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::Def;
  13 use middle::lang_items::{PanicFnLangItem, PanicBoundsCheckFnLangItem};
  14 use trans::base::*;
  15 use trans::basic_block::BasicBlock;
  16 use trans::build::*;
  17 use trans::callee;
  18 use trans::cleanup::CleanupMethods;
  19 use trans::cleanup;
  20 use trans::common::*;
  21 use trans::consts;
  22 use trans::debuginfo;
  23 use trans::debuginfo::{DebugLoc, ToDebugLoc};
  24 use trans::expr;
  25 use trans::machine;
  26 use trans;
  27 use middle::ty;
  28
  29 use rustc_front::hir;
  30 use rustc_front::util as ast_util;
  31
  32 use syntax::ast;
  33 use syntax::parse::token::InternedString;
  34 use syntax::parse::token;
  35
  36 pub fn trans_stmt<'blk, 'tcx>(cx: Block<'blk, 'tcx>,
  37                               s: &hir::Stmt)
  38                               -> Block<'blk, 'tcx> {
  39     let _icx = push_ctxt("trans_stmt");
  40     let fcx = cx.fcx;
  41     debug!("trans_stmt({:?})", s);
  42
  43     if cx.unreachable.get() {
  44         return cx;
  45     }
  46
  47     if cx.sess().asm_comments() {
  48         add_span_comment(cx, s.span, &format!("{:?}", s));
  49     }
  50
  51     let mut bcx = cx;
  52
  53     let id = ast_util::stmt_id(s);
  54     let cleanup_debug_loc =
  55         debuginfo::get_cleanup_debug_loc_for_ast_node(bcx.ccx(), id, s.span, false);
  56     fcx.push_ast_cleanup_scope(cleanup_debug_loc);
  57
  58     match s.node {
  59         hir::StmtExpr(ref e, _) | hir::StmtSemi(ref e, _) => {
  60             bcx = trans_stmt_semi(bcx, &e);
  61         }
  62         hir::StmtDecl(ref d, _) => {
  63             match d.node {
  64                 hir::DeclLocal(ref local) => {
  65                     bcx = init_local(bcx, &local);
  66                     debuginfo::create_local_var_metadata(bcx, &local);
  67                 }
  68                 // Inner items are visited by `trans_item`/`trans_meth`.
  69                 hir::DeclItem(_) => {},
  70             }
  71         }
  72     }
  73
  74     bcx = fcx.pop_and_trans_ast_cleanup_scope(bcx, ast_util::stmt_id(s));
  75
  76     return bcx;
  77 }
  78
  79 pub fn trans_stmt_semi<'blk, 'tcx>(cx: Block<'blk, 'tcx>, e: &hir::Expr)
  80                                    -> Block<'blk, 'tcx> {
  81     let _icx = push_ctxt("trans_stmt_semi");
  82
  83     if cx.unreachable.get() {
  84         return cx;
  85     }
  86
  87     let ty = expr_ty(cx, e);
  88     if cx.fcx.type_needs_drop(ty) {
  89         expr::trans_to_lvalue(cx, e, "stmt").bcx
  90     } else {
  91         expr::trans_into(cx, e, expr::Ignore)
  92     }
  93 }
  94
  95 pub fn trans_block<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
  96                                b: &hir::Block,
  97                                mut dest: expr::Dest)
  98                                -> Block<'blk, 'tcx> {
  99     let _icx = push_ctxt("trans_block");
 100
 101     if bcx.unreachable.get() {
 102         return bcx;
 103     }
 104
 105     let fcx = bcx.fcx;
 106     let mut bcx = bcx;
 107
 108     let cleanup_debug_loc =
 109         debuginfo::get_cleanup_debug_loc_for_ast_node(bcx.ccx(), b.id, b.span, true);
 110     fcx.push_ast_cleanup_scope(cleanup_debug_loc);
 111
 112     for s in &b.stmts {
 113         bcx = trans_stmt(bcx, s);
 114     }
 115
 116     if dest != expr::Ignore {
 117         let block_ty = node_id_type(bcx, b.id);
 118
 119         if b.expr.is_none() || type_is_zero_size(bcx.ccx(), block_ty) {
 120             dest = expr::Ignore;
 121         } else if b.expr.is_some() {
 122             // If the block has an expression, but that expression isn't reachable,
 123             // don't save into the destination given, ignore it.
