Commit Graph

133 Commits

Author SHA1 Message Date
Eduardo Caldas c0e5e3fbfa [Ignore Expressions] Fix performance regression by inlining `Ignore*SingleStep`
We also add a `const` versions of `IgnoreExprNodes`

Differential Revision: https://reviews.llvm.org/D87278
2020-09-09 07:32:40 +00:00
Eduardo Caldas 81aa66f65f Extract infrastructure to ignore intermediate expressions into `clang/AST/IgnoreExpr.h`
Rationale:
This allows users to use `IgnoreExprNodes` and `Ignore*SingleStep` outside of
`clang/AST/Expr.cpp`.

Minor:
Rename `IgnoreImp...SingleStep`  into `IgnoreImplicit...SingleStep`.

Differential Revision: https://reviews.llvm.org/D86778
2020-09-07 09:32:30 +00:00
Valentin Clement d90443b1d9 [openmp] Base of tablegen generated OpenMP common declaration
Summary:
As discussed previously when landing patch for OpenMP in Flang, the idea is
to share common part of the OpenMP declaration between the different Frontend.
While doing this it was thought that moving to tablegen instead of Macros will also
give a cleaner and more powerful way of generating these declaration.
This first part of a future series of patches is setting up the base .td file for
DirectiveLanguage as well as the OpenMP version of it. The base file is meant to
be used by other directive language such as OpenACC.
In this first patch, the Directive and Clause enums are generated with tablegen
instead of the macros on OMPConstants.h. The next pacth will extend this
to other enum and move the Flang frontend to use it.

Reviewers: jdoerfert, DavidTruby, fghanim, ABataev, jdenny, hfinkel, jhuber6, kiranchandramohan, kiranktp

Reviewed By: jdoerfert, jdenny

Subscribers: arphaman, martong, cfe-commits, mgorny, yaxunl, hiraditya, guansong, jfb, sstefan1, aaron.ballman, llvm-commits

Tags: #llvm, #openmp, #clang

Differential Revision: https://reviews.llvm.org/D81736
2020-06-23 10:32:32 -04:00
Haojian Wu 876bb86e26 [AST] Move dependence computations into a separate file
To group the code in one place, simplify it and make it easier to add
the containsErrors bit and find existing bugs.

Reviewers: sammccall

Reviewed By: sammccall

Tags: #clang

Differential Revision: https://reviews.llvm.org/D73638
2020-03-17 09:22:31 +01:00
Haojian Wu 18c9766248 Revert "[AST] Move dependence computations into a separate file"
This reverts commit ddd20ed158.
The patch was landed by accident.
2020-03-16 16:49:38 +01:00
Ilya Biryukov ddd20ed158 [AST] Move dependence computations into a separate file
To group the code in one place, simplify it and make it easier to add
the containsErrors bit and find existing bugs.
2020-03-16 16:48:49 +01:00
Fangrui Song e4df934ca7 [Clang interpreter] Rename Block.{h,cpp} to InterpBlock.{h,cpp}
The Blocks runtime provide a header named Block.h.
It is generally preferable to avoid name collision with system headers
(reducing reliance on -isystem order, more friendly when navigating files in
an editor, etc).

Reviewed By: gribozavr2

Differential Revision: https://reviews.llvm.org/D74934
2020-02-21 09:47:28 -08:00
Reid Kleckner 8a81daaa8b [AST] Split parent map traversal logic into ParentMapContext.h
The only part of ASTContext.h that requires most AST types to be
complete is the parent map. Nothing in Clang proper uses the ParentMap,
so split it out into its own class. Make ASTContext own the
ParentMapContext so there is still a one-to-one relationship.

After this change, 562 fewer files depend on ASTTypeTraits.h, and 66
fewer depend on TypeLoc.h:
  $ diff -u deps-before.txt deps-after.txt | \
    grep '^[-+] ' | sort | uniq -c | sort -nr | less
      562 -    ../clang/include/clang/AST/ASTTypeTraits.h
      340 +    ../clang/include/clang/AST/ParentMapContext.h
       66 -    ../clang/include/clang/AST/TypeLocNodes.def
       66 -    ../clang/include/clang/AST/TypeLoc.h
       15 -    ../clang/include/clang/AST/TemplateBase.h
  ...
I computed deps-before.txt and deps-after.txt with `ninja -t deps`.

This removes a common and key dependency on TemplateBase.h and
TypeLoc.h.

