[PATCH] D120159: [Clang] Implement __builtin_source_location.

[James Y Knight via Phabricator via cfe-commits]

jyknight created this revision.
jyknight added reviewers: aaron.ballman, rsmith.
Herald added subscribers: dexonsmith, arphaman, martong.
Herald added a reviewer: shafik.
jyknight requested review of this revision.
Herald added a project: clang.
Herald added a subscriber: cfe-commits.

This builtin returns the address of a global instance of the
`std::source_location::__impl` type, which must be defined (with an
appropriate shape) before calling the builtin.

It will be used to implement std::source_location in libc++ in a
future change. The builtin is compatible with GCC's implementation,
and libstdc++'s usage. An intentional divergence is that GCC declares
the builtin's return type to be `const void*` (for
ease-of-implementation reasons), while Clang uses the actual type,
`const std::source_location::__impl*`.

In order to support this new functionality, I've also added a new
'UnnamedGlobalConstantDecl'. This artificial Decl is modeled after
MSGuidDecl, and is used to represent a generic concept of an lvalue
constant with global scope, deduplicated by its value. It's possible
that MSGuidDecl itself, or some of the other similar sorts of things
in Clang might be able to be refactored onto this more-generic
concept, but there's enough special-case weirdness in MSGuidDecl that
I gave up attempting to share code there, at least for now.

Finally, for compatibility with libstdc++'s <source_location> header,
I've added a second exception to the "cannot cast from void* to T* in
constant evaluation" rule. This seems a bit distasteful, but feels
like the best available option.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D120159

Files:
  clang/docs/LanguageExtensions.rst
  clang/include/clang/AST/ASTContext.h
  clang/include/clang/AST/DeclCXX.h
  clang/include/clang/AST/Expr.h
  clang/include/clang/AST/RecursiveASTVisitor.h
  clang/include/clang/AST/Stmt.h
  clang/include/clang/Basic/DeclNodes.td
  clang/include/clang/Basic/DiagnosticSemaKinds.td
  clang/include/clang/Basic/TokenKinds.def
  clang/include/clang/Sema/Sema.h
  clang/include/clang/Serialization/ASTBitCodes.h
  clang/lib/AST/ASTContext.cpp
  clang/lib/AST/ASTImporter.cpp
  clang/lib/AST/DeclBase.cpp
  clang/lib/AST/DeclCXX.cpp
  clang/lib/AST/Expr.cpp
  clang/lib/AST/ExprClassification.cpp
  clang/lib/AST/ExprConstant.cpp
  clang/lib/CodeGen/CGDecl.cpp
  clang/lib/CodeGen/CGExprConstant.cpp
  clang/lib/CodeGen/CodeGenModule.cpp
  clang/lib/CodeGen/CodeGenModule.h
  clang/lib/Parse/ParseExpr.cpp
  clang/lib/Sema/Sema.cpp
  clang/lib/Sema/SemaExpr.cpp
  clang/lib/Sema/SemaTemplate.cpp
  clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
  clang/lib/Sema/TreeTransform.h
  clang/lib/Serialization/ASTCommon.cpp
  clang/lib/Serialization/ASTReaderDecl.cpp
  clang/lib/Serialization/ASTWriterDecl.cpp
  clang/test/CodeGenCXX/builtin-source-location.cpp
  clang/test/SemaCXX/source_location.cpp
  clang/test/SemaCXX/source_location_err.cpp
  clang/tools/libclang/CIndex.cpp

-------------- next part --------------
A non-text attachment was scrubbed...
Name: D120159.410007.patch
Type: text/x-patch
Size: 70803 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20220218/785d2dcb/attachment-0001.bin>