Reland [clang][Sema, Lex, Parse] Preprocessor embed in C and C++ (#95802)

This commit implements the entirety of the now-accepted [N3017
-Preprocessor
Embed](https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3017.htm) and
its sister C++ paper [p1967](https://wg21.link/p1967). It implements
everything in the specification, and includes an implementation that
drastically improves the time it takes to embed data in specific
scenarios (the initialization of character type arrays). The mechanisms
used to do this are used under the "as-if" rule, and in general when the
system cannot detect it is initializing an array object in a variable
declaration, will generate EmbedExpr AST node which will be expanded by
AST consumers (CodeGen or constant expression evaluators) or expand
embed directive as a comma expression.

This reverts commit
https://github.com/llvm/llvm-project/commit/682d461d5a231cee54d65910e6341769419a67d7.

---------

Co-authored-by: The Phantom Derpstorm <phdofthehouse@gmail.com>
Co-authored-by: Aaron Ballman <aaron@aaronballman.com>
Co-authored-by: cor3ntin <corentinjabot@gmail.com>
Co-authored-by: H. Vetinari <h.vetinari@gmx.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 58694e5..cde4a84 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -4492,6 +4492,9 @@ static void GeneratePreprocessorArgs(const PreprocessorOptions &Opts,
   if (Opts.DefineTargetOSMacros)
     GenerateArg(Consumer, OPT_fdefine_target_os_macros);
 
+  for (const auto &EmbedEntry : Opts.EmbedEntries)
+    GenerateArg(Consumer, OPT_embed_dir_EQ, EmbedEntry);
+
   // Don't handle LexEditorPlaceholders. It is implied by the action that is
   // generated elsewhere.
 }
@@ -4584,6 +4587,11 @@ static bool ParsePreprocessorArgs(PreprocessorOptions &Opts, ArgList &Args,
     }
   }
 
+  for (const auto *A : Args.filtered(OPT_embed_dir_EQ)) {
+    StringRef Val = A->getValue();
+    Opts.EmbedEntries.push_back(std::string(Val));
+  }
+
   // Always avoid lexing editor placeholders when we're just running the
   // preprocessor as we never want to emit the
   // "editor placeholder in source file" error in PP only mode.