 124             if let Some(ref cfg) = bcx.fcx.cfg {
 125                 if !cfg.node_is_reachable(b.expr.as_ref().unwrap().id) {
 126                     dest = expr::Ignore;
 127                 }
 128             }
 129         }
 130     }
 131
 132     match b.expr {
 133         Some(ref e) => {
 134             if !bcx.unreachable.get() {
 135                 bcx = expr::trans_into(bcx, &e, dest);
 136             }
 137         }
 138         None => {
 139             assert!(dest == expr::Ignore || bcx.unreachable.get());
 140         }
 141     }
 142
 143     bcx = fcx.pop_and_trans_ast_cleanup_scope(bcx, b.id);
 144
 145     return bcx;
 146 }
 147
 148 pub fn trans_if<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
 149                             if_id: ast::NodeId,
 150                             cond: &hir::Expr,
 151                             thn: &hir::Block,
 152                             els: Option<&hir::Expr>,
 153                             dest: expr::Dest)
 154                             -> Block<'blk, 'tcx> {
 155     debug!("trans_if(bcx={}, if_id={}, cond={:?}, thn={}, dest={})",
 156            bcx.to_str(), if_id, cond, thn.id,
 157            dest.to_string(bcx.ccx()));
 158     let _icx = push_ctxt("trans_if");
 159
 160     if bcx.unreachable.get() {
 161         return bcx;
 162     }
 163
 164     let mut bcx = bcx;
 165
 166     let cond_val = unpack_result!(bcx, expr::trans(bcx, cond).to_llbool());
 167
 168     // Drop branches that are known to be impossible
 169     if let Some(cv) = const_to_opt_uint(cond_val) {
 170         if cv == 1 {
 171             // if true { .. } [else { .. }]
 172             bcx = trans_block(bcx, &thn, dest);
 173             trans::debuginfo::clear_source_location(bcx.fcx);
 174         } else {
 175             if let Some(elexpr) = els {
 176                 bcx = expr::trans_into(bcx, &elexpr, dest);
 177                 trans::debuginfo::clear_source_location(bcx.fcx);
 178             }
 179         }
 180
 181         return bcx;
 182     }
 183
 184     let name = format!("then-block-{}-", thn.id);
 185     let then_bcx_in = bcx.fcx.new_id_block(&name[..], thn.id);
 186     let then_bcx_out = trans_block(then_bcx_in, &thn, dest);
 187     trans::debuginfo::clear_source_location(bcx.fcx);
 188
 189     let cond_source_loc = cond.debug_loc();
 190
 191     let next_bcx;
 192     match els {
 193         Some(elexpr) => {
 194             let else_bcx_in = bcx.fcx.new_id_block("else-block", elexpr.id);
 195             let else_bcx_out = expr::trans_into(else_bcx_in, &elexpr, dest);
 196             next_bcx = bcx.fcx.join_blocks(if_id,
 197                                            &[then_bcx_out, else_bcx_out]);
 198             CondBr(bcx, cond_val, then_bcx_in.llbb, else_bcx_in.llbb, cond_source_loc);
 199         }
 200
 201         None => {
 202             next_bcx = bcx.fcx.new_id_block("next-block", if_id);
 203             Br(then_bcx_out, next_bcx.llbb, DebugLoc::None);
 204             CondBr(bcx, cond_val, then_bcx_in.llbb, next_bcx.llbb, cond_source_loc);
 205         }
 206     }
 207
 208     // Clear the source location because it is still set to whatever has been translated
 209     // right before.
