1 //===---- MachineOutliner.cpp - Outline instructions -----------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
11 /// Replaces repeated sequences of instructions with function calls.
13 /// This works by placing every instruction from every basic block in a
14 /// suffix tree, and repeatedly querying that tree for repeated sequences of
15 /// instructions. If a sequence of instructions appears often, then it ought
16 /// to be beneficial to pull out into a function.
18 /// The MachineOutliner communicates with a given target using hooks defined in
19 /// TargetInstrInfo.h. The target supplies the outliner with information on how
20 /// a specific sequence of instructions should be outlined. This information
21 /// is used to deduce the number of instructions necessary to
23 /// * Create an outlined function
24 /// * Call that outlined function
26 /// Targets must implement
27 /// * getOutliningCandidateInfo
28 /// * buildOutlinedFrame
29 /// * insertOutlinedCall
30 /// * isFunctionSafeToOutlineFrom
32 /// in order to make use of the MachineOutliner.
34 /// This was originally presented at the 2016 LLVM Developers' Meeting in the
35 /// talk "Reducing Code Size Using Outlining". For a high-level overview of
36 /// how this pass works, the talk is available on YouTube at
38 /// https://www.youtube.com/watch?v=yorld-WSOeU
40 /// The slides for the talk are available at
42 /// http://www.llvm.org/devmtg/2016-11/Slides/Paquette-Outliner.pdf
44 /// The talk provides an overview of how the outliner finds candidates and
45 /// ultimately outlines them. It describes how the main data structure for this
46 /// pass, the suffix tree, is queried and purged for candidates. It also gives
47 /// a simplified suffix tree construction algorithm for suffix trees based off
48 /// of the algorithm actually used here, Ukkonen's algorithm.
50 /// For the original RFC for this pass, please see
52 /// http://lists.llvm.org/pipermail/llvm-dev/2016-August/104170.html
54 /// For more information on the suffix tree data structure, please see
55 /// https://www.cs.helsinki.fi/u/ukkonen/SuffixT1withFigs.pdf
57 //===----------------------------------------------------------------------===//
58 #include "llvm/CodeGen/MachineOutliner.h"
59 #include "llvm/ADT/DenseMap.h"
60 #include "llvm/ADT/Statistic.h"
61 #include "llvm/ADT/Twine.h"
62 #include "llvm/CodeGen/MachineFunction.h"
63 #include "llvm/CodeGen/MachineModuleInfo.h"
64 #include "llvm/CodeGen/MachineOptimizationRemarkEmitter.h"
65 #include "llvm/CodeGen/MachineRegisterInfo.h"
66 #include "llvm/CodeGen/Passes.h"
67 #include "llvm/CodeGen/TargetInstrInfo.h"
68 #include "llvm/CodeGen/TargetSubtargetInfo.h"
69 #include "llvm/IR/DIBuilder.h"
70 #include "llvm/IR/IRBuilder.h"
71 #include "llvm/IR/Mangler.h"
72 #include "llvm/Support/Allocator.h"
73 #include "llvm/Support/CommandLine.h"
74 #include "llvm/Support/Debug.h"
75 #include "llvm/Support/raw_ostream.h"
82 #define DEBUG_TYPE "machine-outliner"
86 using namespace outliner;
88 STATISTIC(NumOutlined, "Number of candidates outlined");
89 STATISTIC(FunctionsCreated, "Number of functions created");
91 // Set to true if the user wants the outliner to run on linkonceodr linkage
92 // functions. This is false by default because the linker can dedupe linkonceodr
93 // functions. Since the outliner is confined to a single module (modulo LTO),
94 // this is off by default. It should, however, be the default behaviour in
96 static cl::opt<bool> EnableLinkOnceODROutlining(
97 "enable-linkonceodr-outlining",
99 cl::desc("Enable the machine outliner on linkonceodr functions"),
104 /// Represents an undefined index in the suffix tree.
105 const unsigned EmptyIdx = -1;
107 /// A node in a suffix tree which represents a substring or suffix.
109 /// Each node has either no children or at least two children, with the root
110 /// being a exception in the empty tree.
112 /// Children are represented as a map between unsigned integers and nodes. If
113 /// a node N has a child M on unsigned integer k, then the mapping represented
114 /// by N is a proper prefix of the mapping represented by M. Note that this,
115 /// although similar to a trie is somewhat different: each node stores a full
116 /// substring of the full mapping rather than a single character state.
118 /// Each internal node contains a pointer to the internal node representing
119 /// the same string, but with the first character chopped off. This is stored
120 /// in \p Link. Each leaf node stores the start index of its respective
121 /// suffix in \p SuffixIdx.
122 struct SuffixTreeNode {
124 /// The children of this node.
126 /// A child existing on an unsigned integer implies that from the mapping
127 /// represented by the current node, there is a way to reach another
128 /// mapping by tacking that character on the end of the current string.
129 DenseMap<unsigned, SuffixTreeNode *> Children;
131 /// The start index of this node's substring in the main string.
132 unsigned StartIdx = EmptyIdx;
134 /// The end index of this node's substring in the main string.
136 /// Every leaf node must have its \p EndIdx incremented at the end of every
137 /// step in the construction algorithm. To avoid having to update O(N)
138 /// nodes individually at the end of every step, the end index is stored
140 unsigned *EndIdx = nullptr;
142 /// For leaves, the start index of the suffix represented by this node.
144 /// For all other nodes, this is ignored.
145 unsigned SuffixIdx = EmptyIdx;
147 /// For internal nodes, a pointer to the internal node representing
148 /// the same sequence with the first character chopped off.
150 /// This acts as a shortcut in Ukkonen's algorithm. One of the things that
151 /// Ukkonen's algorithm does to achieve linear-time construction is
152 /// keep track of which node the next insert should be at. This makes each
153 /// insert O(1), and there are a total of O(N) inserts. The suffix link
154 /// helps with inserting children of internal nodes.
156 /// Say we add a child to an internal node with associated mapping S. The
157 /// next insertion must be at the node representing S - its first character.
158 /// This is given by the way that we iteratively build the tree in Ukkonen's
159 /// algorithm. The main idea is to look at the suffixes of each prefix in the
160 /// string, starting with the longest suffix of the prefix, and ending with
161 /// the shortest. Therefore, if we keep pointers between such nodes, we can
162 /// move to the next insertion point in O(1) time. If we don't, then we'd
163 /// have to query from the root, which takes O(N) time. This would make the
164 /// construction algorithm O(N^2) rather than O(N).
165 SuffixTreeNode *Link = nullptr;
167 /// The length of the string formed by concatenating the edge labels from the
168 /// root to this node.
169 unsigned ConcatLen = 0;
171 /// Returns true if this node is a leaf.
172 bool isLeaf() const { return SuffixIdx != EmptyIdx; }
174 /// Returns true if this node is the root of its owning \p SuffixTree.
175 bool isRoot() const { return StartIdx == EmptyIdx; }
177 /// Return the number of elements in the substring associated with this node.
178 size_t size() const {
180 // Is it the root? If so, it's the empty string so return 0.