This also has the effect of breaking the ParentMap RecursiveASTVisitor
instantiation into its own file, which roughly halves the compilation
time of ASTContext.cpp (29.75s -> 17.66s). The new file takes 13.8s to
compile.

I left behind forwarding methods for getParents(), but clients will need
to include a new header to make them work:
  #include "clang/AST/ParentMapContext.h"

I noticed that this parent map functionality is unfortunately duplicated
in ParentMap.h, which only works for Stmt nodes.

Reviewed By: rsmith

Differential Revision: https://reviews.llvm.org/D71313
2020-01-24 13:42:28 -08:00
Saar Raz a0f50d7316 [Concepts] Requires Expressions
Implement support for C++2a requires-expressions.

Re-commit after compilation failure on some platforms due to alignment issues with PointerIntPair.

Differential Revision: https://reviews.llvm.org/D50360
2020-01-19 00:23:26 +02:00
Saar Raz baa84d8cde Revert "[Concepts] Requires Expressions"
This reverts commit 0279318997.

There have been some failing tests on some platforms, reverting while investigating.
2020-01-18 14:58:01 +02:00
Saar Raz 0279318997 [Concepts] Requires Expressions
Implement support for C++2a requires-expressions.

Differential Revision: https://reviews.llvm.org/D50360
2020-01-18 09:15:36 +02:00
Johannes Doerfert eb3e81f43f [OpenMP][NFCI] Introduce llvm/IR/OpenMPConstants.h
Summary:
The new OpenMPConstants.h is a location for all OpenMP related constants
(and helpers) to live.

This patch moves the directives there (the enum OpenMPDirectiveKind) and
rewires Clang to use the new location.

Initially part of D69785.

Reviewers: kiranchandramohan, ABataev, RaviNarayanaswamy, gtbercea, grokos, sdmitriev, JonChesterfield, hfinkel, fghanim

Subscribers: jholewinski, ppenzin, penzn, llvm-commits, cfe-commits, jfb, guansong, bollu, hiraditya, mgorny

Tags: #clang, #llvm

Differential Revision: https://reviews.llvm.org/D69853
2019-12-10 00:10:09 -06:00
Saar Raz fdf80e86a5 [Concepts] Constraint Enforcement & Diagnostics
Part of the C++20 concepts implementation effort.
- Associated constraints (requires clauses, currently) are now enforced when instantiating/specializing templates and when considering partial specializations and function overloads.
- Elaborated diagnostics give helpful insight as to why the constraints were not satisfied.
Phabricator: D41569

Re-commit, after fixing some memory bugs.
2019-12-06 01:34:20 +02:00
Vlad Tsyrklevich 38839d08b8 Revert "[Concepts] Constraint Enforcement & Diagnostics"
This reverts commit ffa214ef22, it was
causing ASAN test failures on sanitizer-x86_64-linux-bootstrap.
2019-10-28 15:00:40 -07:00
Saar Raz ffa214ef22 [Concepts] Constraint Enforcement & Diagnostics
Part of the C++20 concepts implementation effort.
- Associated constraints (requires clauses, currently) are now enforced when instantiating/specializing templates and when considering partial specializations and function overloads.
- Elaborated diagnostics give helpful insight as to why the constraints were not satisfied.
Phabricator: D41569
2019-10-25 00:19:51 +03:00
Nandor Licker 950b70dcc7 [Clang Interpreter] Initial patch for the constexpr interpreter
Summary:
This patch introduces the skeleton of the constexpr interpreter,
capable of evaluating a simple constexpr functions consisting of
if statements. The interpreter is described in more detail in the
RFC. Further patches will add more features.

Reviewers: Bigcheese, jfb, rsmith

Subscribers: bruno, uenoku, ldionne, Tyker, thegameg, tschuett, dexonsmith, mgorny, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D64146

llvm-svn: 371834
2019-09-13 09:46:16 +00:00
Roman Lebedev 2c9f83cfab Revert "[Clang Interpreter] Initial patch for the constexpr interpreter"
Breaks BUILD_SHARED_LIBS build, introduces cycles in library dependency
graphs. (clangInterp depends on clangAST which depends on clangInterp)

This reverts r370839, which is an yet another recommit of D64146.

llvm-svn: 370874
2019-09-04 10:57:06 +00:00
Nandor Licker 32f82c9cba [Clang Interpreter] Initial patch for the constexpr interpreter
Summary:
This patch introduces the skeleton of the constexpr interpreter,
capable of evaluating a simple constexpr functions consisting of
if statements. The interpreter is described in more detail in the
RFC. Further patches will add more features.

