//===----------------------------------------------------------------------===//
//
// This file implements the machine register scavenger. It can provide
-// information such as unused register at any point in a machine basic block.
-// It also provides a mechanism to make registers availbale by evicting them
-// to spill slots.
+// information, such as unused registers, at any point in a machine basic block.
+// It also provides a mechanism to make registers available by evicting them to
+// spill slots.
//
//===----------------------------------------------------------------------===//
#include "llvm/ADT/STLExtras.h"
using namespace llvm;
+/// RedefinesSuperRegPart - Return true if the specified register is redefining
+/// part of a super-register.
+static bool RedefinesSuperRegPart(const MachineInstr *MI, unsigned SubReg,
+ const TargetRegisterInfo *TRI) {
+ for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+ const MachineOperand &MO = MI->getOperand(i);
+ if (!MO.isRegister() || !MO.isUse())
+ continue;
+ if (TRI->isSuperRegister(SubReg, MO.getReg()))
+ return true;
+ }
+
+ return false;
+}
+
+static bool RedefinesSuperRegPart(const MachineInstr *MI,
+ const MachineOperand &MO,
+ const TargetRegisterInfo *TRI) {
+ assert(MO.isRegister() && MO.isDef() && "Not a register def!");
+ return RedefinesSuperRegPart(MI, MO.getReg(), TRI);
+}
+
/// setUsed - Set the register and its sub-registers as being used.
void RegScavenger::setUsed(unsigned Reg) {
RegsAvailable.reset(Reg);
}
/// setUnused - Set the register and its sub-registers as being unused.
-void RegScavenger::setUnused(unsigned Reg) {
+void RegScavenger::setUnused(unsigned Reg, const MachineInstr *MI) {
RegsAvailable.set(Reg);
for (const unsigned *SubRegs = TRI->getSubRegisters(Reg);
unsigned SubReg = *SubRegs; ++SubRegs)
- RegsAvailable.set(SubReg);
+ if (!RedefinesSuperRegPart(MI, Reg, TRI))
+ RegsAvailable.set(SubReg);
}
void RegScavenger::enterBasicBlock(MachineBasicBlock *mbb) {
if (MO.isKill() && !isReserved(Reg)) {
ChangedRegs.set(Reg);
+ // Mark sub-registers as changed if they aren't defined in the same
+ // instruction.
for (const unsigned *SubRegs = TRI->getSubRegisters(Reg);
unsigned SubReg = *SubRegs; ++SubRegs)
- ChangedRegs.set(SubReg);
+ if (!RedefinesSuperRegPart(MI, Reg, TRI))
+ ChangedRegs.set(SubReg);
}
}
// If it's dead upon def, then it is now free.
if (MO.isDead()) {
- setUnused(Reg);
+ setUnused(Reg, MI);
continue;
}
continue;
}
+ // Skip is this is merely redefining part of a super-register.
+ if (RedefinesSuperRegPart(MI, MO, TRI))
+ continue;
+
assert((isUnused(Reg) || isReserved(Reg)) &&
"Re-defining a live register!");
setUsed(Reg);
unsigned Reg = MO.getReg();
assert(isUsed(Reg));
if (!isReserved(Reg))
- setUnused(Reg);
+ setUnused(Reg, MI);
}
// Process uses.