/* d-compiler.cc -- D frontend interface to the gcc back-end.
   Copyright (C) 2020-2021 Free Software Foundation, Inc.

GCC is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3, or (at your option)
any later version.

GCC is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING3.  If not see
<http://www.gnu.org/licenses/>.  */

#include "config.h"
#include "system.h"
#include "coretypes.h"

#include "dmd/compiler.h"
#include "dmd/scope.h"
#include "dmd/expression.h"
#include "dmd/identifier.h"
#include "dmd/module.h"
#include "dmd/mtype.h"

#include "tree.h"
#include "fold-const.h"

#include "d-tree.h"


/* Implements the Compiler interface used by the frontend.  */

/* Generate C main() in response to seeing D main().  This used to be in
   libdruntime, but contained a reference to _Dmain which didn't work when
   druntime was made into a shared library and was linked to a program, such
   as a C++ program, that didn't have a _Dmain.  */

void
Compiler::genCmain (Scope *sc)
{
  static bool initialized = false;

  if (initialized)
    return;

  /* The D code to be generated is provided by __entrypoint.di, try to load it,
     but don't fail if unfound.  */
  unsigned errors = global.startGagging ();
  Module *m = Module::load (Loc (), NULL, Identifier::idPool ("__entrypoint"));

  if (global.endGagging (errors))
    m = NULL;

  if (m != NULL)
    {
      m->importedFrom = m;
      m->importAll (NULL);
      dsymbolSemantic (m, NULL);
      semantic2 (m, NULL);
      semantic3 (m, NULL);
      d_add_entrypoint_module (m, sc->_module);
    }

  initialized = true;
}

/* Perform a reinterpret cast of EXPR to type TYPE for use in CTFE.
   The front end should have already ensured that EXPR is a constant,
   so we just lower the value to GCC and return the converted CST.  */

Expression *
Compiler::paintAsType (UnionExp *, Expression *expr, Type *type)
{
  /* We support up to 512-bit values.  */
  unsigned char buffer[64];
  tree cst;

  Type *tb = type->toBasetype ();

  if (expr->type->isintegral ())
    cst = build_integer_cst (expr->toInteger (), build_ctype (expr->type));
  else if (expr->type->isfloating ())
    cst = build_float_cst (expr->toReal (), expr->type);
  else if (expr->op == TOKarrayliteral)
    {
      /* Build array as VECTOR_CST, assumes EXPR is constant.  */
      Expressions *elements = expr->isArrayLiteralExp ()->elements;
      vec <constructor_elt, va_gc> *elms = NULL;

      vec_safe_reserve (elms, elements->length);
      for (size_t i = 0; i < elements->length; i++)
	{
	  Expression *e = (*elements)[i];
	  if (e->type->isintegral ())
	    {
	      tree value = build_integer_cst (e->toInteger (),
					      build_ctype (e->type));
	      CONSTRUCTOR_APPEND_ELT (elms, size_int (i), value);
	    }
	  else if (e->type->isfloating ())
	    {
	      tree value = build_float_cst (e->toReal (), e->type);
	      CONSTRUCTOR_APPEND_ELT (elms, size_int (i), value);
	    }
	  else
	    gcc_unreachable ();
	}

      /* Build vector type.  */
      int nunits = expr->type->isTypeSArray ()->dim->toUInteger ();
      Type *telem = expr->type->nextOf ();
      tree vectype = build_vector_type (build_ctype (telem), nunits);

      cst = build_vector_from_ctor (vectype, elms);
    }
  else
    gcc_unreachable ();

  /* Encode CST to buffer.  */
  int len = native_encode_expr (cst, buffer, sizeof (buffer));

  if (tb->ty == Tsarray)
    {
      /* Interpret value as a vector of the same size,
	 then return the array literal.  */
      int nunits = type->isTypeSArray ()->dim->toUInteger ();
      Type *elem = type->nextOf ();
      tree vectype = build_vector_type (build_ctype (elem), nunits);

      cst = native_interpret_expr (vectype, buffer, len);

      Expression *e = d_eval_constant_expression (expr->loc, cst);
      gcc_assert (e != NULL && e->op == TOKvector);

      return e->isVectorExp ()->e1;
    }
  else
    {
      /* Normal interpret cast.  */
      cst = native_interpret_expr (build_ctype (type), buffer, len);

      Expression *e = d_eval_constant_expression (expr->loc, cst);
      gcc_assert (e != NULL);

      return e;
    }
}

/* Check imported module M for any special processing.
   Modules we look out for are:
    - object: For D runtime type information.
    - gcc.builtins: For all gcc builtins.
    - core.stdc.*: For all gcc library builtins.  */

void
Compiler::onParseModule (Module *m)
{
  ModuleDeclaration *md = m->md;

  if (!md || !md->id || !md->packages)
    {
      Identifier *id = (md && md->id) ? md->id : m->ident;
      if (!strcmp (id->toChars (), "object"))
	create_tinfo_types (m);
    }
  else if (md->packages->length == 1)
    {
      if (!strcmp ((*md->packages)[0]->toChars (), "gcc")
	  && !strcmp (md->id->toChars (), "builtins"))
	d_build_builtins_module (m);
    }
  else if (md->packages->length == 2)
    {
      if (!strcmp ((*md->packages)[0]->toChars (), "core")
	  && !strcmp ((*md->packages)[1]->toChars (), "stdc"))
	d_add_builtin_module (m);
    }
}

/* A callback function that is called once an imported module is parsed.
   If the callback returns true, then it tells the front-end that the
   driver intends on compiling the import.  */

bool
Compiler::onImport (Module *)
{
  return false;
}