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, 30 insertions, 0 deletions

diff --git a/clang/lib/Parse/ParseInit.cpp b/clang/lib/Parse/ParseInit.cpp
index 432ddc7..0a9a359 100644
--- a/clang/lib/Parse/ParseInit.cpp
+++ b/clang/lib/Parse/ParseInit.cpp
@@ -428,6 +428,34 @@ ExprResult Parser::ParseInitializerWithPotentialDesignator(
   return ExprError();
 }
 
+ExprResult Parser::createEmbedExpr() {
+  assert(Tok.getKind() == tok::annot_embed);
+  EmbedAnnotationData *Data =
+      reinterpret_cast<EmbedAnnotationData *>(Tok.getAnnotationValue());
+  ExprResult Res;
+  ASTContext &Context = Actions.getASTContext();
+  SourceLocation StartLoc = ConsumeAnnotationToken();
+  if (Data->BinaryData.size() == 1) {
+    Res = IntegerLiteral::Create(Context,
+                                 llvm::APInt(CHAR_BIT, Data->BinaryData.back()),
+                                 Context.UnsignedCharTy, StartLoc);
+  } else {
+    auto CreateStringLiteralFromStringRef = [&](StringRef Str, QualType Ty) {
+      llvm::APSInt ArraySize =
+          Context.MakeIntValue(Str.size(), Context.getSizeType());
+      QualType ArrayTy = Context.getConstantArrayType(
+          Ty, ArraySize, nullptr, ArraySizeModifier::Normal, 0);
+      return StringLiteral::Create(Context, Str, StringLiteralKind::Ordinary,
+                                   false, ArrayTy, StartLoc);
+    };
+
+    StringLiteral *BinaryDataArg = CreateStringLiteralFromStringRef(
+        Data->BinaryData, Context.UnsignedCharTy);
+    Res = Actions.ActOnEmbedExpr(StartLoc, BinaryDataArg);
+  }
+  return Res;
+}
+
 /// ParseBraceInitializer - Called when parsing an initializer that has a
 /// leading open brace.
 ///
@@ -501,6 +529,8 @@ ExprResult Parser::ParseBraceInitializer() {
     ExprResult SubElt;
     if (MayBeDesignationStart())
       SubElt = ParseInitializerWithPotentialDesignator(DesignatorCompletion);
+    else if (Tok.getKind() == tok::annot_embed)
+      SubElt = createEmbedExpr();
     else
       SubElt = ParseInitializer();