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| 1 | +// Copyright 2016 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 | +//! Def-use analysis. |
| 12 | +
|
| 13 | +use rustc::mir::repr::{Local, Location, Lvalue, Mir}; |
| 14 | +use rustc::mir::visit::{LvalueContext, MutVisitor, Visitor}; |
| 15 | +use rustc_data_structures::indexed_vec::{Idx, IndexVec}; |
| 16 | +use std::marker::PhantomData; |
| 17 | +use std::mem; |
| 18 | + |
| 19 | +pub struct DefUseAnalysis<'tcx> { |
| 20 | + info: IndexVec<Local, Info<'tcx>>, |
| 21 | + mir_summary: MirSummary, |
| 22 | +} |
| 23 | + |
| 24 | +#[derive(Clone)] |
| 25 | +pub struct Info<'tcx> { |
| 26 | + pub defs_and_uses: Vec<Use<'tcx>>, |
| 27 | +} |
| 28 | + |
| 29 | +#[derive(Clone)] |
| 30 | +pub struct Use<'tcx> { |
| 31 | + pub context: LvalueContext<'tcx>, |
| 32 | + pub location: Location, |
| 33 | +} |
| 34 | + |
| 35 | +impl<'tcx> DefUseAnalysis<'tcx> { |
| 36 | + pub fn new(mir: &Mir<'tcx>) -> DefUseAnalysis<'tcx> { |
| 37 | + DefUseAnalysis { |
| 38 | + info: IndexVec::from_elem_n(Info::new(), mir.count_locals()), |
| 39 | + mir_summary: MirSummary::new(mir), |
| 40 | + } |
| 41 | + } |
| 42 | + |
| 43 | + pub fn analyze(&mut self, mir: &Mir<'tcx>) { |
| 44 | + let mut finder = DefUseFinder { |
| 45 | + info: mem::replace(&mut self.info, IndexVec::new()), |
| 46 | + mir_summary: self.mir_summary, |
| 47 | + }; |
| 48 | + finder.visit_mir(mir); |
| 49 | + self.info = finder.info |
| 50 | + } |
| 51 | + |
| 52 | + pub fn local_info(&self, local: Local) -> &Info<'tcx> { |
| 53 | + &self.info[local] |
| 54 | + } |
| 55 | + |
| 56 | + pub fn local_info_mut(&mut self, local: Local) -> &mut Info<'tcx> { |
| 57 | + &mut self.info[local] |
| 58 | + } |
| 59 | + |
| 60 | + fn mutate_defs_and_uses<F>(&self, local: Local, mir: &mut Mir<'tcx>, mut callback: F) |
| 61 | + where F: for<'a> FnMut(&'a mut Lvalue<'tcx>, |
| 62 | + LvalueContext<'tcx>, |
| 63 | + Location) { |
| 64 | + for lvalue_use in &self.info[local].defs_and_uses { |
| 65 | + MutateUseVisitor::new(local, |
| 66 | + &mut callback, |
| 67 | + self.mir_summary, |
| 68 | + mir).visit_location(mir, lvalue_use.location) |
| 69 | + } |
| 70 | + } |
| 71 | + |
| 72 | + /// FIXME(pcwalton): This should update the def-use chains. |
| 73 | + pub fn replace_all_defs_and_uses_with(&self, |
| 74 | + local: Local, |
| 75 | + mir: &mut Mir<'tcx>, |
| 76 | + new_lvalue: Lvalue<'tcx>) { |
| 77 | + self.mutate_defs_and_uses(local, mir, |lvalue, _, _| *lvalue = new_lvalue.clone()) |
| 78 | + } |
| 79 | +} |
| 80 | + |
| 81 | +struct DefUseFinder<'tcx> { |
| 82 | + info: IndexVec<Local, Info<'tcx>>, |
| 83 | + mir_summary: MirSummary, |
| 84 | +} |
| 85 | + |
| 86 | +impl<'tcx> DefUseFinder<'tcx> { |
| 87 | + fn lvalue_mut_info(&mut self, lvalue: &Lvalue<'tcx>) -> Option<&mut Info<'tcx>> { |
| 88 | + let info = &mut self.info; |
| 89 | + self.mir_summary.local_index(lvalue).map(move |local| &mut info[local]) |
| 90 | + } |
| 91 | +} |
| 92 | + |
| 93 | +impl<'tcx> Visitor<'tcx> for DefUseFinder<'tcx> { |
| 94 | + fn visit_lvalue(&mut self, |
| 95 | + lvalue: &Lvalue<'tcx>, |
| 96 | + context: LvalueContext<'tcx>, |
| 97 | + location: Location) { |
| 98 | + if let Some(ref mut info) = self.lvalue_mut_info(lvalue) { |
| 99 | + info.defs_and_uses.push(Use { |
| 100 | + context: context, |
| 101 | + location: location, |
| 102 | + }) |
| 103 | + } |
