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// Copyright 2012-2014 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 libc::c_uint;
use llvm::{self, ValueRef};
use rustc::mir::repr as mir;
use rustc::mir::tcx::LvalueTy;
use trans::base;
use trans::common::{self, Block, BlockAndBuilder};
use trans::expr;
use trans::type_of;
use self::lvalue::LvalueRef;
use self::operand::OperandRef;
// FIXME DebugLoc is always None right now
/// Master context for translating MIR.
pub struct MirContext<'bcx, 'tcx:'bcx> {
mir: &'bcx mir::Mir<'tcx>,
/// Function context
fcx: &'bcx common::FunctionContext<'bcx, 'tcx>,
/// When unwinding is initiated, we have to store this personality
/// value somewhere so that we can load it and re-use it in the
/// resume instruction. The personality is (afaik) some kind of
/// value used for C++ unwinding, which must filter by type: we
/// don't really care about it very much. Anyway, this value
/// contains an alloca into which the personality is stored and
/// then later loaded when generating the DIVERGE_BLOCK.
llpersonalityslot: Option<ValueRef>,
/// A `Block` for each MIR `BasicBlock`
blocks: Vec<Block<'bcx, 'tcx>>,
/// Cached unreachable block
unreachable_block: Option<Block<'bcx, 'tcx>>,
/// An LLVM alloca for each MIR `VarDecl`
vars: Vec<LvalueRef<'tcx>>,
/// The location where each MIR `TempDecl` is stored. This is
/// usually an `LvalueRef` representing an alloca, but not always:
/// sometimes we can skip the alloca and just store the value
/// directly using an `OperandRef`, which makes for tighter LLVM
/// IR. The conditions for using an `OperandRef` are as follows:
///
/// - the type of the temporary must be judged "immediate" by `type_is_immediate`
/// - the operand must never be referenced indirectly
/// - we should not take its address using the `&` operator
/// - nor should it appear in an lvalue path like `tmp.a`
/// - the operand must be defined by an rvalue that can generate immediate
/// values
///
/// Avoiding allocs can also be important for certain intrinsics,
/// notably `expect`.
temps: Vec<TempRef<'tcx>>,
/// The arguments to the function; as args are lvalues, these are
/// always indirect, though we try to avoid creating an alloca
/// when we can (and just reuse the pointer the caller provided).
args: Vec<LvalueRef<'tcx>>,
}
enum TempRef<'tcx> {
Lvalue(LvalueRef<'tcx>),
Operand(Option<OperandRef<'tcx>>),
}
///////////////////////////////////////////////////////////////////////////
pub fn trans_mir<'bcx, 'tcx>(bcx: BlockAndBuilder<'bcx, 'tcx>) {
let fcx = bcx.fcx();
let mir = bcx.mir();
let mir_blocks = bcx.mir().all_basic_blocks();
// Analyze the temps to determine which must be lvalues
// FIXME
let lvalue_temps = bcx.with_block(|bcx| {
analyze::lvalue_temps(bcx, mir)
});
// Allocate variable and temp allocas
let vars = mir.var_decls.iter()
.map(|decl| (bcx.monomorphize(&decl.ty), decl.name))
.map(|(mty, name)| LvalueRef::alloca(&bcx, mty, &name.as_str()))
.collect();
let temps = mir.temp_decls.iter()
.map(|decl| bcx.monomorphize(&decl.ty))
.enumerate()
.map(|(i, mty)| if lvalue_temps.contains(i) {
TempRef::Lvalue(LvalueRef::alloca(&bcx,
mty,
&format!("temp{:?}", i)))
} else {
// If this is an immediate temp, we do not create an
// alloca in advance. Instead we wait until we see the
// definition and update the operand there.
TempRef::Operand(None)
})
.collect();
let args = arg_value_refs(&bcx, mir);
// Allocate a `Block` for every basic block
let block_bcxs: Vec<Block<'bcx,'tcx>> =
mir_blocks.iter()
.map(|&bb|{
// FIXME(#30941) this doesn't handle msvc-style exceptions
fcx.new_block(&format!("{:?}", bb), None)
})
.collect();
// Branch to the START block
let start_bcx = block_bcxs[mir::START_BLOCK.index()];
bcx.br(start_bcx.llbb);
let mut mircx = MirContext {
mir: mir,
fcx: fcx,
llpersonalityslot: None,
blocks: block_bcxs,
unreachable_block: None,
vars: vars,
temps: temps,
args: args,
};
// Translate the body of each block
for &bb in &mir_blocks {
mircx.trans_block(bb);
}
}
/// Produce, for each argument, a `ValueRef` pointing at the
/// argument's value. As arguments are lvalues, these are always
/// indirect.
fn arg_value_refs<'bcx, 'tcx>(bcx: &BlockAndBuilder<'bcx, 'tcx>,
mir: &mir::Mir<'tcx>)
-> Vec<LvalueRef<'tcx>> {
// FIXME tupled_args? I think I'd rather that mapping is done in MIR land though
let fcx = bcx.fcx();
let tcx = bcx.tcx();
let mut idx = fcx.arg_offset() as c_uint;
mir.arg_decls
.iter()
.enumerate()
.map(|(arg_index, arg_decl)| {
let arg_ty = bcx.monomorphize(&arg_decl.ty);
let llval = if type_of::arg_is_indirect(bcx.ccx(), arg_ty) {
// Don't copy an indirect argument to an alloca, the caller
// already put it in a temporary alloca and gave it up, unless
// we emit extra-debug-info, which requires local allocas :(.
// FIXME: lifetimes, debug info
let llarg = llvm::get_param(fcx.llfn, idx);
idx += 1;
llarg
} else if common::type_is_fat_ptr(tcx, arg_ty) {
// we pass fat pointers as two words, but we want to
// represent them internally as a pointer to two words,
// so make an alloca to store them in.
let lldata = llvm::get_param(fcx.llfn, idx);
let llextra = llvm::get_param(fcx.llfn, idx + 1);
idx += 2;
let (lltemp, dataptr, meta) = bcx.with_block(|bcx| {
let lltemp = base::alloc_ty(bcx, arg_ty, &format!("arg{}", arg_index));
(lltemp, expr::get_dataptr(bcx, lltemp), expr::get_meta(bcx, lltemp))
});
bcx.store(lldata, dataptr);
bcx.store(llextra, meta);
lltemp
} else {
// otherwise, arg is passed by value, so make a
// temporary and store it there
let llarg = llvm::get_param(fcx.llfn, idx);
idx += 1;
bcx.with_block(|bcx| {
let lltemp = base::alloc_ty(bcx, arg_ty, &format!("arg{}", arg_index));
base::store_ty(bcx, llarg, lltemp, arg_ty);
lltemp
})
};
LvalueRef::new_sized(llval, LvalueTy::from_ty(arg_ty))
})
.collect()
}
mod analyze;
mod block;
mod constant;
mod drop;
mod lvalue;
mod operand;
mod rvalue;
mod statement;
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