagnosticOptions` is a bit involved.
`DiagnosticOptions` are parsed as part of the cc1-parsing function `CompilerInvocation::CreateFromArgs` which takes `DiagnosticsEngine` as an argument to be able to report errors in command-line arguments. But to create `DiagnosticsEngine`, `DiagnosticOptions` are needed. This is solved by exposing the `ParseDiagnosticArgs` to clients and making its `DiagnosticsEngine` argument optional, essentially breaking the dependency cycle.
The `ParseDiagnosticArgs` function takes `llvm::opt::ArgList &`, which each client needs to create from the command-line (typically represented as `std::vector<const char *>`). Creating this data structure in this context is somewhat particular. This code pattern is copy-pasted in some places across the upstream code base and also in downstream repos. To make things a bit more uniform, this patch extracts the code into a new reusable function: `CreateAndPopulateDiagOpts`.
Reviewed By: dexonsmith
Differential Revision: https://reviews.llvm.org/D108918
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This reverts commit f0514a4d26100239088f08d618f2ba100f59958e.
Test fails on macOS: https://reviews.llvm.org/D107049#2976603
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Original commit message:"
The current infrastructure in lib/Interpreter has a tool, clang-repl, very
similar to clang-interpreter which also allows incremental compilation.
This patch moves clang-interpreter as a test case and drops it as conditionally
built example as we already have clang-repl in place.
Differential revision: https://reviews.llvm.org/D107049
"
This patch also ignores ppc due to missing weak symbol for __gxx_personality_v0
which may be a feature request for the jit infrastructure. Also, adds a missing
build system dependency to the orc jit.
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This reverts commit 319ce98011742141dad8dd95a2f9de9c0449be5c because it fails
on various platforms.
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The current infrastructure in lib/Interpreter has a tool, clang-repl, very
similar to clang-interpreter which also allows incremental compilation.
This patch moves clang-interpreter as a test case and drops it as conditionally
built example as we already have clang-repl in place.
Differential revision: https://reviews.llvm.org/D107049
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Original commit message:
[clang-repl] Implement partial translation units and error recovery.
https://reviews.llvm.org/D96033 contained a discussion regarding efficient
modeling of error recovery. @rjmccall has outlined the key ideas:
Conceptually, we can split the translation unit into a sequence of partial
translation units (PTUs). Every declaration will be associated with a unique PTU
that owns it.
The first key insight here is that the owning PTU isn't always the "active"
(most recent) PTU, and it isn't always the PTU that the declaration
"comes from". A new declaration (that isn't a redeclaration or specialization of
anything) does belong to the active PTU. A template specialization, however,
belongs to the most recent PTU of all the declarations in its signature - mostly
that means that it can be pulled into a more recent PTU by its template
arguments.
The second key insight is that processing a PTU might extend an earlier PTU.
Rolling back the later PTU shouldn't throw that extension away. For example, if
the second PTU defines a template, and the third PTU requires that template to
be instantiated at float, that template specialization is still part of the
second PTU. Similarly, if the fifth PTU uses an inline function belonging to the
fourth, that definition still belongs to the fourth. When we go to emit code in
a new PTU, we map each declaration we have to emit back to its owning PTU and
emit it in a new module for just the extensions to that PTU. We keep track of
all the modules we've emitted for a PTU so that we can unload them all if we
decide to roll it back.
Most declarations/definitions will only refer to entities from the same or
earlier PTUs. However, it is possible (primarily by defining a
previously-declared entity, but also through templates or ADL) for an entity
that belongs to one PTU to refer to something from a later PTU. We will have to
keep track of this and prevent unwinding to later PTU when we recognize it.
Fortunately, this should be very rare; and crucially, we don't have to do the
bookkeeping for this if we've only got one PTU, e.g. in normal compilation.
Otherwise, PTUs after the first just need to record enough metadata to be able
to revert any changes they've made to declarations belonging to earlier PTUs,
e.g. to redeclaration chains or template specialization lists.
It should even eventually be possible for PTUs to provide their own slab
allocators which can be thrown away as part of rolling back the PTU. We can
maintain a notion of the active allocator and allocate things like Stmt/Expr
nodes in it, temporarily changing it to the appropriate PTU whenever we go to do
something like instantiate a function template. More care will be required when
allocating declarations and types, though.
We would want the PTU to be efficiently recoverable from a Decl; I'm not sure
how best to do that. An easy option that would cover most declarations would be
to make multiple TranslationUnitDecls and parent the declarations appropriately,
but I don't think that's good enough for things like member function templates,
since an instantiation of that would still be parented by its original class.
Maybe we can work this into the DC chain somehow, like how lexical DCs are.