| 104 | + self.super_lvalue(lvalue, context, location) |
| 105 | + } |
| 106 | +} |
| 107 | + |
| 108 | +impl<'tcx> Info<'tcx> { |
| 109 | + fn new() -> Info<'tcx> { |
| 110 | + Info { |
| 111 | + defs_and_uses: vec![], |
| 112 | + } |
| 113 | + } |
| 114 | + |
| 115 | + pub fn def_count(&self) -> usize { |
| 116 | + self.defs_and_uses.iter().filter(|lvalue_use| lvalue_use.context.is_mutating_use()).count() |
| 117 | + } |
| 118 | + |
| 119 | + pub fn def_count_not_including_drop(&self) -> usize { |
| 120 | + self.defs_and_uses.iter().filter(|lvalue_use| { |
| 121 | + lvalue_use.context.is_mutating_use() && !lvalue_use.context.is_drop() |
| 122 | + }).count() |
| 123 | + } |
| 124 | + |
| 125 | + pub fn use_count(&self) -> usize { |
| 126 | + self.defs_and_uses.iter().filter(|lvalue_use| { |
| 127 | + lvalue_use.context.is_nonmutating_use() |
| 128 | + }).count() |
| 129 | + } |
| 130 | +} |
| 131 | + |
| 132 | +struct MutateUseVisitor<'tcx, F> { |
| 133 | + query: Local, |
| 134 | + callback: F, |
| 135 | + mir_summary: MirSummary, |
| 136 | + phantom: PhantomData<&'tcx ()>, |
| 137 | +} |
| 138 | + |
| 139 | +impl<'tcx, F> MutateUseVisitor<'tcx, F> { |
| 140 | + fn new(query: Local, callback: F, mir_summary: MirSummary, _: &Mir<'tcx>) |
| 141 | + -> MutateUseVisitor<'tcx, F> |
| 142 | + where F: for<'a> FnMut(&'a mut Lvalue<'tcx>, LvalueContext<'tcx>, Location) { |
| 143 | + MutateUseVisitor { |
| 144 | + query: query, |
| 145 | + callback: callback, |
| 146 | + mir_summary: mir_summary, |
| 147 | + phantom: PhantomData, |
| 148 | + } |
| 149 | + } |
| 150 | +} |
| 151 | + |
| 152 | +impl<'tcx, F> MutVisitor<'tcx> for MutateUseVisitor<'tcx, F> |
| 153 | + where F: for<'a> FnMut(&'a mut Lvalue<'tcx>, LvalueContext<'tcx>, Location) { |
| 154 | + fn visit_lvalue(&mut self, |
| 155 | + lvalue: &mut Lvalue<'tcx>, |
| 156 | + context: LvalueContext<'tcx>, |
| 157 | + location: Location) { |
| 158 | + if self.mir_summary.local_index(lvalue) == Some(self.query) { |
| 159 | + (self.callback)(lvalue, context, location) |
| 160 | + } |
| 161 | + self.super_lvalue(lvalue, context, location) |
| 162 | + } |
| 163 | +} |
| 164 | + |
| 165 | +/// A small structure that enables various metadata of the MIR to be queried |
| 166 | +/// without a reference to the MIR itself. |
| 167 | +#[derive(Clone, Copy)] |
| 168 | +struct MirSummary { |
| 169 | + arg_count: usize, |
| 170 | + var_count: usize, |
| 171 | + temp_count: usize, |
| 172 | +} |
| 173 | + |
| 174 | +impl MirSummary { |
| 175 | + fn new(mir: &Mir) -> MirSummary { |
| 176 | + MirSummary { |
| 177 | + arg_count: mir.arg_decls.len(), |
| 178 | + var_count: mir.var_decls.len(), |
| 179 | + temp_count: mir.temp_decls.len(), |
| 180 | + } |
| 181 | + } |
| 182 | + |
| 183 | + fn local_index<'tcx>(&self, lvalue: &Lvalue<'tcx>) -> Option<Local> { |
| 184 | + match *lvalue { |
| 185 | + Lvalue::Arg(arg) => Some(Local::new(arg.index())), |
| 186 | + Lvalue::Var(var) => Some(Local::new(var.index() + self.arg_count)), |
| 187 | + Lvalue::Temp(temp) => { |
| 188 | + Some(Local::new(temp.index() + self.arg_count + self.var_count)) |
| 189 | + } |
| 190 | + Lvalue::ReturnPointer => { |
| 191 | + Some(Local::new(self.arg_count + self.var_count + self.temp_count)) |
| 192 | + } |
| 193 | + _ => None, |
| 194 | + } |
| 195 | + } |
| 196 | +} |
| 197 | + |
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