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
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
|
//===-- SIAnnotateControlFlow.cpp - ------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
/// \file
/// Annotates the control flow with hardware specific intrinsics.
//
//===----------------------------------------------------------------------===//
#include "AMDGPU.h"
#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Module.h"
#include "llvm/Pass.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/SSAUpdater.h"
using namespace llvm;
#define DEBUG_TYPE "si-annotate-control-flow"
namespace {
// Complex types used in this pass
typedef std::pair<BasicBlock *, Value *> StackEntry;
typedef SmallVector<StackEntry, 16> StackVector;
// Intrinsic names the control flow is annotated with
static const char *const IfIntrinsic = "llvm.SI.if";
static const char *const ElseIntrinsic = "llvm.SI.else";
static const char *const BreakIntrinsic = "llvm.SI.break";
static const char *const IfBreakIntrinsic = "llvm.SI.if.break";
static const char *const ElseBreakIntrinsic = "llvm.SI.else.break";
static const char *const LoopIntrinsic = "llvm.SI.loop";
static const char *const EndCfIntrinsic = "llvm.SI.end.cf";
class SIAnnotateControlFlow : public FunctionPass {
static char ID;
Type *Boolean;
Type *Void;
Type *Int64;
Type *ReturnStruct;
ConstantInt *BoolTrue;
ConstantInt *BoolFalse;
UndefValue *BoolUndef;
Constant *Int64Zero;
Constant *If;
Constant *Else;
Constant *Break;
Constant *IfBreak;
Constant *ElseBreak;
Constant *Loop;
Constant *EndCf;
DominatorTree *DT;
StackVector Stack;
LoopInfo *LI;
bool isTopOfStack(BasicBlock *BB);
Value *popSaved();
void push(BasicBlock *BB, Value *Saved);
bool isElse(PHINode *Phi);
void eraseIfUnused(PHINode *Phi);
void openIf(BranchInst *Term);
void insertElse(BranchInst *Term);
Value *handleLoopCondition(Value *Cond, PHINode *Broken, llvm::Loop *L);
void handleLoop(BranchInst *Term);
void closeControlFlow(BasicBlock *BB);
public:
SIAnnotateControlFlow():
FunctionPass(ID) { }
bool doInitialization(Module &M) override;
bool runOnFunction(Function &F) override;
const char *getPassName() const override {
return "SI annotate control flow";
}
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.addRequired<LoopInfo>();
AU.addRequired<DominatorTreeWrapperPass>();
AU.addPreserved<DominatorTreeWrapperPass>();
FunctionPass::getAnalysisUsage(AU);
}
};
} // end anonymous namespace
char SIAnnotateControlFlow::ID = 0;
/// \brief Initialize all the types and constants used in the pass
bool SIAnnotateControlFlow::doInitialization(Module &M) {
LLVMContext &Context = M.getContext();
Void = Type::getVoidTy(Context);
Boolean = Type::getInt1Ty(Context);
Int64 = Type::getInt64Ty(Context);
ReturnStruct = StructType::get(Boolean, Int64, (Type *)nullptr);
BoolTrue = ConstantInt::getTrue(Context);
BoolFalse = ConstantInt::getFalse(Context);
BoolUndef = UndefValue::get(Boolean);
Int64Zero = ConstantInt::get(Int64, 0);
If = M.getOrInsertFunction(
IfIntrinsic, ReturnStruct, Boolean, (Type *)nullptr);
Else = M.getOrInsertFunction(
ElseIntrinsic, ReturnStruct, Int64, (Type *)nullptr);
Break = M.getOrInsertFunction(
BreakIntrinsic, Int64, Int64, (Type *)nullptr);
IfBreak = M.getOrInsertFunction(
IfBreakIntrinsic, Int64, Boolean, Int64, (Type *)nullptr);
ElseBreak = M.getOrInsertFunction(
ElseBreakIntrinsic, Int64, Int64, Int64, (Type *)nullptr);
Loop = M.getOrInsertFunction(
LoopIntrinsic, Boolean, Int64, (Type *)nullptr);
EndCf = M.getOrInsertFunction(
EndCfIntrinsic, Void, Int64, (Type *)nullptr);
return false;
}
/// \brief Is BB the last block saved on the stack ?
