1 //===- IntervalPartition.cpp - Interval Partition module code -------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file contains the definition of the IntervalPartition class, which
10 // calculates and represent the interval partition of a function.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "llvm/Analysis/IntervalPartition.h"
15 #include "llvm/Analysis/Interval.h"
16 #include "llvm/Analysis/IntervalIterator.h"
17 #include "llvm/Pass.h"
18 #include <cassert>
19 #include <utility>
20 
21 using namespace llvm;
22 
23 char IntervalPartition::ID = 0;
24 
25 INITIALIZE_PASS(IntervalPartition, "intervals",
26                 "Interval Partition Construction", true, true)
27 
28 //===----------------------------------------------------------------------===//
29 // IntervalPartition Implementation
30 //===----------------------------------------------------------------------===//
31 
32 // releaseMemory - Reset state back to before function was analyzed
33 void IntervalPartition::releaseMemory() {
34   for (unsigned i = 0, e = Intervals.size(); i != e; ++i)
35     delete Intervals[i];
36   IntervalMap.clear();
37   Intervals.clear();
38   RootInterval = nullptr;
39 }
40 
41 void IntervalPartition::print(raw_ostream &O, const Module*) const {
42   for(unsigned i = 0, e = Intervals.size(); i != e; ++i)
43     Intervals[i]->print(O);
44 }
45 
46 // addIntervalToPartition - Add an interval to the internal list of intervals,
47 // and then add mappings from all of the basic blocks in the interval to the
48 // interval itself (in the IntervalMap).
49 void IntervalPartition::addIntervalToPartition(Interval *I) {
50   Intervals.push_back(I);
51 
52   // Add mappings for all of the basic blocks in I to the IntervalPartition
53   for (Interval::node_iterator It = I->Nodes.begin(), End = I->Nodes.end();
54        It != End; ++It)
55     IntervalMap.insert(std::make_pair(*It, I));
56 }
57 
58 // updatePredecessors - Interval generation only sets the successor fields of
59 // the interval data structures.  After interval generation is complete,
60 // run through all of the intervals and propagate successor info as
61 // predecessor info.
62 void IntervalPartition::updatePredecessors(Interval *Int) {
63   BasicBlock *Header = Int->getHeaderNode();
64   for (BasicBlock *Successor : Int->Successors)
65     getBlockInterval(Successor)->Predecessors.push_back(Header);
66 }
67 
68 // IntervalPartition ctor - Build the first level interval partition for the
69 // specified function...
70 bool IntervalPartition::runOnFunction(Function &F) {
71   // Pass false to intervals_begin because we take ownership of it's memory
72   function_interval_iterator I = intervals_begin(&F, false);
73   assert(I != intervals_end(&F) && "No intervals in function!?!?!");
74 
75   addIntervalToPartition(RootInterval = *I);
76 
77   ++I;  // After the first one...
78 
79   // Add the rest of the intervals to the partition.
80   for (function_interval_iterator E = intervals_end(&F); I != E; ++I)
81     addIntervalToPartition(*I);
82 
83   // Now that we know all of the successor information, propagate this to the
84   // predecessors for each block.
85   for (unsigned i = 0, e = Intervals.size(); i != e; ++i)
86     updatePredecessors(Intervals[i]);
87   return false;
88 }
89 
90 // IntervalPartition ctor - Build a reduced interval partition from an
91 // existing interval graph.  This takes an additional boolean parameter to
92 // distinguish it from a copy constructor.  Always pass in false for now.
93 IntervalPartition::IntervalPartition(IntervalPartition &IP, bool)
94   : FunctionPass(ID) {
95   assert(IP.getRootInterval() && "Cannot operate on empty IntervalPartitions!");
96 
97   // Pass false to intervals_begin because we take ownership of it's memory
98   interval_part_interval_iterator I = intervals_begin(IP, false);
99   assert(I != intervals_end(IP) && "No intervals in interval partition!?!?!");
100 
101   addIntervalToPartition(RootInterval = *I);
102 
103   ++I;  // After the first one...
104 
105   // Add the rest of the intervals to the partition.
106   for (interval_part_interval_iterator E = intervals_end(IP); I != E; ++I)
107     addIntervalToPartition(*I);
108 
109   // Now that we know all of the successor information, propagate this to the
110   // predecessors for each block.
111   for (unsigned i = 0, e = Intervals.size(); i != e; ++i)
112     updatePredecessors(Intervals[i]);
113 }
114