src/librustc_trans/trans/controlflow.rs

   1 // Copyright 2012 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use llvm::ValueRef;
  12 use middle::def;
  13 use middle::lang_items::{PanicFnLangItem, PanicBoundsCheckFnLangItem};
  14 use trans::_match;
  15 use trans::adt;
  16 use trans::base::*;
  17 use trans::build::*;
  18 use trans::callee;
  19 use trans::cleanup::CleanupMethods;
  20 use trans::cleanup;
  21 use trans::common::*;
  22 use trans::consts;
  23 use trans::datum;
  24 use trans::debuginfo;
  25 use trans::expr;
  26 use trans::meth;
  27 use trans::type_::Type;
  28 use trans;
  29 use middle::ty;
  30 use middle::ty::MethodCall;
  31 use session::config::FullDebugInfo;
  32 use util::ppaux::Repr;
  33 use util::ppaux;
  34
  35 use syntax::ast;
  36 use syntax::ast::Ident;
  37 use syntax::ast_util;
  38 use syntax::codemap::Span;
  39 use syntax::parse::token::InternedString;
  40 use syntax::parse::token;
  41 use syntax::visit::Visitor;
  42
  43 pub fn trans_stmt<'blk, 'tcx>(cx: Block<'blk, 'tcx>,
  44                               s: &ast::Stmt)
  45                               -> Block<'blk, 'tcx> {
  46     let _icx = push_ctxt("trans_stmt");
  47     let fcx = cx.fcx;
  48     debug!("trans_stmt({})", s.repr(cx.tcx()));
  49
  50     if cx.sess().asm_comments() {
  51         add_span_comment(cx, s.span, s.repr(cx.tcx()).as_slice());
  52     }
  53
  54     let mut bcx = cx;
  55
  56     let id = ast_util::stmt_id(s);
  57     let cleanup_debug_loc =
  58         debuginfo::get_cleanup_debug_loc_for_ast_node(bcx.ccx(), id, s.span, false);
  59     fcx.push_ast_cleanup_scope(cleanup_debug_loc);
  60
  61     match s.node {
  62         ast::StmtExpr(ref e, _) | ast::StmtSemi(ref e, _) => {
  63             bcx = trans_stmt_semi(bcx, &**e);
  64         }
  65         ast::StmtDecl(ref d, _) => {
  66             match d.node {
  67                 ast::DeclLocal(ref local) => {
  68                     bcx = init_local(bcx, &**local);
  69                     if cx.sess().opts.debuginfo == FullDebugInfo {
  70                         trans::debuginfo::create_local_var_metadata(bcx,
  71                                                                     &**local);
  72                     }
  73                 }
  74                 // Inner items are visited by `trans_item`/`trans_meth`.
  75                 ast::DeclItem(_) => {},
  76             }
  77         }
  78         ast::StmtMac(..) => cx.tcx().sess.bug("unexpanded macro")
  79     }
  80
  81     bcx = fcx.pop_and_trans_ast_cleanup_scope(bcx, ast_util::stmt_id(s));
  82
  83     return bcx;
  84 }
  85
  86 pub fn trans_stmt_semi<'blk, 'tcx>(cx: Block<'blk, 'tcx>, e: &ast::Expr)
  87                                    -> Block<'blk, 'tcx> {
  88     let _icx = push_ctxt("trans_stmt_semi");
  89     let ty = expr_ty(cx, e);
  90     if ty::type_needs_drop(cx.tcx(), ty) {
  91         expr::trans_to_lvalue(cx, e, "stmt").bcx
  92     } else {
  93         expr::trans_into(cx, e, expr::Ignore)
  94     }
  95 }
  96
  97 pub fn trans_block<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
  98                                b: &ast::Block,
  99                                mut dest: expr::Dest)
 100                                -> Block<'blk, 'tcx> {
 101     let _icx = push_ctxt("trans_block");
 102     let fcx = bcx.fcx;
 103     let mut bcx = bcx;
 104
 105     let cleanup_debug_loc =
 106         debuginfo::get_cleanup_debug_loc_for_ast_node(bcx.ccx(), b.id, b.span, true);
 107     fcx.push_ast_cleanup_scope(cleanup_debug_loc);
 108
 109     for s in b.stmts.iter() {
