rust/src/librustc/middle/trans/controlflow.rs

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// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
use lib::llvm::*;
use middle::lang_items::{FailFnLangItem, FailBoundsCheckFnLangItem};
use middle::trans::base::*;
use middle::trans::build::*;
use middle::trans::callee;
use middle::trans::common::*;
use middle::trans::debuginfo;
use middle::trans::expr;
use middle::ty;
use util::common::indenter;
use util::ppaux;
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use middle::trans::type_::Type;
use syntax::ast;
use syntax::ast::Name;
use syntax::ast_util;
use syntax::codemap::Span;
use syntax::visit::Visitor;
pub fn trans_block(bcx: @mut Block, b: &ast::Block, dest: expr::Dest) -> @mut Block {
let _icx = push_ctxt("trans_block");
let mut bcx = bcx;
for s in b.stmts.iter() {
bcx = trans_stmt(bcx, *s);
}
match b.expr {
Some(e) => {
bcx = expr::trans_into(bcx, e, dest);
}
None => {
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assert!(dest == expr::Ignore || bcx.unreachable);
}
}
return bcx;
}
pub fn trans_if(bcx: @mut Block,
cond: &ast::Expr,
thn: &ast::Block,
els: Option<@ast::Expr>,
dest: expr::Dest)
-> @mut Block {
debug!("trans_if(bcx={}, cond={}, thn={:?}, dest={})",
bcx.to_str(), bcx.expr_to_str(cond), thn.id,
dest.to_str(bcx.ccx()));
let _indenter = indenter();
let _icx = push_ctxt("trans_if");
let Result {bcx, val: cond_val} =
expr::trans_to_datum(bcx, cond).to_result();
let cond_val = bool_to_i1(bcx, cond_val);
// Drop branches that are known to be impossible
if is_const(cond_val) && !is_undef(cond_val) {
if const_to_uint(cond_val) == 1 {
match els {
Some(elexpr) => {
let mut trans = TransItemVisitor { ccx: bcx.fcx.ccx };
trans.visit_expr(elexpr, ());
}
None => {}
}
// if true { .. } [else { .. }]
return with_scope(bcx, thn.info(), "if_true_then", |bcx| {
let bcx_out = trans_block(bcx, thn, dest);
debuginfo::clear_source_location(bcx.fcx);
trans_block_cleanups(bcx_out, block_cleanups(bcx))
})
} else {
let mut trans = TransItemVisitor { ccx: bcx.fcx.ccx } ;
trans.visit_block(thn, ());
match els {
// if false { .. } else { .. }
Some(elexpr) => {
return with_scope(bcx,
elexpr.info(),
"if_false_then",
|bcx| {
let bcx_out = trans_if_else(bcx, elexpr, dest);
debuginfo::clear_source_location(bcx.fcx);
trans_block_cleanups(bcx_out, block_cleanups(bcx))
})
}
// if false { .. }
None => return bcx,
}
}
}
let then_bcx_in = scope_block(bcx, thn.info(), "then");
let then_bcx_out = trans_block(then_bcx_in, thn, dest);
debuginfo::clear_source_location(bcx.fcx);
let then_bcx_out = trans_block_cleanups(then_bcx_out,
block_cleanups(then_bcx_in));
// Calling trans_block directly instead of trans_expr
// because trans_expr will create another scope block
// context for the block, but we've already got the
// 'else' context
let (else_bcx_in, next_bcx) = match els {
Some(elexpr) => {
let else_bcx_in = scope_block(bcx, elexpr.info(), "else");
let else_bcx_out = trans_if_else(else_bcx_in, elexpr, dest);
(else_bcx_in, join_blocks(bcx, [then_bcx_out, else_bcx_out]))
}
_ => {
let next_bcx = sub_block(bcx, "next");
Br(then_bcx_out, next_bcx.llbb);
(next_bcx, next_bcx)
}
};
debug!("then_bcx_in={}, else_bcx_in={}",
then_bcx_in.to_str(), else_bcx_in.to_str());
// Clear the source location because it is still set to whatever has been translated
// right before.