184 assert(*EndIdx != EmptyIdx && "EndIdx is undefined!");
186 // Size = the number of elements in the string.
187 // For example, [0 1 2 3] has length 4, not 3. 3-0 = 3, so we have 3-0+1.
188 return *EndIdx - StartIdx + 1;
191 SuffixTreeNode(unsigned StartIdx, unsigned *EndIdx, SuffixTreeNode *Link)
192 : StartIdx(StartIdx), EndIdx(EndIdx), Link(Link) {}
197 /// A data structure for fast substring queries.
199 /// Suffix trees represent the suffixes of their input strings in their leaves.
200 /// A suffix tree is a type of compressed trie structure where each node
201 /// represents an entire substring rather than a single character. Each leaf
202 /// of the tree is a suffix.
204 /// A suffix tree can be seen as a type of state machine where each state is a
205 /// substring of the full string. The tree is structured so that, for a string
206 /// of length N, there are exactly N leaves in the tree. This structure allows
207 /// us to quickly find repeated substrings of the input string.
209 /// In this implementation, a "string" is a vector of unsigned integers.
210 /// These integers may result from hashing some data type. A suffix tree can
211 /// contain 1 or many strings, which can then be queried as one large string.
213 /// The suffix tree is implemented using Ukkonen's algorithm for linear-time
214 /// suffix tree construction. Ukkonen's algorithm is explained in more detail
215 /// in the paper by Esko Ukkonen "On-line construction of suffix trees. The
216 /// paper is available at
218 /// https://www.cs.helsinki.fi/u/ukkonen/SuffixT1withFigs.pdf
221 /// Each element is an integer representing an instruction in the module.
222 ArrayRef<unsigned> Str;
224 /// A repeated substring in the tree.
225 struct RepeatedSubstring {
226 /// The length of the string.
229 /// The start indices of each occurrence.
230 std::vector<unsigned> StartIndices;
234 /// Maintains each node in the tree.
235 SpecificBumpPtrAllocator<SuffixTreeNode> NodeAllocator;
237 /// The root of the suffix tree.
239 /// The root represents the empty string. It is maintained by the
240 /// \p NodeAllocator like every other node in the tree.
241 SuffixTreeNode *Root = nullptr;
243 /// Maintains the end indices of the internal nodes in the tree.
245 /// Each internal node is guaranteed to never have its end index change
246 /// during the construction algorithm; however, leaves must be updated at
247 /// every step. Therefore, we need to store leaf end indices by reference
248 /// to avoid updating O(N) leaves at every step of construction. Thus,
249 /// every internal node must be allocated its own end index.
250 BumpPtrAllocator InternalEndIdxAllocator;
252 /// The end index of each leaf in the tree.
253 unsigned LeafEndIdx = -1;
255 /// Helper struct which keeps track of the next insertion point in
256 /// Ukkonen's algorithm.
258 /// The next node to insert at.
259 SuffixTreeNode *Node;
261 /// The index of the first character in the substring currently being added.
262 unsigned Idx = EmptyIdx;
264 /// The length of the substring we have to add at the current step.
268 /// The point the next insertion will take place at in the
269 /// construction algorithm.
272 /// Allocate a leaf node and add it to the tree.
274 /// \param Parent The parent of this node.
275 /// \param StartIdx The start index of this node's associated string.
276 /// \param Edge The label on the edge leaving \p Parent to this node.
278 /// \returns A pointer to the allocated leaf node.
279 SuffixTreeNode *insertLeaf(SuffixTreeNode &Parent, unsigned StartIdx,
282 assert(StartIdx <= LeafEndIdx && "String can't start after it ends!");
284 SuffixTreeNode *N = new (NodeAllocator.Allocate())
285 SuffixTreeNode(StartIdx, &LeafEndIdx, nullptr);
286 Parent.Children[Edge] = N;
291 /// Allocate an internal node and add it to the tree.
293 /// \param Parent The parent of this node. Only null when allocating the root.
294 /// \param StartIdx The start index of this node's associated string.
295 /// \param EndIdx The end index of this node's associated string.
296 /// \param Edge The label on the edge leaving \p Parent to this node.
298 /// \returns A pointer to the allocated internal node.
299 SuffixTreeNode *insertInternalNode(SuffixTreeNode *Parent, unsigned StartIdx,
300 unsigned EndIdx, unsigned Edge) {
302 assert(StartIdx <= EndIdx && "String can't start after it ends!");
303 assert(!(!Parent && StartIdx != EmptyIdx) &&
304 "Non-root internal nodes must have parents!");
306 unsigned *E = new (InternalEndIdxAllocator) unsigned(EndIdx);
307 SuffixTreeNode *N = new (NodeAllocator.Allocate())
308 SuffixTreeNode(StartIdx, E, Root);
310 Parent->Children[Edge] = N;
315 /// Set the suffix indices of the leaves to the start indices of their
316 /// respective suffixes.
318 /// \param[in] CurrNode The node currently being visited.
319 /// \param CurrNodeLen The concatenation of all node sizes from the root to
320 /// this node. Used to produce suffix indices.
321 void setSuffixIndices(SuffixTreeNode &CurrNode, unsigned CurrNodeLen) {
323 bool IsLeaf = CurrNode.Children.size() == 0 && !CurrNode.isRoot();
325 // Store the concatenation of lengths down from the root.
326 CurrNode.ConcatLen = CurrNodeLen;
327 // Traverse the tree depth-first.
328 for (auto &ChildPair : CurrNode.Children) {
329 assert(ChildPair.second && "Node had a null child!");
330 setSuffixIndices(*ChildPair.second,
331 CurrNodeLen + ChildPair.second->size());
334 // Is this node a leaf? If it is, give it a suffix index.
336 CurrNode.SuffixIdx = Str.size() - CurrNodeLen;
339 /// Construct the suffix tree for the prefix of the input ending at
342 /// Used to construct the full suffix tree iteratively. At the end of each
343 /// step, the constructed suffix tree is either a valid suffix tree, or a
344 /// suffix tree with implicit suffixes. At the end of the final step, the
345 /// suffix tree is a valid tree.
347 /// \param EndIdx The end index of the current prefix in the main string.
348 /// \param SuffixesToAdd The number of suffixes that must be added
349 /// to complete the suffix tree at the current phase.
351 /// \returns The number of suffixes that have not been added at the end of
353 unsigned extend(unsigned EndIdx, unsigned SuffixesToAdd) {
354 SuffixTreeNode *NeedsLink = nullptr;
356 while (SuffixesToAdd > 0) {
358 // Are we waiting to add anything other than just the last character?
359 if (Active.Len == 0) {
360 // If not, then say the active index is the end index.
364 assert(Active.Idx <= EndIdx && "Start index can't be after end index!");
366 // The first character in the current substring we're looking at.
367 unsigned FirstChar = Str[Active.Idx];
369 // Have we inserted anything starting with FirstChar at the current node?
370 if (Active.Node->Children.count(FirstChar) == 0) {
371 // If not, then we can just insert a leaf and move too the next step.