 110         bcx = trans_stmt(bcx, &**s);
 111     }
 112
 113     if dest != expr::Ignore {
 114         let block_ty = node_id_type(bcx, b.id);
 115         if b.expr.is_none() || type_is_zero_size(bcx.ccx(), block_ty) {
 116             dest = expr::Ignore;
 117         }
 118     }
 119
 120     match b.expr {
 121         Some(ref e) => {
 122             bcx = expr::trans_into(bcx, &**e, dest);
 123         }
 124         None => {
 125             assert!(dest == expr::Ignore || bcx.unreachable.get());
 126         }
 127     }
 128
 129     bcx = fcx.pop_and_trans_ast_cleanup_scope(bcx, b.id);
 130
 131     return bcx;
 132 }
 133
 134 pub fn trans_if<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
 135                             if_id: ast::NodeId,
 136                             cond: &ast::Expr,
 137                             thn: &ast::Block,
 138                             els: Option<&ast::Expr>,
 139                             dest: expr::Dest)
 140                             -> Block<'blk, 'tcx> {
 141     debug!("trans_if(bcx={}, if_id={}, cond={}, thn={}, dest={})",
 142            bcx.to_str(), if_id, bcx.expr_to_string(cond), thn.id,
 143            dest.to_string(bcx.ccx()));
 144     let _icx = push_ctxt("trans_if");
 145     let mut bcx = bcx;
 146
 147     let cond_val = unpack_result!(bcx, expr::trans(bcx, cond).to_llbool());
 148
 149     // Drop branches that are known to be impossible
 150     if is_const(cond_val) && !is_undef(cond_val) {
 151         if const_to_uint(cond_val) == 1 {
 152             match els {
 153                 Some(elexpr) => {
 154                     let mut trans = TransItemVisitor { ccx: bcx.fcx.ccx };
 155                     trans.visit_expr(&*elexpr);
 156                 }
 157                 None => {}
 158             }
 159             // if true { .. } [else { .. }]
 160             bcx = trans_block(bcx, &*thn, dest);
 161             trans::debuginfo::clear_source_location(bcx.fcx);
 162         } else {
 163             let mut trans = TransItemVisitor { ccx: bcx.fcx.ccx } ;
 164             trans.visit_block(&*thn);
 165
 166             match els {
 167                 // if false { .. } else { .. }
 168                 Some(elexpr) => {
 169                     bcx = expr::trans_into(bcx, &*elexpr, dest);
 170                     trans::debuginfo::clear_source_location(bcx.fcx);
 171                 }
 172
 173                 // if false { .. }
 174                 None => { }
 175             }
 176         }
 177
 178         return bcx;
 179     }
 180
 181     let name = format!("then-block-{}-", thn.id);
 182     let then_bcx_in = bcx.fcx.new_id_block(name.as_slice(), thn.id);
 183     let then_bcx_out = trans_block(then_bcx_in, &*thn, dest);
 184     trans::debuginfo::clear_source_location(bcx.fcx);
 185
 186     let next_bcx;
 187     match els {
 188         Some(elexpr) => {
 189             let else_bcx_in = bcx.fcx.new_id_block("else-block", elexpr.id);
 190             let else_bcx_out = expr::trans_into(else_bcx_in, &*elexpr, dest);
 191             next_bcx = bcx.fcx.join_blocks(if_id,
 192                                            &[then_bcx_out, else_bcx_out]);
 193             CondBr(bcx, cond_val, then_bcx_in.llbb, else_bcx_in.llbb);
 194         }
 195
 196         None => {
 197             next_bcx = bcx.fcx.new_id_block("next-block", if_id);
 198             Br(then_bcx_out, next_bcx.llbb);
 199             CondBr(bcx, cond_val, then_bcx_in.llbb, next_bcx.llbb);
 200         }
 201     }
 202
 203     // Clear the source location because it is still set to whatever has been translated
 204     // right before.
