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
|
//===- CodeMetrics.cpp - Code cost measurements ---------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements code cost measurement utilities.
//
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/CodeMetrics.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/CallSite.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/Support/Debug.h"
#define DEBUG_TYPE "code-metrics"
using namespace llvm;
static void completeEphemeralValues(SmallVector<const Value *, 16> &WorkSet,
SmallPtrSetImpl<const Value*> &EphValues) {
SmallPtrSet<const Value *, 32> Visited;
// Make sure that all of the items in WorkSet are in our EphValues set.
EphValues.insert(WorkSet.begin(), WorkSet.end());
// Note: We don't speculate PHIs here, so we'll miss instruction chains kept
// alive only by ephemeral values.
while (!WorkSet.empty()) {
const Value *V = WorkSet.front();
WorkSet.erase(WorkSet.begin());
if (!Visited.insert(V).second)
continue;
// If all uses of this value are ephemeral, then so is this value.
bool FoundNEUse = false;
for (const User *I : V->users())
if (!EphValues.count(I)) {
FoundNEUse = true;
break;
}
if (FoundNEUse)
continue;
EphValues.insert(V);
DEBUG(dbgs() << "Ephemeral Value: " << *V << "\n");
if (const User *U = dyn_cast<User>(V))
for (const Value *J : U->operands()) {
if (isSafeToSpeculativelyExecute(J))
WorkSet.push_back(J);
}
}
}
// Find all ephemeral values.
void CodeMetrics::collectEphemeralValues(
const Loop *L, AssumptionCache *AC,
SmallPtrSetImpl<const Value *> &EphValues) {
SmallVector<const Value *, 16> WorkSet;
for (auto &AssumeVH : AC->assumptions()) {
if (!AssumeVH)
continue;
Instruction *I = cast<Instruction>(AssumeVH);
// Filter out call sites outside of the loop so we don't to a function's
// worth of work for each of its loops (and, in the common case, ephemeral
// values in the loop are likely due to @llvm.assume calls in the loop).
if (!L->contains(I->getParent()))
continue;
WorkSet.push_back(I);
}
completeEphemeralValues(WorkSet, EphValues);
}
void CodeMetrics::collectEphemeralValues(
const Function *F, AssumptionCache *AC,
SmallPtrSetImpl<const Value *> &EphValues) {
SmallVector<const Value *, 16> WorkSet;
for (auto &AssumeVH : AC->assumptions()) {
if (!AssumeVH)
continue;
Instruction *I = cast<Instruction>(AssumeVH);
assert(I->getParent()->getParent() == F &&
"Found assumption for the wrong function!");
WorkSet.push_back(I);
}
completeEphemeralValues(WorkSet, EphValues);
}
/// analyzeBasicBlock - Fill in the current structure with information gleaned
/// from the specified block.
void CodeMetrics::analyzeBasicBlock(const BasicBlock *BB,
const TargetTransformInfo &TTI,
SmallPtrSetImpl<const Value*> &EphValues) {
++NumBlocks;
unsigned NumInstsBeforeThisBB = NumInsts;
for (BasicBlock::const_iterator II = BB->begin(), E = BB->end();
II != E; ++II) {
// Skip ephemeral values.
if (EphValues.count(II))
continue;
// Special handling for calls.
if (isa<CallInst>(II) || isa<InvokeInst>(II)) {
ImmutableCallSite CS(cast<Instruction>(II));
if (const Function *F = CS.getCalledFunction()) {
// If a function is both internal and has a single use, then it is
// extremely likely to get inlined in the future (it was probably
// exposed by an interleaved devirtualization pass).
if (!CS.isNoInline() && F->hasInternalLinkage() && F->hasOneUse())
++NumInlineCandidates;
// If this call is to function itself, then the function is recursive.
// Inlining it into other functions is a bad idea, because this is
// basically just a form of loop peeling, and our metrics aren't useful
// for that case.
if (F == BB->getParent())
isRecursive = true;
if (TTI.isLoweredToCall(F))
++NumCalls;
} else {
// We don't want inline asm to count as a call - that would prevent loop
// unrolling. The argument setup cost is still real, though.
if (!isa<InlineAsm>(CS.getCalledValue()))
++NumCalls;
}
}
if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
if (!AI->isStaticAlloca())
this->usesDynamicAlloca = true;
}
if (isa<ExtractElementInst>(II) || II->getType()->isVectorTy())
++NumVectorInsts;
if (const CallInst *CI = dyn_cast<CallInst>(II))
if (CI->cannotDuplicate())
notDuplicatable = true;
if (const InvokeInst *InvI = dyn_cast<InvokeInst>(II))
if (InvI->cannotDuplicate())
notDuplicatable = true;
NumInsts += TTI.getUserCost(&*II);
}
if (isa<ReturnInst>(BB->getTerminator()))
++NumRets;
// We never want to inline functions that contain an indirectbr. This is
// incorrect because all the blockaddress's (in static global initializers
// for example) would be referring to the original function, and this indirect
// jump would jump from the inlined copy of the function into the original
// function which is extremely undefined behavior.
// FIXME: This logic isn't really right; we can safely inline functions
// with indirectbr's as long as no other function or global references the
// blockaddress of a block within the current function. And as a QOI issue,
// if someone is using a blockaddress without an indirectbr, and that
// reference somehow ends up in another function or global, we probably
// don't want to inline this function.
notDuplicatable |= isa<IndirectBrInst>(BB->getTerminator());
// Remember NumInsts for this BB.
NumBBInsts[BB] = NumInsts - NumInstsBeforeThisBB;
}
|
