--- /dev/null
+//===- IteratedDominanceFrontier.h - Calculate IDF --------------*- C++ -*-===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+/// \brief Compute iterated dominance frontiers using a linear time algorithm.
+///
+/// The algorithm used here is based on:
+///
+/// Sreedhar and Gao. A linear time algorithm for placing phi-nodes.
+/// In Proceedings of the 22nd ACM SIGPLAN-SIGACT Symposium on Principles of
+/// Programming Languages
+/// POPL '95. ACM, New York, NY, 62-73.
+///
+/// It has been modified to not explicitly use the DJ graph data structure and
+/// to directly compute pruned SSA using per-variable liveness information.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ANALYSIS_IDF_H
+#define LLVM_ANALYSIS_IDF_H
+
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/SmallVector.h"
+
+namespace llvm {
+
+class BasicBlock;
+template <class T> class DomTreeNodeBase;
+typedef DomTreeNodeBase<BasicBlock> DomTreeNode;
+class DominatorTree;
+
+/// \brief Determine the iterated dominance frontier, given a set of defining
+/// blocks, and optionally, a set of live-in blocks.
+///
+/// In turn, the results can be used to place phi nodes.
+///
+/// This algorithm is a linear time computation of Iterated Dominance Frontiers,
+/// pruned using the live-in set.
+/// By default, liveness is not used to prune the IDF computation.
+class IDFCalculator {
+
+public:
+ IDFCalculator(DominatorTree &DT) : DT(DT), useLiveIn(false) {}
+
+ /// \brief Give the IDF calculator the set of blocks in which the value is
+ /// defined. This is equivalent to the set of starting blocks it should be
+ /// calculating the IDF for (though later gets pruned based on liveness).
+ ///
+ /// Note: This set *must* live for the entire lifetime of the IDF calculator.
+ void setDefiningBlocks(const SmallPtrSetImpl<BasicBlock *> &Blocks) {
+ DefBlocks = &Blocks;
+ }
+
+ /// \brief Give the IDF calculator the set of blocks in which the value is
+ /// live on entry to the block. This is used to prune the IDF calculation to
+ /// not include blocks where any phi insertion would be dead.
+ ///
+ /// Note: This set *must* live for the entire lifetime of the IDF calculator.
+
+ void setLiveInBlocks(const SmallPtrSetImpl<BasicBlock *> &Blocks) {
+ LiveInBlocks = &Blocks;
+ useLiveIn = true;
+ }
+
+ /// \brief Reset the live-in block set to be empty, and tell the IDF
+ /// calculator to not use liveness anymore.
+ void resetLiveInBlocks() {
+ LiveInBlocks = nullptr;
+ useLiveIn = false;
+ }
+
+ /// \brief Calculate iterated dominance frontiers
+ ///
+ /// This uses the linear-time phi algorithm based on DJ-graphs mentioned in
+ /// the file-level comment. It performs DF->IDF pruning using the live-in
+ /// set, to avoid computing the IDF for blocks where an inserted PHI node
+ /// would be dead.
+ void calculate(SmallVectorImpl<BasicBlock *> &IDFBlocks);
+
+private:
+ DominatorTree &DT;
+ bool useLiveIn;
+ DenseMap<DomTreeNode *, unsigned> DomLevels;
+ const SmallPtrSetImpl<BasicBlock *> *LiveInBlocks;
+ const SmallPtrSetImpl<BasicBlock *> *DefBlocks;
+ SmallVector<BasicBlock *, 32> PHIBlocks;
+};
+}
+#endif
--- /dev/null
+//===- IteratedDominanceFrontier.cpp - Compute IDF ------------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+/// \brief Compute iterated dominance frontiers using a linear time algorithm.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Analysis/IteratedDominanceFrontier.h"
+#include "llvm/IR/CFG.h"
+#include "llvm/IR/Dominators.h"
+#include <queue>
+
+using namespace llvm;
+
+void IDFCalculator::calculate(SmallVectorImpl<BasicBlock *> &PHIBlocks) {
+ // If we haven't computed dominator tree levels, do so now.