 205     trans::debuginfo::clear_source_location(next_bcx.fcx);
 206
 207     next_bcx
 208 }
 209
 210 pub fn trans_while<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
 211                                loop_id: ast::NodeId,
 212                                cond: &ast::Expr,
 213                                body: &ast::Block)
 214                                -> Block<'blk, 'tcx> {
 215     let _icx = push_ctxt("trans_while");
 216     let fcx = bcx.fcx;
 217
 218     //            bcx
 219     //             |
 220     //         cond_bcx_in  <--------+
 221     //             |                 |
 222     //         cond_bcx_out          |
 223     //           |      |            |
 224     //           |    body_bcx_in    |
 225     // cleanup_blk      |            |
 226     //    |           body_bcx_out --+
 227     // next_bcx_in
 228
 229     let next_bcx_in = fcx.new_id_block("while_exit", loop_id);
 230     let cond_bcx_in = fcx.new_id_block("while_cond", cond.id);
 231     let body_bcx_in = fcx.new_id_block("while_body", body.id);
 232
 233     fcx.push_loop_cleanup_scope(loop_id, [next_bcx_in, cond_bcx_in]);
 234
 235     Br(bcx, cond_bcx_in.llbb);
 236
 237     // compile the block where we will handle loop cleanups
 238     let cleanup_llbb = fcx.normal_exit_block(loop_id, cleanup::EXIT_BREAK);
 239
 240     // compile the condition
 241     let Result {bcx: cond_bcx_out, val: cond_val} =
 242         expr::trans(cond_bcx_in, cond).to_llbool();
 243     CondBr(cond_bcx_out, cond_val, body_bcx_in.llbb, cleanup_llbb);
 244
 245     // loop body:
 246     let body_bcx_out = trans_block(body_bcx_in, body, expr::Ignore);
 247     Br(body_bcx_out, cond_bcx_in.llbb);
 248
 249     fcx.pop_loop_cleanup_scope(loop_id);
 250     return next_bcx_in;
 251 }
 252
 253 /// Translates a `for` loop.
 254 pub fn trans_for<'blk, 'tcx>(mut bcx: Block<'blk, 'tcx>,
 255                              loop_info: NodeInfo,
 256                              pat: &ast::Pat,
 257                              head: &ast::Expr,
 258                              body: &ast::Block)
 259                              -> Block<'blk, 'tcx> {
 260     let _icx = push_ctxt("trans_for");
 261
 262     //            bcx
 263     //             |
 264     //      loopback_bcx_in  <-------+
 265     //             |                 |
 266     //      loopback_bcx_out         |
 267     //           |      |            |
 268     //           |    body_bcx_in    |
 269     // cleanup_blk      |            |
 270     //    |           body_bcx_out --+
 271     // next_bcx_in
 272
 273     // Codegen the head to create the iterator value.
 274     let iterator_datum =
 275         unpack_datum!(bcx, expr::trans_to_lvalue(bcx, head, "for_head"));
 276     let iterator_type = node_id_type(bcx, head.id);
 277     debug!("iterator type is {}, datum type is {}",
 278            ppaux::ty_to_string(bcx.tcx(), iterator_type),
 279            ppaux::ty_to_string(bcx.tcx(), iterator_datum.ty));
 280     let lliterator = load_ty(bcx, iterator_datum.val, iterator_datum.ty);
 281
 282     // Create our basic blocks and set up our loop cleanups.
 283     let next_bcx_in = bcx.fcx.new_id_block("for_exit", loop_info.id);
 284     let loopback_bcx_in = bcx.fcx.new_id_block("for_loopback", head.id);
 285     let body_bcx_in = bcx.fcx.new_id_block("for_body", body.id);
 286     bcx.fcx.push_loop_cleanup_scope(loop_info.id,
 287                                     [next_bcx_in, loopback_bcx_in]);
 288     Br(bcx, loopback_bcx_in.llbb);
 289     let cleanup_llbb = bcx.fcx.normal_exit_block(loop_info.id,
 290                                                  cleanup::EXIT_BREAK);
 291
 292     // Set up the method call (to `.next()`).
 293     let method_call = MethodCall::expr(loop_info.id);
 294     let method_type = (*loopback_bcx_in.tcx()
 295                                      .method_map
 296                                      .borrow())[method_call]
 297                                      .ty;
 298     let method_type = monomorphize_type(loopback_bcx_in, method_type);
 299     let method_result_type = ty::ty_fn_ret(method_type).unwrap();
 300     let option_cleanup_scope = body_bcx_in.fcx.push_custom_cleanup_scope();
 301     let option_cleanup_scope_id = cleanup::CustomScope(option_cleanup_scope);
 302
 303     // Compile the method call (to `.next()`).
 304     let mut loopback_bcx_out = loopback_bcx_in;
 305     let option_datum =
 306         unpack_datum!(loopback_bcx_out,
 307                       datum::lvalue_scratch_datum(loopback_bcx_out,
 308                                                   method_result_type,
 309                                                   "loop_option",
 310                                                   false,
 311                                                   option_cleanup_scope_id,
 312                                                   (),
 313                                                   |(), bcx, lloption| {
 314         let Result {
 315             bcx,
 316             val: _
 317         } = callee::trans_call_inner(bcx,
 318                                      Some(loop_info),
 319                                      method_type,
 320                                      |bcx, arg_cleanup_scope| {
 321                                          meth::trans_method_callee(
 322                                              bcx,
 323                                              method_call,
 324                                              None,
 325                                              arg_cleanup_scope)
 326                                      },
 327                                      callee::ArgVals(&[lliterator]),
 328                                      Some(expr::SaveIn(lloption)));
 329         bcx
 330     }));
 331
 332     // Check the discriminant; if the `None` case, exit the loop.