Reviewers: Bigcheese, jfb, rsmith

Subscribers: bruno, uenoku, ldionne, Tyker, thegameg, tschuett, dexonsmith, mgorny, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D64146

llvm-svn: 370839
2019-09-04 05:49:41 +00:00
Nandor Licker c3bdad8c1e Revert [Clang Interpreter] Initial patch for the constexpr interpreter
This reverts r370636 (git commit 8327fed947)

llvm-svn: 370642
2019-09-02 11:34:47 +00:00
Nandor Licker 8327fed947 [Clang Interpreter] Initial patch for the constexpr interpreter
Summary:
This patch introduces the skeleton of the constexpr interpreter,
capable of evaluating a simple constexpr functions consisting of
if statements. The interpreter is described in more detail in the
RFC. Further patches will add more features.

Reviewers: Bigcheese, jfb, rsmith

Subscribers: bruno, uenoku, ldionne, Tyker, thegameg, tschuett, dexonsmith, mgorny, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D64146

llvm-svn: 370636
2019-09-02 10:38:08 +00:00
Nandor Licker a6bef738bf Revert [Clang Interpreter] Initial patch for the constexpr interpreter
This reverts r370584 (git commit afcb3de117)

llvm-svn: 370588
2019-08-31 15:15:39 +00:00
Nandor Licker afcb3de117 [Clang Interpreter] Initial patch for the constexpr interpreter
Summary:
This patch introduces the skeleton of the constexpr interpreter,
capable of evaluating a simple constexpr functions consisting of
if statements. The interpreter is described in more detail in the
RFC. Further patches will add more features.

Reviewers: Bigcheese, jfb, rsmith

Subscribers: bruno, uenoku, ldionne, Tyker, thegameg, tschuett, dexonsmith, mgorny, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D64146

llvm-svn: 370584
2019-08-31 15:00:38 +00:00
Nandor Licker 0300c3536a Revert [Clang Interpreter] Initial patch for the constexpr interpreter
This reverts r370531 (git commit d4c1002e0b)

llvm-svn: 370535
2019-08-30 21:32:00 +00:00
Nandor Licker d4c1002e0b [Clang Interpreter] Initial patch for the constexpr interpreter
Summary:
This patch introduces the skeleton of the constexpr interpreter,
capable of evaluating a simple constexpr functions consisting of
if statements. The interpreter is described in more detail in the
RFC. Further patches will add more features.

Reviewers: Bigcheese, jfb, rsmith

Subscribers: bruno, uenoku, ldionne, Tyker, thegameg, tschuett, dexonsmith, mgorny, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D64146

llvm-svn: 370531
2019-08-30 21:17:03 +00:00
Nandor Licker 5c8b94a672 Revert [Clang Interpreter] Initial patch for the constexpr interpreter
This reverts r370476 (git commit a559095054)

llvm-svn: 370481
2019-08-30 15:41:45 +00:00
Nandor Licker a559095054 [Clang Interpreter] Initial patch for the constexpr interpreter
Summary:
This patch introduces the skeleton of the constexpr interpreter,
capable of evaluating a simple constexpr functions consisting of
if statements. The interpreter is described in more detail in the
RFC. Further patches will add more features.

Reviewers: Bigcheese, jfb, rsmith

Subscribers: bruno, uenoku, ldionne, Tyker, thegameg, tschuett, dexonsmith, mgorny, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D64146

llvm-svn: 370476
2019-08-30 15:02:09 +00:00
Puyan Lotfi 3ff8c3b73f [clang][AST] ASTNameGenerator: A refactoring of CodegenNameGeneratorImpl (NFC).
This is a NFC refactor move of CodegenNameGeneratorImpl from clang::Index to
clang:AST (and rename to ASTNameGenerator). The purpose is to make the
highlevel mangling code more reusable inside of clang (say in places like clang
FrontendAction). This does not affect anything in CodegenNameGenerator, except
that CodegenNameGenerator will now use ASTNameGenerator (in AST).

