[all-commits] [llvm/llvm-project] 08c8d5: Properly track whether a variable is constant-init...

[Richard Smith via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 08c8d5bc51c512e605840b8003fcf38c86d0fc96
      https://github.com/llvm/llvm-project/commit/08c8d5bc51c512e605840b8003fcf38c86d0fc96
  Author: Richard Smith <richard at metafoo.co.uk>
  Date:   2020-10-19 (Mon, 19 Oct 2020)

  Changed paths:
    M clang/include/clang/AST/Decl.h
    M clang/include/clang/AST/Expr.h
    M clang/lib/AST/Decl.cpp
    M clang/lib/AST/ExprConstant.cpp
    M clang/lib/CodeGen/CGExprConstant.cpp
    M clang/test/CodeGenCXX/builtin-is-constant-evaluated.cpp
    A clang/test/PCH/builtin-is-constant-evaluated.cpp
    M clang/test/SemaCXX/attr-require-constant-initialization.cpp
    M clang/test/SemaCXX/builtin-is-constant-evaluated.cpp

  Log Message:
  -----------
  Properly track whether a variable is constant-initialized.

This fixes miscomputation of __builtin_constant_evaluated in the
initializer of a variable that's not usable in constant expressions, but
is readable when constant-folding.

If evaluation of a constant initializer fails, we throw away the
evaluated result instead of keeping it as a non-constant-initializer
value for the variable, because it might not be a correct value.
To avoid regressions for initializers that are foldable but not formally
constant initializers, we now try constant-evaluating some globals in
C++ twice: once to check for a constant initializer (in an mode where
is_constannt_evaluated returns true) and again to determine the runtime
value if the initializer is not a constant initializer.