diff options
| -rw-r--r-- | lib/CodeGen/DeadMachineInstructionElim.cpp | 14 |
1 files changed, 8 insertions, 6 deletions
diff --git a/lib/CodeGen/DeadMachineInstructionElim.cpp b/lib/CodeGen/DeadMachineInstructionElim.cpp index 138b83d4b6..318d922ade 100644 --- a/lib/CodeGen/DeadMachineInstructionElim.cpp +++ b/lib/CodeGen/DeadMachineInstructionElim.cpp @@ -80,9 +80,8 @@ bool DeadMachineInstructionElim::runOnMachineFunction(MachineFunction &MF) { TRI = MF.getTarget().getRegisterInfo(); TII = MF.getTarget().getInstrInfo(); - // Compute a bitvector to represent all non-allocatable physregs. - BitVector NonAllocatableRegs = TRI->getAllocatableSet(MF); - NonAllocatableRegs.flip(); + // Treat reserved registers as always live. + BitVector ReservedRegs = TRI->getReservedRegs(MF); // Loop over all instructions in all blocks, from bottom to top, so that it's // more likely that chains of dependent but ultimately dead instructions will @@ -91,9 +90,8 @@ bool DeadMachineInstructionElim::runOnMachineFunction(MachineFunction &MF) { I != E; ++I) { MachineBasicBlock *MBB = &*I; - // Start out assuming that all non-allocatable registers are live - // out of this block. - LivePhysRegs = NonAllocatableRegs; + // Start out assuming that reserved registers are live out of this block. + LivePhysRegs = ReservedRegs; // Also add any explicit live-out physregs for this block. if (!MBB->empty() && MBB->back().getDesc().isReturn()) @@ -104,6 +102,10 @@ bool DeadMachineInstructionElim::runOnMachineFunction(MachineFunction &MF) { LivePhysRegs.set(Reg); } + // FIXME: Add live-ins from sucessors to LivePhysRegs. Normally, physregs + // are not live across blocks, but some targets (x86) can have flags live + // out of a block. + // Now scan the instructions and delete dead ones, tracking physreg // liveness as we go. for (MachineBasicBlock::reverse_iterator MII = MBB->rbegin(), |