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
|
//===-- CombineBranch.cpp -------------------------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// Pass to instrument loops
//
// At every backedge, insert a counter for that backedge and a call function
//
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/Dominators.h"
#include "llvm/Support/CFG.h"
#include "llvm/Constants.h"
#include "llvm/iMemory.h"
#include "llvm/GlobalVariable.h"
#include "llvm/DerivedTypes.h"
#include "llvm/iOther.h"
#include "llvm/iOperators.h"
#include "llvm/iTerminators.h"
#include "llvm/iPHINode.h"
#include "llvm/Module.h"
#include "llvm/Function.h"
#include "llvm/Pass.h"
//this is used to color vertices
//during DFS
enum Color{
WHITE,
GREY,
BLACK
};
namespace{
struct CombineBranches : public FunctionPass {
private:
//DominatorSet *DS;
void getBackEdgesVisit(BasicBlock *u,
std::map<BasicBlock *, Color > &color,
std::map<BasicBlock *, int > &d,
int &time,
std::map<BasicBlock *, BasicBlock *> &be);
void removeRedundant(std::map<BasicBlock *, BasicBlock *> &be);
void getBackEdges(Function &F);
public:
bool runOnFunction(Function &F);
};
RegisterOpt<CombineBranches> X("branch-combine", "Multiple backedges going to same target are merged");
}
//helper function to get back edges: it is called by
//the "getBackEdges" function below
void CombineBranches::getBackEdgesVisit(BasicBlock *u,
std::map<BasicBlock *, Color > &color,
std::map<BasicBlock *, int > &d,
int &time,
std::map<BasicBlock *, BasicBlock *> &be) {
color[u]=GREY;
time++;
d[u]=time;
for (succ_iterator vl = succ_begin(u), ve = succ_end(u); vl != ve; ++vl){
BasicBlock *BB = *vl;
if(color[BB]!=GREY && color[BB]!=BLACK){
getBackEdgesVisit(BB, color, d, time, be);
}
//now checking for d and f vals
else if(color[BB]==GREY){
//so v is ancestor of u if time of u > time of v
if(d[u] >= d[BB]){
//u->BB is a backedge
be[u] = BB;
}
}
}
color[u]=BLACK;//done with visiting the node and its neighbors
}
//look at all BEs, and remove all BEs that are dominated by other BE's in the
//set
void CombineBranches::removeRedundant(std::map<BasicBlock *, BasicBlock *> &be){
std::vector<BasicBlock *> toDelete;
std::map<BasicBlock *, int> seenBB;
for(std::map<BasicBlock *, BasicBlock *>::iterator MI = be.begin(),
ME = be.end(); MI != ME; ++MI){
if(seenBB[MI->second])
continue;
seenBB[MI->second] = 1;
std::vector<BasicBlock *> sameTarget;
sameTarget.clear();
for(std::map<BasicBlock *, BasicBlock *>::iterator MMI = be.begin(),
MME = be.end(); MMI != MME; ++MMI){
if(MMI->first == MI->first)
continue;
if(MMI->second == MI->second)
sameTarget.push_back(MMI->first);
}
//so more than one branch to same target
if(sameTarget.size()){
sameTarget.push_back(MI->first);
BasicBlock *newBB = new BasicBlock("newCommon", MI->first->getParent());
BranchInst *newBranch = new BranchInst(MI->second);
newBB->getInstList().push_back(newBranch);
std::map<PHINode *, std::vector<unsigned int> > phiMap;
for(std::vector<BasicBlock *>::iterator VBI = sameTarget.begin(),
VBE = sameTarget.end(); VBI != VBE; ++VBI){
//std::cerr<<(*VBI)->getName()<<"\n";
BranchInst *ti = cast<BranchInst>((*VBI)->getTerminator());
unsigned char index = 1;
if(ti->getSuccessor(0) == MI->second){
index = 0;
}
ti->setSuccessor(index, newBB);
for(BasicBlock::iterator BB2Inst = MI->second->begin(),
BBend = MI->second->end(); BB2Inst != BBend; ++BB2Inst){
if (PHINode *phiInst = dyn_cast<PHINode>(BB2Inst)){
int bbIndex;
bbIndex = phiInst->getBasicBlockIndex(*VBI);
if(bbIndex>=0){
phiMap[phiInst].push_back(bbIndex);
//phiInst->setIncomingBlock(bbIndex, newBB);
}
}
}
}
for(std::map<PHINode *, std::vector<unsigned int> >::iterator
PI = phiMap.begin(), PE = phiMap.end(); PI != PE; ++PI){
PHINode *phiNode = new PHINode(PI->first->getType(), "phi", newBranch);
for(std::vector<unsigned int>::iterator II = PI->second.begin(),
IE = PI->second.end(); II != IE; ++II){
phiNode->addIncoming(PI->first->getIncomingValue(*II),
PI->first->getIncomingBlock(*II));
}
std::vector<BasicBlock *> tempBB;
for(std::vector<unsigned int>::iterator II = PI->second.begin(),
IE = PI->second.end(); II != IE; ++II){
tempBB.push_back(PI->first->getIncomingBlock(*II));
}
for(std::vector<BasicBlock *>::iterator II = tempBB.begin(),
IE = tempBB.end(); II != IE; ++II){
PI->first->removeIncomingValue(*II);
}
PI->first->addIncoming(phiNode, newBB);
}
//std::cerr<<"%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%\n";
//std::cerr<<MI->second;
//std::cerr<<"-----------------------------------\n";
//std::cerr<<newBB;
//std::cerr<<"END%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%\n";
}
}
}
//getting the backedges in a graph
//Its a variation of DFS to get the backedges in the graph
//We get back edges by associating a time
//and a color with each vertex.
//The time of a vertex is the time when it was first visited
//The color of a vertex is initially WHITE,
//Changes to GREY when it is first visited,
//and changes to BLACK when ALL its neighbors
//have been visited
//So we have a back edge when we meet a successor of
//a node with smaller time, and GREY color
void CombineBranches::getBackEdges(Function &F){
std::map<BasicBlock *, Color > color;
std::map<BasicBlock *, int> d;
std::map<BasicBlock *, BasicBlock *> be;
int time=0;
getBackEdgesVisit(F.begin(), color, d, time, be);
removeRedundant(be);
}
//Per function pass for inserting counters and call function
bool CombineBranches::runOnFunction(Function &F){
if(F.isExternal()) {
return false;
}
//if(F.getName() == "main"){
// F.setName("llvm_gprof_main");
//}
//std::cerr<<F;
//std::cerr<<"///////////////////////////////////////////////\n";
getBackEdges(F);
return true;
}
|
