| // 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. |
| |
| //! An analysis to determine which locals require allocas and |
| //! which do not. |
| |
| use rustc_data_structures::bitvec::BitVector; |
| use rustc_data_structures::indexed_vec::{Idx, IndexVec}; |
| use rustc::mir::repr as mir; |
| use rustc::mir::repr::TerminatorKind; |
| use rustc::mir::visit::{Visitor, LvalueContext}; |
| use rustc::mir::traversal; |
| use common::{self, Block, BlockAndBuilder}; |
| use glue; |
| use super::rvalue; |
| |
| pub fn lvalue_locals<'bcx, 'tcx>(bcx: Block<'bcx,'tcx>, |
| mir: &mir::Mir<'tcx>) -> BitVector { |
| let bcx = bcx.build(); |
| let mut analyzer = LocalAnalyzer::new(mir, &bcx); |
| |
| analyzer.visit_mir(mir); |
| |
| let local_types = mir.arg_decls.iter().map(|a| a.ty) |
| .chain(mir.var_decls.iter().map(|v| v.ty)) |
| .chain(mir.temp_decls.iter().map(|t| t.ty)) |
| .chain(mir.return_ty.maybe_converging()); |
| for (index, ty) in local_types.enumerate() { |
| let ty = bcx.monomorphize(&ty); |
| debug!("local {} has type {:?}", index, ty); |
| if ty.is_scalar() || |
| ty.is_unique() || |
| ty.is_region_ptr() || |
| ty.is_simd() || |
| common::type_is_zero_size(bcx.ccx(), ty) |
| { |
| // These sorts of types are immediates that we can store |
| // in an ValueRef without an alloca. |
| assert!(common::type_is_immediate(bcx.ccx(), ty) || |
| common::type_is_fat_ptr(bcx.tcx(), ty)); |
| } else if common::type_is_imm_pair(bcx.ccx(), ty) { |
| // We allow pairs and uses of any of their 2 fields. |
| } else { |
| // These sorts of types require an alloca. Note that |
| // type_is_immediate() may *still* be true, particularly |
| // for newtypes, but we currently force some types |
| // (e.g. structs) into an alloca unconditionally, just so |
| // that we don't have to deal with having two pathways |
| // (gep vs extractvalue etc). |
| analyzer.mark_as_lvalue(mir::Local::new(index)); |
| } |
| } |
| |
| analyzer.lvalue_locals |
| } |
| |
| struct LocalAnalyzer<'mir, 'bcx: 'mir, 'tcx: 'bcx> { |
| mir: &'mir mir::Mir<'tcx>, |
| bcx: &'mir BlockAndBuilder<'bcx, 'tcx>, |
| lvalue_locals: BitVector, |
| seen_assigned: BitVector |
| } |
| |
| impl<'mir, 'bcx, 'tcx> LocalAnalyzer<'mir, 'bcx, 'tcx> { |
| fn new(mir: &'mir mir::Mir<'tcx>, |
| bcx: &'mir BlockAndBuilder<'bcx, 'tcx>) |
| -> LocalAnalyzer<'mir, 'bcx, 'tcx> { |
| let local_count = mir.count_locals(); |
| LocalAnalyzer { |
| mir: mir, |
| bcx: bcx, |
| lvalue_locals: BitVector::new(local_count), |
| seen_assigned: BitVector::new(local_count) |
| } |
| } |
| |
| fn mark_as_lvalue(&mut self, local: mir::Local) { |
| debug!("marking {:?} as lvalue", local); |
| self.lvalue_locals.insert(local.index()); |
| } |
| |
| fn mark_assigned(&mut self, local: mir::Local) { |
| if !self.seen_assigned.insert(local.index()) { |
| self.mark_as_lvalue(local); |
| } |
| } |
| } |
| |
| impl<'mir, 'bcx, 'tcx> Visitor<'tcx> for LocalAnalyzer<'mir, 'bcx, 'tcx> { |
| fn visit_assign(&mut self, |
