// Find out which registers are early clobbered, killed, defined, and marked
// def-dead in this instruction.
+ // FIXME: The scavenger is not predication aware. If the instruction is
+ // predicated, conservatively assume "kill" markers do not actually kill the
+ // register. Similarly ignores "dead" markers.
+ bool isPred = TII->isPredicated(MI);
BitVector EarlyClobberRegs(NumPhysRegs);
BitVector KillRegs(NumPhysRegs);
BitVector DefRegs(NumPhysRegs);
if (MO.isUse()) {
// Two-address operands implicitly kill.
- if (MO.isKill() || MI->isRegTiedToDefOperand(i))
+ if (!isPred && (MO.isKill() || MI->isRegTiedToDefOperand(i)))
addRegWithSubRegs(KillRegs, Reg);
} else {
assert(MO.isDef());
- if (MO.isDead())
+ if (!isPred && MO.isDead())
addRegWithSubRegs(DeadRegs, Reg);
else
addRegWithSubRegs(DefRegs, Reg);
return 0;
}
+/// getRegsAvailable - Return all available registers in the register class
+/// in Mask.
+void RegScavenger::getRegsAvailable(const TargetRegisterClass *RC,
+ BitVector &Mask) {
+ for (TargetRegisterClass::iterator I = RC->begin(), E = RC->end();
+ I != E; ++I)
+ if (!isAliasUsed(*I))
+ Mask.set(*I);
+}
+
/// findSurvivorReg - Return the candidate register that is unused for the
-/// longest after MBBI. UseMI is set to the instruction where the search
+/// longest after StargMII. UseMI is set to the instruction where the search
/// stopped.
///
/// No more than InstrLimit instructions are inspected.
Candidates.reset(MO.getReg());
}
+ // Try to find a register that's unused if there is one, as then we won't
+ // have to spill.
+ if ((Candidates & RegsAvailable).any())
+ Candidates &= RegsAvailable;
+
// Find the register whose use is furthest away.
MachineBasicBlock::iterator UseMI;
unsigned SReg = findSurvivorReg(I, Candidates, 25, UseMI);
- // If we found an unused register there is no reason to spill it. We have
- // probably found a callee-saved register that has been saved in the
- // prologue, but happens to be unused at this point.
+ // If we found an unused register there is no reason to spill it.
if (!isAliasUsed(SReg))
return SReg;