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
|
//===- LoopUnroll.cpp - Code to perform loop unrolling --------------------===//
//
// Copyright 2019 The MLIR Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// =============================================================================
//
// This file implements loop unrolling.
//
//===----------------------------------------------------------------------===//
#include "mlir/Transforms/Passes.h"
#include "mlir/AffineOps/AffineOps.h"
#include "mlir/Analysis/LoopAnalysis.h"
#include "mlir/IR/AffineExpr.h"
#include "mlir/IR/AffineMap.h"
#include "mlir/IR/Builders.h"
#include "mlir/IR/BuiltinOps.h"
#include "mlir/Pass.h"
#include "mlir/Transforms/LoopUtils.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
using namespace mlir;
#define DEBUG_TYPE "loop-unroll"
static llvm::cl::OptionCategory clOptionsCategory(DEBUG_TYPE " options");
// Loop unrolling factor.
static llvm::cl::opt<unsigned> clUnrollFactor(
"unroll-factor", llvm::cl::Hidden,
llvm::cl::desc("Use this unroll factor for all loops being unrolled"),
llvm::cl::cat(clOptionsCategory));
static llvm::cl::opt<bool> clUnrollFull("unroll-full", llvm::cl::Hidden,
llvm::cl::desc("Fully unroll loops"),
llvm::cl::cat(clOptionsCategory));
static llvm::cl::opt<unsigned> clUnrollNumRepetitions(
"unroll-num-reps", llvm::cl::Hidden,
llvm::cl::desc("Unroll innermost loops repeatedly this many times"),
llvm::cl::cat(clOptionsCategory));
static llvm::cl::opt<unsigned> clUnrollFullThreshold(
"unroll-full-threshold", llvm::cl::Hidden,
llvm::cl::desc(
"Unroll all loops with trip count less than or equal to this"),
llvm::cl::cat(clOptionsCategory));
namespace {
/// Loop unrolling pass. Unrolls all innermost loops unless full unrolling and a
/// full unroll threshold was specified, in which case, fully unrolls all loops
/// with trip count less than the specified threshold. The latter is for testing
/// purposes, especially for testing outer loop unrolling.
struct LoopUnroll : public FunctionPass {
const Optional<unsigned> unrollFactor;
const Optional<bool> unrollFull;
// Callback to obtain unroll factors; if this has a callable target, takes
// precedence over command-line argument or passed argument.
const std::function<unsigned(ConstOpPointer<AffineForOp>)> getUnrollFactor;
explicit LoopUnroll(Optional<unsigned> unrollFactor = None,
Optional<bool> unrollFull = None,
const std::function<unsigned(ConstOpPointer<AffineForOp>)>
&getUnrollFactor = nullptr)
: FunctionPass(&LoopUnroll::passID), unrollFactor(unrollFactor),
unrollFull(unrollFull), getUnrollFactor(getUnrollFactor) {}
PassResult runOnFunction(Function *f) override;
/// Unroll this for inst. Returns false if nothing was done.
bool runOnAffineForOp(OpPointer<AffineForOp> forOp);
static const unsigned kDefaultUnrollFactor = 4;
static char passID;
};
} // end anonymous namespace
char LoopUnroll::passID = 0;
PassResult LoopUnroll::runOnFunction(Function *f) {
// Gathers all innermost loops through a post order pruned walk.
struct InnermostLoopGatherer {
// Store innermost loops as we walk.
std::vector<OpPointer<AffineForOp>> loops;
void walkPostOrder(Function *f) {
for (auto &b : *f)
walkPostOrder(b.begin(), b.end());
}
bool walkPostOrder(Block::iterator Start, Block::iterator End) {
bool hasInnerLoops = false;
// We need to walk all elements since all innermost loops need to be
// gathered as opposed to determining whether this list has any inner
// loops or not.
while (Start != End)
hasInnerLoops |= walkPostOrder(&(*Start++));
return hasInnerLoops;
}
bool walkPostOrder(Instruction *opInst) {
bool hasInnerLoops = false;
for (auto &blockList : opInst->getBlockLists())
for (auto &block : blockList)
hasInnerLoops |= walkPostOrder(block.begin(), block.end());
if (opInst->isa<AffineForOp>()) {
if (!hasInnerLoops)
loops.push_back(opInst->cast<AffineForOp>());
return true;
}
return hasInnerLoops;
}
};
if (clUnrollFull.getNumOccurrences() > 0 &&
clUnrollFullThreshold.getNumOccurrences() > 0) {
// Store short loops as we walk.
std::vector<OpPointer<AffineForOp>> loops;
// Gathers all loops with trip count <= minTripCount. Do a post order walk
// so that loops are gathered from innermost to outermost (or else unrolling
// an outer one may delete gathered inner ones).
f->walkPostOrder<AffineForOp>([&](OpPointer<AffineForOp> forOp) {
Optional<uint64_t> tripCount = getConstantTripCount(forOp);
if (tripCount.hasValue() && tripCount.getValue() <= clUnrollFullThreshold)
loops.push_back(forOp);
});
for (auto forOp : loops)
loopUnrollFull(forOp);
return success();
}
unsigned numRepetitions = clUnrollNumRepetitions.getNumOccurrences() > 0
? clUnrollNumRepetitions
: 1;
// If the call back is provided, we will recurse until no loops are found.
for (unsigned i = 0; i < numRepetitions || getUnrollFactor; i++) {
InnermostLoopGatherer ilg;
ilg.walkPostOrder(f);
auto &loops = ilg.loops;
if (loops.empty())
break;
bool unrolled = false;
for (auto forOp : loops)
unrolled |= runOnAffineForOp(forOp);
if (!unrolled)
// Break out if nothing was unrolled.
break;
}
return success();
}
/// Unrolls a 'for' inst. Returns true if the loop was unrolled, false
/// otherwise. The default unroll factor is 4.
bool LoopUnroll::runOnAffineForOp(OpPointer<AffineForOp> forOp) {
// Use the function callback if one was provided.
if (getUnrollFactor) {
return loopUnrollByFactor(forOp, getUnrollFactor(forOp));
}
// Unroll by the factor passed, if any.
if (unrollFactor.hasValue())
return loopUnrollByFactor(forOp, unrollFactor.getValue());
// Unroll by the command line factor if one was specified.
if (clUnrollFactor.getNumOccurrences() > 0)
return loopUnrollByFactor(forOp, clUnrollFactor);
// Unroll completely if full loop unroll was specified.
if (clUnrollFull.getNumOccurrences() > 0 ||
(unrollFull.hasValue() && unrollFull.getValue()))
return loopUnrollFull(forOp);
// Unroll by four otherwise.
return loopUnrollByFactor(forOp, kDefaultUnrollFactor);
}
FunctionPass *mlir::createLoopUnrollPass(
int unrollFactor, int unrollFull,
const std::function<unsigned(ConstOpPointer<AffineForOp>)>
&getUnrollFactor) {
return new LoopUnroll(
unrollFactor == -1 ? None : Optional<unsigned>(unrollFactor),
unrollFull == -1 ? None : Optional<bool>(unrollFull), getUnrollFactor);
}
static PassRegistration<LoopUnroll> pass("loop-unroll", "Unroll loops");
|
