From 6db0756f021a7b9c84d3bb7ae50498feb080a013 Mon Sep 17 00:00:00 2001 From: Chris Lattner Date: Mon, 3 Oct 2005 07:22:07 +0000 Subject: [PATCH] clean up this code a bit, no functionality change git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@23609 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/CodeGen/PHIElimination.cpp | 219 ++++++++++++++++++--------------- 1 file changed, 117 insertions(+), 102 deletions(-) diff --git a/lib/CodeGen/PHIElimination.cpp b/lib/CodeGen/PHIElimination.cpp index 80c884dc9ae..91805a93edf 100644 --- a/lib/CodeGen/PHIElimination.cpp +++ b/lib/CodeGen/PHIElimination.cpp @@ -22,10 +22,15 @@ #include "llvm/Target/TargetMachine.h" #include "llvm/ADT/DenseMap.h" #include "llvm/ADT/STLExtras.h" +#include "llvm/ADT/Statistic.h" #include +#include using namespace llvm; namespace { + Statistic<> NumAtomic("phielim", "Number of atomic phis lowered"); + Statistic<> NumSimple("phielim", "Number of simple phis lowered"); + struct PNE : public MachineFunctionPass { bool runOnMachineFunction(MachineFunction &Fn) { bool Changed = false; @@ -49,8 +54,7 @@ namespace { bool EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB); void LowerAtomicPHINode(MachineBasicBlock &MBB, MachineBasicBlock::iterator AfterPHIsIt, - DenseMap &VUC, - unsigned BBIsSuccOfPreds); + DenseMap &VUC); }; RegisterPass X("phi-node-elimination", @@ -72,18 +76,15 @@ bool PNE::EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB) { DenseMap VRegPHIUseCount; VRegPHIUseCount.grow(MF.getSSARegMap()->getLastVirtReg()); - unsigned BBIsSuccOfPreds = 0; // Number of times MBB is a succ of preds for (MachineBasicBlock::pred_iterator PI = MBB.pred_begin(), E = MBB.pred_end(); PI != E; ++PI) for (MachineBasicBlock::succ_iterator SI = (*PI)->succ_begin(), - E = (*PI)->succ_end(); SI != E; ++SI) { - BBIsSuccOfPreds += *SI == &MBB; - for (MachineBasicBlock::iterator BBI = (*SI)->begin(); BBI !=(*SI)->end() && - BBI->getOpcode() == TargetInstrInfo::PHI; ++BBI) - for (unsigned i = 1, e = BBI->getNumOperands(); i != e; i += 2) - VRegPHIUseCount[BBI->getOperand(i).getReg()]++; - } - + E = (*PI)->succ_end(); SI != E; ++SI) + for (MachineBasicBlock::iterator BBI = (*SI)->begin(), E = (*SI)->end(); + BBI != E && BBI->getOpcode() == TargetInstrInfo::PHI; ++BBI) + for (unsigned i = 1, e = BBI->getNumOperands(); i != e; i += 2) + VRegPHIUseCount[BBI->getOperand(i).getReg()]++; + // 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 = MBB.begin(); @@ -92,7 +93,7 @@ bool PNE::EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB) { ++AfterPHIsIt; // Skip over all of the PHI nodes... while (MBB.front().getOpcode() == TargetInstrInfo::PHI) { - LowerAtomicPHINode(MBB, AfterPHIsIt, VRegPHIUseCount, BBIsSuccOfPreds); + LowerAtomicPHINode(MBB, AfterPHIsIt, VRegPHIUseCount); } return true; } @@ -103,8 +104,7 @@ bool PNE::EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB) { /// time. void PNE::LowerAtomicPHINode(MachineBasicBlock &MBB, MachineBasicBlock::iterator AfterPHIsIt, - DenseMap &VRegPHIUseCount, - unsigned BBIsSuccOfPreds) { + DenseMap &VRegPHIUseCount) { // Unlink the PHI node from the basic block, but don't delete the PHI yet. MachineInstr *MPhi = MBB.remove(MBB.begin()); @@ -140,124 +140,139 @@ void PNE::LowerAtomicPHINode(MachineBasicBlock &MBB, // LV->removeVirtualRegistersKilled(MPhi); - std::pair - RKs = LV->dead_range(MPhi); - if (RKs.first != RKs.second) { - for (LiveVariables::killed_iterator I = RKs.first; I != RKs.second; ++I) - LV->addVirtualRegisterDead(*I, PHICopy); + // If the result is dead, update LV. + if (LV->RegisterDefIsDead(MPhi, DestReg)) { + LV->addVirtualRegisterDead(DestReg, PHICopy); LV->removeVirtualRegistersDead(MPhi); } } // Adjust the VRegPHIUseCount map to account for the removal of this PHI // node. + unsigned NumPreds = (MPhi->getNumOperands()-1)/2; for (unsigned i = 1; i != MPhi->getNumOperands(); i += 2) - VRegPHIUseCount[MPhi->getOperand(i).getReg()] -= BBIsSuccOfPreds; + VRegPHIUseCount[MPhi->getOperand(i).getReg()] -= NumPreds; // Now loop over all of the incoming arguments, changing them to copy into // the IncomingReg register in the corresponding predecessor basic block. // + std::set MBBsInsertedInto; for (int i = MPhi->getNumOperands() - 1; i >= 2; i-=2) { - MachineOperand &opVal = MPhi->getOperand(i-1); + unsigned SrcReg = MPhi->getOperand(i-1).getReg(); + assert(MRegisterInfo::isVirtualRegister(SrcReg) && + "Machine PHI Operands must all be virtual registers!"); // Get the MachineBasicBlock equivalent of the BasicBlock that is the // source path the PHI. MachineBasicBlock &opBlock = *MPhi->getOperand(i).getMachineBasicBlock(); - MachineBasicBlock::iterator I = opBlock.getFirstTerminator(); - // Check to make sure we haven't already emitted the copy for this block. // This can happen because PHI nodes may have multiple entries for the - // same basic block. It doesn't matter which entry we use though, because - // all incoming values are guaranteed to be the same for a particular bb. - // - // If we emitted a copy for this basic block already, it will be right - // where we want to insert one now. Just check for a definition of the - // register we are interested in! - // - bool HaveNotEmitted = true; + // same basic block. + if (!MBBsInsertedInto.insert(&opBlock).second) + continue; // If the copy has already been emitted, we're done. + + // Get an iterator pointing to the first terminator in the block (or end()). + // This is the point where we can insert a copy if we'd like to. + MachineBasicBlock::iterator I = opBlock.getFirstTerminator(); + + // Insert the copy. + RegInfo->copyRegToReg(opBlock, I, IncomingReg, SrcReg, RC); - if (I != opBlock.begin()) { - MachineBasicBlock::iterator PrevInst = prior(I); - for (unsigned i = 0, e = PrevInst->getNumOperands(); i != e; ++i) { - MachineOperand &MO = PrevInst->getOperand(i); - if (MO.isRegister() && MO.getReg() == IncomingReg) - if (MO.isDef()) { - HaveNotEmitted = false; - break; - } + // Now update live variable information if we have it. Otherwise we're done + if (!LV) continue; + + // We want to be able to insert a kill of the register if this PHI + // (aka, the copy we just inserted) is the last use of the source + // value. Live variable analysis conservatively handles this by + // saying that the value is live until the end of the block the PHI + // entry lives in. If the value really is dead at the PHI copy, there + // will be no successor blocks which have the value live-in. + // + // Check to see if the copy is the last use, and if so, update the + // live variables information so that it knows the copy source + // instruction kills the incoming value. + // + LiveVariables::VarInfo &InRegVI = LV->getVarInfo(SrcReg); + + // Loop over all of the successors of the basic block, checking to see + // if the value is either live in the block, or if it is killed in the + // block. Also check to see if this register is in use by another PHI + // node which has not yet been eliminated. If so, it will be killed + // at an appropriate point later. + // + + // Is it used by any PHI instructions in this block? + bool ValueIsLive = VRegPHIUseCount[SrcReg] != 0; + + std::vector OpSuccBlocks; + + // Otherwise, scan successors, including the BB the PHI node lives in. + for (MachineBasicBlock::succ_iterator SI = opBlock.succ_begin(), + E = opBlock.succ_end(); SI != E && !ValueIsLive; ++SI) { + MachineBasicBlock *SuccMBB = *SI; + + // Is it alive in this successor? + unsigned SuccIdx = SuccMBB->getNumber(); + if (SuccIdx < InRegVI.AliveBlocks.size() && + InRegVI.AliveBlocks[SuccIdx]) { + ValueIsLive = true; + break; } + + OpSuccBlocks.push_back(SuccMBB); } - if (HaveNotEmitted) { // If the copy has not already been emitted, do