Differential Revision: https://reviews.llvm.org/D63535

llvm-svn: 363878
2019-06-19 20:51:35 +00:00
Aaron Ballman 2ce598a44a Introduce the ability to dump the AST to JSON.
This adds the -ast-dump=json cc1 flag (in addition to -ast-dump=default, which is the default if no dump format is specified), as well as some initial AST dumping functionality and tests.

llvm-svn: 360622
2019-05-13 21:39:55 +00:00
Gabor Marton 54058b5055 [ASTImporter] Add importer specific lookup
Summary:
There are certain cases when normal C/C++ lookup (localUncachedLookup)
does not find AST nodes. E.g.:

Example 1:

  template <class T>
  struct X {
    friend void foo(); // this is never found in the DC of the TU.
  };

Example 2:

  // The fwd decl to Foo is not found in the lookupPtr of the DC of the
  // translation unit decl.
  struct A { struct Foo *p; };

In these cases we create a new node instead of returning with the old one.
To fix it we create a new lookup table which holds every node and we are
not interested in any C++ specific visibility considerations.
Simply, we must know if there is an existing Decl in a given DC.

Reviewers: a_sidorin, a.sidorin

Subscribers: mgorny, rnkovacs, dkrupp, Szelethus, cfe-commits

Differential Revision: https://reviews.llvm.org/D53708

llvm-svn: 349351
2018-12-17 13:53:12 +00:00
Stephen Kelly d8744a7e9f NFC: Extract TextNodeDumper class
Summary:
Start by moving some utilities to it. It will eventually house dumping
of individual nodes (after indentation etc has already been accounted
for).

Reviewers: aaron.ballman

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D55189

llvm-svn: 348412
2018-12-05 21:12:39 +00:00
Tim Northover 314fbfa1c4 Reapply Logging: make os_log buffer size an integer constant expression.
The size of an os_log buffer is known at any stage of compilation, so making it
a constant expression means that the common idiom of declaring a buffer for it
won't result in a VLA. That allows the compiler to skip saving and restoring
the stack pointer around such buffers.

This also moves the OSLog and other FormatString helpers from
libclangAnalysis to libclangAST to avoid a circular dependency.

llvm-svn: 345971
2018-11-02 13:14:11 +00:00
Tim Northover eedc0f0f1a Revert "Reapply Logging: make os_log buffer size an integer constant expression."
Still more dependency hell.

llvm-svn: 345871
2018-11-01 18:37:42 +00:00
Tim Northover c1ac697ab7 Reapply Logging: make os_log buffer size an integer constant expression.
The size of an os_log buffer is known at any stage of compilation, so making it
a constant expression means that the common idiom of declaring a buffer for it
won't result in a VLA. That allows the compiler to skip saving and restoring
the stack pointer around such buffers.

This also moves the OSLog helpers from libclangAnalysis to libclangAST
to avoid a circular dependency.

llvm-svn: 345866
2018-11-01 18:04:49 +00:00
Tim Northover d686dbbc7c Revert "Logging: make os_log buffer size an integer constant expression.
This also reverts a couple of follow-up commits trying to fix the
dependency issues. Latest revision added a cyclic dependency that can't
just be patched up in 5 minutes.

llvm-svn: 345846
2018-11-01 16:15:24 +00:00
Tim Northover 2ef8096a5c Logging: put link against libclangAnalysis rather than libLLVMAnalysis for os_log
llvm-svn: 345835
2018-11-01 14:43:35 +00:00
Tim Northover 32aabc5585 Logging: add CMake dependency so libAST can use OSLog analysis.
Should fix bots on platforms with slightly different symbol resolution
semantics.

llvm-svn: 345833
2018-11-01 14:22:20 +00:00
Eric Fiselier 0683c0e68d [C++2a] Implement operator<=> CodeGen and ExprConstant
Summary:
This patch tackles long hanging fruit for the builtin operator<=> expressions. It is currently needs some cleanup before landing, but I want to get some initial feedback.

The main changes are:

* Lookup, build, and store the required standard library types and expressions in `ASTContext`. By storing them in ASTContext we don't need to store (and duplicate) the required expressions in the BinaryOperator AST nodes. 

* Implement [expr.spaceship] checking, including diagnosing narrowing conversions. 

* Implement `ExprConstant` for builtin spaceship operators.

* Implement builitin operator<=> support in `CodeGenAgg`. Initially I emitted the required comparisons using `ScalarExprEmitter::VisitBinaryOperator`, but this caused the operand expressions to be emitted once for every required cmp.

