//
// The LLVM Compiler Infrastructure
//
-// This file was developed by Owen Anderson and is distributed under the
-// University of Illinois Open Source License. See LICENSE.TXT for details.
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// the left into the right code:
//
// for (...) for (...)
-// if (c) if(c)
+// if (c) if (c)
// X1 = ... X1 = ...
// else else
// X2 = ... X2 = ...
// X3 = phi(X1, X2) X3 = phi(X1, X2)
-// ... = X3 + 4 X4 = phi(X3)
-// ... = X4 + 4
+// ... = X3 + 4 X4 = phi(X3)
+// ... = X4 + 4
//
// This is still valid LLVM; the extra phi nodes are purely redundant, and will
// be trivially eliminated by InstCombine. The major benefit of this
//
//===----------------------------------------------------------------------===//
+#define DEBUG_TYPE "lcssa"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Constants.h"
#include "llvm/Pass.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/Dominators.h"
-#include "llvm/Analysis/LoopInfo.h"
+#include "llvm/Analysis/LoopPass.h"
+#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/Support/CFG.h"
+#include "llvm/Support/Compiler.h"
#include <algorithm>
#include <map>
-
using namespace llvm;
+STATISTIC(NumLCSSA, "Number of live out of a loop variables");
+
namespace {
- static Statistic<> NumLCSSA("lcssa",
- "Number of live out of a loop variables");
-
- struct LCSSA : public FunctionPass {
+ struct VISIBILITY_HIDDEN LCSSA : public LoopPass {
+ static char ID; // Pass identification, replacement for typeid
+ LCSSA() : LoopPass(&ID) {}
+
// Cached analysis information for the current function.
LoopInfo *LI;
DominatorTree *DT;
std::vector<BasicBlock*> LoopBlocks;
- virtual bool runOnFunction(Function &F);
- bool visitSubloop(Loop* L);
+ virtual bool runOnLoop(Loop *L, LPPassManager &LPM);
+
void ProcessInstruction(Instruction* Instr,
- const std::vector<BasicBlock*>& exitBlocks);
+ const SmallVector<BasicBlock*, 8>& exitBlocks);
/// This transformation requires natural loop information & requires that
/// loop preheaders be inserted into the CFG. It maintains both of these,
AU.addRequiredID(LoopSimplifyID);
AU.addPreservedID(LoopSimplifyID);
AU.addRequired<LoopInfo>();
+ AU.addPreserved<LoopInfo>();
AU.addRequired<DominatorTree>();
+ AU.addPreserved<ScalarEvolution>();
+ AU.addPreserved<DominatorTree>();
+
+ // Request DominanceFrontier now, even though LCSSA does
+ // not use it. This allows Pass Manager to schedule Dominance
+ // Frontier early enough such that one LPPassManager can handle
+ // multiple loop transformation passes.
+ AU.addRequired<DominanceFrontier>();
+ AU.addPreserved<DominanceFrontier>();
}
private:
- SetVector<Instruction*> getLoopValuesUsedOutsideLoop(Loop *L);
+ void getLoopValuesUsedOutsideLoop(Loop *L,
+ SetVector<Instruction*> &AffectedValues);
- PHINode *GetValueForBlock(DominatorTree::Node *BB, Instruction *OrigInst,
- std::map<DominatorTree::Node*, PHINode*> &Phis);
+ Value *GetValueForBlock(DomTreeNode *BB, Instruction *OrigInst,
+ DenseMap<DomTreeNode*, Value*> &Phis);
/// inLoop - returns true if the given block is within the current loop
- const bool inLoop(BasicBlock* B) {
+ bool inLoop(BasicBlock* B) {
return std::binary_search(LoopBlocks.begin(), LoopBlocks.end(), B);
}
};
-
- RegisterPass<LCSSA> X("lcssa", "Loop-Closed SSA Form Pass");
}
+
+char LCSSA::ID = 0;
+static RegisterPass<LCSSA> X("lcssa", "Loop-Closed SSA Form Pass");
-FunctionPass *llvm::createLCSSAPass() { return new LCSSA(); }
-const PassInfo *llvm::LCSSAID = X.getPassInfo();
+LoopPass *llvm::createLCSSAPass() { return new LCSSA(); }
+const PassInfo *const llvm::LCSSAID = &X;
/// runOnFunction - Process all loops in the function, inner-most out.
