From 927ce5dfaea00453889080cd1c6daf3eb197ad74 Mon Sep 17 00:00:00 2001 From: Chris Lattner Date: Mon, 12 May 2003 03:55:21 +0000 Subject: [PATCH] * Fix several comments * Update LiveVar info better, fixing bug: Jello/2003-05-11-PHIRegAllocBug.ll git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@6110 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/CodeGen/PHIElimination.cpp | 43 +++++++++++++++++++++++++++++----- 1 file changed, 37 insertions(+), 6 deletions(-) diff --git a/lib/CodeGen/PHIElimination.cpp b/lib/CodeGen/PHIElimination.cpp index 1bb6332c6e4..38ee5e9192c 100644 --- a/lib/CodeGen/PHIElimination.cpp +++ b/lib/CodeGen/PHIElimination.cpp @@ -71,7 +71,7 @@ bool PNE::EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB) { const TargetRegisterClass *RC = MF.getSSARegMap()->getRegClass(DestReg); unsigned IncomingReg = MF.getSSARegMap()->createVirtualRegister(RC); - // Insert a register to register copy in the top of the current block (by + // Insert a register to register copy in the top of the current block (but // after any remaining phi nodes) which copies the new incoming register // into the phi node destination. // @@ -79,18 +79,47 @@ bool PNE::EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB) { if (AfterPHIsIt != MBB.end()) while ((*AfterPHIsIt)->getOpcode() == TargetInstrInfo::PHI) ++AfterPHIsIt; RegInfo->copyRegToReg(MBB, AfterPHIsIt, DestReg, IncomingReg, RC); + + // Update live variable information if there is any... + if (LV) { + MachineInstr *PHICopy = *(AfterPHIsIt-1); - // Add information to LiveVariables to know that the incoming value is dead - if (LV) LV->addVirtualRegisterKill(IncomingReg, *(AfterPHIsIt-1)); + // Add information to LiveVariables to know that the incoming value is + // dead. This says that the register is dead, not killed, because we + // cannot use the live variable information to indicate that the variable + // is defined in multiple entry blocks. Instead, we pretend that this + // instruction defined it and killed it at the same time. + // + LV->addVirtualRegisterDead(IncomingReg, PHICopy); - // Now loop over all of the incoming arguments turning them into copies into + // 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... + // + std::pair + RKs = LV->killed_range(MI); + if (RKs.first != RKs.second) { + for (LiveVariables::killed_iterator I = RKs.first; I != RKs.second; ++I) + LV->addVirtualRegisterKilled(I->second, PHICopy); + LV->removeVirtualRegistersKilled(RKs.first, RKs.second); + } + + RKs = LV->dead_range(MI); + if (RKs.first != RKs.second) { + for (LiveVariables::killed_iterator I = RKs.first; I != RKs.second; ++I) + LV->addVirtualRegisterDead(I->second, PHICopy); + LV->removeVirtualRegistersDead(RKs.first, RKs.second); + } + } + + // 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); // Get the MachineBasicBlock equivalent of the BasicBlock that is the - // source path the phi + // source path the PHI. MachineBasicBlock &opBlock = *MI->getOperand(i).getMachineBasicBlock(); // Check to make sure we haven't already emitted the copy for this block. @@ -99,7 +128,9 @@ bool PNE::EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB) { // all incoming values are guaranteed to be the same for a particular bb. // // Note that this is N^2 in the number of phi node entries, but since the - // # of entries is tiny, this is not a problem. + // # of entries is usually small, this is not a problem. FIXME: this + // should just check to see if there is already a copy in the bottom of + // this basic block! // bool HaveNotEmitted = true; for (int op = MI->getNumOperands() - 1; op != i; op -= 2)