372 insertLeaf(*Active.Node, EndIdx, FirstChar);
374 // The active node is an internal node, and we visited it, so it must
375 // need a link if it doesn't have one.
377 NeedsLink->Link = Active.Node;
381 // There's a match with FirstChar, so look for the point in the tree to
382 // insert a new node.
383 SuffixTreeNode *NextNode = Active.Node->Children[FirstChar];
385 unsigned SubstringLen = NextNode->size();
387 // Is the current suffix we're trying to insert longer than the size of
388 // the child we want to move to?
389 if (Active.Len >= SubstringLen) {
390 // If yes, then consume the characters we've seen and move to the next
392 Active.Idx += SubstringLen;
393 Active.Len -= SubstringLen;
394 Active.Node = NextNode;
398 // Otherwise, the suffix we're trying to insert must be contained in the
399 // next node we want to move to.
400 unsigned LastChar = Str[EndIdx];
402 // Is the string we're trying to insert a substring of the next node?
403 if (Str[NextNode->StartIdx + Active.Len] == LastChar) {
404 // If yes, then we're done for this step. Remember our insertion point
405 // and move to the next end index. At this point, we have an implicit
407 if (NeedsLink && !Active.Node->isRoot()) {
408 NeedsLink->Link = Active.Node;
416 // The string we're trying to insert isn't a substring of the next node,
417 // but matches up to a point. Split the node.
419 // For example, say we ended our search at a node n and we're trying to
420 // insert ABD. Then we'll create a new node s for AB, reduce n to just
421 // representing C, and insert a new leaf node l to represent d. This
422 // allows us to ensure that if n was a leaf, it remains a leaf.
424 // | ABC ---split---> | AB
429 // The node s from the diagram
430 SuffixTreeNode *SplitNode =
431 insertInternalNode(Active.Node, NextNode->StartIdx,
432 NextNode->StartIdx + Active.Len - 1, FirstChar);
434 // Insert the new node representing the new substring into the tree as
435 // a child of the split node. This is the node l from the diagram.
436 insertLeaf(*SplitNode, EndIdx, LastChar);
438 // Make the old node a child of the split node and update its start
439 // index. This is the node n from the diagram.
440 NextNode->StartIdx += Active.Len;
441 SplitNode->Children[Str[NextNode->StartIdx]] = NextNode;
443 // SplitNode is an internal node, update the suffix link.
445 NeedsLink->Link = SplitNode;
447 NeedsLink = SplitNode;
450 // We've added something new to the tree, so there's one less suffix to
454 if (Active.Node->isRoot()) {
455 if (Active.Len > 0) {
457 Active.Idx = EndIdx - SuffixesToAdd + 1;
460 // Start the next phase at the next smallest suffix.
461 Active.Node = Active.Node->Link;
465 return SuffixesToAdd;
469 /// Construct a suffix tree from a sequence of unsigned integers.
471 /// \param Str The string to construct the suffix tree for.
472 SuffixTree(const std::vector<unsigned> &Str) : Str(Str) {
473 Root = insertInternalNode(nullptr, EmptyIdx, EmptyIdx, 0);
476 // Keep track of the number of suffixes we have to add of the current
478 unsigned SuffixesToAdd = 0;
481 // Construct the suffix tree iteratively on each prefix of the string.
482 // PfxEndIdx is the end index of the current prefix.
483 // End is one past the last element in the string.
484 for (unsigned PfxEndIdx = 0, End = Str.size(); PfxEndIdx < End;
487 LeafEndIdx = PfxEndIdx; // Extend each of the leaves.
488 SuffixesToAdd = extend(PfxEndIdx, SuffixesToAdd);
491 // Set the suffix indices of each leaf.
492 assert(Root && "Root node can't be nullptr!");
493 setSuffixIndices(*Root, 0);
497 /// Iterator for finding all repeated substrings in the suffix tree.
498 struct RepeatedSubstringIterator {
500 /// The current node we're visiting.
501 SuffixTreeNode *N = nullptr;
503 /// The repeated substring associated with this node.
504 RepeatedSubstring RS;
506 /// The nodes left to visit.
507 std::vector<SuffixTreeNode *> ToVisit;
509 /// The minimum length of a repeated substring to find.
510 /// Since we're outlining, we want at least two instructions in the range.
511 /// FIXME: This may not be true for targets like X86 which support many
512 /// instruction lengths.
513 const unsigned MinLength = 2;
515 /// Move the iterator to the next repeated substring.
517 // Clear the current state. If we're at the end of the range, then this
518 // is the state we want to be in.
519 RS = RepeatedSubstring();
522 // Each leaf node represents a repeat of a string.
523 std::vector<SuffixTreeNode *> LeafChildren;
525 // Continue visiting nodes until we find one which repeats more than once.
526 while (!ToVisit.empty()) {
527 SuffixTreeNode *Curr = ToVisit.back();
529 LeafChildren.clear();
531 // Keep track of the length of the string associated with the node. If
532 // it's too short, we'll quit.
533 unsigned Length = Curr->ConcatLen;
535 // Iterate over each child, saving internal nodes for visiting, and
536 // leaf nodes in LeafChildren. Internal nodes represent individual
537 // strings, which may repeat.
538 for (auto &ChildPair : Curr->Children) {
539 // Save all of this node's children for processing.
540 if (!ChildPair.second->isLeaf())
541 ToVisit.push_back(ChildPair.second);
543 // It's not an internal node, so it must be a leaf. If we have a
544 // long enough string, then save the leaf children.
545 else if (Length >= MinLength)
546 LeafChildren.push_back(ChildPair.second);
549 // The root never represents a repeated substring. If we're looking at
550 // that, then skip it.
554 // Do we have any repeated substrings?
555 if (LeafChildren.size() >= 2) {
556 // Yes. Update the state to reflect this, and then bail out.
559 for (SuffixTreeNode *Leaf : LeafChildren)
560 RS.StartIndices.push_back(Leaf->SuffixIdx);
565 // At this point, either NewRS is an empty RepeatedSubstring, or it was
566 // set in the above loop. Similarly, N is either nullptr, or the node
567 // associated with NewRS.
571 /// Return the current repeated substring.
572 RepeatedSubstring &operator*() { return RS; }
574 RepeatedSubstringIterator &operator++() {
579 RepeatedSubstringIterator operator++(int I) {
580 RepeatedSubstringIterator It(*this);
585 bool operator==(const RepeatedSubstringIterator &Other) {
588 bool operator!=(const RepeatedSubstringIterator &Other) {
589 return !(*this == Other);
592 RepeatedSubstringIterator(SuffixTreeNode *N) : N(N) {
593 // Do we have a non-null node?
595 // Yes. At the first step, we need to visit all of N's children.
596 // Note: This means that we visit N last.
597 ToVisit.push_back(N);
603 typedef RepeatedSubstringIterator iterator;
604 iterator begin() { return iterator(Root); }
605 iterator end() { return iterator(nullptr); }
608 /// Maps \p MachineInstrs to unsigned integers and stores the mappings.