 210     trans::debuginfo::clear_source_location(next_bcx.fcx);
 211
 212     next_bcx
 213 }
 214
 215 pub fn trans_while<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
 216                                loop_expr: &hir::Expr,
 217                                cond: &hir::Expr,
 218                                body: &hir::Block)
 219                                -> Block<'blk, 'tcx> {
 220     let _icx = push_ctxt("trans_while");
 221
 222     if bcx.unreachable.get() {
 223         return bcx;
 224     }
 225
 226     let fcx = bcx.fcx;
 227
 228     //            bcx
 229     //             |
 230     //         cond_bcx_in  <--------+
 231     //             |                 |
 232     //         cond_bcx_out          |
 233     //           |      |            |
 234     //           |    body_bcx_in    |
 235     // cleanup_blk      |            |
 236     //    |           body_bcx_out --+
 237     // next_bcx_in
 238
 239     let next_bcx_in = fcx.new_id_block("while_exit", loop_expr.id);
 240     let cond_bcx_in = fcx.new_id_block("while_cond", cond.id);
 241     let body_bcx_in = fcx.new_id_block("while_body", body.id);
 242
 243     fcx.push_loop_cleanup_scope(loop_expr.id, [next_bcx_in, cond_bcx_in]);
 244
 245     Br(bcx, cond_bcx_in.llbb, loop_expr.debug_loc());
 246
 247     // compile the block where we will handle loop cleanups
 248     let cleanup_llbb = fcx.normal_exit_block(loop_expr.id, cleanup::EXIT_BREAK);
 249
 250     // compile the condition
 251     let Result {bcx: cond_bcx_out, val: cond_val} =
 252         expr::trans(cond_bcx_in, cond).to_llbool();
 253
 254     CondBr(cond_bcx_out, cond_val, body_bcx_in.llbb, cleanup_llbb, cond.debug_loc());
 255
 256     // loop body:
 257     let body_bcx_out = trans_block(body_bcx_in, body, expr::Ignore);
 258     Br(body_bcx_out, cond_bcx_in.llbb, DebugLoc::None);
 259
 260     fcx.pop_loop_cleanup_scope(loop_expr.id);
 261     return next_bcx_in;
 262 }
 263
 264 pub fn trans_loop<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
 265                               loop_expr: &hir::Expr,
 266                               body: &hir::Block)
 267                               -> Block<'blk, 'tcx> {
 268     let _icx = push_ctxt("trans_loop");
 269
 270     if bcx.unreachable.get() {
 271         return bcx;
 272     }
 273
 274     let fcx = bcx.fcx;
 275
 276     //            bcx
 277     //             |
 278     //         body_bcx_in
 279     //             |
 280     //         body_bcx_out
 281     //
 282     // next_bcx
 283     //
 284     // Links between body_bcx_in and next_bcx are created by
 285     // break statements.
 286
 287     let next_bcx_in = bcx.fcx.new_id_block("loop_exit", loop_expr.id);
 288     let body_bcx_in = bcx.fcx.new_id_block("loop_body", body.id);
 289
 290     fcx.push_loop_cleanup_scope(loop_expr.id, [next_bcx_in, body_bcx_in]);
 291
 292     Br(bcx, body_bcx_in.llbb, loop_expr.debug_loc());
 293     let body_bcx_out = trans_block(body_bcx_in, body, expr::Ignore);
 294     Br(body_bcx_out, body_bcx_in.llbb, DebugLoc::None);
 295
 296     fcx.pop_loop_cleanup_scope(loop_expr.id);
 297
 298     // If there are no predecessors for the next block, we just translated an endless loop and the
 299     // next block is unreachable
 300     if BasicBlock(next_bcx_in.llbb).pred_iter().next().is_none() {
 301         Unreachable(next_bcx_in);
 302     }
 303
 304     return next_bcx_in;
 305 }
 306
 307 pub fn trans_break_cont<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
 308                                     expr: &hir::Expr,
 309                                     opt_label: Option<ast::Name>,
 310                                     exit: usize)
 311                                     -> Block<'blk, 'tcx> {
 312     let _icx = push_ctxt("trans_break_cont");
 313
 314     if bcx.unreachable.get() {
 315         return bcx;
 316     }
 317
 318     let fcx = bcx.fcx;
 319
 320     // Locate loop that we will break to
 321     let loop_id = match opt_label {
 322         None => fcx.top_loop_scope(),
 323         Some(_) => {
 324             match bcx.tcx().def_map.borrow().get(&expr.id).map(|d| d.full_def())  {
 325                 Some(Def::Label(loop_id)) => loop_id,
 326                 r => {
 327                     bcx.tcx().sess.bug(&format!("{:?} in def-map for label", r))
 328                 }
 329             }
 330         }
 331     };
 332
 333     // Generate appropriate cleanup code and branch
 334     let cleanup_llbb = fcx.normal_exit_block(loop_id, exit);
 335     Br(bcx, cleanup_llbb, expr.debug_loc());
 336     Unreachable(bcx); // anything afterwards should be ignored
 337     return bcx;
 338 }
 339
 340 pub fn trans_break<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
 341                                expr: &hir::Expr,
