X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FCodeGen%2FPHIElimination.cpp;h=4df9a92bb459e0f82863e4fd44e3b00e23177ed6;hb=1484089bbf960f7191215dfa6c0bb51c8e30794e;hp=afb87e501f2d798cb35373abae5b9fb64b61a019;hpb=1cbe4d0ad0888e50858cca83cf2a0d3083709513;p=oota-llvm.git diff --git a/lib/CodeGen/PHIElimination.cpp b/lib/CodeGen/PHIElimination.cpp index afb87e501f2..4df9a92bb45 100644 --- a/lib/CodeGen/PHIElimination.cpp +++ b/lib/CodeGen/PHIElimination.cpp @@ -13,15 +13,16 @@ // //===----------------------------------------------------------------------===// +#include "llvm/CodeGen/Passes.h" #include "llvm/CodeGen/MachineFunctionPass.h" #include "llvm/CodeGen/MachineInstr.h" #include "llvm/CodeGen/SSARegMap.h" #include "llvm/CodeGen/LiveVariables.h" #include "llvm/Target/TargetInstrInfo.h" #include "llvm/Target/TargetMachine.h" -#include "llvm/Support/CFG.h" - -namespace llvm { +#include "Support/DenseMap.h" +#include "Support/STLExtras.h" +using namespace llvm; namespace { struct PNE : public MachineFunctionPass { @@ -55,28 +56,52 @@ namespace { } -const PassInfo *PHIEliminationID = X.getPassInfo(); +const PassInfo *llvm::PHIEliminationID = X.getPassInfo(); /// EliminatePHINodes - Eliminate phi nodes by inserting copy instructions in /// predecessor basic blocks. /// bool PNE::EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB) { - if (MBB.empty() || MBB.front()->getOpcode() != TargetInstrInfo::PHI) + if (MBB.empty() || MBB.front().getOpcode() != TargetInstrInfo::PHI) return false; // Quick exit for normal case... LiveVariables *LV = getAnalysisToUpdate(); - const TargetInstrInfo &MII = MF.getTarget().getInstrInfo(); + const TargetInstrInfo &MII = *MF.getTarget().getInstrInfo(); const MRegisterInfo *RegInfo = MF.getTarget().getRegisterInfo(); - while (MBB.front()->getOpcode() == TargetInstrInfo::PHI) { - MachineInstr *MI = MBB.front(); - // Unlink the PHI node from the basic block... but don't delete the PHI yet - MBB.erase(MBB.begin()); + // VRegPHIUseCount - Keep track of the number of times each virtual register + // is used by PHI nodes in successors of this block. + 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()]++; + } - assert(MRegisterInfo::isVirtualRegister(MI->getOperand(0).getReg()) && + // Get an iterator to the first instruction after the last PHI node (this may + // also be the end of the basic block). While we are scanning the PHIs, + // populate the VRegPHIUseCount map. + MachineBasicBlock::iterator AfterPHIsIt = MBB.begin(); + while (AfterPHIsIt != MBB.end() && + AfterPHIsIt->getOpcode() == TargetInstrInfo::PHI) + ++AfterPHIsIt; // Skip over all of the PHI nodes... + + while (MBB.front().getOpcode() == TargetInstrInfo::PHI) { + // Unlink the PHI node from the basic block, but don't delete the PHI yet. + MachineInstr *MPhi = MBB.remove(MBB.begin()); + + assert(MRegisterInfo::isVirtualRegister(MPhi->getOperand(0).getReg()) && "PHI node doesn't write virt reg?"); - unsigned DestReg = MI->getOperand(0).getAllocatedRegNum(); + unsigned DestReg = MPhi->getOperand(0).getReg(); // Create a new register for the incoming PHI arguments const TargetRegisterClass *RC = MF.getSSARegMap()->getRegClass(DestReg); @@ -86,78 +111,55 @@ bool PNE::EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB) { // after any remaining phi nodes) which copies the new incoming register // into the phi node destination. // - MachineBasicBlock::iterator AfterPHIsIt = MBB.begin(); - while (AfterPHIsIt != MBB.end() && - (*AfterPHIsIt)->getOpcode() == TargetInstrInfo::PHI) - ++AfterPHIsIt; // Skip over all of the PHI nodes... RegInfo->copyRegToReg(MBB, AfterPHIsIt, DestReg, IncomingReg, RC); // Update live variable information if there is any... if (LV) { - MachineInstr *PHICopy = *(AfterPHIsIt-1); + MachineInstr *PHICopy = prior(AfterPHIsIt); // Add information to LiveVariables to know that the incoming value is // killed. Note that because the value is defined in several places (once // each for each incoming block), the "def" block and instruction fields // for the VarInfo is not filled in. // - LV->addVirtualRegisterKilled(IncomingReg, &MBB, PHICopy); + LV->addVirtualRegisterKilled(IncomingReg, PHICopy); // Since we are going to be deleting the PHI node, if it is the last use // of any registers, or if the value itself is dead, we need to move this - // information over to the new copy we just