debuginfo::clear_source_location(else_bcx_in.fcx);
CondBr(bcx, cond_val, then_bcx_in.llbb, else_bcx_in.llbb);
return next_bcx;
// trans `else [ if { .. } ... | { .. } ]`
fn trans_if_else(else_bcx_in: @mut Block, elexpr: @ast::Expr,
dest: expr::Dest) -> @mut Block {
let else_bcx_out = match elexpr.node {
ast::ExprIf(_, _, _) => {
let elseif_blk = ast_util::block_from_expr(elexpr);
trans_block(else_bcx_in, &elseif_blk, dest)
}
ast::ExprBlock(ref blk) => {
trans_block(else_bcx_in, blk, dest)
}
// would be nice to have a constraint on ifs
_ => else_bcx_in.tcx().sess.bug("strange alternative in if")
};
debuginfo::clear_source_location(else_bcx_in.fcx);
trans_block_cleanups(else_bcx_out, block_cleanups(else_bcx_in))
}
}
pub fn join_blocks(parent_bcx: @mut Block, in_cxs: &[@mut Block]) -> @mut Block {
let out = sub_block(parent_bcx, "join");
let mut reachable = false;
for bcx in in_cxs.iter() {
if !bcx.unreachable {
Br(*bcx, out.llbb);
reachable = true;
}
}
if !reachable {
Unreachable(out);
}
return out;
}
pub fn trans_while(bcx: @mut Block, cond: &ast::Expr, body: &ast::Block) -> @mut Block {
let _icx = push_ctxt("trans_while");
let next_bcx = sub_block(bcx, "while next");
// bcx
// |
// loop_bcx
// |
// cond_bcx_in <--------+
// | |
// cond_bcx_out |
// | | |
// | body_bcx_in |
// +------+ | |
// | body_bcx_out --+
// next_bcx
let loop_bcx = loop_scope_block(bcx, next_bcx, None, "`while`",
body.info());
let cond_bcx_in = scope_block(loop_bcx, cond.info(), "while loop cond");
let body_bcx_in = scope_block(loop_bcx, body.info(), "while loop body");
Br(bcx, loop_bcx.llbb);
Br(loop_bcx, cond_bcx_in.llbb);
// compile the condition
let Result {bcx: cond_bcx_out, val: cond_val} =
expr::trans_to_datum(cond_bcx_in, cond).to_result();
let cond_val = bool_to_i1(cond_bcx_out, cond_val);
let cond_bcx_out =
trans_block_cleanups(cond_bcx_out, block_cleanups(cond_bcx_in));
CondBr(cond_bcx_out, cond_val, body_bcx_in.llbb, next_bcx.llbb);
// loop body:
let body_bcx_out = trans_block(body_bcx_in, body, expr::Ignore);
cleanup_and_Br(body_bcx_out, body_bcx_in, cond_bcx_in.llbb);
return next_bcx;
}
pub fn trans_loop(bcx:@mut Block,
body: &ast::Block,
opt_label: Option<Name>)
-> @mut Block {
let _icx = push_ctxt("trans_loop");
let next_bcx = sub_block(bcx, "next");
let body_bcx_in = loop_scope_block(bcx, next_bcx, opt_label, "`loop`",
body.info());
Br(bcx, body_bcx_in.llbb);
let body_bcx_out = trans_block(body_bcx_in, body, expr::Ignore);
cleanup_and_Br(body_bcx_out, body_bcx_in, body_bcx_in.llbb);
return next_bcx;
}
pub fn trans_break_cont(bcx: @mut Block,
opt_label: Option<Name>,
to_end: bool)
-> @mut Block {
let _icx = push_ctxt("trans_break_cont");
// Locate closest loop block, outputting cleanup as we go.
let mut unwind = bcx;
let mut cur_scope = unwind.scope;
let mut target;
loop {
cur_scope = match cur_scope {
Some(@ScopeInfo {
loop_break: Some(brk),
loop_label: l,
parent,
_
}) => {
// If we're looking for a labeled loop, check the label...