 342                                label_opt: Option<ast::Name>)
 343                                -> Block<'blk, 'tcx> {
 344     return trans_break_cont(bcx, expr, label_opt, cleanup::EXIT_BREAK);
 345 }
 346
 347 pub fn trans_cont<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
 348                               expr: &hir::Expr,
 349                               label_opt: Option<ast::Name>)
 350                               -> Block<'blk, 'tcx> {
 351     return trans_break_cont(bcx, expr, label_opt, cleanup::EXIT_LOOP);
 352 }
 353
 354 pub fn trans_ret<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
 355                              return_expr: &hir::Expr,
 356                              retval_expr: Option<&hir::Expr>)
 357                              -> Block<'blk, 'tcx> {
 358     let _icx = push_ctxt("trans_ret");
 359
 360     if bcx.unreachable.get() {
 361         return bcx;
 362     }
 363
 364     let fcx = bcx.fcx;
 365     let mut bcx = bcx;
 366     let dest = match (fcx.llretslotptr.get(), retval_expr) {
 367         (Some(_), Some(retval_expr)) => {
 368             let ret_ty = expr_ty_adjusted(bcx, &retval_expr);
 369             expr::SaveIn(fcx.get_ret_slot(bcx, ty::FnConverging(ret_ty), "ret_slot"))
 370         }
 371         _ => expr::Ignore,
 372     };
 373     if let Some(x) = retval_expr {
 374         bcx = expr::trans_into(bcx, &x, dest);
 375         match dest {
 376             expr::SaveIn(slot) if fcx.needs_ret_allocas => {
 377                 Store(bcx, slot, fcx.llretslotptr.get().unwrap());
 378             }
 379             _ => {}
 380         }
 381     }
 382     let cleanup_llbb = fcx.return_exit_block();
 383     Br(bcx, cleanup_llbb, return_expr.debug_loc());
 384     Unreachable(bcx);
 385     return bcx;
 386 }
 387
 388 pub fn trans_fail<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
 389                               call_info: NodeIdAndSpan,
 390                               fail_str: InternedString)
 391                               -> Block<'blk, 'tcx> {
 392     let ccx = bcx.ccx();
 393     let _icx = push_ctxt("trans_fail_value");
 394
 395     if bcx.unreachable.get() {
 396         return bcx;
 397     }
 398
 399     let v_str = C_str_slice(ccx, fail_str);
 400     let loc = bcx.sess().codemap().lookup_char_pos(call_info.span.lo);
 401     let filename = token::intern_and_get_ident(&loc.file.name);
 402     let filename = C_str_slice(ccx, filename);
 403     let line = C_u32(ccx, loc.line as u32);
 404     let expr_file_line_const = C_struct(ccx, &[v_str, filename, line], false);
 405     let align = machine::llalign_of_min(ccx, val_ty(expr_file_line_const));
 406     let expr_file_line = consts::addr_of(ccx, expr_file_line_const, align, "panic_loc");
 407     let args = vec!(expr_file_line);
 408     let did = langcall(bcx, Some(call_info.span), "", PanicFnLangItem);
 409     let bcx = callee::trans_lang_call(bcx,
 410                                       did,
 411                                       &args[..],
 412                                       Some(expr::Ignore),
 413                                       call_info.debug_loc()).bcx;
 414     Unreachable(bcx);
 415     return bcx;
 416 }
 417
 418 pub fn trans_fail_bounds_check<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
 419                                            call_info: NodeIdAndSpan,
 420                                            index: ValueRef,
 421                                            len: ValueRef)
 422                                            -> Block<'blk, 'tcx> {
 423     let ccx = bcx.ccx();
 424     let _icx = push_ctxt("trans_fail_bounds_check");
 425
 426     if bcx.unreachable.get() {
 427         return bcx;
 428     }
 429
 430     // Extract the file/line from the span
 431     let loc = bcx.sess().codemap().lookup_char_pos(call_info.span.lo);
 432     let filename = token::intern_and_get_ident(&loc.file.name);
 433
 434     // Invoke the lang item
 435     let filename = C_str_slice(ccx,  filename);
 436     let line = C_u32(ccx, loc.line as u32);
 437     let file_line_const = C_struct(ccx, &[filename, line], false);
 438     let align = machine::llalign_of_min(ccx, val_ty(file_line_const));
 439     let file_line = consts::addr_of(ccx, file_line_const, align, "panic_bounds_check_loc");
 440     let args = vec!(file_line, index, len);
 441     let did = langcall(bcx, Some(call_info.span), "", PanicBoundsCheckFnLangItem);
 442     let bcx = callee::trans_lang_call(bcx,
 443                                       did,
 444                                       &args[..],
 445                                       Some(expr::Ignore),
 446                                       call_info.debug_loc()).bcx;
 447     Unreachable(bcx);
 448     return bcx;
 449 }