bool SIAnnotateControlFlow::isTopOfStack(BasicBlock *BB) {
return !Stack.empty() && Stack.back().first == BB;
}
/// \brief Pop the last saved value from the control flow stack
Value *SIAnnotateControlFlow::popSaved() {
return Stack.pop_back_val().second;
}
/// \brief Push a BB and saved value to the control flow stack
void SIAnnotateControlFlow::push(BasicBlock *BB, Value *Saved) {
Stack.push_back(std::make_pair(BB, Saved));
}
/// \brief Can the condition represented by this PHI node treated like
/// an "Else" block?
bool SIAnnotateControlFlow::isElse(PHINode *Phi) {
BasicBlock *IDom = DT->getNode(Phi->getParent())->getIDom()->getBlock();
for (unsigned i = 0, e = Phi->getNumIncomingValues(); i != e; ++i) {
if (Phi->getIncomingBlock(i) == IDom) {
if (Phi->getIncomingValue(i) != BoolTrue)
return false;
} else {
if (Phi->getIncomingValue(i) != BoolFalse)
return false;
}
}
return true;
}
// \brief Erase "Phi" if it is not used any more
void SIAnnotateControlFlow::eraseIfUnused(PHINode *Phi) {
if (!Phi->hasNUsesOrMore(1))
Phi->eraseFromParent();
}
/// \brief Open a new "If" block
void SIAnnotateControlFlow::openIf(BranchInst *Term) {
Value *Ret = CallInst::Create(If, Term->getCondition(), "", Term);
Term->setCondition(ExtractValueInst::Create(Ret, 0, "", Term));
push(Term->getSuccessor(1), ExtractValueInst::Create(Ret, 1, "", Term));
}
/// \brief Close the last "If" block and open a new "Else" block
void SIAnnotateControlFlow::insertElse(BranchInst *Term) {
Value *Ret = CallInst::Create(Else, popSaved(), "", Term);
Term->setCondition(ExtractValueInst::Create(Ret, 0, "", Term));
push(Term->getSuccessor(1), ExtractValueInst::Create(Ret, 1, "", Term));
}
/// \brief Recursively handle the condition leading to a loop
Value *SIAnnotateControlFlow::handleLoopCondition(Value *Cond, PHINode *Broken,
llvm::Loop *L) {
// Only search through PHI nodes which are inside the loop. If we try this
// with PHI nodes that are outside of the loop, we end up inserting new PHI
// nodes outside of the loop which depend on values defined inside the loop.
// This will break the module with
// 'Instruction does not dominate all users!' errors.
PHINode *Phi = nullptr;
if ((Phi = dyn_cast<PHINode>(Cond)) && L->contains(Phi)) {
BasicBlock *Parent = Phi->getParent();
PHINode *NewPhi = PHINode::Create(Int64, 0, "", &Parent->front());
Value *Ret = NewPhi;
// Handle all non-constant incoming values first
for (unsigned i = 0, e = Phi->getNumIncomingValues(); i != e; ++i) {
Value *Incoming = Phi->getIncomingValue(i);
BasicBlock *From = Phi->getIncomingBlock(i);
if (isa<ConstantInt>(Incoming)) {
NewPhi->addIncoming(Broken, From);
continue;
}
Phi->setIncomingValue(i, BoolFalse);
Value *PhiArg = handleLoopCondition(Incoming, Broken, L);
NewPhi->addIncoming(PhiArg, From);
}
BasicBlock *IDom = DT->getNode(Parent)->getIDom()->getBlock();
for (unsigned i = 0, e = Phi->getNumIncomingValues(); i != e; ++i) {
Value *Incoming = Phi->getIncomingValue(i);
if (Incoming != BoolTrue)
continue;
BasicBlock *From = Phi->getIncomingBlock(i);
if (From == IDom) {
CallInst *OldEnd = dyn_cast<CallInst>(Parent->getFirstInsertionPt());
if (OldEnd && OldEnd->getCalledFunction() == EndCf) {
