//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "phielim"
-#include "PHIElimination.h"
+#include "PHIEliminationUtils.h"
#include "llvm/CodeGen/LiveVariables.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/Statistic.h"
+#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include <algorithm>
#include <map>
using namespace llvm;
+static cl::opt<bool>
+DisableEdgeSplitting("disable-phi-elim-edge-splitting", cl::init(false),
+ cl::Hidden, cl::desc("Disable critical edge splitting "
+ "during PHI elimination"));
+
+namespace {
+ class PHIElimination : public MachineFunctionPass {
+ MachineRegisterInfo *MRI; // Machine register information
+
+ public:
+ static char ID; // Pass identification, replacement for typeid
+ PHIElimination() : MachineFunctionPass(ID) {
+ initializePHIEliminationPass(*PassRegistry::getPassRegistry());
+ }
+
+ virtual bool runOnMachineFunction(MachineFunction &Fn);
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const;
+
+ private:
+ /// EliminatePHINodes - Eliminate phi nodes by inserting copy instructions
+ /// in predecessor basic blocks.
+ ///
+ bool EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB);
+ void LowerAtomicPHINode(MachineBasicBlock &MBB,
+ MachineBasicBlock::iterator AfterPHIsIt);
+
+ /// analyzePHINodes - Gather information about the PHI nodes in
+ /// here. In particular, we want to map the number of uses of a virtual
+ /// register which is used in a PHI node. We map that to the BB the
+ /// vreg is coming from. This is used later to determine when the vreg
+ /// is killed in the BB.
+ ///
+ void analyzePHINodes(const MachineFunction& Fn);
+
+ /// Split critical edges where necessary for good coalescer performance.
+ bool SplitPHIEdges(MachineFunction &MF, MachineBasicBlock &MBB,
+ LiveVariables &LV, MachineLoopInfo *MLI);
+
+ typedef std::pair<unsigned, unsigned> BBVRegPair;
+ typedef DenseMap<BBVRegPair, unsigned> VRegPHIUse;
+
+ VRegPHIUse VRegPHIUseCount;
+
+ // Defs of PHI sources which are implicit_def.
+ SmallPtrSet<MachineInstr*, 4> ImpDefs;
+
+ // Map reusable lowered PHI node -> incoming join register.
+ typedef DenseMap<MachineInstr*, unsigned,
+ MachineInstrExpressionTrait> LoweredPHIMap;
+ LoweredPHIMap LoweredPHIs;
+ };
+}
+
STATISTIC(NumAtomic, "Number of atomic phis lowered");
+STATISTIC(NumCriticalEdgesSplit, "Number of critical edges split");
STATISTIC(NumReused, "Number of reused lowered phis");
char PHIElimination::ID = 0;
-static RegisterPass<PHIElimination>
-X("phi-node-elimination", "Eliminate PHI nodes for register allocation");
+INITIALIZE_PASS(PHIElimination, "phi-node-elimination",
+ "Eliminate PHI nodes for register allocation", false, false)
-char &llvm::PHIEliminationID = PHIElimination::ID;
+char& llvm::PHIEliminationID = PHIElimination::ID;
-void llvm::PHIElimination::getAnalysisUsage(AnalysisUsage &AU) const {
+void PHIElimination::getAnalysisUsage(AnalysisUsage &AU) const {
AU.addPreserved<LiveVariables>();
AU.addPreserved<MachineDominatorTree>();
AU.addPreserved<MachineLoopInfo>();
MachineFunctionPass::getAnalysisUsage(AU);
}
-bool llvm::PHIElimination::runOnMachineFunction(MachineFunction &MF) {
+bool PHIElimination::runOnMachineFunction(MachineFunction &MF) {
MRI = &MF.getRegInfo();
bool Changed = false;
// Split critical edges to help the coalescer
- if (LiveVariables *LV = getAnalysisIfAvailable<LiveVariables>()) {
- MachineLoopInfo *MLI = getAnalysisIfAvailable<MachineLoopInfo>();
- for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I)
- Changed |= SplitPHIEdges(MF, *I, *LV, MLI);
+ if (!DisableEdgeSplitting) {
+ if (LiveVariables *LV = getAnalysisIfAvailable<LiveVariables>()) {
+ MachineLoopInfo *MLI = getAnalysisIfAvailable<MachineLoopInfo>();
+ for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I)
+ Changed |= SplitPHIEdges(MF, *I, *LV, MLI);
+ }
}
// Populate VRegPHIUseCount
/// EliminatePHINodes - Eliminate phi nodes by inserting copy instructions in
/// predecessor basic blocks.
///
-bool llvm::PHIElimination::EliminatePHINodes(MachineFunction &MF,
+bool PHIElimination::EliminatePHINodes(MachineFunction &MF,
MachineBasicBlock &MBB) {
if (MBB.empty() || !MBB.front().isPHI())
return false; // Quick exit for basic blocks without PHIs.
// Get an iterator to the first instruction after the last PHI node (this may
// also be the end of the basic block).
- MachineBasicBlock::iterator AfterPHIsIt = SkipPHIsAndLabels(MBB, MBB.begin());
+ MachineBasicBlock::iterator AfterPHIsIt = MBB.SkipPHIsAndLabels(MBB.begin());
while (MBB.front().isPHI())
LowerAtomicPHINode(MBB, AfterPHIsIt);
return true;
}
-// FindCopyInsertPoint - Find a safe place in MBB to insert a copy from SrcReg
-// when following the CFG edge to SuccMBB. This needs to be after any def of
-// SrcReg, but before any subsequent point where control flow might jump out of
-// the basic block.
