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
|
//===--------- LoopSimplifyCFG.cpp - Loop CFG Simplification Pass ---------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the Loop SimplifyCFG Pass. This pass is responsible for
// basic loop CFG cleanup, primarily to assist other loop passes. If you
// encounter a noncanonical CFG construct that causes another loop pass to
// perform suboptimally, this is the place to fix it up.
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Scalar.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/BasicAliasAnalysis.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/DependenceAnalysis.h"
#include "llvm/Analysis/GlobalsModRef.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/LoopPass.h"
#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/Analysis/ScalarEvolutionAliasAnalysis.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/IR/Dominators.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Utils/LoopUtils.h"
using namespace llvm;
#define DEBUG_TYPE "loop-simplifycfg"
namespace {
class LoopSimplifyCFG : public LoopPass {
public:
static char ID; // Pass ID, replacement for typeid
LoopSimplifyCFG() : LoopPass(ID) {
initializeLoopSimplifyCFGPass(*PassRegistry::getPassRegistry());
}
bool runOnLoop(Loop *L, LPPassManager &) override;
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.addPreserved<DependenceAnalysis>();
getLoopAnalysisUsage(AU);
}
};
}
char LoopSimplifyCFG::ID = 0;
INITIALIZE_PASS_BEGIN(LoopSimplifyCFG, "loop-simplifycfg", "Simplify loop CFG",
false, false)
INITIALIZE_PASS_DEPENDENCY(LoopPass)
INITIALIZE_PASS_END(LoopSimplifyCFG, "loop-simplifycfg", "Simplify loop CFG",
false, false)
Pass *llvm::createLoopSimplifyCFGPass() { return new LoopSimplifyCFG(); }
static bool simplifyLoopCFG(Loop *L, DominatorTree *DT, LoopInfo *LI) {
bool Changed = false;
// Copy blocks into a temporary array to avoid iterator invalidation issues
// as we remove them.
SmallVector<WeakVH, 16> Blocks(L->blocks());
for (auto &Block : Blocks) {
// Attempt to merge blocks in the trivial case. Don't modify blocks which
// belong to other loops.
BasicBlock *Succ = cast_or_null<BasicBlock>(Block);
if (!Succ)
continue;
BasicBlock *Pred = Succ->getSinglePredecessor();
if (!Pred || !Pred->getSingleSuccessor() || LI->getLoopFor(Pred) != L)
continue;
// Pred is going to disappear, so we need to update the loop info.
if (L->getHeader() == Pred)
L->moveToHeader(Succ);
LI->removeBlock(Pred);
MergeBasicBlockIntoOnlyPred(Succ, DT);
Changed = true;
}
return Changed;
}
/// runOnLoop - Perform basic CFG simplifications to assist other loop passes.
/// For now, this only attempts to merge blocks in the trivial case.
bool LoopSimplifyCFG::runOnLoop(Loop *L, LPPassManager &) {
if (skipLoop(L))
return false;
DominatorTree *DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
LoopInfo *LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
return simplifyLoopCFG(L, DT, LI);
}
|
