[CIR][CodeGen][NFC] Add documentation regarding memory emission deferral (#1279)

Author: orbiri

clang/lib/CIR/CodeGen/CIRGenFunction.h

@@ -1114,6 +1114,10 @@ class CIRGenFunction : public CIRGenTypeCache {
   /// addressed later.
   RValue GetUndefRValue(clang::QualType Ty);
 
+  /// Given a value and its clang type, returns the value casted from its memory
+  /// representation.
+  /// Note: CIR defers most of the special casting to the final lowering passes
+  /// to conserve the high level information.
   mlir::Value emitFromMemory(mlir::Value Value, clang::QualType Ty);
 
   mlir::LogicalResult emitAsmStmt(const clang::AsmStmt &S);
@@ -1339,7 +1343,12 @@ class CIRGenFunction : public CIRGenTypeCache {
   }
   void emitStoreOfScalar(mlir::Value value, LValue lvalue, bool isInit);
 
+  /// Given a value and its clang type, returns the value casted to its memory
+  /// representation.
+  /// Note: CIR defers most of the special casting to the final lowering passes
+  /// to conserve the high level information.
   mlir::Value emitToMemory(mlir::Value Value, clang::QualType Ty);
+
   void emitDeclRefExprDbgValue(const DeclRefExpr *E, const APValue &Init);
 
   /// Store the specified rvalue into the specified

clang/lib/CIR/CodeGen/CIRGenTypes.h

@@ -186,7 +186,8 @@ class CIRGenTypes {
   /// convertType in that it is used to convert to the memory representation
   /// for a type. For example, the scalar representation for _Bool is i1, but
   /// the memory representation is usually i8 or i32, depending on the target.
-  // TODO: convert this comment to account for MLIR's equivalence
+  /// Note: CIR defers most of the special conversions to the final lowering
+  /// passes to conserve the high level information.
   mlir::Type convertTypeForMem(clang::QualType, bool forBitField = false);
 
   /// Get the CIR function type for \arg Info.