#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AliasAnalysis.h"
+#include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineLoopInfo.h"
#include "llvm/CodeGen/MachinePostDominators.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetInstrInfo.h"
-#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Target/TargetSubtargetInfo.h"
using namespace llvm;
cl::desc("Split critical edges during machine sinking"),
cl::init(true), cl::Hidden);
+static cl::opt<bool>
+UseBlockFreqInfo("machine-sink-bfi",
+ cl::desc("Use block frequency info to find successors to sink"),
+ cl::init(true), cl::Hidden);
+
+
STATISTIC(NumSunk, "Number of machine instructions sunk");
STATISTIC(NumSplit, "Number of critical edges split");
STATISTIC(NumCoalesces, "Number of copies coalesced");
MachineDominatorTree *DT; // Machine dominator tree
MachinePostDominatorTree *PDT; // Machine post dominator tree
MachineLoopInfo *LI;
+ const MachineBlockFrequencyInfo *MBFI;
AliasAnalysis *AA;
// Remember which edges have been considered for breaking.
AU.addPreserved<MachineDominatorTree>();
AU.addPreserved<MachinePostDominatorTree>();
AU.addPreserved<MachineLoopInfo>();
+ if (UseBlockFreqInfo)
+ AU.addRequired<MachineBlockFrequencyInfo>();
}
void releaseMemory() override {
DEBUG(dbgs() << "*** to: " << *MI);
MRI->replaceRegWith(DstReg, SrcReg);
MI->eraseFromParent();
+
+ // Conservatively, clear any kill flags, since it's possible that they are no
+ // longer correct.
+ MRI->clearKillFlags(SrcReg);
+
++NumCoalesces;
return true;
}
DEBUG(dbgs() << "******** Machine Sinking ********\n");
- const TargetMachine &TM = MF.getTarget();
- TII = TM.getSubtargetImpl()->getInstrInfo();
- TRI = TM.getSubtargetImpl()->getRegisterInfo();
+ TII = MF.getSubtarget().getInstrInfo();
+ TRI = MF.getSubtarget().getRegisterInfo();
MRI = &MF.getRegInfo();
DT = &getAnalysis<MachineDominatorTree>();
PDT = &getAnalysis<MachinePostDominatorTree>();
LI = &getAnalysis<MachineLoopInfo>();
+ MBFI = UseBlockFreqInfo ? &getAnalysis<MachineBlockFrequencyInfo>() : nullptr;
AA = &getAnalysis<AliasAnalysis>();
bool EverMadeChange = false;
if (!PDT->dominates(SuccToSinkTo, MBB))
return true;
+ // It is profitable to sink an instruction from a deeper loop to a shallower
+ // loop, even if the latter post-dominates the former (PR21115).
+ if (LI->getLoopDepth(MBB) > LI->getLoopDepth(SuccToSinkTo))
+ return true;
+
// Check if only use in post dominated block is PHI instruction.
bool NonPHIUse = false;
for (MachineInstr &UseInst : MRI->use_nodbg_instructions(Reg)) {
}
// Otherwise, we should look at all the successors and decide which one
- // we should sink to.
- // We give successors with smaller loop depth higher priority.
- SmallVector<MachineBasicBlock*, 4> Succs(MBB->succ_begin(), MBB->succ_end());
- // Sort Successors according to their loop depth.
+ // we should sink to. If we have reliable block frequency information
+ // (frequency != 0) available, give successors with smaller frequencies
+ // higher priority, otherwise prioritize smaller loop depths.
+ SmallVector<MachineBasicBlock*, 4> Succs(MBB->succ_begin(),
+ MBB->succ_end());
+ // Sort Successors according to their loop depth or block frequency info.
std::stable_sort(
Succs.begin(), Succs.end(),
- [this](const MachineBasicBlock *LHS, const MachineBasicBlock *RHS) {
- return LI->getLoopDepth(LHS) < LI->getLoopDepth(RHS);
+ [this](const MachineBasicBlock *L, const MachineBasicBlock *R) {
+ uint64_t LHSFreq = MBFI ? MBFI->getBlockFreq(L).getFrequency() : 0;
+ uint64_t RHSFreq = MBFI ? MBFI->getBlockFreq(R).getFrequency() : 0;
+ bool HasBlockFreq = LHSFreq != 0 && RHSFreq != 0;
+ return HasBlockFreq ? LHSFreq < RHSFreq
+ : LI->getLoopDepth(L) < LI->getLoopDepth(R);
});
for (SmallVectorImpl<MachineBasicBlock *>::iterator SI = Succs.begin(),
E = Succs.end(); SI != E; ++SI) {
++MachineBasicBlock::iterator(DbgMI));
}
- // When sinking the instruction the live time of its operands can be extended
- // bejond their original last use (marked with a kill flag). Conservatively
- // clear the kill flag in all instructions that use the same operand
- // registers.
- for (auto &MO : MI->uses())
- if (MO.isReg() && MO.isUse()) {
- // Preserve the kill flag for this instruction.
- bool IsKill = MO.isKill();
- // Clear the kill flag in all instruction that use this operand.
- MRI->clearKillFlags(MO.getReg());
- // Restore the kill flag for only this instruction.
- MO.setIsKill(IsKill);
- }
+ // Conservatively, clear any kill flags, since it's possible that they are no
+ // longer correct.
+ MI->clearKillInfo();
return true;
}