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When a live virtual register is being clobbered by an implicit def, it is spilled

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and the spill is its kill. However, if the local allocator has determined the
register has not been modified (possible when its value was reloaded), it would
not issue a restore. In that case, mark the last use of the virtual register as
kill.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@46111 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng
2008-01-17 02:08:17 +00:00
parent ab04e13a1f
commit 839b759c38
2 changed files with 55 additions and 2 deletions
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22
lib/CodeGen/RegAllocLocal.cpp
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@ -86,6 +86,16 @@ namespace {
//
std::vector<unsigned> PhysRegsUseOrder;
// Virt2LastUseMap - This maps each virtual register to its last use
// (MachineInstr*, operand index pair).
IndexedMap<std::pair<MachineInstr*, unsigned>, VirtReg2IndexFunctor>
Virt2LastUseMap;
std::pair<MachineInstr*,unsigned>& getVirtRegLastUse(unsigned Reg) {
assert(MRegisterInfo::isVirtualRegister(Reg) && "Illegal VirtReg!");
return Virt2LastUseMap[Reg];
}
// VirtRegModified - This bitset contains information about which virtual
// registers need to be spilled back to memory when their registers are
// scavenged. If a virtual register has simply been rematerialized, there
@ -282,8 +292,12 @@ void RALocal::spillVirtReg(MachineBasicBlock &MBB,
const TargetInstrInfo* TII = MBB.getParent()->getTarget().getInstrInfo();
if (!isVirtRegModified(VirtReg))
if (!isVirtRegModified(VirtReg)) {
DOUT << " which has not been modified, so no store necessary!";
std::pair<MachineInstr*, unsigned> &LastUse = getVirtRegLastUse(VirtReg);
if (LastUse.first)
LastUse.first->getOperand(LastUse.second).setIsKill();
}
// Otherwise, there is a virtual register corresponding to this physical
// register. We only need to spill it into its stack slot if it has been
@ -507,6 +521,7 @@ MachineInstr *RALocal::reloadVirtReg(MachineBasicBlock &MBB, MachineInstr *MI,
MF->getRegInfo().setPhysRegUsed(PhysReg);
MI->getOperand(OpNum).setReg(PhysReg); // Assign the input register
getVirtRegLastUse(VirtReg) = std::make_pair(MI, OpNum);
return MI;
}
@ -722,6 +737,7 @@ void RALocal::AllocateBasicBlock(MachineBasicBlock &MBB) {
DestPhysReg = getReg(MBB, MI, DestVirtReg);
MF->getRegInfo().setPhysRegUsed(DestPhysReg);
markVirtRegModified(DestVirtReg);
getVirtRegLastUse(DestVirtReg) = std::make_pair((MachineInstr*)0, 0);
MI->getOperand(i).setReg(DestPhysReg); // Assign the output register
}
}
@ -823,7 +839,8 @@ bool RALocal::runOnMachineFunction(MachineFunction &Fn) {
// mapping for all virtual registers
unsigned LastVirtReg = MF->getRegInfo().getLastVirtReg();
Virt2PhysRegMap.grow(LastVirtReg);
VirtRegModified.resize(LastVirtReg-MRegisterInfo::FirstVirtualRegister);
Virt2LastUseMap.grow(LastVirtReg);
VirtRegModified.resize(LastVirtReg+1-MRegisterInfo::FirstVirtualRegister);
// Loop over all of the basic blocks, eliminating virtual register references
for (MachineFunction::iterator MBB = Fn.begin(), MBBe = Fn.end();
@ -834,6 +851,7 @@ bool RALocal::runOnMachineFunction(MachineFunction &Fn) {
PhysRegsUsed.clear();
VirtRegModified.clear();
Virt2PhysRegMap.clear();
Virt2LastUseMap.clear();
return true;
}