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//===- MachineCycleAnalysis.cpp - Compute CycleInfo for Machine IR --------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/MachineCycleAnalysis.h"
#include "llvm/ADT/GenericCycleImpl.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/MachineSSAContext.h"
#include "llvm/CodeGen/TargetInstrInfo.h"
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include "llvm/InitializePasses.h"
using namespace llvm;
template class llvm::GenericCycleInfo<llvm::MachineSSAContext>;
template class llvm::GenericCycle<llvm::MachineSSAContext>;
char MachineCycleInfoWrapperPass::ID = 0;
MachineCycleInfoWrapperPass::MachineCycleInfoWrapperPass()
: MachineFunctionPass(ID) {
initializeMachineCycleInfoWrapperPassPass(*PassRegistry::getPassRegistry());
}
INITIALIZE_PASS_BEGIN(MachineCycleInfoWrapperPass, "machine-cycles",
"Machine Cycle Info Analysis", true, true)
INITIALIZE_PASS_END(MachineCycleInfoWrapperPass, "machine-cycles",
"Machine Cycle Info Analysis", true, true)
void MachineCycleInfoWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesAll();
MachineFunctionPass::getAnalysisUsage(AU);
}
bool MachineCycleInfoWrapperPass::runOnMachineFunction(MachineFunction &Func) {
CI.clear();
F = &Func;
CI.compute(Func);
return false;
}
void MachineCycleInfoWrapperPass::print(raw_ostream &OS, const Module *) const {
OS << "MachineCycleInfo for function: " << F->getName() << "\n";
CI.print(OS);
}
void MachineCycleInfoWrapperPass::releaseMemory() {
CI.clear();
F = nullptr;
}
namespace {
class MachineCycleInfoPrinterPass : public MachineFunctionPass {
public:
static char ID;
MachineCycleInfoPrinterPass();
bool runOnMachineFunction(MachineFunction &F) override;
void getAnalysisUsage(AnalysisUsage &AU) const override;
};
} // namespace
char MachineCycleInfoPrinterPass::ID = 0;
MachineCycleInfoPrinterPass::MachineCycleInfoPrinterPass()
: MachineFunctionPass(ID) {
initializeMachineCycleInfoPrinterPassPass(*PassRegistry::getPassRegistry());
}
INITIALIZE_PASS_BEGIN(MachineCycleInfoPrinterPass, "print-machine-cycles",
"Print Machine Cycle Info Analysis", true, true)
INITIALIZE_PASS_DEPENDENCY(MachineCycleInfoWrapperPass)
INITIALIZE_PASS_END(MachineCycleInfoPrinterPass, "print-machine-cycles",
"Print Machine Cycle Info Analysis", true, true)
void MachineCycleInfoPrinterPass::getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesAll();
AU.addRequired<MachineCycleInfoWrapperPass>();
MachineFunctionPass::getAnalysisUsage(AU);
}
bool MachineCycleInfoPrinterPass::runOnMachineFunction(MachineFunction &F) {
auto &CI = getAnalysis<MachineCycleInfoWrapperPass>();
CI.print(errs());
return false;
}
bool llvm::isCycleInvariant(const MachineCycle *Cycle, MachineInstr &I) {
MachineFunction *MF = I.getParent()->getParent();
MachineRegisterInfo *MRI = &MF->getRegInfo();
const TargetSubtargetInfo &ST = MF->getSubtarget();
const TargetRegisterInfo *TRI = ST.getRegisterInfo();
const TargetInstrInfo *TII = ST.getInstrInfo();
// The instruction is cycle invariant if all of its operands are.
for (const MachineOperand &MO : I.operands()) {
if (!MO.isReg())
continue;
Register Reg = MO.getReg();
if (Reg == 0)
continue;
// An instruction that uses or defines a physical register can't e.g. be
// hoisted, so mark this as not invariant.
if (Reg.isPhysical()) {
if (MO.isUse()) {
// If the physreg has no defs anywhere, it's just an ambient register
// and we can freely move its uses. Alternatively, if it's allocatable,
// it could get allocated to something with a def during allocation.
// However, if the physreg is known to always be caller saved/restored
// then this use is safe to hoist.
if (!MRI->isConstantPhysReg(Reg) &&
!(TRI->isCallerPreservedPhysReg(Reg.asMCReg(), *I.getMF())) &&
!TII->isIgnorableUse(MO))
return false;
// Otherwise it's safe to move.
continue;
} else if (!MO.isDead()) {
// A def that isn't dead can't be moved.
return false;
} else if (any_of(Cycle->getEntries(),
[&](const MachineBasicBlock *Block) {
return Block->isLiveIn(Reg);
})) {
// If the reg is live into any header of the cycle we can't hoist an
// instruction which would clobber it.
return false;
}
}
if (!MO.isUse())
continue;
assert(MRI->getVRegDef(Reg) && "Machine instr not mapped for this vreg?!");
// If the cycle contains the definition of an operand, then the instruction
// isn't cycle invariant.
if (Cycle->contains(MRI->getVRegDef(Reg)->getParent()))
return false;
}
// If we got this far, the instruction is cycle invariant!
return true;
}
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