target = if to_end {
brk
} else {
unwind
};
match opt_label {
Some(desired) => match l {
Some(actual) if actual == desired => break,
// If it doesn't match the one we want,
// don't break
_ => parent,
},
None => break,
}
}
Some(inf) => inf.parent,
None => {
unwind = match unwind.parent {
Some(bcx) => bcx,
// This is a return from a loop body block
None => {
Store(bcx, C_bool(!to_end), bcx.fcx.llretptr.unwrap());
cleanup_and_leave(bcx, None, Some(bcx.fcx.get_llreturn()));
Unreachable(bcx);
return bcx;
}
};
unwind.scope
}
}
}
cleanup_and_Br(bcx, unwind, target.llbb);
Unreachable(bcx);
return bcx;
}
pub fn trans_break(bcx: @mut Block, label_opt: Option<Name>) -> @mut Block {
return trans_break_cont(bcx, label_opt, true);
}
pub fn trans_cont(bcx: @mut Block, label_opt: Option<Name>) -> @mut Block {
return trans_break_cont(bcx, label_opt, false);
}
pub fn trans_ret(bcx: @mut Block, e: Option<@ast::Expr>) -> @mut Block {
let _icx = push_ctxt("trans_ret");
let mut bcx = bcx;
let dest = match bcx.fcx.llretptr {
None => expr::Ignore,
Some(retptr) => expr::SaveIn(retptr),
};
match e {
Some(x) => {
bcx = expr::trans_into(bcx, x, dest);
}
_ => ()
}
cleanup_and_leave(bcx, None, Some(bcx.fcx.get_llreturn()));
Unreachable(bcx);
return bcx;
}
pub fn trans_fail_expr(bcx: @mut Block,
sp_opt: Option<Span>,
fail_expr: Option<@ast::Expr>)
-> @mut Block {
let _icx = push_ctxt("trans_fail_expr");
let mut bcx = bcx;
match fail_expr {
Some(arg_expr) => {
let ccx = bcx.ccx();
let tcx = ccx.tcx;
let arg_datum = unpack_datum!(
bcx, expr::trans_to_datum(bcx, arg_expr));
if ty::type_is_str(arg_datum.ty) {
let (lldata, _) = arg_datum.get_vec_base_and_len_no_root(bcx);
return trans_fail_value(bcx, sp_opt, lldata);
} else if bcx.unreachable || ty::type_is_bot(arg_datum.ty) {
return bcx;
} else {
bcx.sess().span_bug(
arg_expr.span, ~"fail called with unsupported type " +
ppaux::ty_to_str(tcx, arg_datum.ty));
}
}
_ => trans_fail(bcx, sp_opt, @"explicit failure")
}
}
pub fn trans_fail(bcx: @mut Block,
sp_opt: Option<Span>,
fail_str: @str)
-> @mut Block {
let _icx = push_ctxt("trans_fail");
let V_fail_str = C_cstr(bcx.ccx(), fail_str);
return trans_fail_value(bcx, sp_opt, V_fail_str);
}
fn trans_fail_value(bcx: @mut Block,
sp_opt: Option<Span>,
V_fail_str: ValueRef)
-> @mut Block {
let _icx = push_ctxt("trans_fail_value");
let ccx = bcx.ccx();
let (V_filename, V_line) = match sp_opt {
Some(sp) => {
let sess = bcx.sess();
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let loc = sess.parse_sess.cm.lookup_char_pos(sp.lo);
(C_cstr(bcx.ccx(), loc.file.name),
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loc.line as int)
}
None => {
(C_cstr(bcx.ccx(), @"<runtime>"), 0)
}
};
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let V_str = PointerCast(bcx, V_fail_str, Type::i8p());
let V_filename = PointerCast(bcx, V_filename, Type::i8p());
let args = ~[V_str, V_filename, C_int(ccx, V_line)];
let did = langcall(bcx, sp_opt, "", FailFnLangItem);
let bcx = callee::trans_lang_call(bcx, did, args, Some(expr::Ignore)).bcx;
Unreachable(bcx);
return bcx;
}
pub fn trans_fail_bounds_check(bcx: @mut Block, sp: Span,
index: ValueRef, len: ValueRef) -> @mut Block {
let _icx = push_ctxt("trans_fail_bounds_check");
let (filename, line) = filename_and_line_num_from_span(bcx, sp);
let args = ~[filename, line, index, len];
let did = langcall(bcx, Some(sp), "", FailBoundsCheckFnLangItem);
let bcx = callee::trans_lang_call(bcx, did, args, Some(expr::Ignore)).bcx;
Unreachable(bcx);
return bcx;
}