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
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
|
#
#
# The Nimrod Compiler
# (c) Copyright 2012 Andreas Rumpf
#
# See the file "copying.txt", included in this
# distribution, for details about the copyright.
#
## Simple alias analysis for the HLO and the code generators.
import
ast, astalgo, types, trees, intsets, msgs
type
TAnalysisResult* = enum
arNo, arMaybe, arYes
proc isPartOfAux(a, b: PType, marker: var TIntSet): TAnalysisResult
proc isPartOfAux(n: PNode, b: PType, marker: var TIntSet): TAnalysisResult =
result = arNo
case n.kind
of nkRecList:
for i in countup(0, sonsLen(n) - 1):
result = isPartOfAux(n.sons[i], b, marker)
if result == arYes: return
of nkRecCase:
assert(n.sons[0].kind == nkSym)
result = isPartOfAux(n.sons[0], b, marker)
if result == arYes: return
for i in countup(1, sonsLen(n) - 1):
case n.sons[i].kind
of nkOfBranch, nkElse:
result = isPartOfAux(lastSon(n.sons[i]), b, marker)
if result == arYes: return
else: internalError("isPartOfAux(record case branch)")
of nkSym:
result = isPartOfAux(n.sym.typ, b, marker)
else: internalError(n.info, "isPartOfAux()")
proc isPartOfAux(a, b: PType, marker: var TIntSet): TAnalysisResult =
result = arNo
if a == nil or b == nil: return
if ContainsOrIncl(marker, a.id): return
if compareTypes(a, b, dcEqIgnoreDistinct): return arYes
case a.kind
of tyObject:
result = isPartOfAux(a.sons[0], b, marker)
if result == arNo: result = isPartOfAux(a.n, b, marker)
of tyGenericInst, tyDistinct:
result = isPartOfAux(lastSon(a), b, marker)
of tyArray, tyArrayConstr, tySet, tyTuple:
for i in countup(0, sonsLen(a) - 1):
result = isPartOfAux(a.sons[i], b, marker)
if result == arYes: return
else: nil
proc isPartOf(a, b: PType): TAnalysisResult =
## checks iff 'a' can be part of 'b'. Iterates over VALUE types!
var marker = InitIntSet()
# watch out: parameters reversed because I'm too lazy to change the code...
result = isPartOfAux(b, a, marker)
proc isPartOf*(a, b: PNode): TAnalysisResult =
## checks if location `a` can be part of location `b`. We treat seqs and
## strings as pointers because the code gen often just passes them as such.
##
## Note: `a` can only be part of `b`, if `a`'s type can be part of `b`'s
## type. Since however type analysis is more expensive, we perform it only
## if necessary.
##
## cases:
##
## YES-cases:
## x <| x # for general trees
## x[] <| x
## x[i] <| x
## x.f <| x
##
## NO-cases:
## x !<| y # depending on type and symbol kind
## x[constA] !<| x[constB]
## x.f !<| x.g
## x.f !<| y.f iff x !<= y
##
## MAYBE-cases:
##
## x[] ?<| y[] iff compatible type
##
##
## x[] ?<| y depending on type
##
if a.kind == b.kind:
case a.kind
of nkSym:
const varKinds = {skVar, skTemp, skProc}
# same symbol: aliasing:
if a.sym.id == b.sym.id: result = arYes
elif a.sym.kind in varKinds or b.sym.kind in varKinds:
# actually, a param could alias a var but we know that cannot happen
# here. XXX make this more generic
result = arNo
else:
# use expensive type check:
if isPartOf(a.sym.typ, b.sym.typ) != arNo:
result = arMaybe
of nkBracketExpr:
result = isPartOf(a[0], b[0])
if len(a) >= 2 and len(b) >= 2:
# array accesses:
if result == arYes and isDeepConstExpr(a[1]) and isDeepConstExpr(b[1]):
# we know it's the same array and we have 2 constant indexes;
# if they are
var x = if a[1].kind == nkHiddenStdConv: a[1][1] else: a[1]
var y = if b[1].kind == nkHiddenStdConv: b[1][1] else: b[1]
if SameValue(x, y): result = arYes
else: result = arNo
# else: maybe and no are accurate
else:
# pointer derefs:
if result != arYes:
if isPartOf(a.typ, b.typ) != arNo: result = arMaybe
of nkDotExpr:
result = isPartOf(a[0], b[0])
if result != arNo:
# if the fields are different, it's not the same location
if a[1].sym.id != b[1].sym.id:
result = arNo
of nkHiddenDeref, nkDerefExpr:
result = isPartOf(a[0], b[0])
# weaken because of indirection:
if result != arYes:
if isPartOf(a.typ, b.typ) != arNo: result = arMaybe
of nkHiddenStdConv, nkHiddenSubConv, nkConv:
result = isPartOf(a[1], b[1])
of nkObjUpConv, nkObjDownConv, nkCheckedFieldExpr:
result = isPartOf(a[0], b[0])
else: nil
# Calls return a new location, so a default of ``arNo`` is fine.
else:
# go down recursively; this is quite demanding:
const
Ix0Kinds = {nkDotExpr, nkBracketExpr, nkObjUpConv, nkObjDownConv,
nkCheckedFieldExpr}
Ix1Kinds = {nkHiddenStdConv, nkHiddenSubConv, nkConv}
DerefKinds = {nkHiddenDeref, nkDerefExpr}
case b.kind
of Ix0Kinds:
# a* !<| b.f iff a* !<| b
result = isPartOf(a, b[0])
of DerefKinds:
# a* !<| b[] iff
if isPartOf(a.typ, b.typ) != arNo:
result = isPartOf(a, b[0])
if result == arNo: result = arMaybe
of Ix1Kinds:
# a* !<| T(b) iff a* !<| b
result = isPartOf(a, b[1])
of nkSym:
# b is an atom, so we have to check a:
case a.kind
of Ix0Kinds:
# a.f !<| b* iff a.f !<| b*
result = isPartOf(a[0], b)
of Ix1Kinds:
result = isPartOf(a[1], b)
of DerefKinds:
if isPartOf(a.typ, b.typ) != arNo:
result = isPartOf(a[0], b)
if result == arNo: result = arMaybe
else: nil
else: nil
|