[all-commits] [llvm/llvm-project] 8cba72: Implement literal suffixes for _BitInt

[Aaron Ballman via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 8cba72177dcd8de5d37177dbaf2347e5c1f0f1e8
      https://github.com/llvm/llvm-project/commit/8cba72177dcd8de5d37177dbaf2347e5c1f0f1e8
  Author: Aaron Ballman <aaron at aaronballman.com>
  Date:   2022-03-14 (Mon, 14 Mar 2022)

  Changed paths:
    M clang/docs/ReleaseNotes.rst
    M clang/include/clang/Basic/DiagnosticCommonKinds.td
    M clang/include/clang/Lex/LiteralSupport.h
    M clang/lib/AST/StmtPrinter.cpp
    M clang/lib/Lex/LiteralSupport.cpp
    M clang/lib/Lex/PPExpressions.cpp
    M clang/lib/Sema/SemaExpr.cpp
    A clang/test/AST/bitint-suffix.c
    A clang/test/Lexer/bitint-constants-compat.c
    A clang/test/Lexer/bitint-constants.c
    M llvm/include/llvm/ADT/APInt.h
    M llvm/lib/Support/APInt.cpp

  Log Message:
  -----------
  Implement literal suffixes for _BitInt

WG14 adopted N2775 (http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2775.pdf)
at our Feb 2022 meeting. This paper adds a literal suffix for
bit-precise types that automatically sizes the bit-precise type to be
the smallest possible legal _BitInt type that can represent the literal
value. The suffix chosen is wb (for a signed bit-precise type) which
can be combined with the u suffix (for an unsigned bit-precise type).

The preprocessor continues to operate as-if all integer types were
intmax_t/uintmax_t, including bit-precise integer types. It is a
constraint violation if the bit-precise literal is too large to fit
within that type in the context of the preprocessor (when still using
a pp-number preprocessing token), but it is not a constraint violation
in other circumstances. This allows you to make bit-precise integer
literals that are wider than what the preprocessor currently supports
in order to initialize variables, etc.