When a live virtual register is being clobbered by an implicit def, it is spilled
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
diff --git a/lib/CodeGen/RegAllocLocal.cpp b/lib/CodeGen/RegAllocLocal.cpp
index 3654efd..4ed1849 100644
--- a/lib/CodeGen/RegAllocLocal.cpp
+++ b/lib/CodeGen/RegAllocLocal.cpp
@@ -86,6 +86,16 @@
//
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 @@
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 @@
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 @@
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 @@
// 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 @@
PhysRegsUsed.clear();
VirtRegModified.clear();
Virt2PhysRegMap.clear();
+ Virt2LastUseMap.clear();
return true;
}