609 struct InstructionMapper {
611 /// The next available integer to assign to a \p MachineInstr that
612 /// cannot be outlined.
614 /// Set to -3 for compatability with \p DenseMapInfo<unsigned>.
615 unsigned IllegalInstrNumber = -3;
617 /// The next available integer to assign to a \p MachineInstr that can
619 unsigned LegalInstrNumber = 0;
621 /// Correspondence from \p MachineInstrs to unsigned integers.
622 DenseMap<MachineInstr *, unsigned, MachineInstrExpressionTrait>
623 InstructionIntegerMap;
625 /// Correspondence between \p MachineBasicBlocks and target-defined flags.
626 DenseMap<MachineBasicBlock *, unsigned> MBBFlagsMap;
628 /// The vector of unsigned integers that the module is mapped to.
629 std::vector<unsigned> UnsignedVec;
631 /// Stores the location of the instruction associated with the integer
632 /// at index i in \p UnsignedVec for each index i.
633 std::vector<MachineBasicBlock::iterator> InstrList;
635 // Set if we added an illegal number in the previous step.
636 // Since each illegal number is unique, we only need one of them between
637 // each range of legal numbers. This lets us make sure we don't add more
638 // than one illegal number per range.
639 bool AddedIllegalLastTime = false;
641 /// Maps \p *It to a legal integer.
643 /// Updates \p CanOutlineWithPrevInstr, \p HaveLegalRange, \p InstrListForMBB,
644 /// \p UnsignedVecForMBB, \p InstructionIntegerMap, and \p LegalInstrNumber.
646 /// \returns The integer that \p *It was mapped to.
647 unsigned mapToLegalUnsigned(
648 MachineBasicBlock::iterator &It, bool &CanOutlineWithPrevInstr,
649 bool &HaveLegalRange, unsigned &NumLegalInBlock,
650 std::vector<unsigned> &UnsignedVecForMBB,
651 std::vector<MachineBasicBlock::iterator> &InstrListForMBB) {
652 // We added something legal, so we should unset the AddedLegalLastTime
654 AddedIllegalLastTime = false;
656 // If we have at least two adjacent legal instructions (which may have
657 // invisible instructions in between), remember that.
658 if (CanOutlineWithPrevInstr)
659 HaveLegalRange = true;
660 CanOutlineWithPrevInstr = true;
662 // Keep track of the number of legal instructions we insert.
665 // Get the integer for this instruction or give it the current
667 InstrListForMBB.push_back(It);
668 MachineInstr &MI = *It;
670 DenseMap<MachineInstr *, unsigned, MachineInstrExpressionTrait>::iterator
672 std::tie(ResultIt, WasInserted) =
673 InstructionIntegerMap.insert(std::make_pair(&MI, LegalInstrNumber));
674 unsigned MINumber = ResultIt->second;
676 // There was an insertion.
680 UnsignedVecForMBB.push_back(MINumber);
682 // Make sure we don't overflow or use any integers reserved by the DenseMap.
683 if (LegalInstrNumber >= IllegalInstrNumber)
684 report_fatal_error("Instruction mapping overflow!");
686 assert(LegalInstrNumber != DenseMapInfo<unsigned>::getEmptyKey() &&
687 "Tried to assign DenseMap tombstone or empty key to instruction.");
688 assert(LegalInstrNumber != DenseMapInfo<unsigned>::getTombstoneKey() &&
689 "Tried to assign DenseMap tombstone or empty key to instruction.");
694 /// Maps \p *It to an illegal integer.
696 /// Updates \p InstrListForMBB, \p UnsignedVecForMBB, and \p
697 /// IllegalInstrNumber.
699 /// \returns The integer that \p *It was mapped to.
700 unsigned mapToIllegalUnsigned(MachineBasicBlock::iterator &It,
701 bool &CanOutlineWithPrevInstr, std::vector<unsigned> &UnsignedVecForMBB,
702 std::vector<MachineBasicBlock::iterator> &InstrListForMBB) {
703 // Can't outline an illegal instruction. Set the flag.
704 CanOutlineWithPrevInstr = false;
706 // Only add one illegal number per range of legal numbers.
707 if (AddedIllegalLastTime)
708 return IllegalInstrNumber;
710 // Remember that we added an illegal number last time.
711 AddedIllegalLastTime = true;
712 unsigned MINumber = IllegalInstrNumber;
714 InstrListForMBB.push_back(It);
715 UnsignedVecForMBB.push_back(IllegalInstrNumber);
716 IllegalInstrNumber--;
718 assert(LegalInstrNumber < IllegalInstrNumber &&
719 "Instruction mapping overflow!");
721 assert(IllegalInstrNumber != DenseMapInfo<unsigned>::getEmptyKey() &&
722 "IllegalInstrNumber cannot be DenseMap tombstone or empty key!");
724 assert(IllegalInstrNumber != DenseMapInfo<unsigned>::getTombstoneKey() &&
725 "IllegalInstrNumber cannot be DenseMap tombstone or empty key!");
730 /// Transforms a \p MachineBasicBlock into a \p vector of \p unsigneds
731 /// and appends it to \p UnsignedVec and \p InstrList.
733 /// Two instructions are assigned the same integer if they are identical.
734 /// If an instruction is deemed unsafe to outline, then it will be assigned an
735 /// unique integer. The resulting mapping is placed into a suffix tree and
736 /// queried for candidates.
738 /// \param MBB The \p MachineBasicBlock to be translated into integers.
739 /// \param TII \p TargetInstrInfo for the function.
740 void convertToUnsignedVec(MachineBasicBlock &MBB,
741 const TargetInstrInfo &TII) {
744 // Don't even map in this case.
745 if (!TII.isMBBSafeToOutlineFrom(MBB, Flags))
748 // Store info for the MBB for later outlining.
749 MBBFlagsMap[&MBB] = Flags;
751 MachineBasicBlock::iterator It = MBB.begin();
753 // The number of instructions in this block that will be considered for
755 unsigned NumLegalInBlock = 0;
757 // True if we have at least two legal instructions which aren't separated
758 // by an illegal instruction.
759 bool HaveLegalRange = false;
761 // True if we can perform outlining given the last mapped (non-invisible)
762 // instruction. This lets us know if we have a legal range.
763 bool CanOutlineWithPrevInstr = false;
765 // FIXME: Should this all just be handled in the target, rather than using
766 // repeated calls to getOutliningType?
767 std::vector<unsigned> UnsignedVecForMBB;
768 std::vector<MachineBasicBlock::iterator> InstrListForMBB;
770 for (MachineBasicBlock::iterator Et = MBB.end(); It != Et; It++) {
771 // Keep track of where this instruction is in the module.