We add a different kind of translation unit `TU_Incremental` which is a
complete translation unit that we might nonetheless incrementally extend later.
Because it is complete (and we might want to generate code for it), we do
perform template instantiation, but because it might be extended later, we don't
warn if it declares or uses undefined internal-linkage symbols.
This patch teaches clang-repl how to recover from errors by disconnecting the
most recent PTU and update the primary PTU lookup tables. For instance:
```./clang-repl
clang-repl> int i = 12; error;
In file included from <<< inputs >>>:1:
input_line_0:1:13: error: C++ requires a type specifier for all declarations
int i = 12; error;
^
error: Parsing failed.
clang-repl> int i = 13; extern "C" int printf(const char*,...);
clang-repl> auto r1 = printf("i=%d\n", i);
i=13
clang-repl> quit
```
Differential revision: https://reviews.llvm.org/D104918
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This reverts commit 6775fc6ffa3ca1c36b20c25fa4e7f48f81213cf2.
It also reverts "[lldb] Fix compilation by adjusting to the new ASTContext signature."
This reverts commit 03a3f86071c10a1f6cbbf7375aa6fe9d94168972.
We see some failures on the lldb infrastructure, these changes might play a role
in it. Let's revert it now and see if the bots will become green.
Ref: https://reviews.llvm.org/D104918
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https://reviews.llvm.org/D96033 contained a discussion regarding efficient
modeling of error recovery. @rjmccall has outlined the key ideas:
Conceptually, we can split the translation unit into a sequence of partial
translation units (PTUs). Every declaration will be associated with a unique PTU
that owns it.
The first key insight here is that the owning PTU isn't always the "active"
(most recent) PTU, and it isn't always the PTU that the declaration
"comes from". A new declaration (that isn't a redeclaration or specialization of
anything) does belong to the active PTU. A template specialization, however,
belongs to the most recent PTU of all the declarations in its signature - mostly
that means that it can be pulled into a more recent PTU by its template
arguments.
The second key insight is that processing a PTU might extend an earlier PTU.
Rolling back the later PTU shouldn't throw that extension away. For example, if
the second PTU defines a template, and the third PTU requires that template to
be instantiated at float, that template specialization is still part of the
second PTU. Similarly, if the fifth PTU uses an inline function belonging to the
fourth, that definition still belongs to the fourth. When we go to emit code in
a new PTU, we map each declaration we have to emit back to its owning PTU and
emit it in a new module for just the extensions to that PTU. We keep track of
all the modules we've emitted for a PTU so that we can unload them all if we
decide to roll it back.
Most declarations/definitions will only refer to entities from the same or
earlier PTUs. However, it is possible (primarily by defining a
previously-declared entity, but also through templates or ADL) for an entity
that belongs to one PTU to refer to something from a later PTU. We will have to
keep track of this and prevent unwinding to later PTU when we recognize it.
Fortunately, this should be very rare; and crucially, we don't have to do the
bookkeeping for this if we've only got one PTU, e.g. in normal compilation.
Otherwise, PTUs after the first just need to record enough metadata to be able
to revert any changes they've made to declarations belonging to earlier PTUs,
e.g. to redeclaration chains or template specialization lists.
It should even eventually be possible for PTUs to provide their own slab
allocators which can be thrown away as part of rolling back the PTU. We can
maintain a notion of the active allocator and allocate things like Stmt/Expr
nodes in it, temporarily changing it to the appropriate PTU whenever we go to do
something like instantiate a function template. More care will be required when
allocating declarations and types, though.
We would want the PTU to be efficiently recoverable from a Decl; I'm not sure
how best to do that. An easy option that would cover most declarations would be
to make multiple TranslationUnitDecls and parent the declarations appropriately,
but I don't think that's good enough for things like member function templates,
since an instantiation of that would still be parented by its original class.
Maybe we can work this into the DC chain somehow, like how lexical DCs are.
We add a different kind of translation unit `TU_Incremental` which is a
complete translation unit that we might nonetheless incrementally extend later.
Because it is complete (and we might want to generate code for it), we do
perform template instantiation, but because it might be extended later, we don't
warn if it declares or uses undefined internal-linkage symbols.
This patch teaches clang-repl how to recover from errors by disconnecting the
most recent PTU and update the primary PTU lookup tables. For instance:
```./clang-repl
clang-repl> int i = 12; error;
In file included from <<< inputs >>>:1:
input_line_0:1:13: error: C++ requires a type specifier for all declarations
int i = 12; error;
^
error: Parsing failed.
clang-repl> int i = 13; extern "C" int printf(const char*,...);
clang-repl> auto r1 = printf("i=%d\n", i);
i=13
clang-repl> quit
```
Differential revision: https://reviews.llvm.org/D104918
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