* Implement [builtin.over] with modifications to support the intent of P0946R0. See the note on `BuiltinOperatorOverloadBuilder::addThreeWayArithmeticOverloads` for more information about the workaround.




Reviewers: rsmith, aaron.ballman, majnemer, rnk, compnerd, rjmccall

Reviewed By: rjmccall

Subscribers: rjmccall, rsmith, aaron.ballman, junbuml, mgorny, cfe-commits

Differential Revision: https://reviews.llvm.org/D45476

llvm-svn: 331677
2018-05-07 21:07:10 +00:00
Ilya Biryukov cc3cf58cd2 Moved QualTypeNames.h from Tooling to AST.
Summary:
For code reuse in SemaCodeComplete.
Note that the tests for QualTypeNames are still in Tooling as they use
Tooling's common testing code.

Reviewers: rsmith, saugustine, rnk, klimek, bkramer

Reviewed By: rnk

Subscribers: cfe-commits, mgorny

Differential Revision: https://reviews.llvm.org/D39224

llvm-svn: 317676
2017-11-08 10:39:03 +00:00
Johannes Altmanninger 1a2676924a [analyzer] Make StmtDataCollector customizable
Summary:
This moves the data collection macro calls for Stmt nodes
to lib/AST/StmtDataCollectors.inc

Users can subclass ConstStmtVisitor and include StmtDataCollectors.inc
to define visitor methods for each Stmt subclass. This makes it also
possible to customize the visit methods as exemplified in
lib/Analysis/CloneDetection.cpp.

Move helper methods for data collection to a new module,
AST/DataCollection.

Add data collection for DeclRefExpr, MemberExpr and some literals.

Reviewers: arphaman, teemperor!

Subscribers: mgorny, xazax.hun, cfe-commits

Differential Revision: https://reviews.llvm.org/D36664

llvm-svn: 311569
2017-08-23 16:28:26 +00:00
NAKAMURA Takumi 92c99cd6dc Update libdeps to add BinaryFormat, introduced in r304864.
llvm-svn: 304869
2017-06-07 04:48:49 +00:00
NAKAMURA Takumi ef9d9481b5 Reorder and reformat.
llvm-svn: 304868
2017-06-07 04:48:45 +00:00
Bruno Cardoso Lopes 95ff11b7d1 [ASTImporter] Move structural equivalence context to its own file. NFCI
Create a header and impl file for the structural equivalence context.
This is to allow other users outside clang importer. NFCI

Differential Revision: https://reviews.llvm.org/D31777

rdar://problem/30167717

llvm-svn: 301604
2017-04-28 00:31:30 +00:00
Sean Callanan b7160ca466 [clang-import-test] Lookup inside contexts
clang-import-test has until now been only able to report top-level Decls.
This is clearly insufficient; we should be able to look inside structs 
and namespaces also.  This patch adds new test cases for a variety of 
lookups inside existing ASTContexts, and adds the functionality necessar
to make most of these testcases work.  (One testcase is known to fail 
because of ASTImporter limitations when importing templates; I'll look 
into that separately.)

This patch also separates the core functionality out into 
ExternalASTMerger, an interface that allows clients like LLDB to make 
use of it.  clang-import-test now only has the machinery necessary to
set up the tests.

Differential revision: https://reviews.llvm.org/D30435

llvm-svn: 299976
2017-04-11 19:33:35 +00:00
Richard Trieu e7f7ed2be7 Add more ODR checking.
Add the basics for the ODRHash class, which will only process Decl's from
a whitelist, which currently only has AccessSpecDecl.  Different access
specifiers in merged classes can now be detected.

Differential Revision: https://reviews.llvm.org/D21675

llvm-svn: 295800
2017-02-22 01:11:25 +00:00
Richard Trieu dc4cb02470 Revert r295421, new ODR checker for modules, to fix build bot.
llvm-svn: 295427
2017-02-17 07:19:24 +00:00
Richard Trieu cb6b72628e Add better ODR checking for modules.
A slightly weaker form of ODR checking than previous attempts, but hopefully
won't break the modules build bot.  Future work will be needed to catch all
cases.

When objects are imported for modules, there is a chance that a name collision
will cause an ODR violation.  Previously, only a small number of such
violations were detected.  This patch provides a stronger check based on
AST nodes.

