diff --git a/llvm/lib/CodeGen/PrologEpilogInserter.cpp b/llvm/lib/CodeGen/PrologEpilogInserter.cpp index 734bf6325265..66138f6782cb 100644 --- a/llvm/lib/CodeGen/PrologEpilogInserter.cpp +++ b/llvm/lib/CodeGen/PrologEpilogInserter.cpp @@ -793,38 +793,6 @@ void PEI::replaceFrameIndices(MachineFunction &Fn) { } } -/// findLastUseReg - find the killing use of the specified register within -/// the instruciton range. Return the operand number of the kill in Operand. -static MachineBasicBlock::iterator -findLastUseReg(MachineBasicBlock::iterator I, MachineBasicBlock::iterator ME, - unsigned Reg) { - // Scan forward to find the last use of this virtual register - for (++I; I != ME; ++I) { - MachineInstr *MI = I; - bool isDefInsn = false; - bool isKillInsn = false; - for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) - if (MI->getOperand(i).isReg()) { - unsigned OpReg = MI->getOperand(i).getReg(); - if (OpReg == 0 || !TargetRegisterInfo::isVirtualRegister(OpReg)) - continue; - assert (OpReg == Reg - && "overlapping use of scavenged index register!"); - // If this is the killing use, we have a candidate. - if (MI->getOperand(i).isKill()) - isKillInsn = true; - else if (MI->getOperand(i).isDef()) - isDefInsn = true; - } - if (isKillInsn && !isDefInsn) - return I; - } - // If we hit the end of the basic block, there was no kill of - // the virtual register, which is wrong. - assert (0 && "scavenged index register never killed!"); - return ME; -} - /// scavengeFrameVirtualRegs - Replace all frame index virtual registers /// with physical registers. Use the register scavenger to find an /// appropriate register to use. @@ -834,27 +802,14 @@ void PEI::scavengeFrameVirtualRegs(MachineFunction &Fn) { E = Fn.end(); BB != E; ++BB) { RS->enterBasicBlock(BB); - // FIXME: The logic flow in this function is still too convoluted. - // It needs a cleanup refactoring. Do that in preparation for tracking - // more than one scratch register value and using ranges to find - // available scratch registers. - unsigned CurrentVirtReg = 0; - unsigned CurrentScratchReg = 0; - bool havePrevValue = false; - TargetRegisterInfo::FrameIndexValue PrevValue(0,0); - TargetRegisterInfo::FrameIndexValue Value(0,0); - MachineInstr *PrevLastUseMI = NULL; - unsigned PrevLastUseOp = 0; - bool trackingCurrentValue = false; + unsigned VirtReg = 0; + unsigned ScratchReg = 0; int SPAdj = 0; // The instruction stream may change in the loop, so check BB->end() // directly. for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ) { MachineInstr *MI = I; - bool isDefInsn = false; - bool isKillInsn = false; - bool clobbersScratchReg = false; bool DoIncr = true; for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { if (MI->getOperand(i).isReg()) { @@ -862,124 +817,30 @@ void PEI::scavengeFrameVirtualRegs(MachineFunction &Fn) { unsigned Reg = MO.getReg(); if (Reg == 0) continue; - if (!TargetRegisterInfo::isVirtualRegister(Reg)) { - // If we have a previous scratch reg, check and see if anything - // here kills whatever value is in there. - if (Reg == CurrentScratchReg) { - if (MO.isUse()) { - // Two-address operands implicitly kill - if (MO.isKill() || MI->isRegTiedToDefOperand(i)) - clobbersScratchReg = true; - } else { - assert (MO.isDef()); - clobbersScratchReg = true; - } - } + if (!TargetRegisterInfo::isVirtualRegister(Reg)) continue; - } + ++NumVirtualFrameRegs; - // If this is a def, remember that this insn defines the value. - // This lets us properly consider insns which re-use the scratch - // register, such as r2 = sub r2, #imm, in the middle of the - // scratch range. - if (MO.isDef()) - isDefInsn = true; - // Have we already allocated a scratch register for this virtual? - if (Reg != CurrentVirtReg) { + if (Reg != VirtReg) { // When we first encounter a new virtual register, it // must be a definition. assert(MI->getOperand(i).isDef() && "frame index virtual missing def!"); - // We can't have nested virtual register live ranges because - // there's only a guarantee of one scavenged register at a time. - assert (CurrentVirtReg == 0 && - "overlapping frame index virtual registers!"); - - // If the target gave us information about what's in the register, - // we can use that to re-use scratch regs. - DenseMap::iterator Entry = - FrameConstantRegMap.find(Reg); - trackingCurrentValue = Entry != FrameConstantRegMap.end(); - if (trackingCurrentValue) { - SPAdj = (*Entry).second.second; - Value = (*Entry).second.first; - } else { - SPAdj = 0; - Value.first = 0; - Value.second = 0; - } - - // If the scratch register from the last allocation is still - // available, see if the value matches. If it does, just re-use it. - if (trackingCurrentValue && havePrevValue && PrevValue == Value) { - // FIXME: This assumes that the instructions in the live range - // for the virtual register are exclusively for the purpose - // of populating the value in the register. That's reasonable - // for these frame index registers, but it's still a very, very - // strong assumption. rdar://7322732. Better would be to - // explicitly check each instruction in the range for references - // to the virtual register. Only delete those insns that - // touch the virtual register. - - // Find the last use of the new virtual register. Remove all - // instruction between here and there, and update the current - // instruction to reference the last use insn instead. - MachineBasicBlock::iterator LastUseMI = - findLastUseReg(I, BB->end(), Reg); - - // Remove all instructions up 'til the last use, since they're - // just calculating the value we already have. - BB->erase(I, LastUseMI); - I = LastUseMI; - - // Extend the live range of the scratch register - PrevLastUseMI->getOperand(PrevLastUseOp).setIsKill(false); - RS->setUsed(CurrentScratchReg); - CurrentVirtReg = Reg; - - // We deleted the instruction we were scanning the operands of. - // Jump back to the instruction iterator loop. Don't increment - // past this instruction since we updated the iterator already. - DoIncr = false; - break; - } - // Scavenge a new scratch register - CurrentVirtReg = Reg; + VirtReg = Reg; const TargetRegisterClass *RC = Fn.getRegInfo().getRegClass(Reg); - CurrentScratchReg = RS->scavengeRegister(RC, I, SPAdj); - PrevValue = Value; + ScratchReg = RS->scavengeRegister(RC, I, SPAdj); ++NumScavengedRegs; } // replace this reference to the virtual register with the // scratch register. - assert (CurrentScratchReg && "Missing scratch register!"); - MI->getOperand(i).setReg(CurrentScratchReg); + assert (ScratchReg && "Missing scratch register!"); + MI->getOperand(i).setReg(ScratchReg); - if (MI->getOperand(i).isKill()) { - isKillInsn = true; - PrevLastUseOp = i; - PrevLastUseMI = MI; - } } } - // If this is the last use of the scratch, stop tracking it. The - // last use will be a kill operand in an instruction that does - // not also define the scratch register. - if (isKillInsn && !isDefInsn) { - CurrentVirtReg = 0; - havePrevValue = trackingCurrentValue; - } - // Similarly, notice if instruction clobbered the value in the - // register we're tracking for possible later reuse. This is noted - // above, but enforced here since the value is still live while we - // process the rest of the operands of the instruction. - if (clobbersScratchReg) { - havePrevValue = false; - CurrentScratchReg = 0; - } if (DoIncr) { RS->forward(I); ++I;