it. - assert(MRegisterInfo::isVirtualRegister(opVal.getReg()) && - "Machine PHI Operands must all be virtual registers!"); - unsigned SrcReg = opVal.getReg(); - RegInfo->copyRegToReg(opBlock, I, IncomingReg, SrcReg, RC); - - // Now update live variable information if we have it. - if (LV) { - // We want to be able to insert a kill of the register if this PHI - // (aka, the copy we just inserted) is the last use of the source - // value. Live variable analysis conservatively handles this by - // saying that the value is live until the end of the block the PHI - // entry lives in. If the value really is dead at the PHI copy, there - // will be no successor blocks which have the value live-in. - // - // Check to see if the copy is the last use, and if so, update the - // live variables information so that it knows the copy source - // instruction kills the incoming value. - // - LiveVariables::VarInfo &InRegVI = LV->getVarInfo(SrcReg); - - // Loop over all of the successors of the basic block, checking to see - // if the value is either live in the block, or if it is killed in the - // block. Also check to see if this register is in use by another PHI - // node which has not yet been eliminated. If so, it will be killed - // at an appropriate point later. - // - bool ValueIsLive = false; - for (MachineBasicBlock::succ_iterator SI = opBlock.succ_begin(), - E = opBlock.succ_end(); SI != E && !ValueIsLive; ++SI) { - MachineBasicBlock *SuccMBB = *SI; - - // Is it alive in this successor? - unsigned SuccIdx = SuccMBB->getNumber(); - if (SuccIdx < InRegVI.AliveBlocks.size() && - InRegVI.AliveBlocks[SuccIdx]) { + // Check to see if this value is live because there is a use in a successor + // that kills it. + if (!ValueIsLive) { + switch (OpSuccBlocks.size()) { + case 1: { + MachineBasicBlock *MBB = OpSuccBlocks[0]; + for (unsigned i = 0, e = InRegVI.Kills.size(); i != e; ++i) + if (InRegVI.Kills[i]->getParent() == MBB) { ValueIsLive = true; break; } - - // Is it killed in this successor? - for (unsigned i = 0, e = InRegVI.Kills.size(); i != e; ++i) - if (InRegVI.Kills[i]->getParent() == SuccMBB) { - ValueIsLive = true; - break; - } - - // Is it used by any PHI instructions in this block? - if (!ValueIsLive) - ValueIsLive = VRegPHIUseCount[SrcReg] != 0; - } - - // Okay, if we now know that the value is not live out of the block, - // we can add a kill marker to the copy we inserted saying that it - // kills the incoming value! - // - if (!ValueIsLive) { - MachineBasicBlock::iterator Prev = prior(I); - LV->addVirtualRegisterKilled(SrcReg, Prev); - - // This vreg no longer lives all of the way through opBlock. - unsigned opBlockNum = opBlock.getNumber(); - if (opBlockNum < InRegVI.AliveBlocks.size()) - InRegVI.AliveBlocks[opBlockNum] = false; - } + break; } + case 2: { + MachineBasicBlock *MBB1 = OpSuccBlocks[0], *MBB2 = OpSuccBlocks[1]; + for (unsigned i = 0, e = InRegVI.Kills.size(); i != e; ++i) + if (InRegVI.Kills[i]->getParent() == MBB1 || + InRegVI.Kills[i]->getParent() == MBB2) { + ValueIsLive = true; + break; + } + break; + } + default: + std::sort(OpSuccBlocks.begin(), OpSuccBlocks.end()); + for (unsigned i = 0, e = InRegVI.Kills.size(); i != e; ++i) + if (std::binary_search(OpSuccBlocks.begin(), OpSuccBlocks.end(), + InRegVI.Kills[i]->getParent())) { + ValueIsLive = true; + break; + } + } + } + + // Okay, if we now know that the value is not live out of the block, + // we can add a kill marker to the copy we inserted saying that it + // kills the incoming value! + // + if (!ValueIsLive) { + MachineBasicBlock::iterator Prev = prior(I); + LV->addVirtualRegisterKilled(SrcReg, Prev); + + // This vreg no longer lives all of the way through opBlock. + unsigned opBlockNum = opBlock.getNumber(); + if (opBlockNum < InRegVI.AliveBlocks.size()) + InRegVI.AliveBlocks[opBlockNum] = false; } } // Really delete the PHI instruction now! delete MPhi; + ++NumAtomic; }