[Serialization] Support loading template specializations lazily (#119333)

Reland https://github.com/llvm/llvm-project/pull/83237

---

(Original comments)

Currently all the specializations of

[Serialization] Support loading template specializations lazily (#119333)

Reland https://github.com/llvm/llvm-project/pull/83237

---

(Original comments)

Currently all the specializations of a template (including
instantiation, specialization and partial specializations) will be
loaded at once if we want to instantiate another instance for the
template, or find instantiation for the template, or just want to
complete the redecl chain.

This means basically we need to load every specializations for the
template once the template declaration got loaded. This is bad since
when we load a specialization, we need to load all of its template
arguments. Then we have to deserialize a lot of unnecessary
declarations.

For example,

```
// M.cppm
export module M;
export template <class T>
class A {};

export class ShouldNotBeLoaded {};

export class Temp {
A<ShouldNotBeLoaded> AS;
};

// use.cpp
import M;
A<int> a;
```

We have a specialization ` A<ShouldNotBeLoaded>` in `M.cppm` and we
instantiate the template `A` in `use.cpp`. Then we will deserialize
`ShouldNotBeLoaded` surprisingly when compiling `use.cpp`. And this
patch tries to avoid that.

Given that the templates are heavily used in C++, this is a pain point
for the performance.

This patch adds MultiOnDiskHashTable for specializations in the
ASTReader. Then we will only deserialize the specializations with the
same template arguments. We made that by using ODRHash for the template
arguments as the key of the hash table.

To review this patch, I think `ASTReaderDecl::AddLazySpecializations`
may be a good entry point.

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Revert "[Serialization] Support load lazy specialization lazily"

This reverts commit b5bd19211118c6d43bc525a4e3fb65d2c750d61e.
It brokes multiple llvm bots including clang-x64-windows-msvc

[Serialization] Support load lazy specialization lazily

Currently all the specializations of a template (including
instantiation, specialization and partial specializations) will be
loaded at once

[Serialization] Support load lazy specialization lazily

Currently all the specializations of a template (including
instantiation, specialization and partial specializations) will be
loaded at once if we want to instantiate another instance for the
template, or find instantiation for the template, or just want to
complete the redecl chain.

This means basically we need to load every specializations for the
template once the template declaration got loaded. This is bad since
when we load a specialization, we need to load all of its template
arguments. Then we have to deserialize a lot of unnecessary
declarations.

For example,

```
// M.cppm
export module M;
export template <class T>
class A {};

export class ShouldNotBeLoaded {};

export class Temp {
A<ShouldNotBeLoaded> AS;
};

// use.cpp
import M;
A<int> a;
```

We should a specialization ` A<ShouldNotBeLoaded>` in `M.cppm` and we
instantiate the template `A` in `use.cpp`. Then we will deserialize
`ShouldNotBeLoaded` surprisingly when compiling `use.cpp`. And this
patch tries to avoid that.

Given that the templates are heavily used in C++, this is a pain point
for the performance.

This patch adds MultiOnDiskHashTable for specializations in the
ASTReader. Then we will only deserialize the specializations with the
same template arguments. We made that by using ODRHash for the template
arguments as the key of the hash table.

To review this patch, I think `ASTReaderDecl::AddLazySpecializations`
may be a good entry point.

The patch was reviewed in
https://github.com/llvm/llvm-project/pull/83237 but that PR is a stacked
PR. But I feel the intention of the stacked PRs get lost during the
review process. So I feel it is better to merge the commits into a
single commit instead of merging them in the PR page. It is better for
us to cherry-pick and revert.

