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
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
|
#include "slang-ir-legalize-empty-array.h"
#include "slang-ir-insts.h"
#include "slang-ir-util.h"
#include "slang-ir.h"
namespace Slang
{
struct EmptyArrayLoweringContext
{
IRModule* module;
DiagnosticSink* sink;
InstWorkList workList;
InstHashSet workListSet;
Dictionary<IRInst*, IRInst*> replacements;
EmptyArrayLoweringContext(IRModule* module)
: module(module), workList(module), workListSet(module)
{
}
void addToWorkList(IRInst* inst)
{
for (auto ii = inst->getParent(); ii; ii = ii->getParent())
{
if (as<IRGeneric>(ii))
return;
}
if (workListSet.contains(inst))
return;
workList.add(inst);
workListSet.add(inst);
}
bool isEmptyArray(IRType* t)
{
const auto lenLit = composeGetters<IRIntLit>(t, &IRArrayType::getElementCount);
return lenLit ? getIntVal(lenLit) == 0 : false;
};
bool hasEmptyArrayType(IRInst* i) { return isEmptyArray(i->getDataType()); }
bool hasEmptyArrayPtrType(IRInst* i)
{
const auto ptr = as<IRPtrTypeBase>(i->getDataType());
return ptr && isEmptyArray(ptr->getValueType());
}
// Visit each instruction and replace it with legalized instructions if necessary.
void processInst(IRInst* inst)
{
//
// This function is handling several different replacements at once:
//
// * Instructions that would create an empty array value are changed
// to create a unit value (`void`) instead.
//
// * Instruction that would try to read an element from an empty array,
// or form a pointer to such an element, instead yield a `poison`
// (undefined) value. Note that they do not yield `LoadFromUninitializedMemory`
// because there is no guarantee that there would be anything in the
// memory corresponding to an index into an empty array.
//
// * Instructions that would try to read from an undefined pointer,
// buffer, image, etc. yield `poison`.
//
// * Instructions that would try to write to an undefined pointer,
// buffer, image, etc. are skipped (the behavior is undefined, so
// "do nothing" is a valid choice for the behavior, which has the
// nice side effect of potentially rendering other code redundant).
//
IRInst* replacement = nullptr;
IRBuilder builder(module);
builder.setInsertBefore(inst);
replacement = instMatch<IRInst*>(
inst,
nullptr,
// The following match instructions which take a 0-sized array as an
// operand and produces a result value for the inst.
[&](IRGetElement* getElement)
{
const auto base = getElement->getBase();
return hasEmptyArrayType(base) ? builder.emitPoison(getElement->getDataType())
: nullptr;
},
[&](IRGetElementPtr* gep)
{
const auto base = gep->getBase();
return hasEmptyArrayPtrType(gep) || hasEmptyArrayPtrType(base) ||
as<IRUndefined>(base)
? builder.emitPoison(gep->getDataType())
: nullptr;
},
[&](IRFieldAddress* gep)
{
const auto base = gep->getBase();
return hasEmptyArrayPtrType(gep) || as<IRUndefined>(base)
? builder.emitPoison(gep->getDataType())
: nullptr;
},
[&](IRLoad* load)
{
return as<IRUndefined>(load->getOperand(0))
? builder.emitPoison(load->getDataType())
: nullptr;
},
[&](IRImageLoad* load)
{
return as<IRUndefined>(load->getOperand(0))
? builder.emitPoison(load->getDataType())
: nullptr;
},
[&](IRStore* store)
{
if (as<IRUndefined>(store->getPtr()))
store->removeAndDeallocate();
return nullptr;
},
[&](IRAtomicStore* store)
{
if (as<IRUndefined>(store->getPtr()))
store->removeAndDeallocate();
return nullptr;
},
[&](IRImageStore* store)
{
if (as<IRUndefined>(store->getImage()))
store->removeAndDeallocate();
return nullptr;
},
[&](IRImageSubscript* subscript)
{
return as<IRUndefined>(subscript->getImage())
? builder.emitPoison(subscript->getDataType())
: nullptr;
},
[&](IRAtomicOperation* atomic)
{
return as<IRUndefined>(atomic->getOperand(0))
? builder.emitPoison(atomic->getDataType())
: nullptr;
},
// The following should match any instruction which can construct a 0-sized array.
[&](IRMakeArray* makeArray) {
return hasEmptyArrayType(makeArray->getDataType()) ? builder.getVoidValue()
: nullptr;
},
[&](IRMakeArrayFromElement* makeArray) {
return hasEmptyArrayType(makeArray->getDataType()) ? builder.getVoidValue()
: nullptr;
});
// If we did get a replacement, add that to our mapping and return
// it, otherwise return the original (to maybe be updated later)
if (replacement)
{
inst->replaceUsesWith(replacement);
inst->removeAndDeallocate();
addToWorkList(replacement);
for (auto use = replacement->firstUse; use; use = use->nextUse)
{
addToWorkList(use->getUser());
}
}
else if (isEmptyArray((IRType*)inst))
{
replacements.add(inst, builder.getVoidType());
}
}
void processModule()
{
addToWorkList(module->getModuleInst());
while (workList.getCount() != 0)
{
IRInst* inst = workList.getLast();
workList.removeLast();
workListSet.remove(inst);
// Run this inst through the replacer
processInst(inst);
for (auto child = inst->getLastChild(); child; child = child->getPrevInst())
{
addToWorkList(child);
}
}
// Apply all deferred replacements
//
// It's important to defer this as if we were updating things
// on-the-fly we would be losing information about what was
// actually a 0-array or not.
for (const auto& [old, replacement] : replacements)
{
if (old != replacement)
{
old->replaceUsesWith(replacement);
old->removeAndDeallocate();
}
}
}
};
void legalizeEmptyArray(IRModule* module, DiagnosticSink* sink)
{
EmptyArrayLoweringContext context(module);
context.sink = sink;
context.processModule();
}
} // namespace Slang
|