Value *Args[] = { OldEnd->getArgOperand(0), NewPhi };
Ret = CallInst::Create(ElseBreak, Args, "", OldEnd);
continue;
}
}
TerminatorInst *Insert = From->getTerminator();
Value *PhiArg = CallInst::Create(Break, Broken, "", Insert);
NewPhi->setIncomingValue(i, PhiArg);
}
eraseIfUnused(Phi);
return Ret;
} else if (Instruction *Inst = dyn_cast<Instruction>(Cond)) {
BasicBlock *Parent = Inst->getParent();
Instruction *Insert;
if (L->contains(Inst)) {
Insert = Parent->getTerminator();
} else {
Insert = L->getHeader()->getFirstNonPHIOrDbgOrLifetime();
}
Value *Args[] = { Cond, Broken };
return CallInst::Create(IfBreak, Args, "", Insert);
} else {
llvm_unreachable("Unhandled loop condition!");
}
return 0;
}
/// \brief Handle a back edge (loop)
void SIAnnotateControlFlow::handleLoop(BranchInst *Term) {
BasicBlock *BB = Term->getParent();
llvm::Loop *L = LI->getLoopFor(BB);
BasicBlock *Target = Term->getSuccessor(1);
PHINode *Broken = PHINode::Create(Int64, 0, "", &Target->front());
Value *Cond = Term->getCondition();
Term->setCondition(BoolTrue);
Value *Arg = handleLoopCondition(Cond, Broken, L);
for (pred_iterator PI = pred_begin(Target), PE = pred_end(Target);
PI != PE; ++PI) {
Broken->addIncoming(*PI == BB ? Arg : Int64Zero, *PI);
}
Term->setCondition(CallInst::Create(Loop, Arg, "", Term));
push(Term->getSuccessor(0), Arg);
}/// \brief Close the last opened control flow
void SIAnnotateControlFlow::closeControlFlow(BasicBlock *BB) {
llvm::Loop *L = LI->getLoopFor(BB);
if (L && L->getHeader() == BB) {
// We can't insert an EndCF call into a loop header, because it will
// get executed on every iteration of the loop, when it should be
// executed only once before the loop.
SmallVector <BasicBlock*, 8> Latches;
L->getLoopLatches(Latches);
std::vector<BasicBlock*> Preds;
for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB); PI != PE; ++PI) {
if (std::find(Latches.begin(), Latches.end(), *PI) == Latches.end())
Preds.push_back(*PI);
}
BB = llvm::SplitBlockPredecessors(BB, Preds, "endcf.split", this);
}
CallInst::Create(EndCf, popSaved(), "", BB->getFirstInsertionPt());
}
/// \brief Annotate the control flow with intrinsics so the backend can
/// recognize if/then/else and loops.
bool SIAnnotateControlFlow::runOnFunction(Function &F) {
DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
LI = &getAnalysis<LoopInfo>();
for (df_iterator<BasicBlock *> I = df_begin(&F.getEntryBlock()),
E = df_end(&F.getEntryBlock()); I != E; ++I) {
BranchInst *Term = dyn_cast<BranchInst>((*I)->getTerminator());
if (!Term || Term->isUnconditional()) {
if (isTopOfStack(*I))
closeControlFlow(*I);
continue;
}
if (I.nodeVisited(Term->getSuccessor(1))) {
if (isTopOfStack(*I))
closeControlFlow(*I);
handleLoop(Term);
continue;
}
if (isTopOfStack(*I)) {
PHINode *Phi = dyn_cast<PHINode>(Term->getCondition());
if (Phi && Phi->getParent() == *I && isElse(Phi)) {
insertElse(Term);
eraseIfUnused(Phi);
continue;
}
closeControlFlow(*I);
}
openIf(Term);
}
assert(Stack.empty());
return true;
}
/// \brief Create the annotation pass
FunctionPass *llvm::createSIAnnotateControlFlowPass() {
return new SIAnnotateControlFlow();
}
|