 333     let option_representation = adt::represent_type(loopback_bcx_out.ccx(),
 334                                                     method_result_type);
 335     let lldiscriminant = adt::trans_get_discr(loopback_bcx_out,
 336                                               &*option_representation,
 337                                               option_datum.val,
 338                                               None);
 339     let i1_type = Type::i1(loopback_bcx_out.ccx());
 340     let llcondition = Trunc(loopback_bcx_out, lldiscriminant, i1_type);
 341     CondBr(loopback_bcx_out, llcondition, body_bcx_in.llbb, cleanup_llbb);
 342
 343     // Now we're in the body. Unpack the `Option` value into the programmer-
 344     // supplied pattern.
 345     let llpayload = adt::trans_field_ptr(body_bcx_in,
 346                                          &*option_representation,
 347                                          option_datum.val,
 348                                          1,
 349                                          0);
 350     let binding_cleanup_scope = body_bcx_in.fcx.push_custom_cleanup_scope();
 351     let binding_cleanup_scope_id =
 352         cleanup::CustomScope(binding_cleanup_scope);
 353     let mut body_bcx_out =
 354         _match::store_for_loop_binding(body_bcx_in,
 355                                        pat,
 356                                        llpayload,
 357                                        binding_cleanup_scope_id);
 358
 359     // Codegen the body.
 360     body_bcx_out = trans_block(body_bcx_out, body, expr::Ignore);
 361     body_bcx_out =
 362         body_bcx_out.fcx
 363                     .pop_and_trans_custom_cleanup_scope(body_bcx_out,
 364                                                         binding_cleanup_scope);
 365     body_bcx_out =
 366         body_bcx_out.fcx
 367                     .pop_and_trans_custom_cleanup_scope(body_bcx_out,
 368                                                         option_cleanup_scope);
 369     Br(body_bcx_out, loopback_bcx_in.llbb);
 370
 371     // Codegen cleanups and leave.
 372     next_bcx_in.fcx.pop_loop_cleanup_scope(loop_info.id);
 373     next_bcx_in
 374 }
 375
 376 pub fn trans_loop<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
 377                               loop_id: ast::NodeId,
 378                               body: &ast::Block)
 379                               -> Block<'blk, 'tcx> {
 380     let _icx = push_ctxt("trans_loop");
 381     let fcx = bcx.fcx;
 382
 383     //            bcx
 384     //             |
 385     //         body_bcx_in
 386     //             |
 387     //         body_bcx_out
 388     //
 389     // next_bcx
 390     //
 391     // Links between body_bcx_in and next_bcx are created by
 392     // break statements.
 393
 394     let next_bcx_in = bcx.fcx.new_id_block("loop_exit", loop_id);
 395     let body_bcx_in = bcx.fcx.new_id_block("loop_body", body.id);
 396
 397     fcx.push_loop_cleanup_scope(loop_id, [next_bcx_in, body_bcx_in]);
 398
 399     Br(bcx, body_bcx_in.llbb);
 400     let body_bcx_out = trans_block(body_bcx_in, body, expr::Ignore);
 401     Br(body_bcx_out, body_bcx_in.llbb);
 402
 403     fcx.pop_loop_cleanup_scope(loop_id);
 404
 405     return next_bcx_in;
 406 }
 407
 408 pub fn trans_break_cont<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
 409                                     expr_id: ast::NodeId,
 410                                     opt_label: Option<Ident>,
 411                                     exit: uint)
 412                                     -> Block<'blk, 'tcx> {
 413     let _icx = push_ctxt("trans_break_cont");
 414     let fcx = bcx.fcx;
 415
 416     if bcx.unreachable.get() {
 417         return bcx;
 418     }
 419
 420     // Locate loop that we will break to
 421     let loop_id = match opt_label {
 422         None => fcx.top_loop_scope(),
 423         Some(_) => {
 424             match bcx.tcx().def_map.borrow().get(&expr_id) {
 425                 Some(&def::DefLabel(loop_id)) => loop_id,
 426                 ref r => {
 427                     bcx.tcx().sess.bug(format!("{} in def-map for label",
 428                                                r).as_slice())
 429                 }
 430             }
 431         }
 432     };
 433
 434     // Generate appropriate cleanup code and branch