-bool LCSSA::runOnFunction(Function &F) {
- bool changed = false;
+bool LCSSA::runOnLoop(Loop *L, LPPassManager &LPM) {
- LI = &getAnalysis<LoopInfo>();
+ LI = &LPM.getAnalysis<LoopInfo>();
DT = &getAnalysis<DominatorTree>();
-
- for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I)
- changed |= visitSubloop(*I);
-
- return changed;
-}
-/// visitSubloop - Recursively process all subloops, and then process the given
-/// loop if it has live-out values.
-bool LCSSA::visitSubloop(Loop* L) {
- for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I)
- visitSubloop(*I);
-
// Speed up queries by creating a sorted list of blocks
LoopBlocks.clear();
LoopBlocks.insert(LoopBlocks.end(), L->block_begin(), L->block_end());
std::sort(LoopBlocks.begin(), LoopBlocks.end());
- SetVector<Instruction*> AffectedValues = getLoopValuesUsedOutsideLoop(L);
+ SetVector<Instruction*> AffectedValues;
+ getLoopValuesUsedOutsideLoop(L, AffectedValues);
// If no values are affected, we can save a lot of work, since we know that
// nothing will be changed.
if (AffectedValues.empty())
return false;
- std::vector<BasicBlock*> exitBlocks;
- L->getExitBlocks(exitBlocks);
-
+ SmallVector<BasicBlock*, 8> exitBlocks;
+ L->getExitBlocks(exitBlocks);
// Iterate over all affected values for this loop and insert Phi nodes
// for them in the appropriate exit blocks
/// processInstruction - Given a live-out instruction, insert LCSSA Phi nodes,
/// eliminate all out-of-loop uses.
void LCSSA::ProcessInstruction(Instruction *Instr,
- const std::vector<BasicBlock*>& exitBlocks) {
+ const SmallVector<BasicBlock*, 8>& exitBlocks) {
++NumLCSSA; // We are applying the transformation
// Keep track of the blocks that have the value available already.
- std::map<DominatorTree::Node*, PHINode*> Phis;
+ DenseMap<DomTreeNode*, Value*> Phis;
- DominatorTree::Node *InstrNode = DT->getNode(Instr->getParent());
+ DomTreeNode *InstrNode = DT->getNode(Instr->getParent());
// Insert the LCSSA phi's into the exit blocks (dominated by the value), and
// add them to the Phi's map.
- for (std::vector<BasicBlock*>::const_iterator BBI = exitBlocks.begin(),
+ for (SmallVector<BasicBlock*, 8>::const_iterator BBI = exitBlocks.begin(),
BBE = exitBlocks.end(); BBI != BBE; ++BBI) {
BasicBlock *BB = *BBI;
- DominatorTree::Node *ExitBBNode = DT->getNode(BB);
- PHINode *&Phi = Phis[ExitBBNode];
- if (!Phi && InstrNode->dominates(ExitBBNode)) {
- Phi = new PHINode(Instr->getType(), Instr->getName()+".lcssa",
- BB->begin());
- Phi->reserveOperandSpace(std::distance(pred_begin(BB), pred_end(BB)));
+ DomTreeNode *ExitBBNode = DT->getNode(BB);
+ Value *&Phi = Phis[ExitBBNode];
+ if (!Phi && DT->dominates(InstrNode, ExitBBNode)) {
+ PHINode *PN = PHINode::Create(Instr->getType(), Instr->getName()+".lcssa",
+ BB->begin());
+ PN->reserveOperandSpace(std::distance(pred_begin(BB), pred_end(BB)));
+
+ // Remember that this phi makes the value alive in this block.
