//
//===----------------------------------------------------------------------===//
-#define DEBUG_TYPE "branchfolding"
#include "BranchFolding.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallSet.h"
#include <algorithm>
using namespace llvm;
+#define DEBUG_TYPE "branchfolding"
+
STATISTIC(NumDeadBlocks, "Number of dead blocks removed");
STATISTIC(NumBranchOpts, "Number of branches optimized");
STATISTIC(NumTailMerge , "Number of block tails merged");
static char ID;
explicit BranchFolderPass(): MachineFunctionPass(ID) {}
- virtual bool runOnMachineFunction(MachineFunction &MF);
+ bool runOnMachineFunction(MachineFunction &MF) override;
- virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.addRequired<TargetPassConfig>();
MachineFunctionPass::getAnalysisUsage(AU);
}
"Control Flow Optimizer", false, false)
bool BranchFolderPass::runOnMachineFunction(MachineFunction &MF) {
+ if (skipOptnoneFunction(*MF.getFunction()))
+ return false;
+
TargetPassConfig *PassConfig = &getAnalysis<TargetPassConfig>();
- BranchFolder Folder(PassConfig->getEnableTailMerge(), /*CommonHoist=*/true);
+ // TailMerge can create jump into if branches that make CFG irreducible for
+ // HW that requires structurized CFG.
+ bool EnableTailMerge = !MF.getTarget().requiresStructuredCFG() &&
+ PassConfig->getEnableTailMerge();
+ BranchFolder Folder(EnableTailMerge, /*CommonHoist=*/true);
return Folder.OptimizeFunction(MF,
MF.getTarget().getInstrInfo(),
MF.getTarget().getRegisterInfo(),
if (!I->isImplicitDef())
break;
unsigned Reg = I->getOperand(0).getReg();
- ImpDefRegs.insert(Reg);
- for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs)
+ for (MCSubRegIterator SubRegs(Reg, TRI, /*IncludeSelf=*/true);
+ SubRegs.isValid(); ++SubRegs)
ImpDefRegs.insert(*SubRegs);
++I;
}
TII = tii;
TRI = tri;
MMI = mmi;
- RS = NULL;
+ RS = nullptr;
// Use a RegScavenger to help update liveness when required.
MachineRegisterInfo &MRI = MF.getRegInfo();
// Fix CFG. The later algorithms expect it to be right.
bool MadeChange = false;
for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; I++) {
- MachineBasicBlock *MBB = I, *TBB = 0, *FBB = 0;
+ MachineBasicBlock *MBB = I, *TBB = nullptr, *FBB = nullptr;
SmallVector<MachineOperand, 4> Cond;
if (!TII->AnalyzeBranch(*MBB, TBB, FBB, Cond, true))
MadeChange |= MBB->CorrectExtraCFGEdges(TBB, FBB, !Cond.empty());
// See if any jump tables have become dead as the code generator
// did its thing.
MachineJumpTableInfo *JTI = MF.getJumpTableInfo();
- if (JTI == 0) {
+ if (!JTI) {
delete RS;
return MadeChange;
}
if (RS) {
RS->enterBasicBlock(CurMBB);
if (!CurMBB->empty())
- RS->forward(prior(CurMBB->end()));
+ RS->forward(std::prev(CurMBB->end()));
BitVector RegsLiveAtExit(TRI->getNumRegs());
RS->getRegsUsed(RegsLiveAtExit, false);
for (unsigned int i = 0, e = TRI->getNumRegs(); i != e; i++)
/// MBB so that the part before the iterator falls into the part starting at the
/// iterator. This returns the new MBB.
MachineBasicBlock *BranchFolder::SplitMBBAt(MachineBasicBlock &CurMBB,
- MachineBasicBlock::iterator BBI1) {
+ MachineBasicBlock::iterator BBI1,
+ const BasicBlock *BB) {
if (!TII->isLegalToSplitMBBAt(CurMBB, BBI1))
- return 0;
+ return nullptr;
MachineFunction &MF = *CurMBB.getParent();
// Create the fall-through block.