 435     let cleanup_llbb = fcx.normal_exit_block(loop_id, exit);
 436     Br(bcx, cleanup_llbb);
 437     Unreachable(bcx); // anything afterwards should be ignored
 438     return bcx;
 439 }
 440
 441 pub fn trans_break<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
 442                                expr_id: ast::NodeId,
 443                                label_opt: Option<Ident>)
 444                                -> Block<'blk, 'tcx> {
 445     return trans_break_cont(bcx, expr_id, label_opt, cleanup::EXIT_BREAK);
 446 }
 447
 448 pub fn trans_cont<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
 449                               expr_id: ast::NodeId,
 450                               label_opt: Option<Ident>)
 451                               -> Block<'blk, 'tcx> {
 452     return trans_break_cont(bcx, expr_id, label_opt, cleanup::EXIT_LOOP);
 453 }
 454
 455 pub fn trans_ret<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
 456                              e: Option<&ast::Expr>)
 457                              -> Block<'blk, 'tcx> {
 458     let _icx = push_ctxt("trans_ret");
 459     let fcx = bcx.fcx;
 460     let mut bcx = bcx;
 461     let dest = match (fcx.llretslotptr.get(), e) {
 462         (Some(_), Some(e)) => {
 463             let ret_ty = expr_ty(bcx, &*e);
 464             expr::SaveIn(fcx.get_ret_slot(bcx, ty::FnConverging(ret_ty), "ret_slot"))
 465         }
 466         _ => expr::Ignore,
 467     };
 468     if let Some(x) = e {
 469         bcx = expr::trans_into(bcx, &*x, dest);
 470         match dest {
 471             expr::SaveIn(slot) if fcx.needs_ret_allocas => {
 472                 Store(bcx, slot, fcx.llretslotptr.get().unwrap());
 473             }
 474             _ => {}
 475         }
 476     }
 477     let cleanup_llbb = fcx.return_exit_block();
 478     Br(bcx, cleanup_llbb);
 479     Unreachable(bcx);
 480     return bcx;
 481 }
 482
 483 pub fn trans_fail<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
 484                               sp: Span,
 485                               fail_str: InternedString)
 486                               -> Block<'blk, 'tcx> {
 487     let ccx = bcx.ccx();
 488     let _icx = push_ctxt("trans_fail_value");
 489
 490     let v_str = C_str_slice(ccx, fail_str);
 491     let loc = bcx.sess().codemap().lookup_char_pos(sp.lo);
 492     let filename = token::intern_and_get_ident(loc.file.name.as_slice());
 493     let filename = C_str_slice(ccx, filename);
 494     let line = C_uint(ccx, loc.line);
 495     let expr_file_line_const = C_struct(ccx, &[v_str, filename, line], false);
 496     let expr_file_line = consts::const_addr_of(ccx, expr_file_line_const, ast::MutImmutable);
 497     let args = vec!(expr_file_line);
 498     let did = langcall(bcx, Some(sp), "", PanicFnLangItem);
 499     let bcx = callee::trans_lang_call(bcx,
 500                                       did,
 501                                       args.as_slice(),
 502                                       Some(expr::Ignore)).bcx;
 503     Unreachable(bcx);
 504     return bcx;
 505 }
 506
 507 pub fn trans_fail_bounds_check<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
 508                                            sp: Span,
 509                                            index: ValueRef,
 510                                            len: ValueRef)
 511                                            -> Block<'blk, 'tcx> {
 512     let ccx = bcx.ccx();
 513     let _icx = push_ctxt("trans_fail_bounds_check");
 514
 515     // Extract the file/line from the span
 516     let loc = bcx.sess().codemap().lookup_char_pos(sp.lo);
 517     let filename = token::intern_and_get_ident(loc.file.name.as_slice());
 518
 519     // Invoke the lang item
 520     let filename = C_str_slice(ccx,  filename);
 521     let line = C_uint(ccx, loc.line);
 522     let file_line_const = C_struct(ccx, &[filename, line], false);
 523     let file_line = consts::const_addr_of(ccx, file_line_const, ast::MutImmutable);
 524     let args = vec!(file_line, index, len);
 525     let did = langcall(bcx, Some(sp), "", PanicBoundsCheckFnLangItem);
 526     let bcx = callee::trans_lang_call(bcx,
 527                                       did,
 528                                       args.as_slice(),
 529                                       Some(expr::Ignore)).bcx;
 530     Unreachable(bcx);
 531     return bcx;
 532 }