-MachineBasicBlock::iterator
-llvm::PHIElimination::FindCopyInsertPoint(MachineBasicBlock &MBB,
- MachineBasicBlock &SuccMBB,
- unsigned SrcReg) {
- // Handle the trivial case trivially.
- if (MBB.empty())
- return MBB.begin();
-
- // Usually, we just want to insert the copy before the first terminator
- // instruction. However, for the edge going to a landing pad, we must insert
- // the copy before the call/invoke instruction.
- if (!SuccMBB.isLandingPad())
- return MBB.getFirstTerminator();
-
- // Discover any defs/uses in this basic block.
- SmallPtrSet<MachineInstr*, 8> DefUsesInMBB;
- for (MachineRegisterInfo::reg_iterator RI = MRI->reg_begin(SrcReg),
- RE = MRI->reg_end(); RI != RE; ++RI) {
- MachineInstr *DefUseMI = &*RI;
- if (DefUseMI->getParent() == &MBB)
- DefUsesInMBB.insert(DefUseMI);
- }
- MachineBasicBlock::iterator InsertPoint;
- if (DefUsesInMBB.empty()) {
- // No defs. Insert the copy at the start of the basic block.
- InsertPoint = MBB.begin();
- } else if (DefUsesInMBB.size() == 1) {
- // Insert the copy immediately after the def/use.
- InsertPoint = *DefUsesInMBB.begin();
- ++InsertPoint;
- } else {
- // Insert the copy immediately after the last def/use.
- InsertPoint = MBB.end();
- while (!DefUsesInMBB.count(&*--InsertPoint)) {}
- ++InsertPoint;
- }
-
- // Make sure the copy goes after any phi nodes however.
- return SkipPHIsAndLabels(MBB, InsertPoint);
-}
/// LowerAtomicPHINode - Lower the PHI node at the top of the specified block,
/// under the assuption that it needs to be lowered in a way that supports
/// atomic execution of PHIs. This lowering method is always correct all of the
/// time.
///
-void llvm::PHIElimination::LowerAtomicPHINode(
+void PHIElimination::LowerAtomicPHINode(
MachineBasicBlock &MBB,
MachineBasicBlock::iterator AfterPHIsIt) {
++NumAtomic;
IncomingReg = entry;
reusedIncoming = true;
++NumReused;
- DEBUG(dbgs() << "Reusing %reg" << IncomingReg << " for " << *MPhi);
+ DEBUG(dbgs() << "Reusing " << PrintReg(IncomingReg) << " for " << *MPhi);
} else {
const TargetRegisterClass *RC = MF.getRegInfo().getRegClass(DestReg);
entry = IncomingReg = MF.getRegInfo().createVirtualRegister(RC);
// Find a safe location to insert the copy, this may be the first terminator
// in the block (or end()).
MachineBasicBlock::iterator InsertPos =
- FindCopyInsertPoint(opBlock, MBB, SrcReg);
+ findPHICopyInsertPoint(&opBlock, &MBB, SrcReg);
// Insert the copy.
if (!reusedIncoming && IncomingReg)
#ifndef NDEBUG
for (MachineBasicBlock::iterator TI = llvm::next(Term);
TI != opBlock.end(); ++TI) {
+ if (TI->isDebugValue())
+ continue;
assert(!TI->readsRegister(SrcReg) &&
"Terminator instructions cannot use virtual registers unless"
"they are the first terminator in a block!");
} else if (reusedIncoming || !IncomingReg) {
// We may have to rewind a bit if we didn't insert a copy this time.
KillInst = Term;
- while (KillInst != opBlock.begin())
- if ((--KillInst)->readsRegister(SrcReg))
+ while (KillInst != opBlock.begin()) {
+ --KillInst;
+ if (KillInst->isDebugValue())
+ continue;
+ if (KillInst->readsRegister(SrcReg))
break;
+ }
} else {
// We just inserted this copy.
KillInst = prior(InsertPos);
/// used in a PHI node. We map that to the BB the vreg is coming from. This is
/// used later to determine when the vreg is killed in the BB.
///
-void llvm::PHIElimination::analyzePHINodes(const MachineFunction& MF) {
+void PHIElimination::analyzePHINodes(const MachineFunction& MF) {
for (MachineFunction::const_iterator I = MF.begin(), E = MF.end();
I != E; ++I)
for (MachineBasicBlock::const_iterator BBI = I->begin(), BBE = I->end();
BBI->getOperand(i).getReg())];
}
-bool llvm::PHIElimination::SplitPHIEdges(MachineFunction &MF,
- MachineBasicBlock &MBB,
- LiveVariables &LV,
- MachineLoopInfo *MLI) {
+bool PHIElimination::SplitPHIEdges(MachineFunction &MF,
+ MachineBasicBlock &MBB,
+ LiveVariables &LV,
+ MachineLoopInfo *MLI) {
if (MBB.empty() || !MBB.front().isPHI() || MBB.isLandingPad())
return false; // Quick exit for basic blocks without PHIs.
!LV.isLiveIn(Reg, MBB) && LV.isLiveOut(Reg, *PreMBB)) {
if (!MLI ||
!(MLI->getLoopFor(PreMBB) == MLI->getLoopFor(&MBB) &&
- MLI->isLoopHeader(&MBB)))
- Changed |= PreMBB->SplitCriticalEdge(&MBB, this) != 0;
+ MLI->isLoopHeader(&MBB))) {
+ if (PreMBB->SplitCriticalEdge(&MBB, this)) {
+ Changed = true;
+ ++NumCriticalEdgesSplit;
+ }
+ }
}
}
}
- return true;
+ return Changed;
}
projects / oota-llvm.git / blobdiff