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1 | // Copyright 2012-2014 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 | //! An analysis to determine which temporaries require allocas and | |
12 | //! which do not. | |
13 | ||
7453a54e | 14 | use rustc_data_structures::bitvec::BitVector; |
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15 | use rustc::mir::repr as mir; |
16 | use rustc::mir::visit::{Visitor, LvalueContext}; | |
17 | use trans::common::{self, Block}; | |
18 | use super::rvalue; | |
19 | ||
20 | pub fn lvalue_temps<'bcx,'tcx>(bcx: Block<'bcx,'tcx>, | |
21 | mir: &mir::Mir<'tcx>) | |
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22 | -> BitVector { |
23 | let mut analyzer = TempAnalyzer::new(mir.temp_decls.len()); | |
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24 | |
25 | analyzer.visit_mir(mir); | |
26 | ||
27 | for (index, temp_decl) in mir.temp_decls.iter().enumerate() { | |
28 | let ty = bcx.monomorphize(&temp_decl.ty); | |
29 | debug!("temp {:?} has type {:?}", index, ty); | |
30 | if ty.is_scalar() || | |
31 | ty.is_unique() || | |
32 | ty.is_region_ptr() || | |
33 | ty.is_simd() | |
34 | { | |
35 | // These sorts of types are immediates that we can store | |
36 | // in an ValueRef without an alloca. | |
37 | assert!(common::type_is_immediate(bcx.ccx(), ty) || | |
38 | common::type_is_fat_ptr(bcx.tcx(), ty)); | |
39 | } else { | |
40 | // These sorts of types require an alloca. Note that | |
41 | // type_is_immediate() may *still* be true, particularly | |
42 | // for newtypes, but we currently force some types | |
43 | // (e.g. structs) into an alloca unconditionally, just so | |
44 | // that we don't have to deal with having two pathways | |
45 | // (gep vs extractvalue etc). | |
46 | analyzer.mark_as_lvalue(index); | |
47 | } | |
48 | } | |
49 | ||
50 | analyzer.lvalue_temps | |
51 | } | |
52 | ||
53 | struct TempAnalyzer { | |
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54 | lvalue_temps: BitVector, |
55 | seen_assigned: BitVector | |
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56 | } |
57 | ||
58 | impl TempAnalyzer { | |
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59 | fn new(temp_count: usize) -> TempAnalyzer { |
60 | TempAnalyzer { | |
61 | lvalue_temps: BitVector::new(temp_count), | |
62 | seen_assigned: BitVector::new(temp_count) | |
63 | } | |
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64 | } |
65 | ||
66 | fn mark_as_lvalue(&mut self, temp: usize) { | |
67 | debug!("marking temp {} as lvalue", temp); | |
68 | self.lvalue_temps.insert(temp); | |
69 | } | |
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70 | |
71 | fn mark_assigned(&mut self, temp: usize) { | |
72 | if !self.seen_assigned.insert(temp) { | |
73 | self.mark_as_lvalue(temp); | |
74 | } | |
75 | } | |
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76 | } |
77 | ||
78 | impl<'tcx> Visitor<'tcx> for TempAnalyzer { | |
79 | fn visit_assign(&mut self, | |
80 | block: mir::BasicBlock, | |
81 | lvalue: &mir::Lvalue<'tcx>, | |
82 | rvalue: &mir::Rvalue<'tcx>) { | |
83 | debug!("visit_assign(block={:?}, lvalue={:?}, rvalue={:?})", block, lvalue, rvalue); | |
84 | ||
85 | match *lvalue { | |
86 | mir::Lvalue::Temp(index) => { | |
7453a54e | 87 | self.mark_assigned(index as usize); |
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88 | if !rvalue::rvalue_creates_operand(rvalue) { |
89 | self.mark_as_lvalue(index as usize); | |
90 | } | |
91 | } | |
92 | _ => { | |
93 | self.visit_lvalue(lvalue, LvalueContext::Store); | |
94 | } | |
95 | } | |
96 | ||
97 | self.visit_rvalue(rvalue); | |
98 | } | |
99 | ||
100 | fn visit_lvalue(&mut self, | |
101 | lvalue: &mir::Lvalue<'tcx>, | |
102 | context: LvalueContext) { | |
103 | debug!("visit_lvalue(lvalue={:?}, context={:?})", lvalue, context); | |
104 | ||
105 | match *lvalue { | |
106 | mir::Lvalue::Temp(index) => { | |
107 | match context { | |
108 | LvalueContext::Consume => { | |
109 | } | |
110 | LvalueContext::Store | | |
111 | LvalueContext::Drop | | |
112 | LvalueContext::Inspect | | |
113 | LvalueContext::Borrow { .. } | | |
114 | LvalueContext::Slice { .. } | | |
115 | LvalueContext::Projection => { | |
116 | self.mark_as_lvalue(index as usize); | |
117 | } | |
118 | } | |
119 | } | |
120 | _ => { | |
121 | } | |
122 | } | |
123 | ||
124 | self.super_lvalue(lvalue, context); | |
125 | } | |
126 | } |