| block: mir::BasicBlock, |
| lvalue: &mir::Lvalue<'tcx>, |
| rvalue: &mir::Rvalue<'tcx>) { |
| debug!("visit_assign(block={:?}, lvalue={:?}, rvalue={:?})", block, lvalue, rvalue); |
| |
| if let Some(index) = self.mir.local_index(lvalue) { |
| self.mark_assigned(index); |
| if !rvalue::rvalue_creates_operand(self.mir, self.bcx, rvalue) { |
| self.mark_as_lvalue(index); |
| } |
| } else { |
| self.visit_lvalue(lvalue, LvalueContext::Store); |
| } |
| |
| self.visit_rvalue(rvalue); |
| } |
| |
| fn visit_terminator_kind(&mut self, |
| block: mir::BasicBlock, |
| kind: &mir::TerminatorKind<'tcx>) { |
| match *kind { |
| mir::TerminatorKind::Call { |
| func: mir::Operand::Constant(mir::Constant { |
| literal: mir::Literal::Item { def_id, .. }, .. |
| }), |
| ref args, .. |
| } if Some(def_id) == self.bcx.tcx().lang_items.box_free_fn() => { |
| // box_free(x) shares with `drop x` the property that it |
| // is not guaranteed to be statically dominated by the |
| // definition of x, so x must always be in an alloca. |
| if let mir::Operand::Consume(ref lvalue) = args[0] { |
| self.visit_lvalue(lvalue, LvalueContext::Drop); |
| } |
| } |
| _ => {} |
| } |
| |
| self.super_terminator_kind(block, kind); |
| } |
| |
| fn visit_lvalue(&mut self, |
| lvalue: &mir::Lvalue<'tcx>, |
| context: LvalueContext) { |
| debug!("visit_lvalue(lvalue={:?}, context={:?})", lvalue, context); |
| |
| // Allow uses of projections of immediate pair fields. |
| if let mir::Lvalue::Projection(ref proj) = *lvalue { |
| if self.mir.local_index(&proj.base).is_some() { |
| let ty = self.mir.lvalue_ty(self.bcx.tcx(), &proj.base); |
| let ty = self.bcx.monomorphize(&ty.to_ty(self.bcx.tcx())); |
| if common::type_is_imm_pair(self.bcx.ccx(), ty) { |
| if let mir::ProjectionElem::Field(..) = proj.elem { |
| if let LvalueContext::Consume = context { |
| return; |
| } |
| } |
| } |
| } |
| } |
| |
| if let Some(index) = self.mir.local_index(lvalue) { |
| match context { |
| LvalueContext::Call => { |
| self.mark_assigned(index); |
| } |
| LvalueContext::Consume => { |
| } |
| LvalueContext::Store | |
| LvalueContext::Inspect | |
| LvalueContext::Borrow { .. } | |
| LvalueContext::Slice { .. } | |
| LvalueContext::Projection => { |
| self.mark_as_lvalue(index); |
| } |
| LvalueContext::Drop => { |
| let ty = self.mir.lvalue_ty(self.bcx.tcx(), lvalue); |
| let ty = self.bcx.monomorphize(&ty.to_ty(self.bcx.tcx())); |
| |
| // Only need the lvalue if we're actually dropping it. |
| if glue::type_needs_drop(self.bcx.tcx(), ty) { |
| self.mark_as_lvalue(index); |
| } |
| } |
| } |
| } |
| |
| // A deref projection only reads the pointer, never needs the lvalue. |
| if let mir::Lvalue::Projection(ref proj) = *lvalue { |
| if let mir::ProjectionElem::Deref = proj.elem { |
| return self.visit_lvalue(&proj.base, LvalueContext::Consume); |
| } |
| } |
| |
| self.super_lvalue(lvalue, context); |
| } |
| } |
| |
| #[derive(Copy, Clone, Debug, PartialEq, Eq)] |
| pub enum CleanupKind { |
| NotCleanup, |
