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Add more comments... err debug statements to the fast allocator.

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llvm-svn: 129400
This commit is contained in:
Eric Christopher 2011-04-12 22:17:44 +00:00
parent aa5a552f10
commit 553418ccd4
1 changed files with 16 additions and 3 deletions
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19
lib/CodeGen/RegAllocFast.cpp
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@ -420,20 +420,25 @@ void RAFast::definePhysReg(MachineInstr *MI, unsigned PhysReg,
// can be allocated directly.
// Returns spillImpossible when PhysReg or an alias can't be spilled.
unsigned RAFast::calcSpillCost(unsigned PhysReg) const {
if (UsedInInstr.test(PhysReg))
if (UsedInInstr.test(PhysReg)) {
DEBUG(dbgs() << "PhysReg: " << PhysReg << " is already used in instr.\n");
return spillImpossible;
}
switch (unsigned VirtReg = PhysRegState[PhysReg]) {
case regDisabled:
break;
case regFree:
return 0;
case regReserved:
DEBUG(dbgs() << "VirtReg: " << VirtReg << " corresponding to PhysReg: "
<< PhysReg << " is reserved already.\n");
return spillImpossible;
default:
return LiveVirtRegs.lookup(VirtReg).Dirty ? spillDirty : spillClean;
}
// This is a disabled register, add up cost of aliases.
DEBUG(dbgs() << "\tRegister: " << PhysReg << " is disabled.\n");
unsigned Cost = 0;
for (const unsigned *AS = TRI->getAliasSet(PhysReg);
unsigned Alias = *AS; ++AS) {
@ -511,9 +516,14 @@ void RAFast::allocVirtReg(MachineInstr *MI, LiveRegEntry &LRE, unsigned Hint) {
unsigned BestReg = 0, BestCost = spillImpossible;
for (TargetRegisterClass::iterator I = AOB; I != AOE; ++I) {
if (!Allocatable.test(*I))
if (!Allocatable.test(*I)) {
DEBUG(dbgs() << "\tRegister " << *I << " is not allocatable.\n");
continue;
}
unsigned Cost = calcSpillCost(*I);
DEBUG(dbgs() << "\tRegister: " << *I << "\n");
DEBUG(dbgs() << "\tCost: " << Cost << "\n");
DEBUG(dbgs() << "\tBestCost: " << BestCost << "\n");
// Cost is 0 when all aliases are already disabled.
if (Cost == 0)
return assignVirtToPhysReg(LRE, *I);
@ -722,9 +732,12 @@ void RAFast::handleThroughOperands(MachineInstr *MI,
if (!MO.isReg() || (MO.isDef() && !MO.isEarlyClobber())) continue;
unsigned Reg = MO.getReg();
if (!Reg || !TargetRegisterInfo::isPhysicalRegister(Reg)) continue;
DEBUG(dbgs() << "\tSetting reg " << Reg << " as used in instr\n");
UsedInInstr.set(Reg);
for (const unsigned *AS = TRI->getAliasSet(Reg); *AS; ++AS)
for (const unsigned *AS = TRI->getAliasSet(Reg); *AS; ++AS) {
DEBUG(dbgs() << "\tSetting alias reg " << *AS << " as used in instr\n");
UsedInInstr.set(*AS);
}
}
// Also mark PartialDefs as used to avoid reallocation.