MachineFunction::iterator MBBI = &CurMBB;
- MachineBasicBlock *NewMBB =MF.CreateMachineBasicBlock(CurMBB.getBasicBlock());
+ MachineBasicBlock *NewMBB =MF.CreateMachineBasicBlock(BB);
CurMBB.getParent()->insert(++MBBI, NewMBB);
// Move all the successors of this block to the specified block.
static void FixTail(MachineBasicBlock *CurMBB, MachineBasicBlock *SuccBB,
const TargetInstrInfo *TII) {
MachineFunction *MF = CurMBB->getParent();
- MachineFunction::iterator I = llvm::next(MachineFunction::iterator(CurMBB));
- MachineBasicBlock *TBB = 0, *FBB = 0;
+ MachineFunction::iterator I = std::next(MachineFunction::iterator(CurMBB));
+ MachineBasicBlock *TBB = nullptr, *FBB = nullptr;
SmallVector<MachineOperand, 4> Cond;
DebugLoc dl; // FIXME: this is nowhere
if (I != MF->end() &&
if (TBB == NextBB && !Cond.empty() && !FBB) {
if (!TII->ReverseBranchCondition(Cond)) {
TII->RemoveBranch(*CurMBB);
- TII->InsertBranch(*CurMBB, SuccBB, NULL, Cond, dl);
+ TII->InsertBranch(*CurMBB, SuccBB, nullptr, Cond, dl);
return;
}
}
}
- TII->InsertBranch(*CurMBB, SuccBB, NULL,
+ TII->InsertBranch(*CurMBB, SuccBB, nullptr,
SmallVector<MachineOperand, 0>(), dl);
}
unsigned maxCommonTailLength = 0U;
SameTails.clear();
MachineBasicBlock::iterator TrialBBI1, TrialBBI2;
- MPIterator HighestMPIter = prior(MergePotentials.end());
- for (MPIterator CurMPIter = prior(MergePotentials.end()),
+ MPIterator HighestMPIter = std::prev(MergePotentials.end());
+ for (MPIterator CurMPIter = std::prev(MergePotentials.end()),
B = MergePotentials.begin();
- CurMPIter != B && CurMPIter->getHash() == CurHash;
- --CurMPIter) {
- for (MPIterator I = prior(CurMPIter); I->getHash() == CurHash ; --I) {
+ CurMPIter != B && CurMPIter->getHash() == CurHash; --CurMPIter) {
+ for (MPIterator I = std::prev(CurMPIter); I->getHash() == CurHash; --I) {
unsigned CommonTailLen;
if (ProfitableToMerge(CurMPIter->getBlock(), I->getBlock(),
minCommonTailLength,
MachineBasicBlock *SuccBB,
MachineBasicBlock *PredBB) {
MPIterator CurMPIter, B;
- for (CurMPIter = prior(MergePotentials.end()), B = MergePotentials.begin();
- CurMPIter->getHash() == CurHash;
- --CurMPIter) {
+ for (CurMPIter = std::prev(MergePotentials.end()),
+ B = MergePotentials.begin();
+ CurMPIter->getHash() == CurHash; --CurMPIter) {
// Put the unconditional branch back, if we need one.
MachineBasicBlock *CurMBB = CurMPIter->getBlock();
if (SuccBB && CurMBB != PredBB)
/// CreateCommonTailOnlyBlock - None of the blocks to be tail-merged consist
/// only of the common tail. Create a block that does by splitting one.
bool BranchFolder::CreateCommonTailOnlyBlock(MachineBasicBlock *&PredBB,
+ MachineBasicBlock *SuccBB,
unsigned maxCommonTailLength,
unsigned &commonTailIndex) {
commonTailIndex = 0;
DEBUG(dbgs() << "\nSplitting BB#" << MBB->getNumber() << ", size "
<< maxCommonTailLength);
- MachineBasicBlock *newMBB = SplitMBBAt(*MBB, BBI);
+ // If the split block unconditionally falls-thru to SuccBB, it will be
+ // merged. In control flow terms it should then take SuccBB's name. e.g. If
+ // SuccBB is an inner loop, the common tail is still part of the inner loop.
+ const BasicBlock *BB = (SuccBB && MBB->succ_size() == 1) ?
+ SuccBB->getBasicBlock() : MBB->getBasicBlock();
+ MachineBasicBlock *newMBB = SplitMBBAt(*MBB, BBI, BB);
if (!newMBB) {
DEBUG(dbgs() << "... failed!");
return false;
!SameTails[commonTailIndex].tailIsWholeBlock())) {
// None of the blocks consist entirely of the common tail.
// Split a block so that one does.
- if (!CreateCommonTailOnlyBlock(PredBB,
+ if (!CreateCommonTailOnlyBlock(PredBB, SuccBB,
maxCommonTailLength, commonTailIndex)) {
RemoveBlocksWithHash(CurHash, SuccBB, PredBB);
continue;
// See if we can do any tail merging on those.
if (MergePotentials.size() >= 2)
- MadeChange |= TryTailMergeBlocks(NULL, NULL);
+ MadeChange |= TryTailMergeBlocks(nullptr, nullptr);
// Look at blocks (IBB) with multiple predecessors (PBB).
// We change each predecessor to a canonical form, by
// a compile-time infinite loop repeatedly doing and undoing the same
// transformations.)
- for (MachineFunction::iterator I = llvm::next(MF.begin()), E = MF.end();
+ for (MachineFunction::iterator I = std::next(MF.begin()), E = MF.end();
I != E; ++I) {
if (I->pred_size() < 2) continue;
SmallPtrSet<MachineBasicBlock *, 8> UniquePreds;
MachineBasicBlock *IBB = I;
- MachineBasicBlock *PredBB = prior(I);
+ MachineBasicBlock *PredBB = std::prev(I);
MergePotentials.clear();
for (MachineBasicBlock::pred_iterator P = I->pred_begin(),
E2 = I->pred_end();
if (PBB->getLandingPadSuccessor())
continue;
- MachineBasicBlock *TBB = 0, *FBB = 0;
+ MachineBasicBlock *TBB = nullptr, *FBB = nullptr;
SmallVector<MachineOperand, 4> Cond;
if (!TII->AnalyzeBranch(*PBB, TBB, FBB, Cond, true)) {
// Failing case: IBB is the target of a cbr, and we cannot reverse the
continue;
// This is the QBB case described above
if (!FBB)
- FBB = llvm::next(MachineFunction::iterator(PBB));
+ FBB = std::next(MachineFunction::iterator(PBB));
}
// Failing case: the only way IBB can be reached from PBB is via
// a bit in the edge so we didn't have to do all this.
if (IBB->isLandingPad()) {
MachineFunction::iterator IP = PBB; IP++;
- MachineBasicBlock *PredNextBB = NULL;
+ MachineBasicBlock *PredNextBB = nullptr;
if (IP != MF.end())
PredNextBB = IP;
- if (TBB == NULL) {
+ if (!TBB) {
if (IBB != PredNextBB) // fallthrough
continue;
} else if (FBB) {
TII->RemoveBranch(*PBB);
if (!Cond.empty())
// reinsert conditional branch only, for now
- TII->InsertBranch(*PBB, (TBB == IBB) ? FBB : TBB, 0, NewCond, dl);
+ TII->InsertBranch(*PBB, (TBB == IBB) ? FBB : TBB, nullptr,
+ NewCond, dl);
}
MergePotentials.push_back(MergePotentialsElt(HashEndOfMBB(PBB), *P));
// Reinsert an unconditional branch if needed. The 1 below can occur as a
// result of removing blocks in TryTailMergeBlocks.
- PredBB = prior(I); // this may have been changed in TryTailMergeBlocks
+ PredBB = std::prev(I); // this may have been changed in TryTailMergeBlocks
if (MergePotentials.size() == 1 &&
MergePotentials.begin()->getBlock() != PredBB)
FixTail(MergePotentials.begin()->getBlock(), IBB, TII);
// Make sure blocks are numbered in order
MF.RenumberBlocks();
- for (MachineFunction::iterator I = llvm::next(MF.begin()), E = MF.end();
+ for (MachineFunction::iterator I = std::next(MF.begin()), E = MF.end();
I != E; ) {
MachineBasicBlock *MBB = I++;
MadeChange |= OptimizeBlock(MBB);
// Check to see if we can simplify the terminator of the block before this
// one.
- MachineBasicBlock &PrevBB = *prior(MachineFunction::iterator(MBB));
+ MachineBasicBlock &PrevBB = *std::prev(MachineFunction::iterator(MBB));
- MachineBasicBlock *PriorTBB = 0, *PriorFBB = 0;
+ MachineBasicBlock *PriorTBB = nullptr, *PriorFBB = nullptr;
SmallVector<MachineOperand, 4> PriorCond;
bool PriorUnAnalyzable =
TII->AnalyzeBranch(PrevBB, PriorTBB, PriorFBB, PriorCond, true);
TII->RemoveBranch(PrevBB);
PriorCond.clear();
if (PriorTBB != MBB)
- TII->InsertBranch(PrevBB, PriorTBB, 0, PriorCond, dl);
+ TII->InsertBranch(PrevBB, PriorTBB, nullptr, PriorCond, dl);
MadeChange = true;
++NumBranchOpts;
goto ReoptimizeBlock;
// If the previous branch *only* branches to *this* block (conditional or
// not) remove the branch.
- if (PriorTBB == MBB && PriorFBB == 0) {
+ if (PriorTBB == MBB && !PriorFBB) {
TII->RemoveBranch(PrevBB);
MadeChange = true;
++NumBranchOpts;
if (PriorFBB == MBB) {
DebugLoc dl = getBranchDebugLoc(PrevBB);
TII->RemoveBranch(PrevBB);
- TII->InsertBranch(PrevBB, PriorTBB, 0, PriorCond, dl);
+ TII->InsertBranch(PrevBB, PriorTBB, nullptr, PriorCond, dl);
MadeChange = true;
++NumBranchOpts;
goto ReoptimizeBlock;
if (!TII->ReverseBranchCondition(NewPriorCond)) {
DebugLoc dl = getBranchDebugLoc(PrevBB);
TII->RemoveBranch(PrevBB);
- TII->InsertBranch(PrevBB, PriorFBB, 0, NewPriorCond, dl);
+ TII->InsertBranch(PrevBB, PriorFBB, nullptr, NewPriorCond, dl);
MadeChange = true;
++NumBranchOpts;
goto ReoptimizeBlock;
// We consider it more likely that execution will stay in the function (e.g.
// due to loops) than it is to exit it. This asserts in loops etc, moving
// the assert condition out of the loop body.
- if (MBB->succ_empty() && !PriorCond.empty() && PriorFBB == 0 &&
+ if (MBB->succ_empty() && !PriorCond.empty() && !PriorFBB &&
MachineFunction::iterator(PriorTBB) == FallThrough &&
!MBB->canFallThrough()) {
bool DoTransform = true;
DebugLoc dl = getBranchDebugLoc(PrevBB);
TII->RemoveBranch(PrevBB);
- TII->InsertBranch(PrevBB, MBB, 0, NewPriorCond, dl);
+ TII->InsertBranch(PrevBB, MBB, nullptr, NewPriorCond, dl);
// Move this block to the end of the function.
MBB->moveAfter(--MF.end());
}
// Analyze the branch in the current block.
- MachineBasicBlock *CurTBB = 0, *CurFBB = 0;
+ MachineBasicBlock *CurTBB = nullptr, *CurFBB = nullptr;
SmallVector<MachineOperand, 4> CurCond;
bool CurUnAnalyzable= TII->AnalyzeBranch(*MBB, CurTBB, CurFBB, CurCond, true);
if (!CurUnAnalyzable) {
// If this branch is the only thing in its block, see if we can forward
// other blocks across it.
- if (CurTBB && CurCond.empty() && CurFBB == 0 &&
+ if (CurTBB && CurCond.empty() && !CurFBB &&
IsBranchOnlyBlock(MBB) && CurTBB != MBB &&
!MBB->hasAddressTaken()) {
DebugLoc dl = getBranchDebugLoc(*MBB);
// explicit branch to us to make updates simpler.
if (!PredHasNoFallThrough && PrevBB.isSuccessor(MBB) &&
PriorTBB != MBB && PriorFBB != MBB) {
- if (PriorTBB == 0) {
- assert(PriorCond.empty() && PriorFBB == 0 &&
+ if (!PriorTBB) {
+ assert(PriorCond.empty() && !PriorFBB &&
"Bad branch analysis");
PriorTBB = MBB;
} else {
- assert(PriorFBB == 0 && "Machine CFG out of date!");
+ assert(!PriorFBB && "Machine CFG out of date!");
PriorFBB = MBB;
}
DebugLoc pdl = getBranchDebugLoc(PrevBB);
// If this change resulted in PMBB ending in a conditional
// branch where both conditions go to the same destination,
// change this to an unconditional branch (and fix the CFG).
- MachineBasicBlock *NewCurTBB = 0, *NewCurFBB = 0;
+ MachineBasicBlock *NewCurTBB = nullptr, *NewCurFBB = nullptr;
SmallVector<MachineOperand, 4> NewCurCond;
bool NewCurUnAnalyzable = TII->AnalyzeBranch(*PMBB, NewCurTBB,
NewCurFBB, NewCurCond, true);
DebugLoc pdl = getBranchDebugLoc(*PMBB);
TII->RemoveBranch(*PMBB);
NewCurCond.clear();
- TII->InsertBranch(*PMBB, NewCurTBB, 0, NewCurCond, pdl);
+ TII->InsertBranch(*PMBB, NewCurTBB, nullptr, NewCurCond, pdl);
MadeChange = true;
++NumBranchOpts;
- PMBB->CorrectExtraCFGEdges(NewCurTBB, 0, false);
+ PMBB->CorrectExtraCFGEdges(NewCurTBB, nullptr, false);
}
}
}
}
// Add the branch back if the block is more than just an uncond branch.
- TII->InsertBranch(*MBB, CurTBB, 0, CurCond, dl);
+ TII->InsertBranch(*MBB, CurTBB, nullptr, CurCond, dl);
}
}
// Analyze the branch at the end of the pred.
MachineBasicBlock *PredBB = *PI;
MachineFunction::iterator PredFallthrough = PredBB; ++PredFallthrough;
- MachineBasicBlock *PredTBB = 0, *PredFBB = 0;
+ MachineBasicBlock *PredTBB = nullptr, *PredFBB = nullptr;
SmallVector<MachineOperand, 4> PredCond;
if (PredBB != MBB && !PredBB->canFallThrough() &&
!TII->AnalyzeBranch(*PredBB, PredTBB, PredFBB, PredCond, true)
// B elsewhere
// next:
if (CurFallsThru) {
- MachineBasicBlock *NextBB = llvm::next(MachineFunction::iterator(MBB));
+ MachineBasicBlock *NextBB =
+ std::next(MachineFunction::iterator(MBB));
CurCond.clear();
- TII->InsertBranch(*MBB, NextBB, 0, CurCond, DebugLoc());
+ TII->InsertBranch(*MBB, NextBB, nullptr, CurCond, DebugLoc());
}
MBB->moveAfter(PredBB);
MadeChange = true;
// Okay, there is no really great place to put this block. If, however,
// the block before this one would be a fall-through if this block were
// removed, move this block to the end of the function.
- MachineBasicBlock *PrevTBB = 0, *PrevFBB = 0;
+ MachineBasicBlock *PrevTBB = nullptr, *PrevFBB = nullptr;
SmallVector<MachineOperand, 4> PrevCond;
if (FallThrough != MF.end() &&
!TII->AnalyzeBranch(PrevBB, PrevTBB, PrevFBB, PrevCond, true) &&
if (SuccBB != TrueBB)
return SuccBB;
}
- return NULL;
+ return nullptr;
}
/// findHoistingInsertPosAndDeps - Find the location to move common instructions
if (MO.isUse()) {
for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI)
Uses.insert(*AI);
- } else if (!MO.isDead())
- // Don't try to hoist code in the rare case the terminator defines a
- // register that is later used.
- return MBB->end();
+ } else {
+ if (!MO.isDead())
+ // Don't try to hoist code in the rare case the terminator defines a
+ // register that is later used.
+ return MBB->end();
+
+ // If the terminator defines a register, make sure we don't hoist
+ // the instruction whose def might be clobbered by the terminator.
+ for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI)
+ Defs.insert(*AI);
+ }
}
if (Uses.empty())
// branch from condition setting instruction.
MachineBasicBlock::iterator PI = Loc;
--PI;
- while (PI != MBB->begin() && Loc->isDebugValue())
+ while (PI != MBB->begin() && PI->isDebugValue())
--PI;
bool IsDef = false;
// Also avoid moving code above predicated instruction since it's hard to
// reason about register liveness with predicated instruction.
bool DontMoveAcrossStore = true;
- if (!PI->isSafeToMove(TII, 0, DontMoveAcrossStore) ||
+ if (!PI->isSafeToMove(TII, nullptr, DontMoveAcrossStore) ||
TII->isPredicated(PI))
return MBB->end();
/// sequence at the start of the function, move the instructions before MBB
/// terminator if it's legal.
bool BranchFolder::HoistCommonCodeInSuccs(MachineBasicBlock *MBB) {
- MachineBasicBlock *TBB = 0, *FBB = 0;
+ MachineBasicBlock *TBB = nullptr, *FBB = nullptr;
SmallVector<MachineOperand, 4> Cond;
if (TII->AnalyzeBranch(*MBB, TBB, FBB, Cond, true) || !TBB || Cond.empty())
return false;
break;
bool DontMoveAcrossStore = true;
- if (!TIB->isSafeToMove(TII, 0, DontMoveAcrossStore))
+ if (!TIB->isSafeToMove(TII, nullptr, DontMoveAcrossStore))
break;
// Remove kills from LocalDefsSet, these registers had short live ranges.