772 switch (TII.getOutliningType(It, Flags)) {
773 case InstrType::Illegal:
774 mapToIllegalUnsigned(It, CanOutlineWithPrevInstr,
775 UnsignedVecForMBB, InstrListForMBB);
778 case InstrType::Legal:
779 mapToLegalUnsigned(It, CanOutlineWithPrevInstr, HaveLegalRange,
780 NumLegalInBlock, UnsignedVecForMBB, InstrListForMBB);
783 case InstrType::LegalTerminator:
784 mapToLegalUnsigned(It, CanOutlineWithPrevInstr, HaveLegalRange,
785 NumLegalInBlock, UnsignedVecForMBB, InstrListForMBB);
786 // The instruction also acts as a terminator, so we have to record that
788 mapToIllegalUnsigned(It, CanOutlineWithPrevInstr, UnsignedVecForMBB,
792 case InstrType::Invisible:
793 // Normally this is set by mapTo(Blah)Unsigned, but we just want to
794 // skip this instruction. So, unset the flag here.
795 AddedIllegalLastTime = false;
800 // Are there enough legal instructions in the block for outlining to be
802 if (HaveLegalRange) {
803 // After we're done every insertion, uniquely terminate this part of the
804 // "string". This makes sure we won't match across basic block or function
805 // boundaries since the "end" is encoded uniquely and thus appears in no
806 // repeated substring.
807 mapToIllegalUnsigned(It, CanOutlineWithPrevInstr, UnsignedVecForMBB,
809 InstrList.insert(InstrList.end(), InstrListForMBB.begin(),
810 InstrListForMBB.end());
811 UnsignedVec.insert(UnsignedVec.end(), UnsignedVecForMBB.begin(),
812 UnsignedVecForMBB.end());
816 InstructionMapper() {
817 // Make sure that the implementation of DenseMapInfo<unsigned> hasn't
819 assert(DenseMapInfo<unsigned>::getEmptyKey() == (unsigned)-1 &&
820 "DenseMapInfo<unsigned>'s empty key isn't -1!");
821 assert(DenseMapInfo<unsigned>::getTombstoneKey() == (unsigned)-2 &&
822 "DenseMapInfo<unsigned>'s tombstone key isn't -2!");
826 /// An interprocedural pass which finds repeated sequences of
827 /// instructions and replaces them with calls to functions.
829 /// Each instruction is mapped to an unsigned integer and placed in a string.
830 /// The resulting mapping is then placed in a \p SuffixTree. The \p SuffixTree
831 /// is then repeatedly queried for repeated sequences of instructions. Each
832 /// non-overlapping repeated sequence is then placed in its own
833 /// \p MachineFunction and each instance is then replaced with a call to that
835 struct MachineOutliner : public ModulePass {
839 /// Set to true if the outliner should consider functions with
840 /// linkonceodr linkage.
841 bool OutlineFromLinkOnceODRs = false;
843 /// Set to true if the outliner should run on all functions in the module
844 /// considered safe for outlining.
845 /// Set to true by default for compatibility with llc's -run-pass option.
846 /// Set when the pass is constructed in TargetPassConfig.
847 bool RunOnAllFunctions = true;
849 StringRef getPassName() const override { return "Machine Outliner"; }
851 void getAnalysisUsage(AnalysisUsage &AU) const override {
852 AU.addRequired<MachineModuleInfo>();
853 AU.addPreserved<MachineModuleInfo>();
854 AU.setPreservesAll();
855 ModulePass::getAnalysisUsage(AU);
858 MachineOutliner() : ModulePass(ID) {
859 initializeMachineOutlinerPass(*PassRegistry::getPassRegistry());
862 /// Remark output explaining that not outlining a set of candidates would be
863 /// better than outlining that set.
864 void emitNotOutliningCheaperRemark(
865 unsigned StringLen, std::vector<Candidate> &CandidatesForRepeatedSeq,
866 OutlinedFunction &OF);
868 /// Remark output explaining that a function was outlined.
869 void emitOutlinedFunctionRemark(OutlinedFunction &OF);
871 /// Find all repeated substrings that satisfy the outlining cost model by
872 /// constructing a suffix tree.
874 /// If a substring appears at least twice, then it must be represented by
875 /// an internal node which appears in at least two suffixes. Each suffix
876 /// is represented by a leaf node. To do this, we visit each internal node
877 /// in the tree, using the leaf children of each internal node. If an
878 /// internal node represents a beneficial substring, then we use each of
879 /// its leaf children to find the locations of its substring.
881 /// \param Mapper Contains outlining mapping information.
882 /// \param[out] FunctionList Filled with a list of \p OutlinedFunctions
883 /// each type of candidate.
884 void findCandidates(InstructionMapper &Mapper,
885 std::vector<OutlinedFunction> &FunctionList);
887 /// Replace the sequences of instructions represented by \p OutlinedFunctions
888 /// with calls to functions.
890 /// \param M The module we are outlining from.
891 /// \param FunctionList A list of functions to be inserted into the module.
892 /// \param Mapper Contains the instruction mappings for the module.
893 bool outline(Module &M, std::vector<OutlinedFunction> &FunctionList,
894 InstructionMapper &Mapper);
896 /// Creates a function for \p OF and inserts it into the module.
897 MachineFunction *createOutlinedFunction(Module &M, OutlinedFunction &OF,
898 InstructionMapper &Mapper,
901 /// Construct a suffix tree on the instructions in \p M and outline repeated
902 /// strings from that tree.
903 bool runOnModule(Module &M) override;
905 /// Return a DISubprogram for OF if one exists, and null otherwise. Helper
906 /// function for remark emission.
907 DISubprogram *getSubprogramOrNull(const OutlinedFunction &OF) {
909 for (const Candidate &C : OF.Candidates)
910 if (C.getMF() && (SP = C.getMF()->getFunction().getSubprogram()))
915 /// Populate and \p InstructionMapper with instruction-to-integer mappings.
916 /// These are used to construct a suffix tree.
917 void populateMapper(InstructionMapper &Mapper, Module &M,
918 MachineModuleInfo &MMI);
920 /// Initialize information necessary to output a size remark.
921 /// FIXME: This should be handled by the pass manager, not the outliner.
922 /// FIXME: This is nearly identical to the initSizeRemarkInfo in the legacy
924 void initSizeRemarkInfo(
925 const Module &M, const MachineModuleInfo &MMI,
926 StringMap<unsigned> &FunctionToInstrCount);
929 // FIXME: This should be handled by the pass manager, not the outliner.
930 void emitInstrCountChangedRemark(
931 const Module &M, const MachineModuleInfo &MMI,
932 const StringMap<unsigned> &FunctionToInstrCount);
934 } // Anonymous namespace.
936 char MachineOutliner::ID = 0;
939 ModulePass *createMachineOutlinerPass(bool RunOnAllFunctions) {
940 MachineOutliner *OL = new MachineOutliner();
941 OL->RunOnAllFunctions = RunOnAllFunctions;
947 INITIALIZE_PASS(MachineOutliner, DEBUG_TYPE, "Machine Function Outliner", false,
950 void MachineOutliner::emitNotOutliningCheaperRemark(
951 unsigned StringLen, std::vector<Candidate> &CandidatesForRepeatedSeq,
952 OutlinedFunction &OF) {
953 // FIXME: Right now, we arbitrarily choose some Candidate from the
954 // OutlinedFunction. This isn't necessarily fixed, nor does it have to be.
