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Refactor the code for unfolding a load into a separate function.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@85515 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2009-10-29 17:47:20 +00:00
parent a33ac6a4c1
commit 5c95230f25
1 changed files with 62 additions and 50 deletions
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112
lib/CodeGen/MachineLICM.cpp
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@ -105,6 +105,12 @@ namespace {
///
void HoistRegion(MachineDomTreeNode *N);
/// ExtractHoistableLoad - Unfold a load from the given machineinstr if
/// the load itself could be hoisted. Return the unfolded and hoistable
/// load, or null if the load couldn't be unfolded or if it wouldn't
/// be hoistable.
MachineInstr *ExtractHoistableLoad(MachineInstr *MI);
/// Hoist - When an instruction is found to only use loop invariant operands
/// that is safe to hoist, this instruction is called to do the dirty work.
///
@ -369,62 +375,68 @@ static const MachineInstr *LookForDuplicate(const MachineInstr *MI,
return 0;
}
MachineInstr *MachineLICM::ExtractHoistableLoad(MachineInstr *MI) {
// If not, we may be able to unfold a load and hoist that.
// First test whether the instruction is loading from an amenable
// memory location.
if (!MI->getDesc().mayLoad()) return 0;
if (!MI->hasOneMemOperand()) return 0;
MachineMemOperand *MMO = *MI->memoperands_begin();
if (MMO->isVolatile()) return 0;
MachineFunction &MF = *MI->getParent()->getParent();
if (!MMO->getValue()) return 0;
if (const PseudoSourceValue *PSV =
dyn_cast<PseudoSourceValue>(MMO->getValue())) {
if (!PSV->isConstant(MF.getFrameInfo())) return 0;
} else {
if (!AA->pointsToConstantMemory(MMO->getValue())) return 0;
}
// Next determine the register class for a temporary register.
unsigned NewOpc =
TII->getOpcodeAfterMemoryUnfold(MI->getOpcode(),
/*UnfoldLoad=*/true,
/*UnfoldStore=*/false);
if (NewOpc == 0) return 0;
const TargetInstrDesc &TID = TII->get(NewOpc);
if (TID.getNumDefs() != 1) return 0;
const TargetRegisterClass *RC = TID.OpInfo[0].getRegClass(TRI);
// Ok, we're unfolding. Create a temporary register and do the unfold.
unsigned Reg = RegInfo->createVirtualRegister(RC);
SmallVector<MachineInstr *, 2> NewMIs;
bool Success =
TII->unfoldMemoryOperand(MF, MI, Reg,
/*UnfoldLoad=*/true, /*UnfoldStore=*/false,
NewMIs);
(void)Success;
assert(Success &&
"unfoldMemoryOperand failed when getOpcodeAfterMemoryUnfold "
"succeeded!");
assert(NewMIs.size() == 2 &&
"Unfolded a load into multiple instructions!");
MachineBasicBlock *MBB = MI->getParent();
MBB->insert(MI, NewMIs[0]);
MBB->insert(MI, NewMIs[1]);
// If unfolding produced a load that wasn't loop-invariant or profitable to
// hoist, discard the new instructions and bail.
if (!IsLoopInvariantInst(*NewMIs[0]) || !IsProfitableToHoist(*NewMIs[0])) {
NewMIs[0]->eraseFromParent();
NewMIs[1]->eraseFromParent();
return 0;
}
// Otherwise we successfully unfolded a load that we can hoist.
MI->eraseFromParent();
return NewMIs[0];
}
/// Hoist - When an instruction is found to use only loop invariant operands
/// that are safe to hoist, this instruction is called to do the dirty work.
///
void MachineLICM::Hoist(MachineInstr *MI) {
// First check whether we should hoist this instruction.
if (!IsLoopInvariantInst(*MI) || !IsProfitableToHoist(*MI)) {
// If not, we may be able to unfold a load and hoist that.
// First test whether the instruction is loading from an amenable
// memory location.
if (!MI->getDesc().mayLoad()) return;
if (!MI->hasOneMemOperand()) return;
MachineMemOperand *MMO = *MI->memoperands_begin();
if (MMO->isVolatile()) return;
MachineFunction &MF = *MI->getParent()->getParent();
if (!MMO->getValue()) return;
if (const PseudoSourceValue *PSV =
dyn_cast<PseudoSourceValue>(MMO->getValue())) {
if (!PSV->isConstant(MF.getFrameInfo())) return;
} else {
if (!AA->pointsToConstantMemory(MMO->getValue())) return;
}
// Next determine the register class for a temporary register.
unsigned NewOpc =
TII->getOpcodeAfterMemoryUnfold(MI->getOpcode(),
/*UnfoldLoad=*/true,
/*UnfoldStore=*/false);
if (NewOpc == 0) return;
const TargetInstrDesc &TID = TII->get(NewOpc);
if (TID.getNumDefs() != 1) return;
const TargetRegisterClass *RC = TID.OpInfo[0].getRegClass(TRI);
// Ok, we're unfolding. Create a temporary register and do the unfold.
unsigned Reg = RegInfo->createVirtualRegister(RC);
SmallVector<MachineInstr *, 2> NewMIs;
bool Success =
TII->unfoldMemoryOperand(MF, MI, Reg,
/*UnfoldLoad=*/true, /*UnfoldStore=*/false,
NewMIs);
(void)Success;
assert(Success &&
"unfoldMemoryOperand failed when getOpcodeAfterMemoryUnfold "
"succeeded!");
assert(NewMIs.size() == 2 &&
"Unfolded a load into multiple instructions!");
MachineBasicBlock *MBB = MI->getParent();
MBB->insert(MI, NewMIs[0]);
MBB->insert(MI, NewMIs[1]);
// If unfolding produced a load that wasn't loop-invariant or profitable to
// hoist, discard the new instructions and bail.
if (!IsLoopInvariantInst(*NewMIs[0]) || !IsProfitableToHoist(*NewMIs[0])) {
NewMIs[0]->eraseFromParent();
NewMIs[1]->eraseFromParent();
return;
}
// Otherwise we successfully unfolded a load that we can hoist.
MI->eraseFromParent();
MI = NewMIs[0];
// If not, try unfolding a hoistable load.
MI = ExtractHoistableLoad(MI);
if (!MI) return;
}
// Now move the instructions to the predecessor, inserting it before any