1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
|
//! Performs various peephole optimizations.
use rustc::mir::{Constant, Location, Place, Mir, Operand, ProjectionElem, Rvalue, Local};
use rustc::mir::visit::{MutVisitor, Visitor};
use rustc::ty::{TyCtxt, TyKind};
use rustc::util::nodemap::{FxHashMap, FxHashSet};
use rustc_data_structures::indexed_vec::Idx;
use std::mem;
use crate::transform::{MirPass, MirSource};
pub struct InstCombine;
impl MirPass for InstCombine {
fn run_pass<'a, 'tcx>(&self,
tcx: TyCtxt<'a, 'tcx, 'tcx>,
_: MirSource<'tcx>,
mir: &mut Mir<'tcx>) {
// We only run when optimizing MIR (at any level).
if tcx.sess.opts.debugging_opts.mir_opt_level == 0 {
return
}
// First, find optimization opportunities. This is done in a pre-pass to keep the MIR
// read-only so that we can do global analyses on the MIR in the process (e.g.
// `Place::ty()`).
let optimizations = {
let mut optimization_finder = OptimizationFinder::new(mir, tcx);
optimization_finder.visit_mir(mir);
optimization_finder.optimizations
};
// Then carry out those optimizations.
MutVisitor::visit_mir(&mut InstCombineVisitor { optimizations }, mir);
}
}
pub struct InstCombineVisitor<'tcx> {
optimizations: OptimizationList<'tcx>,
}
impl<'tcx> MutVisitor<'tcx> for InstCombineVisitor<'tcx> {
fn visit_rvalue(&mut self, rvalue: &mut Rvalue<'tcx>, location: Location) {
if self.optimizations.and_stars.remove(&location) {
debug!("Replacing `&*`: {:?}", rvalue);
let new_place = match *rvalue {
Rvalue::Ref(_, _, Place::Projection(ref mut projection)) => {
// Replace with dummy
mem::replace(&mut projection.base, Place::Local(Local::new(0)))
}
_ => bug!("Detected `&*` but didn't find `&*`!"),
};
*rvalue = Rvalue::Use(Operand::Copy(new_place))
}
if let Some(constant) = self.optimizations.arrays_lengths.remove(&location) {
debug!("Replacing `Len([_; N])`: {:?}", rvalue);
*rvalue = Rvalue::Use(Operand::Constant(box constant));
}
self.super_rvalue(rvalue, location)
}
}
/// Finds optimization opportunities on the MIR.
struct OptimizationFinder<'b, 'a, 'tcx:'a+'b> {
mir: &'b Mir<'tcx>,
tcx: TyCtxt<'a, 'tcx, 'tcx>,
optimizations: OptimizationList<'tcx>,
}
impl<'b, 'a, 'tcx:'b> OptimizationFinder<'b, 'a, 'tcx> {
fn new(mir: &'b Mir<'tcx>, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> OptimizationFinder<'b, 'a, 'tcx> {
OptimizationFinder {
mir,
tcx,
optimizations: OptimizationList::default(),
}
}
}
impl<'b, 'a, 'tcx> Visitor<'tcx> for OptimizationFinder<'b, 'a, 'tcx> {
fn visit_rvalue(&mut self, rvalue: &Rvalue<'tcx>, location: Location) {
if let Rvalue::Ref(_, _, Place::Projection(ref projection)) = *rvalue {
if let ProjectionElem::Deref = projection.elem {
if projection.base.ty(self.mir, self.tcx).to_ty(self.tcx).is_region_ptr() {
self.optimizations.and_stars.insert(location);
}
}
}
if let Rvalue::Len(ref place) = *rvalue {
let place_ty = place.ty(&self.mir.local_decls, self.tcx).to_ty(self.tcx);
if let TyKind::Array(_, len) = place_ty.sty {
let span = self.mir.source_info(location).span;
let ty = self.tcx.types.usize;
let constant = Constant { span, ty, literal: len, user_ty: None };
self.optimizations.arrays_lengths.insert(location, constant);
}
}
self.super_rvalue(rvalue, location)
}
}
#[derive(Default)]
struct OptimizationList<'tcx> {
and_stars: FxHashSet<Location>,
arrays_lengths: FxHashMap<Location, Constant<'tcx>>,
}
|