955 // We should probably sort these by function name or something to make sure
956 // the remarks are stable.
957 Candidate &C = CandidatesForRepeatedSeq.front();
958 MachineOptimizationRemarkEmitter MORE(*(C.getMF()), nullptr);
960 MachineOptimizationRemarkMissed R(DEBUG_TYPE, "NotOutliningCheaper",
961 C.front()->getDebugLoc(), C.getMBB());
962 R << "Did not outline " << NV("Length", StringLen) << " instructions"
963 << " from " << NV("NumOccurrences", CandidatesForRepeatedSeq.size())
965 << " Bytes from outlining all occurrences ("
966 << NV("OutliningCost", OF.getOutliningCost()) << ")"
967 << " >= Unoutlined instruction bytes ("
968 << NV("NotOutliningCost", OF.getNotOutlinedCost()) << ")"
969 << " (Also found at: ";
971 // Tell the user the other places the candidate was found.
972 for (unsigned i = 1, e = CandidatesForRepeatedSeq.size(); i < e; i++) {
973 R << NV((Twine("OtherStartLoc") + Twine(i)).str(),
974 CandidatesForRepeatedSeq[i].front()->getDebugLoc());
984 void MachineOutliner::emitOutlinedFunctionRemark(OutlinedFunction &OF) {
985 MachineBasicBlock *MBB = &*OF.MF->begin();
986 MachineOptimizationRemarkEmitter MORE(*OF.MF, nullptr);
987 MachineOptimizationRemark R(DEBUG_TYPE, "OutlinedFunction",
988 MBB->findDebugLoc(MBB->begin()), MBB);
989 R << "Saved " << NV("OutliningBenefit", OF.getBenefit()) << " bytes by "
990 << "outlining " << NV("Length", OF.getNumInstrs()) << " instructions "
991 << "from " << NV("NumOccurrences", OF.getOccurrenceCount())
995 // Tell the user the other places the candidate was found.
996 for (size_t i = 0, e = OF.Candidates.size(); i < e; i++) {
998 R << NV((Twine("StartLoc") + Twine(i)).str(),
999 OF.Candidates[i].front()->getDebugLoc());
1010 MachineOutliner::findCandidates(InstructionMapper &Mapper,
1011 std::vector<OutlinedFunction> &FunctionList) {
1012 FunctionList.clear();
1013 SuffixTree ST(Mapper.UnsignedVec);
1015 // First, find dall of the repeated substrings in the tree of minimum length
1017 std::vector<Candidate> CandidatesForRepeatedSeq;
1018 for (auto It = ST.begin(), Et = ST.end(); It != Et; ++It) {
1019 CandidatesForRepeatedSeq.clear();
1020 SuffixTree::RepeatedSubstring RS = *It;
1021 unsigned StringLen = RS.Length;
1022 for (const unsigned &StartIdx : RS.StartIndices) {
1023 unsigned EndIdx = StartIdx + StringLen - 1;
1024 // Trick: Discard some candidates that would be incompatible with the
1025 // ones we've already found for this sequence. This will save us some
1026 // work in candidate selection.
1028 // If two candidates overlap, then we can't outline them both. This
1029 // happens when we have candidates that look like, say
1031 // AA (where each "A" is an instruction).
1033 // We might have some portion of the module that looks like this:
1036 // In this case, there are 5 different copies of "AA" in this range, but
1037 // at most 3 can be outlined. If only outlining 3 of these is going to
1038 // be unbeneficial, then we ought to not bother.
1040 // Note that two things DON'T overlap when they look like this:
1041 // start1...end1 .... start2...end2
1042 // That is, one must either
1043 // * End before the other starts
1044 // * Start after the other ends
1046 CandidatesForRepeatedSeq.begin(), CandidatesForRepeatedSeq.end(),
1047 [&StartIdx, &EndIdx](const Candidate &C) {
1048 return (EndIdx < C.getStartIdx() || StartIdx > C.getEndIdx());
1050 // It doesn't overlap with anything, so we can outline it.
1051 // Each sequence is over [StartIt, EndIt].
1052 // Save the candidate and its location.
1054 MachineBasicBlock::iterator StartIt = Mapper.InstrList[StartIdx];
1055 MachineBasicBlock::iterator EndIt = Mapper.InstrList[EndIdx];
1056 MachineBasicBlock *MBB = StartIt->getParent();
1058 CandidatesForRepeatedSeq.emplace_back(StartIdx, StringLen, StartIt,
1059 EndIt, MBB, FunctionList.size(),
1060 Mapper.MBBFlagsMap[MBB]);
1064 // We've found something we might want to outline.
1065 // Create an OutlinedFunction to store it and check if it'd be beneficial
1067 if (CandidatesForRepeatedSeq.size() < 2)
1070 // Arbitrarily choose a TII from the first candidate.
1071 // FIXME: Should getOutliningCandidateInfo move to TargetMachine?
1072 const TargetInstrInfo *TII =
1073 CandidatesForRepeatedSeq[0].getMF()->getSubtarget().getInstrInfo();
1075 OutlinedFunction OF =
1076 TII->getOutliningCandidateInfo(CandidatesForRepeatedSeq);
1078 // If we deleted too many candidates, then there's nothing worth outlining.
1079 // FIXME: This should take target-specified instruction sizes into account.
1080 if (OF.Candidates.size() < 2)
1083 // Is it better to outline this candidate than not?
1084 if (OF.getBenefit() < 1) {
1085 emitNotOutliningCheaperRemark(StringLen, CandidatesForRepeatedSeq, OF);
1089 FunctionList.push_back(OF);
1094 MachineOutliner::createOutlinedFunction(Module &M, OutlinedFunction &OF,
1095 InstructionMapper &Mapper,
1098 // Create the function name. This should be unique. For now, just hash the
1099 // module name and include it in the function name plus the number of this
1101 std::ostringstream NameStream;
1102 // FIXME: We should have a better naming scheme. This should be stable,
1103 // regardless of changes to the outliner's cost model/traversal order.
1104 NameStream << "OUTLINED_FUNCTION_" << Name;
1106 // Create the function using an IR-level function.
1107 LLVMContext &C = M.getContext();
1108 Function *F = dyn_cast<Function>(
1109 M.getOrInsertFunction(NameStream.str(), Type::getVoidTy(C)));
1110 assert(F && "Function was null!");
1112 // NOTE: If this is linkonceodr, then we can take advantage of linker deduping
1113 // which gives us better results when we outline from linkonceodr functions.
1114 F->setLinkage(GlobalValue::InternalLinkage);
1115 F->setUnnamedAddr(GlobalValue::UnnamedAddr::Global);
1117 // FIXME: Set nounwind, so we don't generate eh_frame? Haven't verified it's
1120 // Set optsize/minsize, so we don't insert padding between outlined
1122 F->addFnAttr(Attribute::OptimizeForSize);
1123 F->addFnAttr(Attribute::MinSize);
1125 // Include target features from an arbitrary candidate for the outlined
1126 // function. This makes sure the outlined function knows what kinds of
1127 // instructions are going into it. This is fine, since all parent functions
1128 // must necessarily support the instructions that are in the outlined region.