+ if (DomLevels.empty()) {
+ for (auto DFI = df_begin(DT.getRootNode()), DFE = df_end(DT.getRootNode());
+ DFI != DFE; ++DFI) {
+ DomLevels[*DFI] = DFI.getPathLength() - 1;
+ }
+ }
+
+ // Use a priority queue keyed on dominator tree level so that inserted nodes
+ // are handled from the bottom of the dominator tree upwards.
+ typedef std::pair<DomTreeNode *, unsigned> DomTreeNodePair;
+ typedef std::priority_queue<DomTreeNodePair, SmallVector<DomTreeNodePair, 32>,
+ less_second> IDFPriorityQueue;
+ IDFPriorityQueue PQ;
+
+ for (BasicBlock *BB : *DefBlocks) {
+ if (DomTreeNode *Node = DT.getNode(BB))
+ PQ.push(std::make_pair(Node, DomLevels.lookup(Node)));
+ }
+
+ SmallVector<DomTreeNode *, 32> Worklist;
+ SmallPtrSet<DomTreeNode *, 32> VisitedPQ;
+ SmallPtrSet<DomTreeNode *, 32> VisitedWorklist;
+
+ while (!PQ.empty()) {
+ DomTreeNodePair RootPair = PQ.top();
+ PQ.pop();
+ DomTreeNode *Root = RootPair.first;
+ unsigned RootLevel = RootPair.second;
+
+ // Walk all dominator tree children of Root, inspecting their CFG edges with
+ // targets elsewhere on the dominator tree. Only targets whose level is at
+ // most Root's level are added to the iterated dominance frontier of the
+ // definition set.
+
+ Worklist.clear();
+ Worklist.push_back(Root);
+ VisitedWorklist.insert(Root);
+
+ while (!Worklist.empty()) {
+ DomTreeNode *Node = Worklist.pop_back_val();
+ BasicBlock *BB = Node->getBlock();
+
+ for (auto Succ : successors(BB)) {
+ DomTreeNode *SuccNode = DT.getNode(Succ);
+
+ // Quickly skip all CFG edges that are also dominator tree edges instead
+ // of catching them below.
+ if (SuccNode->getIDom() == Node)
+ continue;
+
+ unsigned SuccLevel = DomLevels.lookup(SuccNode);
+ if (SuccLevel > RootLevel)
+ continue;
+
+ if (!VisitedPQ.insert(SuccNode).second)
+ continue;
+
+ BasicBlock *SuccBB = SuccNode->getBlock();
+ if (useLiveIn && !LiveInBlocks->count(SuccBB))
+ continue;
+
+ PHIBlocks.emplace_back(SuccBB);
+ if (!DefBlocks->count(SuccBB))
+ PQ.push(std::make_pair(SuccNode, SuccLevel));
+ }
+
+ for (auto DomChild : *Node) {
+ if (VisitedWorklist.insert(DomChild).second)
+ Worklist.push_back(DomChild);
+ }
+ }
+ }
+}
// traversing the function in depth-first order to rewrite loads and stores as
// appropriate.
//
-// The algorithm used here is based on:
-//
-// Sreedhar and Gao. A linear time algorithm for placing phi-nodes.
-// In Proceedings of the 22nd ACM SIGPLAN-SIGACT Symposium on Principles of
-// Programming Languages
-// POPL '95. ACM, New York, NY, 62-73.
-//
-// It has been modified to not explicitly use the DJ graph data structure and to
-// directly compute pruned SSA using per-variable liveness information.
-//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Utils/PromoteMemToReg.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AliasSetTracker.h"
#include "llvm/Analysis/InstructionSimplify.h"
+#include "llvm/Analysis/IteratedDominanceFrontier.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/CFG.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/Module.h"
#include "llvm/Transforms/Utils/Local.h"
#include <algorithm>
-#include <queue>
using namespace llvm;
#define DEBUG_TYPE "mem2reg"
/// behavior.