The information needed to uniquely identify an object is taken from the AST and
put into a one-dimensional byte stream.  This stream is then hashed to give
a value to represent the object, which is stored with the other object data
in the module.

When modules are loaded, and Decl's are merged, the hash values of the two
Decl's are compared.  Only Decl's with matched hash values will be merged.
Mismatch hashes will generate a module error, and if possible, point to the
first difference between the two objects.

The transform from AST to byte stream is a modified depth first algorithm.
Due to references between some AST nodes, a pure depth first algorithm could
generate loops.  For Stmt nodes, a straight depth first processing occurs.
For Type and Decl nodes, they are replaced with an index number and only on
first visit will these nodes be processed.  As an optimization, boolean
values are saved and stored together in reverse order at the end of the
byte stream to lower the ammount of data that needs to be hashed.

Compile time impact was measured at 1.5-2.0% during module building, and
negligible during builds without module building.

Differential Revision: https://reviews.llvm.org/D21675

llvm-svn: 295421
2017-02-17 05:54:30 +00:00
Richard Trieu e55fb7f6f1 Revert r295284: Add better ODR checking for modules.
Fix modules build bot.

llvm-svn: 295293
2017-02-16 07:09:18 +00:00
Richard Trieu f351ac8987 Add better ODR checking for modules.
Recommit r293585 that was reverted in r293611 with new fixes.  The previous
issue was determined to be an overly aggressive AST visitor from forward
declared objects.  The visitor will now only deeply visit certain Decl's and
only do a shallow information extraction from all other Decl's.

When objects are imported for modules, there is a chance that a name collision
will cause an ODR violation.  Previously, only a small number of such
violations were detected.  This patch provides a stronger check based on
AST nodes.

The information needed to uniquely identify an object is taken from the AST and
put into a one-dimensional byte stream.  This stream is then hashed to give
a value to represent the object, which is stored with the other object data
in the module.

When modules are loaded, and Decl's are merged, the hash values of the two
Decl's are compared.  Only Decl's with matched hash values will be merged.
Mismatch hashes will generate a module error, and if possible, point to the
first difference between the two objects.

The transform from AST to byte stream is a modified depth first algorithm.
Due to references between some AST nodes, a pure depth first algorithm could
generate loops.  For Stmt nodes, a straight depth first processing occurs.
For Type and Decl nodes, they are replaced with an index number and only on
first visit will these nodes be processed.  As an optimization, boolean
values are saved and stored together in reverse order at the end of the
byte stream to lower the ammount of data that needs to be hashed.

Compile time impact was measured at 1.5-2.0% during module building, and
negligible during builds without module building.

Differential Revision: https://reviews.llvm.org/D21675

llvm-svn: 295284
2017-02-16 04:53:40 +00:00
Sam McCall 61e29aafa7 Revert r293585 "Add better ODR checking for modules."
We're seeing what we believe are false positives. (It's hard to tell with the
available diagnostics, and I'm not sure how to reduce them yet).
I'll send Richard reproduction details offline.

djasper/chandlerc suggested this should be a warning for now, to make rolling it
out feasible.

llvm-svn: 293611
2017-01-31 08:24:40 +00:00
Richard Trieu fa3d93a148 Add better ODR checking for modules.
When objects are imported for modules, there is a chance that a name collision
will cause an ODR violation.  Previously, only a small number of such
violations were detected.  This patch provides a stronger check based on
AST nodes.

The information needed to uniquely identify an object is taked from the AST and
put into a one-dimensional byte stream.  This stream is then hashed to give
a value to represent the object, which is stored with the other object data
in the module.

When modules are loaded, and Decl's are merged, the hash values of the two
Decl's are compared.  Only Decl's with matched hash values will be merged.
Mismatch hashes will generate a module error, and if possible, point to the
first difference between the two objects.

The transform from AST to byte stream is a modified depth first algorithm.
Due to references between some AST nodes, a pure depth first algorithm could
generate loops.  For Stmt nodes, a straight depth first processing occurs.
For Type and Decl nodes, they are replaced with an index number and only on
first visit will these nodes be processed.  As an optimization, boolean
values are saved and stored together in reverse order at the end of the
byte stream to lower the ammount of data that needs to be hashed.

Compile time impact was measured at 1.5-2.0% during module building, and
negligible during builds without module building.

Differential Revision: https://reviews.llvm.org/D21675

llvm-svn: 293585
2017-01-31 01:44:15 +00:00