1129 Candidate &FirstCand = OF.Candidates.front();
1130 const Function &ParentFn = FirstCand.getMF()->getFunction();
1131 if (ParentFn.hasFnAttribute("target-features"))
1132 F->addFnAttr(ParentFn.getFnAttribute("target-features"));
1134 BasicBlock *EntryBB = BasicBlock::Create(C, "entry", F);
1135 IRBuilder<> Builder(EntryBB);
1136 Builder.CreateRetVoid();
1138 MachineModuleInfo &MMI = getAnalysis<MachineModuleInfo>();
1139 MachineFunction &MF = MMI.getOrCreateMachineFunction(*F);
1140 MachineBasicBlock &MBB = *MF.CreateMachineBasicBlock();
1141 const TargetSubtargetInfo &STI = MF.getSubtarget();
1142 const TargetInstrInfo &TII = *STI.getInstrInfo();
1144 // Insert the new function into the module.
1145 MF.insert(MF.begin(), &MBB);
1147 for (auto I = FirstCand.front(), E = std::next(FirstCand.back()); I != E;
1149 MachineInstr *NewMI = MF.CloneMachineInstr(&*I);
1150 NewMI->dropMemRefs(MF);
1152 // Don't keep debug information for outlined instructions.
1153 NewMI->setDebugLoc(DebugLoc());
1154 MBB.insert(MBB.end(), NewMI);
1157 TII.buildOutlinedFrame(MBB, MF, OF);
1159 // Outlined functions shouldn't preserve liveness.
1160 MF.getProperties().reset(MachineFunctionProperties::Property::TracksLiveness);
1161 MF.getRegInfo().freezeReservedRegs(MF);
1163 // If there's a DISubprogram associated with this outlined function, then
1164 // emit debug info for the outlined function.
1165 if (DISubprogram *SP = getSubprogramOrNull(OF)) {
1166 // We have a DISubprogram. Get its DICompileUnit.
1167 DICompileUnit *CU = SP->getUnit();
1168 DIBuilder DB(M, true, CU);
1169 DIFile *Unit = SP->getFile();
1171 // Get the mangled name of the function for the linkage name.
1173 llvm::raw_string_ostream MangledNameStream(Dummy);
1174 Mg.getNameWithPrefix(MangledNameStream, F, false);
1176 DISubprogram *OutlinedSP = DB.createFunction(
1177 Unit /* Context */, F->getName(), StringRef(MangledNameStream.str()),
1179 0 /* Line 0 is reserved for compiler-generated code. */,
1180 DB.createSubroutineType(DB.getOrCreateTypeArray(None)), /* void type */
1181 0, /* Line 0 is reserved for compiler-generated code. */
1182 DINode::DIFlags::FlagArtificial /* Compiler-generated code. */,
1183 /* Outlined code is optimized code by definition. */
1184 DISubprogram::SPFlagDefinition | DISubprogram::SPFlagOptimized);
1186 // Don't add any new variables to the subprogram.
1187 DB.finalizeSubprogram(OutlinedSP);
1189 // Attach subprogram to the function.
1190 F->setSubprogram(OutlinedSP);
1191 // We're done with the DIBuilder.
1198 bool MachineOutliner::outline(Module &M,
1199 std::vector<OutlinedFunction> &FunctionList,
1200 InstructionMapper &Mapper) {
1202 bool OutlinedSomething = false;
1204 // Number to append to the current outlined function.
1205 unsigned OutlinedFunctionNum = 0;
1207 // Sort by benefit. The most beneficial functions should be outlined first.
1209 FunctionList.begin(), FunctionList.end(),
1210 [](const OutlinedFunction &LHS, const OutlinedFunction &RHS) {
1211 return LHS.getBenefit() > RHS.getBenefit();
1214 // Walk over each function, outlining them as we go along. Functions are
1215 // outlined greedily, based off the sort above.
1216 for (OutlinedFunction &OF : FunctionList) {
1217 // If we outlined something that overlapped with a candidate in a previous
1218 // step, then we can't outline from it.
1219 erase_if(OF.Candidates, [&Mapper](Candidate &C) {
1221 Mapper.UnsignedVec.begin() + C.getStartIdx(),
1222 Mapper.UnsignedVec.begin() + C.getEndIdx() + 1,
1223 [](unsigned I) { return (I == static_cast<unsigned>(-1)); });
1226 // If we made it unbeneficial to outline this function, skip it.
1227 if (OF.getBenefit() < 1)
1230 // It's beneficial. Create the function and outline its sequence's
1232 OF.MF = createOutlinedFunction(M, OF, Mapper, OutlinedFunctionNum);
1233 emitOutlinedFunctionRemark(OF);
1235 OutlinedFunctionNum++; // Created a function, move to the next name.
1236 MachineFunction *MF = OF.MF;
1237 const TargetSubtargetInfo &STI = MF->getSubtarget();
1238 const TargetInstrInfo &TII = *STI.getInstrInfo();
1240 // Replace occurrences of the sequence with calls to the new function.
1241 for (Candidate &C : OF.Candidates) {
1242 MachineBasicBlock &MBB = *C.getMBB();
1243 MachineBasicBlock::iterator StartIt = C.front();
1244 MachineBasicBlock::iterator EndIt = C.back();
1247 auto CallInst = TII.insertOutlinedCall(M, MBB, StartIt, *MF, C);
1249 // If the caller tracks liveness, then we need to make sure that
1250 // anything we outline doesn't break liveness assumptions. The outlined
1251 // functions themselves currently don't track liveness, but we should
1252 // make sure that the ranges we yank things out of aren't wrong.
1253 if (MBB.getParent()->getProperties().hasProperty(
1254 MachineFunctionProperties::Property::TracksLiveness)) {
1255 // Helper lambda for adding implicit def operands to the call
1257 auto CopyDefs = [&CallInst](MachineInstr &MI) {
1258 for (MachineOperand &MOP : MI.operands()) {
1259 // Skip over anything that isn't a register.
1263 // If it's a def, add it to the call instruction.
1265 CallInst->addOperand(MachineOperand::CreateReg(
1266 MOP.getReg(), true, /* isDef = true */
1267 true /* isImp = true */));
1270 // Copy over the defs in the outlined range.
1271 // First inst in outlined range <-- Anything that's defined in this
1272 // ... .. range has to be added as an
1273 // implicit Last inst in outlined range <-- def to the call
1275 std::for_each(CallInst, std::next(EndIt), CopyDefs);
1278 // Erase from the point after where the call was inserted up to, and
1279 // including, the final instruction in the sequence.
1280 // Erase needs one past the end, so we need std::next there too.
1281 MBB.erase(std::next(StartIt), std::next(EndIt));
1283 // Keep track of what we removed by marking them all as -1.