DenseMap<BasicBlock *, unsigned> BBNumbers;
- /// Maps DomTreeNodes to their level in the dominator tree.
- DenseMap<DomTreeNode *, unsigned> DomLevels;
-
/// Lazily compute the number of predecessors a block has.
DenseMap<const BasicBlock *, unsigned> BBNumPreds;
return NP - 1;
}
- void DetermineInsertionPoint(AllocaInst *AI, unsigned AllocaNum,
- AllocaInfo &Info);
void ComputeLiveInBlocks(AllocaInst *AI, AllocaInfo &Info,
const SmallPtrSetImpl<BasicBlock *> &DefBlocks,
SmallPtrSetImpl<BasicBlock *> &LiveInBlocks);
AllocaInfo Info;
LargeBlockInfo LBI;
+ IDFCalculator IDF(DT);
for (unsigned AllocaNum = 0; AllocaNum != Allocas.size(); ++AllocaNum) {
AllocaInst *AI = Allocas[AllocaNum];
continue;
}
- // If we haven't computed dominator tree levels, do so now.
- if (DomLevels.empty()) {
- SmallVector<DomTreeNode *, 32> Worklist;
-
- DomTreeNode *Root = DT.getRootNode();
- DomLevels[Root] = 0;
- Worklist.push_back(Root);
-
- while (!Worklist.empty()) {
- DomTreeNode *Node = Worklist.pop_back_val();
- unsigned ChildLevel = DomLevels[Node] + 1;
- for (DomTreeNode::iterator CI = Node->begin(), CE = Node->end();
- CI != CE; ++CI) {
- DomLevels[*CI] = ChildLevel;
- Worklist.push_back(*CI);
- }
- }
- }
-
// If we haven't computed a numbering for the BB's in the function, do so
// now.
if (BBNumbers.empty()) {
unsigned ID = 0;
- for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
- BBNumbers[I] = ID++;
+ for (auto &BB : F)
+ BBNumbers[&BB] = ID++;
}
// If we have an AST to keep updated, remember some pointer value that is
// the standard SSA construction algorithm. Determine which blocks need PHI
// nodes and see if we can optimize out some work by avoiding insertion of
// dead phi nodes.
- DetermineInsertionPoint(AI, AllocaNum, Info);
+
+
+ // Unique the set of defining blocks for efficient lookup.
+ SmallPtrSet<BasicBlock *, 32> DefBlocks;
+ DefBlocks.insert(Info.DefiningBlocks.begin(), Info.DefiningBlocks.end());
+
+ // Determine which blocks the value is live in. These are blocks which lead
+ // to uses.
+ SmallPtrSet<BasicBlock *, 32> LiveInBlocks;
+ ComputeLiveInBlocks(AI, Info, DefBlocks, LiveInBlocks);
+
+ // At this point, we're committed to promoting the alloca using IDF's, and
+ // the standard SSA construction algorithm. Determine which blocks need phi
+ // nodes and see if we can optimize out some work by avoiding insertion of
+ // dead phi nodes.
+ IDF.setLiveInBlocks(LiveInBlocks);
+ IDF.setDefiningBlocks(DefBlocks);
+ SmallVector<BasicBlock *, 32> PHIBlocks;
+ IDF.calculate(PHIBlocks);
+ if (PHIBlocks.size() > 1)
+ std::sort(PHIBlocks.begin(), PHIBlocks.end(),
+ [this](BasicBlock *A, BasicBlock *B) {
+ return BBNumbers.lookup(A) < BBNumbers.lookup(B);
+ });
+
+ unsigned CurrentVersion = 0;
+ for (unsigned i = 0, e = PHIBlocks.size(); i != e; ++i)
+ QueuePhiNode(PHIBlocks[i], AllocaNum, CurrentVersion);
}
if (Allocas.empty())
}
}
-/// At this point, we're committed to promoting the alloca using IDF's, and the
-/// standard SSA construction algorithm. Determine which blocks need phi nodes
-/// and see if we can optimize out some work by avoiding insertion of dead phi
-/// nodes.