inserted... + // information over to the new copy we just inserted. // std::pair - RKs = LV->killed_range(MI); + RKs = LV->killed_range(MPhi); std::vector > Range; - if (RKs.first != RKs.second) { - // Copy the range into a vector... - Range.assign(RKs.first, RKs.second); - - // Delete the range... + if (RKs.first != RKs.second) // Delete the range. LV->removeVirtualRegistersKilled(RKs.first, RKs.second); - // Add all of the kills back, which will update the appropriate info... - for (unsigned i = 0, e = Range.size(); i != e; ++i) - LV->addVirtualRegisterKilled(Range[i].second, &MBB, PHICopy); - } - - RKs = LV->dead_range(MI); + RKs = LV->dead_range(MPhi); if (RKs.first != RKs.second) { // Works as above... Range.assign(RKs.first, RKs.second); LV->removeVirtualRegistersDead(RKs.first, RKs.second); for (unsigned i = 0, e = Range.size(); i != e; ++i) - LV->addVirtualRegisterDead(Range[i].second, &MBB, PHICopy); + LV->addVirtualRegisterDead(Range[i].second, PHICopy); } } + // Adjust the VRegPHIUseCount map to account for the removal of this PHI + // node. + for (unsigned i = 1; i != MPhi->getNumOperands(); i += 2) + VRegPHIUseCount[MPhi->getOperand(i).getReg()] -= BBIsSuccOfPreds; + // Now loop over all of the incoming arguments, changing them to copy into // the IncomingReg register in the corresponding predecessor basic block. // - for (int i = MI->getNumOperands() - 1; i >= 2; i-=2) { - MachineOperand &opVal = MI->getOperand(i-1); + for (int i = MPhi->getNumOperands() - 1; i >= 2; i-=2) { + MachineOperand &opVal = MPhi->getOperand(i-1); // Get the MachineBasicBlock equivalent of the BasicBlock that is the // source path the PHI. - MachineBasicBlock &opBlock = *MI->getOperand(i).getMachineBasicBlock(); + MachineBasicBlock &opBlock = *MPhi->getOperand(i).getMachineBasicBlock(); - // Figure out where to insert the copy, which is at the end of the - // predecessor basic block, but before any terminator/branch - // instructions... - MachineBasicBlock::iterator I = opBlock.end(); - if (I != opBlock.begin()) { // Handle empty blocks - --I; - // must backtrack over ALL the branches in the previous block - while (MII.isTerminatorInstr((*I)->getOpcode()) && - I != opBlock.begin()) - --I; - - // move back to the first branch instruction so new instructions - // are inserted right in front of it and not in front of a non-branch - if (!MII.isTerminatorInstr((*I)->getOpcode())) - ++I; - } + 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 @@ -171,7 +173,7 @@ bool PNE::EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB) { bool HaveNotEmitted = true; if (I != opBlock.begin()) { - MachineInstr *PrevInst = *(I-1); + 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) @@ -210,14 +212,12 @@ bool PNE::EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB) { // at an appropriate point later. // bool ValueIsLive = false; - const BasicBlock *BB = opBlock.getBasicBlock(); - for (succ_const_iterator SI = succ_begin(BB), E = succ_end(BB); - SI != E && !ValueIsLive; ++SI) { - const std::pair & - SuccInfo = LV->getBasicBlockInfo(*SI); + 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 = SuccInfo.second; + unsigned SuccIdx = SuccMBB->getNumber(); if (SuccIdx < InRegVI.AliveBlocks.size() && InRegVI.AliveBlocks[SuccIdx]) { ValueIsLive = true; @@ -225,43 +225,36 @@ bool PNE::EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB) { } // Is it killed in this successor? - MachineBasicBlock *MBB = SuccInfo.first; for (unsigned i = 0, e = InRegVI.Kills.size(); i != e; ++i) - if (InRegVI.Kills[i].first == MBB) { + if (InRegVI.Kills[i]->getParent() == SuccMBB) { ValueIsLive = true; break; } // Is it used by any PHI instructions in this block? - if (ValueIsLive) break; - - // Loop over all of the PHIs in this successor, checking to see if - // the register is being used... - for (MachineBasicBlock::iterator BBI = MBB->begin(), E=MBB->end(); - BBI != E && (*BBI)->getOpcode() == TargetInstrInfo::PHI; - ++BBI) - for (unsigned i = 1, e = (*BBI)->getNumOperands(); i < e; i += 2) - if ((*BBI)->getOperand(i).getReg() == SrcReg) { - ValueIsLive = true; - break; - } + 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) - LV->addVirtualRegisterKilled(SrcReg, &opBlock, *(I-1)); + 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 MI; + // Really delete the PHI instruction now! + delete MPhi; } - return true; } - -} // End llvm namespace