1284 std::for_each(Mapper.UnsignedVec.begin() + C.getStartIdx(),
1285 Mapper.UnsignedVec.begin() + C.getEndIdx() + 1,
1286 [](unsigned &I) { I = static_cast<unsigned>(-1); });
1287 OutlinedSomething = true;
1294 LLVM_DEBUG(dbgs() << "OutlinedSomething = " << OutlinedSomething << "\n";);
1296 return OutlinedSomething;
1299 void MachineOutliner::populateMapper(InstructionMapper &Mapper, Module &M,
1300 MachineModuleInfo &MMI) {
1301 // Build instruction mappings for each function in the module. Start by
1302 // iterating over each Function in M.
1303 for (Function &F : M) {
1305 // If there's nothing in F, then there's no reason to try and outline from
1310 // There's something in F. Check if it has a MachineFunction associated with
1312 MachineFunction *MF = MMI.getMachineFunction(F);
1314 // If it doesn't, then there's nothing to outline from. Move to the next
1319 const TargetInstrInfo *TII = MF->getSubtarget().getInstrInfo();
1321 if (!RunOnAllFunctions && !TII->shouldOutlineFromFunctionByDefault(*MF))
1324 // We have a MachineFunction. Ask the target if it's suitable for outlining.
1325 // If it isn't, then move on to the next Function in the module.
1326 if (!TII->isFunctionSafeToOutlineFrom(*MF, OutlineFromLinkOnceODRs))
1329 // We have a function suitable for outlining. Iterate over every
1330 // MachineBasicBlock in MF and try to map its instructions to a list of
1331 // unsigned integers.
1332 for (MachineBasicBlock &MBB : *MF) {
1333 // If there isn't anything in MBB, then there's no point in outlining from
1335 // If there are fewer than 2 instructions in the MBB, then it can't ever
1336 // contain something worth outlining.
1337 // FIXME: This should be based off of the maximum size in B of an outlined
1338 // call versus the size in B of the MBB.
1339 if (MBB.empty() || MBB.size() < 2)
1342 // Check if MBB could be the target of an indirect branch. If it is, then
1343 // we don't want to outline from it.
1344 if (MBB.hasAddressTaken())
1347 // MBB is suitable for outlining. Map it to a list of unsigneds.
1348 Mapper.convertToUnsignedVec(MBB, *TII);
1353 void MachineOutliner::initSizeRemarkInfo(
1354 const Module &M, const MachineModuleInfo &MMI,
1355 StringMap<unsigned> &FunctionToInstrCount) {
1356 // Collect instruction counts for every function. We'll use this to emit
1357 // per-function size remarks later.
1358 for (const Function &F : M) {
1359 MachineFunction *MF = MMI.getMachineFunction(F);
1361 // We only care about MI counts here. If there's no MachineFunction at this
1362 // point, then there won't be after the outliner runs, so let's move on.
1365 FunctionToInstrCount[F.getName().str()] = MF->getInstructionCount();
1369 void MachineOutliner::emitInstrCountChangedRemark(
1370 const Module &M, const MachineModuleInfo &MMI,
1371 const StringMap<unsigned> &FunctionToInstrCount) {
1372 // Iterate over each function in the module and emit remarks.
1373 // Note that we won't miss anything by doing this, because the outliner never
1374 // deletes functions.
1375 for (const Function &F : M) {
1376 MachineFunction *MF = MMI.getMachineFunction(F);
1378 // The outliner never deletes functions. If we don't have a MF here, then we
1379 // didn't have one prior to outlining either.
1383 std::string Fname = F.getName();
1384 unsigned FnCountAfter = MF->getInstructionCount();
1385 unsigned FnCountBefore = 0;
1387 // Check if the function was recorded before.
1388 auto It = FunctionToInstrCount.find(Fname);
1390 // Did we have a previously-recorded size? If yes, then set FnCountBefore
1392 if (It != FunctionToInstrCount.end())
1393 FnCountBefore = It->second;
1395 // Compute the delta and emit a remark if there was a change.
1396 int64_t FnDelta = static_cast<int64_t>(FnCountAfter) -
1397 static_cast<int64_t>(FnCountBefore);
1401 MachineOptimizationRemarkEmitter MORE(*MF, nullptr);
1403 MachineOptimizationRemarkAnalysis R("size-info", "FunctionMISizeChange",
1404 DiagnosticLocation(),
1406 R << DiagnosticInfoOptimizationBase::Argument("Pass", "Machine Outliner")
1408 << DiagnosticInfoOptimizationBase::Argument("Function", F.getName())
1409 << ": MI instruction count changed from "
1410 << DiagnosticInfoOptimizationBase::Argument("MIInstrsBefore",
1413 << DiagnosticInfoOptimizationBase::Argument("MIInstrsAfter",
1416 << DiagnosticInfoOptimizationBase::Argument("Delta", FnDelta);
1422 bool MachineOutliner::runOnModule(Module &M) {
1423 // Check if there's anything in the module. If it's empty, then there's
1424 // nothing to outline.
1428 MachineModuleInfo &MMI = getAnalysis<MachineModuleInfo>();
1430 // If the user passed -enable-machine-outliner=always or
1431 // -enable-machine-outliner, the pass will run on all functions in the module.
1432 // Otherwise, if the target supports default outlining, it will run on all
1433 // functions deemed by the target to be worth outlining from by default. Tell
1434 // the user how the outliner is running.
1436 dbgs() << "Machine Outliner: Running on ";
1437 if (RunOnAllFunctions)
1438 dbgs() << "all functions";
1440 dbgs() << "target-default functions";
1444 // If the user specifies that they want to outline from linkonceodrs, set
1446 OutlineFromLinkOnceODRs = EnableLinkOnceODROutlining;
1447 InstructionMapper Mapper;
1449 // Prepare instruction mappings for the suffix tree.
1450 populateMapper(Mapper, M, MMI);
1451 std::vector<OutlinedFunction> FunctionList;
1453 // Find all of the outlining candidates.
1454 findCandidates(Mapper, FunctionList);
1456 // If we've requested size remarks, then collect the MI counts of every
1457 // function before outlining, and the MI counts after outlining.
1458 // FIXME: This shouldn't be in the outliner at all; it should ultimately be
1459 // the pass manager's responsibility.
1460 // This could pretty easily be placed in outline instead, but because we
1461 // really ultimately *don't* want this here, it's done like this for now
1464 // Check if we want size remarks.
1465 bool ShouldEmitSizeRemarks = M.shouldEmitInstrCountChangedRemark();
1466 StringMap<unsigned> FunctionToInstrCount;
1467 if (ShouldEmitSizeRemarks)
1468 initSizeRemarkInfo(M, MMI, FunctionToInstrCount);
1470 // Outline each of the candidates and return true if something was outlined.
1471 bool OutlinedSomething = outline(M, FunctionList, Mapper);
1473 // If we outlined something, we definitely changed the MI count of the
1474 // module. If we've asked for size remarks, then output them.
1475 // FIXME: This should be in the pass manager.
1476 if (ShouldEmitSizeRemarks && OutlinedSomething)
1477 emitInstrCountChangedRemark(M, MMI, FunctionToInstrCount);
1479 return OutlinedSomething;