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[test] %clang_cc1: remove redundant actions

[OpenMP] Update the default version of OpenMP to 5.1

The default version of OpenMP is updated from 5.0 to 5.1 which means if -fopenmp is specified but -fopenmp-version is not specified with clang, t

[OpenMP] Update the default version of OpenMP to 5.1

The default version of OpenMP is updated from 5.0 to 5.1 which means if -fopenmp is specified but -fopenmp-version is not specified with clang, the default version of OpenMP is taken to be 5.1. After modifying the Frontend for that, various LIT tests were updated. This patch contains all such changes. At a high level, these are the patterns of changes observed in LIT tests -

# RUN lines which mentioned `-fopenmp-version=50` need to kept only if the IR for version 5.0 and 5.1 are different. Otherwise only one RUN line with no version info(i.e. default version) needs to be there.

# Test cases of this sort already had the RUN lines with respect to the older default version 5.0 and the version 5.1. Only swapping the version specification flag `-fopenmp-version` from newer version RUN line to older version RUN line is required.

# Diagnostics: Remove the 5.0 version specific RUN lines if there was no difference in the Diagnostics messages with respect to the default 5.1.

# Diagnostics: In case there was any difference in diagnostics messages between 5.0 and 5.1, mention version specific messages in tests.

# If the test contained version specific ifdef's e.g. "#ifdef OMP5" but there were no RUN lines for any other version than 5.X, then bring the code guarded by ifdef's outside and remove the ifdef's.

# Some tests had RUN lines for both 5.0 and 5.1 versions, but it is found that the IR for 5.0 is not different from the 5.1, therefore such RUN lines are redundant. So, such duplicated lines are removed.

# To generate CHECK lines automatically, use the script llvm/utils/update_cc_test_checks.py

Reviewed By: saiislam, ABataev

Differential Revision: https://reviews.llvm.org/D129635

(cherry picked from commit 9dd2999907dc791136a75238a6000f69bf67cf4e)

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[OPENMP]Consider 'omp_null_allocator' as a predefined allocator.

Summary:
omp.h header file defines omp_null_allocator as a predefined allocator,
need to consider it also as a predefined allocator.

[OPENMP]Consider 'omp_null_allocator' as a predefined allocator.

Summary:
omp.h header file defines omp_null_allocator as a predefined allocator,
need to consider it also as a predefined allocator.

Reviewers: jdoerfert

Subscribers: jholewinski, yaxunl, guansong, cfe-commits, caomhin

Tags: #clang

Differential Revision: https://reviews.llvm.org/D79186

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[OPENMP50]Basic support for uses_allocators clause.

Summary: Added parsing/sema/serialization supoprt for uses_allocators clause.

Reviewers: jdoerfert

Subscribers: yaxunl, guansong, arphaman, cfe-

[OPENMP50]Basic support for uses_allocators clause.

Summary: Added parsing/sema/serialization supoprt for uses_allocators clause.

Reviewers: jdoerfert

Subscribers: yaxunl, guansong, arphaman, cfe-commits, caomhin

Tags: #clang

Differential Revision: https://reviews.llvm.org/D78577

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[OPENMP]Allow cancellation constructs in target parallel regions.

Summary:
omp cancellation point parallel and omp cancel parallel directives are
allowed in target paralle regions.

Reviewers: jdoer

[OPENMP]Allow cancellation constructs in target parallel regions.

Summary:
omp cancellation point parallel and omp cancel parallel directives are
allowed in target paralle regions.

Reviewers: jdoerfert

Subscribers: yaxunl, guansong, caomhin, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D78941

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[OPENMP50]Support 'task' modifier in reduction clauses.

Summary:
Added basic support for 'task' modifier in the reduction clauses in
non-simd parallel and worksharing constructs.

Reviewers: jdoerfe

[OPENMP50]Support 'task' modifier in reduction clauses.

Summary:
Added basic support for 'task' modifier in the reduction clauses in
non-simd parallel and worksharing constructs.

Reviewers: jdoerfert

Subscribers: yaxunl, guansong, cfe-commits, caomhin

Tags: #clang

Differential Revision: https://reviews.llvm.org/D78738

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[OPENMP]Initial support for 'allocate' clause.