+ Phi = PN;
// Add inputs from inside the loop for this PHI.
for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
- Phi->addIncoming(Instr, *PI);
-
- // Remember that this phi makes the value alive in this block.
- Phis[ExitBBNode] = Phi;
+ PN->addIncoming(Instr, *PI);
}
}
/// getLoopValuesUsedOutsideLoop - Return any values defined in the loop that
/// are used by instructions outside of it.
-SetVector<Instruction*> LCSSA::getLoopValuesUsedOutsideLoop(Loop *L) {
-
+void LCSSA::getLoopValuesUsedOutsideLoop(Loop *L,
+ SetVector<Instruction*> &AffectedValues) {
// FIXME: For large loops, we may be able to avoid a lot of use-scanning
// by using dominance information. In particular, if a block does not
// dominate any of the loop exits, then none of the values defined in the
// block could be used outside the loop.
-
- SetVector<Instruction*> AffectedValues;
for (Loop::block_iterator BB = L->block_begin(), E = L->block_end();
BB != E; ++BB) {
for (BasicBlock::iterator I = (*BB)->begin(), E = (*BB)->end(); I != E; ++I)
}
}
}
- return AffectedValues;
}
/// GetValueForBlock - Get the value to use within the specified basic block.
/// available values are in Phis.
-PHINode *LCSSA::GetValueForBlock(DominatorTree::Node *BB, Instruction *OrigInst,
- std::map<DominatorTree::Node*, PHINode*> &Phis) {
+Value *LCSSA::GetValueForBlock(DomTreeNode *BB, Instruction *OrigInst,
+ DenseMap<DomTreeNode*, Value*> &Phis) {
+ // If there is no dominator info for this BB, it is unreachable.
+ if (BB == 0)
+ return UndefValue::get(OrigInst->getType());
+
// If we have already computed this value, return the previously computed val.
- PHINode *&V = Phis[BB];
- if (V) return V;
+ if (Phis.count(BB)) return Phis[BB];
- DominatorTree::Node *IDom = BB->getIDom();
+ DomTreeNode *IDom = BB->getIDom();
// Otherwise, there are two cases: we either have to insert a PHI node or we
// don't. We need to insert a PHI node if this block is not dominated by one
if (!inLoop(IDom->getBlock())) {
// Idom is not in the loop, we must still be "below" the exit block and must
// be fully dominated by the value live in the idom.
- return V = GetValueForBlock(IDom, OrigInst, Phis);
+ Value* val = GetValueForBlock(IDom, OrigInst, Phis);
+ Phis.insert(std::make_pair(BB, val));
+ return val;
}
BasicBlock *BBN = BB->getBlock();
// Otherwise, the idom is the loop, so we need to insert a PHI node. Do so
// now, then get values to fill in the incoming values for the PHI.
- V = new PHINode(OrigInst->getType(), OrigInst->getName()+".lcssa",
- BBN->begin());
- V->reserveOperandSpace(std::distance(pred_begin(BBN), pred_end(BBN)));
-
+ PHINode *PN = PHINode::Create(OrigInst->getType(),
+ OrigInst->getName() + ".lcssa", BBN->begin());
+ PN->reserveOperandSpace(std::distance(pred_begin(BBN), pred_end(BBN)));
+ Phis.insert(std::make_pair(BB, PN));
+
// Fill in the incoming values for the block.
for (pred_iterator PI = pred_begin(BBN), E = pred_end(BBN); PI != E; ++PI)
- V->addIncoming(GetValueForBlock(DT->getNode(*PI), OrigInst, Phis), *PI);
- return V;
+ PN->addIncoming(GetValueForBlock(DT->getNode(*PI), OrigInst, Phis), *PI);
+ return PN;
}
projects / oota-llvm.git / blobdiff