| Funclet, |
| Internal { funclet: mir::BasicBlock } |
| } |
| |
| pub fn cleanup_kinds<'bcx,'tcx>(_bcx: Block<'bcx,'tcx>, |
| mir: &mir::Mir<'tcx>) |
| -> IndexVec<mir::BasicBlock, CleanupKind> |
| { |
| fn discover_masters<'tcx>(result: &mut IndexVec<mir::BasicBlock, CleanupKind>, |
| mir: &mir::Mir<'tcx>) { |
| for (bb, data) in mir.basic_blocks().iter_enumerated() { |
| match data.terminator().kind { |
| TerminatorKind::Goto { .. } | |
| TerminatorKind::Resume | |
| TerminatorKind::Return | |
| TerminatorKind::Unreachable | |
| TerminatorKind::If { .. } | |
| TerminatorKind::Switch { .. } | |
| TerminatorKind::SwitchInt { .. } => { |
| /* nothing to do */ |
| } |
| TerminatorKind::Call { cleanup: unwind, .. } | |
| TerminatorKind::Assert { cleanup: unwind, .. } | |
| TerminatorKind::DropAndReplace { unwind, .. } | |
| TerminatorKind::Drop { unwind, .. } => { |
| if let Some(unwind) = unwind { |
| debug!("cleanup_kinds: {:?}/{:?} registering {:?} as funclet", |
| bb, data, unwind); |
| result[unwind] = CleanupKind::Funclet; |
| } |
| } |
| } |
| } |
| } |
| |
| fn propagate<'tcx>(result: &mut IndexVec<mir::BasicBlock, CleanupKind>, |
| mir: &mir::Mir<'tcx>) { |
| let mut funclet_succs = IndexVec::from_elem(None, mir.basic_blocks()); |
| |
| let mut set_successor = |funclet: mir::BasicBlock, succ| { |
| match funclet_succs[funclet] { |
| ref mut s @ None => { |
| debug!("set_successor: updating successor of {:?} to {:?}", |
| funclet, succ); |
| *s = Some(succ); |
| }, |
| Some(s) => if s != succ { |
| span_bug!(mir.span, "funclet {:?} has 2 parents - {:?} and {:?}", |
| funclet, s, succ); |
| } |
| } |
| }; |
| |
| for (bb, data) in traversal::reverse_postorder(mir) { |
| let funclet = match result[bb] { |
| CleanupKind::NotCleanup => continue, |
| CleanupKind::Funclet => bb, |
| CleanupKind::Internal { funclet } => funclet, |
| }; |
| |
| debug!("cleanup_kinds: {:?}/{:?}/{:?} propagating funclet {:?}", |
| bb, data, result[bb], funclet); |
| |
| for &succ in data.terminator().successors().iter() { |
| let kind = result[succ]; |
| debug!("cleanup_kinds: propagating {:?} to {:?}/{:?}", |
| funclet, succ, kind); |
| match kind { |
| CleanupKind::NotCleanup => { |
| result[succ] = CleanupKind::Internal { funclet: funclet }; |
| } |
| CleanupKind::Funclet => { |
| set_successor(funclet, succ); |
| } |
| CleanupKind::Internal { funclet: succ_funclet } => { |
| if funclet != succ_funclet { |
| // `succ` has 2 different funclet going into it, so it must |
| // be a funclet by itself. |
| |
| debug!("promoting {:?} to a funclet and updating {:?}", succ, |
| succ_funclet); |
| result[succ] = CleanupKind::Funclet; |
| set_successor(succ_funclet, succ); |
| set_successor(funclet, succ); |
| } |
| } |
| } |
| } |
| } |
| } |
| |
| let mut result = IndexVec::from_elem(CleanupKind::NotCleanup, mir.basic_blocks()); |
| |
| discover_masters(&mut result, mir); |
| propagate(&mut result, mir); |
| debug!("cleanup_kinds: result={:?}", result); |
| result |
| } |