-void PromoteMem2Reg::DetermineInsertionPoint(AllocaInst *AI, unsigned AllocaNum,
- AllocaInfo &Info) {
- // Unique the set of defining blocks for efficient lookup.
- SmallPtrSet<BasicBlock *, 32> DefBlocks;
- DefBlocks.insert(Info.DefiningBlocks.begin(), Info.DefiningBlocks.end());
-
- // Determine which blocks the value is live in. These are blocks which lead
- // to uses.
- SmallPtrSet<BasicBlock *, 32> LiveInBlocks;
- ComputeLiveInBlocks(AI, Info, DefBlocks, LiveInBlocks);
-
- // Use a priority queue keyed on dominator tree level so that inserted nodes
- // are handled from the bottom of the dominator tree upwards.
- typedef std::pair<DomTreeNode *, unsigned> DomTreeNodePair;
- typedef std::priority_queue<DomTreeNodePair, SmallVector<DomTreeNodePair, 32>,
- less_second> IDFPriorityQueue;
- IDFPriorityQueue PQ;
-
- for (BasicBlock *BB : DefBlocks) {
- if (DomTreeNode *Node = DT.getNode(BB))
- PQ.push(std::make_pair(Node, DomLevels[Node]));
- }
-
- SmallVector<std::pair<unsigned, BasicBlock *>, 32> DFBlocks;
- SmallVector<DomTreeNode *, 32> Worklist;
- SmallPtrSet<DomTreeNode *, 32> VisitedPQ;
- SmallPtrSet<DomTreeNode *, 32> VisitedWorklist;
-
- while (!PQ.empty()) {
- DomTreeNodePair RootPair = PQ.top();
- PQ.pop();
- DomTreeNode *Root = RootPair.first;
- unsigned RootLevel = RootPair.second;
-
- // Walk all dominator tree children of Root, inspecting their CFG edges with
- // targets elsewhere on the dominator tree. Only targets whose level is at
- // most Root's level are added to the iterated dominance frontier of the
- // definition set.
-
- Worklist.clear();
- Worklist.push_back(Root);
- VisitedWorklist.insert(Root);
-
- while (!Worklist.empty()) {
- DomTreeNode *Node = Worklist.pop_back_val();
- BasicBlock *BB = Node->getBlock();
-
- for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE;
- ++SI) {
- DomTreeNode *SuccNode = DT.getNode(*SI);
-
- // Quickly skip all CFG edges that are also dominator tree edges instead
- // of catching them below.
- if (SuccNode->getIDom() == Node)
- continue;
-
- unsigned SuccLevel = DomLevels[SuccNode];
- if (SuccLevel > RootLevel)
- continue;
-
- if (!VisitedPQ.insert(SuccNode).second)
- continue;
-
- BasicBlock *SuccBB = SuccNode->getBlock();
- if (!LiveInBlocks.count(SuccBB))
- continue;
-
- DFBlocks.push_back(std::make_pair(BBNumbers[SuccBB], SuccBB));
- if (!DefBlocks.count(SuccBB))
- PQ.push(std::make_pair(SuccNode, SuccLevel));
- }
-
- for (DomTreeNode::iterator CI = Node->begin(), CE = Node->end(); CI != CE;
- ++CI) {
- if (VisitedWorklist.insert(*CI).second)
- Worklist.push_back(*CI);
- }
- }
- }
-
- if (DFBlocks.size() > 1)
- std::sort(DFBlocks.begin(), DFBlocks.end());
-
- unsigned CurrentVersion = 0;
- for (unsigned i = 0, e = DFBlocks.size(); i != e; ++i)
- QueuePhiNode(DFBlocks[i].second, AllocaNum, CurrentVersion);
-}
-
/// \brief Queue a phi-node to be added to a basic-block for a specific Alloca.
///
/// Returns true if there wasn't already a phi-node for that variable
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