Added parsing/sema analysis of the allocate clause.

llvm-svn: 357068

[OpenMP] Fix trailing space when printing pragmas, by Joel. E. Denny

Summary:
-ast-print prints omp pragmas with a trailing space. While this
behavior is likely of little concern to most users, sur

[OpenMP] Fix trailing space when printing pragmas, by Joel. E. Denny

Summary:
-ast-print prints omp pragmas with a trailing space. While this
behavior is likely of little concern to most users, surely it's
unintentional, and it's annoying for some source-level work I'm
pursuing. This patch focuses on omp pragmas, but it also fixes
init_seg and loop hint pragmas because they share implementation.

The testing strategy here is to add usually just one '{{$}}' per
relevant -ast-print test file. This seems to achieve good code
coverage. However, this strategy is probably easy to forget as the
tests evolve. That's probably fine as this fix is far from critical.
The main goal of the testing is to aid the initial review.

This patch also adds a fixme for "#pragma unroll", which prints as
"#pragma unroll (enable)", which is invalid syntax.

Reviewers: ABataev

Reviewed By: ABataev

Subscribers: guansong, cfe-commits

Differential Revision: https://reviews.llvm.org/D43204

llvm-svn: 325145

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[OPENMP] Support for -fopenmp-simd option with compilation of simd loops
only.

Added support for -fopenmp-simd option that allows compilation of
simd-based constructs without emission of OpenMP runt

[OPENMP] Support for -fopenmp-simd option with compilation of simd loops
only.

Added support for -fopenmp-simd option that allows compilation of
simd-based constructs without emission of OpenMP runtime calls.

llvm-svn: 321560

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[OPENMP] Fix for PR31428: variable named like directive name modifier

Directive name modifiers in 'if' clause are allowed only for OpenMP 4.5
and higher + in OpenMP 4.5 parsing procedure emits error

[OPENMP] Fix for PR31428: variable named like directive name modifier

Directive name modifiers in 'if' clause are allowed only for OpenMP 4.5
and higher + in OpenMP 4.5 parsing procedure emits error message if ':'
is not found after directive name modifier.

llvm-svn: 290175

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Make output of -ast-print a valid C++ code.

Output generated by option -ast-print looks like C/C++ code, and it
really is for plain C. For C++ the produced output was not valid C++
code, but the dif

Make output of -ast-print a valid C++ code.

Output generated by option -ast-print looks like C/C++ code, and it
really is for plain C. For C++ the produced output was not valid C++
code, but the differences were small. With this change the output
is fixed and can be compiled. Tests are changed so that output produced
by -ast-print is compiled again with the same flags and both outputs are
compared.

Option -ast-print is extensively used in clang tests but it itself
was tested poorly, existing tests only checked that compiler did not
crash. There are unit tests in file DeclPrinterTest.cpp, but they test
only terse output mode.

Differential Revision: https://reviews.llvm.org/D26452

llvm-svn: 286439

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Warn if function or variable cannot be implicitly instantiated

With this patch compiler emits warning if it tries to make implicit instantiation
of a template but cannot find the template definition

Warn if function or variable cannot be implicitly instantiated

With this patch compiler emits warning if it tries to make implicit instantiation
of a template but cannot find the template definition. The warning can be suppressed
by explicit instantiation declaration or by command line options
-Wundefined-var-template and -Wundefined-func-template. The implementation follows
the discussion of http://reviews.llvm.org/D12326.

Differential Revision: http://reviews.llvm.org/D16396

llvm-svn: 266719

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[OpenMP] Parsing + sema for target parallel directive.

Summary:
This patch adds parsing + sema for the target parallel directive and its clauses along with testcases.

Reviewers: ABataev

Differenti

[OpenMP] Parsing + sema for target parallel directive.

Summary:
This patch adds parsing + sema for the target parallel directive and its clauses along with testcases.

Reviewers: ABataev

Differential Revision: http://reviews.llvm.org/D16553

Rebased to current trunk and updated test cases.

llvm-svn: 258832

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