Unverified Commit 4cc791bc authored by philnik777's avatar philnik777 Committed by GitHub
Browse files

[Clang] Add __datasizeof (#67805) 

The data size is required for implementing the `memmove` optimization
for `std::copy`, `std::move` etc. correctly as well as replacing
`__compressed_pair` with `[[no_unique_address]]` in libc++. Since the
compiler already knows the data size, we can avoid some complexity by
exposing that information.
parent 0515ccc0

clang/docs/LanguageExtensions.rst

+12 −0
Original line number Diff line number Diff line
@@ -424,6 +424,18 @@ Builtin Macros 
  "UTF-16" or "UTF-32" (but may change in the future if the

  ``-fwide-exec-charset="Encoding-Name"`` option is implemented.)



Implementation-defined keywords

===============================



__datasizeof

------------



``__datasizeof`` behaves like ``sizeof``, except that it returns the size of the

type ignoring tail padding.



..

  FIXME: This should list all the keyword extensions



.. _langext-vectors:



Vectors and Extended Vectors

clang/docs/ReleaseNotes.rst

+2 −0
Original line number Diff line number Diff line
@@ -217,6 +217,8 @@ Non-comprehensive list of changes in this release 
  (e.g., ``uint16x8_t``), this returns the constant number of elements at compile-time.

  For scalable vectors, e.g., SVE or RISC-V V, the number of elements is not known at compile-time and is

  determined at runtime.

* The ``__datasizeof`` keyword has been added. It is similar to ``sizeof``

  except that it returns the size of a type ignoring tail padding.



New Compiler Flags

------------------

clang/include/clang/Basic/Features.def

+1 −0
Original line number Diff line number Diff line
@@ -277,6 +277,7 @@ EXTENSION(gnu_asm_goto_with_outputs_full, LangOpts.GNUAsm) 
EXTENSION(matrix_types, LangOpts.MatrixTypes)

EXTENSION(matrix_types_scalar_division, true)

EXTENSION(cxx_attributes_on_using_declarations, LangOpts.CPlusPlus11)

EXTENSION(datasizeof, LangOpts.CPlusPlus)



FEATURE(builtin_headers_in_system_modules, LangOpts.BuiltinHeadersInSystemModules)

FEATURE(cxx_abi_relative_vtable, LangOpts.CPlusPlus && LangOpts.RelativeCXXABIVTables)

clang/include/clang/Basic/TokenKinds.def

+1 −0
Original line number Diff line number Diff line
@@ -310,6 +310,7 @@ KEYWORD(return , KEYALL) 
KEYWORD(short                       , KEYALL)

KEYWORD(signed                      , KEYALL)

UNARY_EXPR_OR_TYPE_TRAIT(sizeof, SizeOf, KEYALL)

UNARY_EXPR_OR_TYPE_TRAIT(__datasizeof, DataSizeOf, KEYCXX)

KEYWORD(static                      , KEYALL)

KEYWORD(struct                      , KEYALL)

KEYWORD(switch                      , KEYALL)

clang/lib/AST/ExprConstant.cpp

+16 −4
Original line number Diff line number Diff line
@@ -3184,9 +3184,14 @@ static bool HandleLValueIndirectMember(EvalInfo &Info, const Expr *E, 
  return true;

}













enum class SizeOfType {













  SizeOf,













  DataSizeOf,













};



























/// Get the size of the given type in char units.













static bool HandleSizeof(EvalInfo &Info, SourceLocation Loc,













                         QualType Type, CharUnits &Size) {













static bool HandleSizeof(EvalInfo &Info, SourceLocation Loc, QualType Type,













                         CharUnits &Size, SizeOfType SOT = SizeOfType::SizeOf) {















  // sizeof(void), __alignof__(void), sizeof(function) = 1 as a gcc















  // extension.















  if (Type->isVoidType() || Type->isFunctionType()) {









@@ -3206,7 +3211,10 @@ static bool HandleSizeof(EvalInfo &Info, SourceLocation Loc,













    return false;















  }



























  if (SOT == SizeOfType::SizeOf)















    Size = Info.Ctx.getTypeSizeInChars(Type);













  else













    Size = Info.Ctx.getTypeInfoDataSizeInChars(Type).Width;















  return true;















}
























@@ -13689,6 +13697,7 @@ bool IntExprEvaluator::VisitUnaryExprOrTypeTraitExpr(













      return Success(1, E);















  }



























  case UETT_DataSizeOf:















  case UETT_SizeOf: {















    QualType SrcTy = E->getTypeOfArgument();















    // C++ [expr.sizeof]p2: "When applied to a reference or a reference type,









@@ -13697,8 +13706,11 @@ bool IntExprEvaluator::VisitUnaryExprOrTypeTraitExpr(













      SrcTy = Ref->getPointeeType();





























    CharUnits Sizeof;













    if (!HandleSizeof(Info, E->getExprLoc(), SrcTy, Sizeof))













    if (!HandleSizeof(Info, E->getExprLoc(), SrcTy, Sizeof,













                      E->getKind() == UETT_DataSizeOf ? SizeOfType::DataSizeOf













                                                      : SizeOfType::SizeOf)) {















      return false;













    }















    return Success(Sizeof, E);















  }















  case UETT_OpenMPRequiredSimdAlign: