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Whitespace cleanups.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86855 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2009-11-11 18:38:14 +00:00
parent a127edceae
commit 4e3f125e18
1 changed files with 92 additions and 93 deletions
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185
lib/CodeGen/BranchFolding.cpp
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@ -40,18 +40,18 @@ using namespace llvm;
STATISTIC(NumDeadBlocks, "Number of dead blocks removed"); STATISTIC(NumDeadBlocks, "Number of dead blocks removed");
STATISTIC(NumBranchOpts, "Number of branches optimized"); STATISTIC(NumBranchOpts, "Number of branches optimized");
STATISTIC(NumTailMerge , "Number of block tails merged"); STATISTIC(NumTailMerge , "Number of block tails merged");
static cl::opt<cl::boolOrDefault> FlagEnableTailMerge("enable-tail-merge", static cl::opt<cl::boolOrDefault> FlagEnableTailMerge("enable-tail-merge",
cl::init(cl::BOU_UNSET), cl::Hidden); cl::init(cl::BOU_UNSET), cl::Hidden);
// Throttle for huge numbers of predecessors (compile speed problems) // Throttle for huge numbers of predecessors (compile speed problems)
static cl::opt<unsigned> static cl::opt<unsigned>
TailMergeThreshold("tail-merge-threshold", TailMergeThreshold("tail-merge-threshold",
cl::desc("Max number of predecessors to consider tail merging"), cl::desc("Max number of predecessors to consider tail merging"),
cl::init(150), cl::Hidden); cl::init(150), cl::Hidden);
char BranchFolderPass::ID = 0; char BranchFolderPass::ID = 0;
FunctionPass *llvm::createBranchFoldingPass(bool DefaultEnableTailMerge) { FunctionPass *llvm::createBranchFoldingPass(bool DefaultEnableTailMerge) {
return new BranchFolderPass(DefaultEnableTailMerge); return new BranchFolderPass(DefaultEnableTailMerge);
} }
@ -63,7 +63,6 @@ bool BranchFolderPass::runOnMachineFunction(MachineFunction &MF) {
} }
BranchFolder::BranchFolder(bool defaultEnableTailMerge) { BranchFolder::BranchFolder(bool defaultEnableTailMerge) {
switch (FlagEnableTailMerge) { switch (FlagEnableTailMerge) {
case cl::BOU_UNSET: EnableTailMerge = defaultEnableTailMerge; break; case cl::BOU_UNSET: EnableTailMerge = defaultEnableTailMerge; break;
@ -77,12 +76,12 @@ BranchFolder::BranchFolder(bool defaultEnableTailMerge) {
void BranchFolder::RemoveDeadBlock(MachineBasicBlock *MBB) { void BranchFolder::RemoveDeadBlock(MachineBasicBlock *MBB) {
assert(MBB->pred_empty() && "MBB must be dead!"); assert(MBB->pred_empty() && "MBB must be dead!");
DEBUG(errs() << "\nRemoving MBB: " << *MBB); DEBUG(errs() << "\nRemoving MBB: " << *MBB);
MachineFunction *MF = MBB->getParent(); MachineFunction *MF = MBB->getParent();
// drop all successors. // drop all successors.
while (!MBB->succ_empty()) while (!MBB->succ_empty())
MBB->removeSuccessor(MBB->succ_end()-1); MBB->removeSuccessor(MBB->succ_end()-1);
// If there are any labels in the basic block, unregister them from // If there are any labels in the basic block, unregister them from
// MachineModuleInfo. // MachineModuleInfo.
if (MMI && !MBB->empty()) { if (MMI && !MBB->empty()) {
@ -93,7 +92,7 @@ void BranchFolder::RemoveDeadBlock(MachineBasicBlock *MBB) {
MMI->InvalidateLabel(I->getOperand(0).getImm()); MMI->InvalidateLabel(I->getOperand(0).getImm());
} }
} }
// Remove the block. // Remove the block.
MF->erase(MBB); MF->erase(MBB);
} }
@ -190,7 +189,7 @@ bool BranchFolder::OptimizeFunction(MachineFunction &MF,
// Figure out how these jump tables should be merged. // Figure out how these jump tables should be merged.
std::vector<unsigned> JTMapping; std::vector<unsigned> JTMapping;
JTMapping.reserve(JTs.size()); JTMapping.reserve(JTs.size());
// We always keep the 0th jump table. // We always keep the 0th jump table.
JTMapping.push_back(0); JTMapping.push_back(0);
@ -202,7 +201,7 @@ bool BranchFolder::OptimizeFunction(MachineFunction &MF,
else else
JTMapping.push_back(JTI->getJumpTableIndex(JTs[i].MBBs)); JTMapping.push_back(JTI->getJumpTableIndex(JTs[i].MBBs));
} }
// If a jump table was merge with another one, walk the function rewriting // If a jump table was merge with another one, walk the function rewriting
// references to jump tables to reference the new JT ID's. Keep track of // references to jump tables to reference the new JT ID's. Keep track of
// whether we see a jump table idx, if not, we can delete the JT. // whether we see a jump table idx, if not, we can delete the JT.
@ -221,7 +220,7 @@ bool BranchFolder::OptimizeFunction(MachineFunction &MF,
JTIsLive.set(NewIdx); JTIsLive.set(NewIdx);
} }
} }
// Finally, remove dead jump tables. This happens either because the // Finally, remove dead jump tables. This happens either because the
// indirect jump was unreachable (and thus deleted) or because the jump // indirect jump was unreachable (and thus deleted) or because the jump
// table was merged with some other one. // table was merged with some other one.
@ -245,7 +244,7 @@ static unsigned HashMachineInstr(const MachineInstr *MI) {
unsigned Hash = MI->getOpcode(); unsigned Hash = MI->getOpcode();
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
const MachineOperand &Op = MI->getOperand(i); const MachineOperand &Op = MI->getOperand(i);
// Merge in bits from the operand if easy. // Merge in bits from the operand if easy.
unsigned OperandHash = 0; unsigned OperandHash = 0;
switch (Op.getType()) { switch (Op.getType()) {
@ -267,31 +266,30 @@ static unsigned HashMachineInstr(const MachineInstr *MI) {
break; break;
default: break; default: break;
} }
Hash += ((OperandHash << 3) | Op.getType()) << (i&31); Hash += ((OperandHash << 3) | Op.getType()) << (i&31);
} }
return Hash; return Hash;
} }
/// HashEndOfMBB - Hash the last few instructions in the MBB. For blocks /// HashEndOfMBB - Hash the last few instructions in the MBB. For blocks
/// with no successors, we hash two instructions, because cross-jumping /// with no successors, we hash two instructions, because cross-jumping
/// only saves code when at least two instructions are removed (since a /// only saves code when at least two instructions are removed (since a
/// branch must be inserted). For blocks with a successor, one of the /// branch must be inserted). For blocks with a successor, one of the
/// two blocks to be tail-merged will end with a branch already, so /// two blocks to be tail-merged will end with a branch already, so
/// it gains to cross-jump even for one instruction. /// it gains to cross-jump even for one instruction.
static unsigned HashEndOfMBB(const MachineBasicBlock *MBB, static unsigned HashEndOfMBB(const MachineBasicBlock *MBB,
unsigned minCommonTailLength) { unsigned minCommonTailLength) {
MachineBasicBlock::const_iterator I = MBB->end(); MachineBasicBlock::const_iterator I = MBB->end();
if (I == MBB->begin()) if (I == MBB->begin())
return 0; // Empty MBB. return 0; // Empty MBB.
--I; --I;
unsigned Hash = HashMachineInstr(I); unsigned Hash = HashMachineInstr(I);
if (I == MBB->begin() || minCommonTailLength == 1) if (I == MBB->begin() || minCommonTailLength == 1)
return Hash; // Single instr MBB. return Hash; // Single instr MBB.
--I; --I;
// Hash in the second-to-last instruction. // Hash in the second-to-last instruction.
Hash ^= HashMachineInstr(I) << 2; Hash ^= HashMachineInstr(I) << 2;
@ -307,11 +305,11 @@ static unsigned ComputeCommonTailLength(MachineBasicBlock *MBB1,
MachineBasicBlock::iterator &I2) { MachineBasicBlock::iterator &I2) {
I1 = MBB1->end(); I1 = MBB1->end();
I2 = MBB2->end(); I2 = MBB2->end();
unsigned TailLen = 0; unsigned TailLen = 0;
while (I1 != MBB1->begin() && I2 != MBB2->begin()) { while (I1 != MBB1->begin() && I2 != MBB2->begin()) {
--I1; --I2; --I1; --I2;
if (!I1->isIdenticalTo(I2) || if (!I1->isIdenticalTo(I2) ||
// FIXME: This check is dubious. It's used to get around a problem where // FIXME: This check is dubious. It's used to get around a problem where
// people incorrectly expect inline asm directives to remain in the same // people incorrectly expect inline asm directives to remain in the same
// relative order. This is untenable because normal compiler // relative order. This is untenable because normal compiler
@ -332,11 +330,11 @@ static unsigned ComputeCommonTailLength(MachineBasicBlock *MBB1,
void BranchFolder::ReplaceTailWithBranchTo(MachineBasicBlock::iterator OldInst, void BranchFolder::ReplaceTailWithBranchTo(MachineBasicBlock::iterator OldInst,
MachineBasicBlock *NewDest) { MachineBasicBlock *NewDest) {
MachineBasicBlock *OldBB = OldInst->getParent(); MachineBasicBlock *OldBB = OldInst->getParent();
// Remove all the old successors of OldBB from the CFG. // Remove all the old successors of OldBB from the CFG.
while (!OldBB->succ_empty()) while (!OldBB->succ_empty())
OldBB->removeSuccessor(OldBB->succ_begin()); OldBB->removeSuccessor(OldBB->succ_begin());
// Remove all the dead instructions from the end of OldBB. // Remove all the dead instructions from the end of OldBB.
OldBB->erase(OldInst, OldBB->end()); OldBB->erase(OldInst, OldBB->end());
@ -361,10 +359,10 @@ MachineBasicBlock *BranchFolder::SplitMBBAt(MachineBasicBlock &CurMBB,
// Move all the successors of this block to the specified block. // Move all the successors of this block to the specified block.
NewMBB->transferSuccessors(&CurMBB); NewMBB->transferSuccessors(&CurMBB);
// Add an edge from CurMBB to NewMBB for the fall-through. // Add an edge from CurMBB to NewMBB for the fall-through.
CurMBB.addSuccessor(NewMBB); CurMBB.addSuccessor(NewMBB);
// Splice the code over. // Splice the code over.
NewMBB->splice(NewMBB->end(), &CurMBB, BBI1, CurMBB.end()); NewMBB->splice(NewMBB->end(), &CurMBB, BBI1, CurMBB.end());
@ -404,7 +402,6 @@ static unsigned EstimateRuntime(MachineBasicBlock::iterator I,
// branches temporarily for tail merging). In the case where CurMBB ends // branches temporarily for tail merging). In the case where CurMBB ends
// with a conditional branch to the next block, optimize by reversing the // with a conditional branch to the next block, optimize by reversing the
// test and conditionally branching to SuccMBB instead. // test and conditionally branching to SuccMBB instead.
static void FixTail(MachineBasicBlock* CurMBB, MachineBasicBlock *SuccBB, static void FixTail(MachineBasicBlock* CurMBB, MachineBasicBlock *SuccBB,
const TargetInstrInfo *TII) { const TargetInstrInfo *TII) {
MachineFunction *MF = CurMBB->getParent(); MachineFunction *MF = CurMBB->getParent();
@ -476,26 +473,26 @@ static bool ProfitableToMerge(MachineBasicBlock *MBB1,
} }
/// ComputeSameTails - Look through all the blocks in MergePotentials that have /// ComputeSameTails - Look through all the blocks in MergePotentials that have
/// hash CurHash (guaranteed to match the last element). Build the vector /// hash CurHash (guaranteed to match the last element). Build the vector
/// SameTails of all those that have the (same) largest number of instructions /// SameTails of all those that have the (same) largest number of instructions
/// in common of any pair of these blocks. SameTails entries contain an /// in common of any pair of these blocks. SameTails entries contain an
/// iterator into MergePotentials (from which the MachineBasicBlock can be /// iterator into MergePotentials (from which the MachineBasicBlock can be
/// found) and a MachineBasicBlock::iterator into that MBB indicating the /// found) and a MachineBasicBlock::iterator into that MBB indicating the
/// instruction where the matching code sequence begins. /// instruction where the matching code sequence begins.
/// Order of elements in SameTails is the reverse of the order in which /// Order of elements in SameTails is the reverse of the order in which
/// those blocks appear in MergePotentials (where they are not necessarily /// those blocks appear in MergePotentials (where they are not necessarily
/// consecutive). /// consecutive).
unsigned BranchFolder::ComputeSameTails(unsigned CurHash, unsigned BranchFolder::ComputeSameTails(unsigned CurHash,
unsigned minCommonTailLength) { unsigned minCommonTailLength) {
unsigned maxCommonTailLength = 0U; unsigned maxCommonTailLength = 0U;
SameTails.clear(); SameTails.clear();
MachineBasicBlock::iterator TrialBBI1, TrialBBI2; MachineBasicBlock::iterator TrialBBI1, TrialBBI2;
MPIterator HighestMPIter = prior(MergePotentials.end()); MPIterator HighestMPIter = prior(MergePotentials.end());
for (MPIterator CurMPIter = prior(MergePotentials.end()), for (MPIterator CurMPIter = prior(MergePotentials.end()),
B = MergePotentials.begin(); B = MergePotentials.begin();
CurMPIter!=B && CurMPIter->first==CurHash; CurMPIter!=B && CurMPIter->first == CurHash;
--CurMPIter) { --CurMPIter) {
for (MPIterator I = prior(CurMPIter); I->first==CurHash ; --I) { for (MPIterator I = prior(CurMPIter); I->first == CurHash ; --I) {
unsigned CommonTailLen; unsigned CommonTailLen;
if (ProfitableToMerge(CurMPIter->second, I->second, minCommonTailLength, if (ProfitableToMerge(CurMPIter->second, I->second, minCommonTailLength,
CommonTailLen, TrialBBI1, TrialBBI2)) { CommonTailLen, TrialBBI1, TrialBBI2)) {
@ -509,7 +506,7 @@ unsigned BranchFolder::ComputeSameTails(unsigned CurHash,
CommonTailLen == maxCommonTailLength) CommonTailLen == maxCommonTailLength)
SameTails.push_back(std::make_pair(I, TrialBBI2)); SameTails.push_back(std::make_pair(I, TrialBBI2));
} }
if (I==B) if (I == B)
break; break;
} }
} }
@ -518,18 +515,18 @@ unsigned BranchFolder::ComputeSameTails(unsigned CurHash,
/// RemoveBlocksWithHash - Remove all blocks with hash CurHash from /// RemoveBlocksWithHash - Remove all blocks with hash CurHash from
/// MergePotentials, restoring branches at ends of blocks as appropriate. /// MergePotentials, restoring branches at ends of blocks as appropriate.
void BranchFolder::RemoveBlocksWithHash(unsigned CurHash, void BranchFolder::RemoveBlocksWithHash(unsigned CurHash,
MachineBasicBlock* SuccBB, MachineBasicBlock* SuccBB,
MachineBasicBlock* PredBB) { MachineBasicBlock* PredBB) {
MPIterator CurMPIter, B; MPIterator CurMPIter, B;
for (CurMPIter = prior(MergePotentials.end()), B = MergePotentials.begin(); for (CurMPIter = prior(MergePotentials.end()), B = MergePotentials.begin();
CurMPIter->first==CurHash; CurMPIter->first == CurHash;
--CurMPIter) { --CurMPIter) {
// Put the unconditional branch back, if we need one. // Put the unconditional branch back, if we need one.
MachineBasicBlock *CurMBB = CurMPIter->second; MachineBasicBlock *CurMBB = CurMPIter->second;
if (SuccBB && CurMBB != PredBB) if (SuccBB && CurMBB != PredBB)
FixTail(CurMBB, SuccBB, TII); FixTail(CurMBB, SuccBB, TII);
if (CurMPIter==B) if (CurMPIter == B)
break; break;
} }
if (CurMPIter->first!=CurHash) if (CurMPIter->first!=CurHash)
@ -545,15 +542,15 @@ unsigned BranchFolder::CreateCommonTailOnlyBlock(MachineBasicBlock *&PredBB,
unsigned TimeEstimate = ~0U; unsigned TimeEstimate = ~0U;
for (i=0, commonTailIndex=0; i<SameTails.size(); i++) { for (i=0, commonTailIndex=0; i<SameTails.size(); i++) {
// Use PredBB if possible; that doesn't require a new branch. // Use PredBB if possible; that doesn't require a new branch.
if (SameTails[i].first->second==PredBB) { if (SameTails[i].first->second == PredBB) {
commonTailIndex = i; commonTailIndex = i;
break; break;
} }
// Otherwise, make a (fairly bogus) choice based on estimate of // Otherwise, make a (fairly bogus) choice based on estimate of
// how long it will take the various blocks to execute. // how long it will take the various blocks to execute.
unsigned t = EstimateRuntime(SameTails[i].first->second->begin(), unsigned t = EstimateRuntime(SameTails[i].first->second->begin(),
SameTails[i].second); SameTails[i].second);
if (t<=TimeEstimate) { if (t <= TimeEstimate) {
TimeEstimate = t; TimeEstimate = t;
commonTailIndex = i; commonTailIndex = i;
} }
@ -568,8 +565,9 @@ unsigned BranchFolder::CreateCommonTailOnlyBlock(MachineBasicBlock *&PredBB,
MachineBasicBlock *newMBB = SplitMBBAt(*MBB, BBI); MachineBasicBlock *newMBB = SplitMBBAt(*MBB, BBI);
SameTails[commonTailIndex].first->second = newMBB; SameTails[commonTailIndex].first->second = newMBB;
SameTails[commonTailIndex].second = newMBB->begin(); SameTails[commonTailIndex].second = newMBB->begin();
// If we split PredBB, newMBB is the new predecessor. // If we split PredBB, newMBB is the new predecessor.
if (PredBB==MBB) if (PredBB == MBB)
PredBB = newMBB; PredBB = newMBB;
return commonTailIndex; return commonTailIndex;
@ -579,7 +577,7 @@ unsigned BranchFolder::CreateCommonTailOnlyBlock(MachineBasicBlock *&PredBB,
// successor, or all have no successor) can be tail-merged. If there is a // successor, or all have no successor) can be tail-merged. If there is a
// successor, any blocks in MergePotentials that are not tail-merged and // successor, any blocks in MergePotentials that are not tail-merged and
// are not immediately before Succ must have an unconditional branch to // are not immediately before Succ must have an unconditional branch to
// Succ added (but the predecessor/successor lists need no adjustment). // Succ added (but the predecessor/successor lists need no adjustment).
// The lone predecessor of Succ that falls through into Succ, // The lone predecessor of Succ that falls through into Succ,
// if any, is given in PredBB. // if any, is given in PredBB.
@ -591,7 +589,7 @@ bool BranchFolder::TryMergeBlocks(MachineBasicBlock *SuccBB,
// will add a jump. // will add a jump.
// FIXME: Ask the target to provide the threshold? // FIXME: Ask the target to provide the threshold?
unsigned minCommonTailLength = (SuccBB ? 1 : 2) + 1; unsigned minCommonTailLength = (SuccBB ? 1 : 2) + 1;
DEBUG(errs() << "\nTryMergeBlocks " << MergePotentials.size() << '\n'); DEBUG(errs() << "\nTryMergeBlocks " << MergePotentials.size() << '\n');
// Sort by hash value so that blocks with identical end sequences sort // Sort by hash value so that blocks with identical end sequences sort
@ -601,13 +599,13 @@ bool BranchFolder::TryMergeBlocks(MachineBasicBlock *SuccBB,
// Walk through equivalence sets looking for actual exact matches. // Walk through equivalence sets looking for actual exact matches.
while (MergePotentials.size() > 1) { while (MergePotentials.size() > 1) {
unsigned CurHash = MergePotentials.back().first; unsigned CurHash = MergePotentials.back().first;
// Build SameTails, identifying the set of blocks with this hash code // Build SameTails, identifying the set of blocks with this hash code
// and with the maximum number of instructions in common. // and with the maximum number of instructions in common.
unsigned maxCommonTailLength = ComputeSameTails(CurHash, unsigned maxCommonTailLength = ComputeSameTails(CurHash,
minCommonTailLength); minCommonTailLength);
// If we didn't find any pair that has at least minCommonTailLength // If we didn't find any pair that has at least minCommonTailLength
// instructions in common, remove all blocks with this hash code and retry. // instructions in common, remove all blocks with this hash code and retry.
if (SameTails.empty()) { if (SameTails.empty()) {
RemoveBlocksWithHash(CurHash, SuccBB, PredBB); RemoveBlocksWithHash(CurHash, SuccBB, PredBB);
@ -625,12 +623,12 @@ bool BranchFolder::TryMergeBlocks(MachineBasicBlock *SuccBB,
MachineBasicBlock *MBB = SameTails[i].first->second; MachineBasicBlock *MBB = SameTails[i].first->second;
if (MBB->begin() == SameTails[i].second && MBB != EntryBB) { if (MBB->begin() == SameTails[i].second && MBB != EntryBB) {
commonTailIndex = i; commonTailIndex = i;
if (MBB==PredBB) if (MBB == PredBB)
break; break;
} }
} }
if (commonTailIndex==SameTails.size()) { if (commonTailIndex == SameTails.size()) {
// None of the blocks consist entirely of the common tail. // None of the blocks consist entirely of the common tail.
// Split a block so that one does. // Split a block so that one does.
commonTailIndex = CreateCommonTailOnlyBlock(PredBB, maxCommonTailLength); commonTailIndex = CreateCommonTailOnlyBlock(PredBB, maxCommonTailLength);
@ -641,7 +639,7 @@ bool BranchFolder::TryMergeBlocks(MachineBasicBlock *SuccBB,
// Traversal must be forwards so erases work. // Traversal must be forwards so erases work.
DEBUG(errs() << "\nUsing common tail BB#" << MBB->getNumber() << " for "); DEBUG(errs() << "\nUsing common tail BB#" << MBB->getNumber() << " for ");
for (unsigned int i=0; i<SameTails.size(); ++i) { for (unsigned int i=0; i<SameTails.size(); ++i) {
if (commonTailIndex==i) if (commonTailIndex == i)
continue; continue;
DEBUG(errs() << "BB#" << SameTails[i].first->second->getNumber() << ", "); DEBUG(errs() << "BB#" << SameTails[i].first->second->getNumber() << ", ");
// Hack the end off BB i, making it jump to BB commonTailIndex instead. // Hack the end off BB i, making it jump to BB commonTailIndex instead.
@ -660,7 +658,7 @@ bool BranchFolder::TryMergeBlocks(MachineBasicBlock *SuccBB,
bool BranchFolder::TailMergeBlocks(MachineFunction &MF) { bool BranchFolder::TailMergeBlocks(MachineFunction &MF) {
if (!EnableTailMerge) return false; if (!EnableTailMerge) return false;
bool MadeChange = false; bool MadeChange = false;
// First find blocks with no successors. // First find blocks with no successors.
@ -669,6 +667,7 @@ bool BranchFolder::TailMergeBlocks(MachineFunction &MF) {
if (I->succ_empty()) if (I->succ_empty())
MergePotentials.push_back(std::make_pair(HashEndOfMBB(I, 2U), I)); MergePotentials.push_back(std::make_pair(HashEndOfMBB(I, 2U), I));
} }
// See if we can do any tail merging on those. // See if we can do any tail merging on those.
if (MergePotentials.size() < TailMergeThreshold && if (MergePotentials.size() < TailMergeThreshold &&
MergePotentials.size() >= 2) MergePotentials.size() >= 2)
@ -679,7 +678,7 @@ bool BranchFolder::TailMergeBlocks(MachineFunction &MF) {
// (1) temporarily removing any unconditional branch from the predecessor // (1) temporarily removing any unconditional branch from the predecessor
// to IBB, and // to IBB, and
// (2) alter conditional branches so they branch to the other block // (2) alter conditional branches so they branch to the other block
// not IBB; this may require adding back an unconditional branch to IBB // not IBB; this may require adding back an unconditional branch to IBB
// later, where there wasn't one coming in. E.g. // later, where there wasn't one coming in. E.g.
// Bcc IBB // Bcc IBB
// fallthrough to QBB // fallthrough to QBB
@ -699,12 +698,12 @@ bool BranchFolder::TailMergeBlocks(MachineFunction &MF) {
MachineBasicBlock *IBB = I; MachineBasicBlock *IBB = I;
MachineBasicBlock *PredBB = prior(I); MachineBasicBlock *PredBB = prior(I);
MergePotentials.clear(); MergePotentials.clear();
for (MachineBasicBlock::pred_iterator P = I->pred_begin(), for (MachineBasicBlock::pred_iterator P = I->pred_begin(),
E2 = I->pred_end(); E2 = I->pred_end();
P != E2; ++P) { P != E2; ++P) {
MachineBasicBlock* PBB = *P; MachineBasicBlock* PBB = *P;
// Skip blocks that loop to themselves, can't tail merge these. // Skip blocks that loop to themselves, can't tail merge these.
if (PBB==IBB) if (PBB == IBB)
continue; continue;
// Visit each predecessor only once. // Visit each predecessor only once.
if (!UniquePreds.insert(PBB)) if (!UniquePreds.insert(PBB))
@ -715,7 +714,7 @@ bool BranchFolder::TailMergeBlocks(MachineFunction &MF) {
// Failing case: IBB is the target of a cbr, and // Failing case: IBB is the target of a cbr, and
// we cannot reverse the branch. // we cannot reverse the branch.
SmallVector<MachineOperand, 4> NewCond(Cond); SmallVector<MachineOperand, 4> NewCond(Cond);
if (!Cond.empty() && TBB==IBB) { if (!Cond.empty() && TBB == IBB) {
if (TII->ReverseBranchCondition(NewCond)) if (TII->ReverseBranchCondition(NewCond))
continue; continue;
// This is the QBB case described above // This is the QBB case described above
@ -730,7 +729,7 @@ bool BranchFolder::TailMergeBlocks(MachineFunction &MF) {
MachineBasicBlock* PredNextBB = NULL; MachineBasicBlock* PredNextBB = NULL;
if (IP!=MF.end()) if (IP!=MF.end())
PredNextBB = IP; PredNextBB = IP;
if (TBB==NULL) { if (TBB == NULL) {
if (IBB!=PredNextBB) // fallthrough if (IBB!=PredNextBB) // fallthrough
continue; continue;
} else if (FBB) { } else if (FBB) {
@ -749,7 +748,7 @@ bool BranchFolder::TailMergeBlocks(MachineFunction &MF) {
TII->RemoveBranch(*PBB); TII->RemoveBranch(*PBB);
if (!Cond.empty()) if (!Cond.empty())
// reinsert conditional branch only, for now // reinsert conditional branch only, for now
TII->InsertBranch(*PBB, (TBB==IBB) ? FBB : TBB, 0, NewCond); TII->InsertBranch(*PBB, (TBB == IBB) ? FBB : TBB, 0, NewCond);
} }
MergePotentials.push_back(std::make_pair(HashEndOfMBB(PBB, 1U), *P)); MergePotentials.push_back(std::make_pair(HashEndOfMBB(PBB, 1U), *P));
} }
@ -759,7 +758,7 @@ bool BranchFolder::TailMergeBlocks(MachineFunction &MF) {
// Reinsert an unconditional branch if needed. // Reinsert an unconditional branch if needed.
// The 1 below can occur as a result of removing blocks in TryMergeBlocks. // The 1 below can occur as a result of removing blocks in TryMergeBlocks.
PredBB = prior(I); // this may have been changed in TryMergeBlocks PredBB = prior(I); // this may have been changed in TryMergeBlocks
if (MergePotentials.size()==1 && if (MergePotentials.size() == 1 &&
MergePotentials.begin()->second != PredBB) MergePotentials.begin()->second != PredBB)
FixTail(MergePotentials.begin()->second, I, TII); FixTail(MergePotentials.begin()->second, I, TII);
} }
@ -773,14 +772,14 @@ bool BranchFolder::TailMergeBlocks(MachineFunction &MF) {
bool BranchFolder::OptimizeBranches(MachineFunction &MF) { bool BranchFolder::OptimizeBranches(MachineFunction &MF) {
bool MadeChange = false; bool MadeChange = false;
// Make sure blocks are numbered in order // Make sure blocks are numbered in order
MF.RenumberBlocks(); MF.RenumberBlocks();
for (MachineFunction::iterator I = ++MF.begin(), E = MF.end(); I != E; ) { for (MachineFunction::iterator I = ++MF.begin(), E = MF.end(); I != E; ) {
MachineBasicBlock *MBB = I++; MachineBasicBlock *MBB = I++;
MadeChange |= OptimizeBlock(MBB); MadeChange |= OptimizeBlock(MBB);
// If it is dead, remove it. // If it is dead, remove it.
if (MBB->pred_empty()) { if (MBB->pred_empty()) {
RemoveDeadBlock(MBB); RemoveDeadBlock(MBB);
@ -801,7 +800,7 @@ bool BranchFolder::OptimizeBranches(MachineFunction &MF) {
/// ///
bool BranchFolder::CanFallThrough(MachineBasicBlock *CurBB, bool BranchFolder::CanFallThrough(MachineBasicBlock *CurBB,
bool BranchUnAnalyzable, bool BranchUnAnalyzable,
MachineBasicBlock *TBB, MachineBasicBlock *TBB,
MachineBasicBlock *FBB, MachineBasicBlock *FBB,
const SmallVectorImpl<MachineOperand> &Cond) { const SmallVectorImpl<MachineOperand> &Cond) {
MachineFunction::iterator Fallthrough = CurBB; MachineFunction::iterator Fallthrough = CurBB;
@ -809,14 +808,14 @@ bool BranchFolder::CanFallThrough(MachineBasicBlock *CurBB,
// If FallthroughBlock is off the end of the function, it can't fall through. // If FallthroughBlock is off the end of the function, it can't fall through.
if (Fallthrough == CurBB->getParent()->end()) if (Fallthrough == CurBB->getParent()->end())
return false; return false;
// If FallthroughBlock isn't a successor of CurBB, no fallthrough is possible. // If FallthroughBlock isn't a successor of CurBB, no fallthrough is possible.
if (!CurBB->isSuccessor(Fallthrough)) if (!CurBB->isSuccessor(Fallthrough))
return false; return false;
// If we couldn't analyze the branch, assume it could fall through. // If we couldn't analyze the branch, assume it could fall through.
if (BranchUnAnalyzable) return true; if (BranchUnAnalyzable) return true;
// If there is no branch, control always falls through. // If there is no branch, control always falls through.
if (TBB == 0) return true; if (TBB == 0) return true;
@ -825,11 +824,11 @@ bool BranchFolder::CanFallThrough(MachineBasicBlock *CurBB,
if (MachineFunction::iterator(TBB) == Fallthrough || if (MachineFunction::iterator(TBB) == Fallthrough ||
MachineFunction::iterator(FBB) == Fallthrough) MachineFunction::iterator(FBB) == Fallthrough)
return true; return true;
// If it's an unconditional branch to some block not the fall through, it // If it's an unconditional branch to some block not the fall through, it
// doesn't fall through. // doesn't fall through.
if (Cond.empty()) return false; if (Cond.empty()) return false;
// Otherwise, if it is conditional and has no explicit false block, it falls // Otherwise, if it is conditional and has no explicit false block, it falls
// through. // through.
return FBB == 0; return FBB == 0;
@ -853,14 +852,14 @@ bool BranchFolder::CanFallThrough(MachineBasicBlock *CurBB) {
/// fall-through to MBB1 than to fall through into MBB2. This has to return /// fall-through to MBB1 than to fall through into MBB2. This has to return
/// a strict ordering, returning true for both (MBB1,MBB2) and (MBB2,MBB1) will /// a strict ordering, returning true for both (MBB1,MBB2) and (MBB2,MBB1) will
/// result in infinite loops. /// result in infinite loops.
static bool IsBetterFallthrough(MachineBasicBlock *MBB1, static bool IsBetterFallthrough(MachineBasicBlock *MBB1,
MachineBasicBlock *MBB2) { MachineBasicBlock *MBB2) {
// Right now, we use a simple heuristic. If MBB2 ends with a call, and // Right now, we use a simple heuristic. If MBB2 ends with a call, and
// MBB1 doesn't, we prefer to fall through into MBB1. This allows us to // MBB1 doesn't, we prefer to fall through into MBB1. This allows us to
// optimize branches that branch to either a return block or an assert block // optimize branches that branch to either a return block or an assert block
// into a fallthrough to the return. // into a fallthrough to the return.
if (MBB1->empty() || MBB2->empty()) return false; if (MBB1->empty() || MBB2->empty()) return false;
// If there is a clear successor ordering we make sure that one block // If there is a clear successor ordering we make sure that one block
// will fall through to the next // will fall through to the next
if (MBB1->isSuccessor(MBB2)) return true; if (MBB1->isSuccessor(MBB2)) return true;
@ -879,7 +878,7 @@ bool BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
MachineFunction::iterator FallThrough = MBB; MachineFunction::iterator FallThrough = MBB;
++FallThrough; ++FallThrough;
// If this block is empty, make everyone use its fall-through, not the block // If this block is empty, make everyone use its fall-through, not the block
// explicitly. Landing pads should not do this since the landing-pad table // explicitly. Landing pads should not do this since the landing-pad table
// points to this block. Blocks with their addresses taken shouldn't be // points to this block. Blocks with their addresses taken shouldn't be
@ -887,7 +886,7 @@ bool BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
if (MBB->empty() && !MBB->isLandingPad() && !MBB->hasAddressTaken()) { if (MBB->empty() && !MBB->isLandingPad() && !MBB->hasAddressTaken()) {
// Dead block? Leave for cleanup later. // Dead block? Leave for cleanup later.
if (MBB->pred_empty()) return MadeChange; if (MBB->pred_empty()) return MadeChange;
if (FallThrough == MF.end()) { if (FallThrough == MF.end()) {
// TODO: Simplify preds to not branch here if possible! // TODO: Simplify preds to not branch here if possible!
} else { } else {
@ -917,20 +916,20 @@ bool BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
// If the CFG for the prior block has extra edges, remove them. // If the CFG for the prior block has extra edges, remove them.
MadeChange |= PrevBB.CorrectExtraCFGEdges(PriorTBB, PriorFBB, MadeChange |= PrevBB.CorrectExtraCFGEdges(PriorTBB, PriorFBB,
!PriorCond.empty()); !PriorCond.empty());
// If the previous branch is conditional and both conditions go to the same // If the previous branch is conditional and both conditions go to the same
// destination, remove the branch, replacing it with an unconditional one or // destination, remove the branch, replacing it with an unconditional one or
// a fall-through. // a fall-through.
if (PriorTBB && PriorTBB == PriorFBB) { if (PriorTBB && PriorTBB == PriorFBB) {
TII->RemoveBranch(PrevBB); TII->RemoveBranch(PrevBB);
PriorCond.clear(); PriorCond.clear();
if (PriorTBB != MBB) if (PriorTBB != MBB)
TII->InsertBranch(PrevBB, PriorTBB, 0, PriorCond); TII->InsertBranch(PrevBB, PriorTBB, 0, PriorCond);
MadeChange = true; MadeChange = true;
++NumBranchOpts; ++NumBranchOpts;
return OptimizeBlock(MBB); return OptimizeBlock(MBB);
} }
// If the previous branch *only* branches to *this* block (conditional or // If the previous branch *only* branches to *this* block (conditional or
// not) remove the branch. // not) remove the branch.
if (PriorTBB == MBB && PriorFBB == 0) { if (PriorTBB == MBB && PriorFBB == 0) {
@ -939,7 +938,7 @@ bool BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
++NumBranchOpts; ++NumBranchOpts;
return OptimizeBlock(MBB); return OptimizeBlock(MBB);
} }
// If the prior block branches somewhere else on the condition and here if // If the prior block branches somewhere else on the condition and here if
// the condition is false, remove the uncond second branch. // the condition is false, remove the uncond second branch.
if (PriorFBB == MBB) { if (PriorFBB == MBB) {
@ -949,7 +948,7 @@ bool BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
++NumBranchOpts; ++NumBranchOpts;
return OptimizeBlock(MBB); return OptimizeBlock(MBB);
} }
// If the prior block branches here on true and somewhere else on false, and // If the prior block branches here on true and somewhere else on false, and
// if the branch condition is reversible, reverse the branch to create a // if the branch condition is reversible, reverse the branch to create a
// fall-through. // fall-through.
@ -963,7 +962,7 @@ bool BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
return OptimizeBlock(MBB); return OptimizeBlock(MBB);
} }
} }
// If this block has no successors (e.g. it is a return block or ends with // If this block has no successors (e.g. it is a return block or ends with
// a call to a no-return function like abort or __cxa_throw) and if the pred // a call to a no-return function like abort or __cxa_throw) and if the pred
// falls through into this block, and if it would otherwise fall through // falls through into this block, and if it would otherwise fall through
@ -976,7 +975,7 @@ bool BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
MachineFunction::iterator(PriorTBB) == FallThrough && MachineFunction::iterator(PriorTBB) == FallThrough &&
!CanFallThrough(MBB)) { !CanFallThrough(MBB)) {
bool DoTransform = true; bool DoTransform = true;
// We have to be careful that the succs of PredBB aren't both no-successor // We have to be careful that the succs of PredBB aren't both no-successor
// blocks. If neither have successors and if PredBB is the second from // blocks. If neither have successors and if PredBB is the second from
// last block in the function, we'd just keep swapping the two blocks for // last block in the function, we'd just keep swapping the two blocks for
@ -1000,15 +999,15 @@ bool BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
if (DoTransform && !MBB->succ_empty() && if (DoTransform && !MBB->succ_empty() &&
(!CanFallThrough(PriorTBB) || PriorTBB->empty())) (!CanFallThrough(PriorTBB) || PriorTBB->empty()))
DoTransform = false; DoTransform = false;
if (DoTransform) { if (DoTransform) {
// Reverse the branch so we will fall through on the previous true cond. // Reverse the branch so we will fall through on the previous true cond.
SmallVector<MachineOperand, 4> NewPriorCond(PriorCond); SmallVector<MachineOperand, 4> NewPriorCond(PriorCond);
if (!TII->ReverseBranchCondition(NewPriorCond)) { if (!TII->ReverseBranchCondition(NewPriorCond)) {
DEBUG(errs() << "\nMoving MBB: " << *MBB DEBUG(errs() << "\nMoving MBB: " << *MBB
<< "To make fallthrough to: " << *PriorTBB << "\n"); << "To make fallthrough to: " << *PriorTBB << "\n");
TII->RemoveBranch(PrevBB); TII->RemoveBranch(PrevBB);
TII->InsertBranch(PrevBB, MBB, 0, NewPriorCond); TII->InsertBranch(PrevBB, MBB, 0, NewPriorCond);
@ -1021,7 +1020,7 @@ bool BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
} }
} }
} }
// Analyze the branch in the current block. // Analyze the branch in the current block.
MachineBasicBlock *CurTBB = 0, *CurFBB = 0; MachineBasicBlock *CurTBB = 0, *CurFBB = 0;
SmallVector<MachineOperand, 4> CurCond; SmallVector<MachineOperand, 4> CurCond;
@ -1030,7 +1029,7 @@ bool BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
// If the CFG for the prior block has extra edges, remove them. // If the CFG for the prior block has extra edges, remove them.
MadeChange |= MBB->CorrectExtraCFGEdges(CurTBB, CurFBB, !CurCond.empty()); MadeChange |= MBB->CorrectExtraCFGEdges(CurTBB, CurFBB, !CurCond.empty());
// If this is a two-way branch, and the FBB branches to this block, reverse // If this is a two-way branch, and the FBB branches to this block, reverse
// the condition so the single-basic-block loop is faster. Instead of: // the condition so the single-basic-block loop is faster. Instead of:
// Loop: xxx; jcc Out; jmp Loop // Loop: xxx; jcc Out; jmp Loop
// we want: // we want:
@ -1045,11 +1044,11 @@ bool BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
return OptimizeBlock(MBB); return OptimizeBlock(MBB);
} }
} }
// If this branch is the only thing in its block, see if we can forward // If this branch is the only thing in its block, see if we can forward
// other blocks across it. // other blocks across it.
if (CurTBB && CurCond.empty() && CurFBB == 0 && if (CurTBB && CurCond.empty() && CurFBB == 0 &&
MBB->begin()->getDesc().isBranch() && CurTBB != MBB && MBB->begin()->getDesc().isBranch() && CurTBB != MBB &&
!MBB->hasAddressTaken()) { !MBB->hasAddressTaken()) {
// This block may contain just an unconditional branch. Because there can // This block may contain just an unconditional branch. Because there can
@ -1068,7 +1067,7 @@ bool BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
!PrevBB.isSuccessor(MBB)) { !PrevBB.isSuccessor(MBB)) {
// If the prior block falls through into us, turn it into an // If the prior block falls through into us, turn it into an
// explicit branch to us to make updates simpler. // explicit branch to us to make updates simpler.
if (!PredHasNoFallThrough && PrevBB.isSuccessor(MBB) && if (!PredHasNoFallThrough && PrevBB.isSuccessor(MBB) &&
PriorTBB != MBB && PriorFBB != MBB) { PriorTBB != MBB && PriorFBB != MBB) {
if (PriorTBB == 0) { if (PriorTBB == 0) {
assert(PriorCond.empty() && PriorFBB == 0 && assert(PriorCond.empty() && PriorFBB == 0 &&
@ -1104,7 +1103,7 @@ bool BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
NewCurFBB, NewCurCond, true); NewCurFBB, NewCurCond, true);
if (!NewCurUnAnalyzable && NewCurTBB && NewCurTBB == NewCurFBB) { if (!NewCurUnAnalyzable && NewCurTBB && NewCurTBB == NewCurFBB) {
TII->RemoveBranch(*PMBB); TII->RemoveBranch(*PMBB);
NewCurCond.clear(); NewCurCond.clear();
TII->InsertBranch(*PMBB, NewCurTBB, 0, NewCurCond); TII->InsertBranch(*PMBB, NewCurTBB, 0, NewCurCond);
MadeChange = true; MadeChange = true;
++NumBranchOpts; ++NumBranchOpts;
@ -1122,7 +1121,7 @@ bool BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
} }
} }
} }
// Add the branch back if the block is more than just an uncond branch. // Add the branch back if the block is more than just an uncond branch.
TII->InsertBranch(*MBB, CurTBB, 0, CurCond); TII->InsertBranch(*MBB, CurTBB, 0, CurCond);
} }
@ -1135,7 +1134,7 @@ bool BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
PriorTBB, PriorFBB, PriorCond)) { PriorTBB, PriorFBB, PriorCond)) {
// Now we know that there was no fall-through into this block, check to // Now we know that there was no fall-through into this block, check to
// see if it has a fall-through into its successor. // see if it has a fall-through into its successor.
bool CurFallsThru = CanFallThrough(MBB, CurUnAnalyzable, CurTBB, CurFBB, bool CurFallsThru = CanFallThrough(MBB, CurUnAnalyzable, CurTBB, CurFBB,
CurCond); CurCond);
if (!MBB->isLandingPad()) { if (!MBB->isLandingPad()) {
@ -1151,7 +1150,7 @@ bool BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
&& (!CurFallsThru || MBB->getNumber() >= PredBB->getNumber())) { && (!CurFallsThru || MBB->getNumber() >= PredBB->getNumber())) {
// If the current block doesn't fall through, just move it. // If the current block doesn't fall through, just move it.
// If the current block can fall through and does not end with a // If the current block can fall through and does not end with a
// conditional branch, we need to append an unconditional jump to // conditional branch, we need to append an unconditional jump to
// the (current) next block. To avoid a possible compile-time // the (current) next block. To avoid a possible compile-time
// infinite loop, move blocks only backward in this case. // infinite loop, move blocks only backward in this case.
// Also, if there are already 2 branches here, we cannot add a third; // Also, if there are already 2 branches here, we cannot add a third;
@ -1170,7 +1169,7 @@ bool BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
} }
} }
} }
if (!CurFallsThru) { if (!CurFallsThru) {
// Check all successors to see if we can move this block before it. // Check all successors to see if we can move this block before it.
for (MachineBasicBlock::succ_iterator SI = MBB->succ_begin(), for (MachineBasicBlock::succ_iterator SI = MBB->succ_begin(),
@ -1178,7 +1177,7 @@ bool BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
// Analyze the branch at the end of the block before the succ. // Analyze the branch at the end of the block before the succ.
MachineBasicBlock *SuccBB = *SI; MachineBasicBlock *SuccBB = *SI;
MachineFunction::iterator SuccPrev = SuccBB; --SuccPrev; MachineFunction::iterator SuccPrev = SuccBB; --SuccPrev;
// If this block doesn't already fall-through to that successor, and if // If this block doesn't already fall-through to that successor, and if
// the succ doesn't already have a block that can fall through into it, // the succ doesn't already have a block that can fall through into it,
// and if the successor isn't an EH destination, we can arrange for the // and if the successor isn't an EH destination, we can arrange for the
@ -1190,7 +1189,7 @@ bool BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
return OptimizeBlock(MBB); return OptimizeBlock(MBB);
} }
} }
// Okay, there is no really great place to put this block. If, however, // 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 // the block before this one would be a fall-through if this block were
// removed, move this block to the end of the function. // removed, move this block to the end of the function.