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Add support for tail duplication to BranchFolding, and extend

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tail merging support to handle more cases.
 - Recognize several cases where tail merging is beneficial even when
   the tail size is smaller than the generic threshold.
 - Make use of MachineInstrDesc::isBarrier to help detect
   non-fallthrough blocks.
 - Check for and avoid disrupting fall-through edges in more cases.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86871 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2009-11-11 19:48:59 +00:00
parent 3e20475fee
commit 2210c0bea8
6 changed files with 572 additions and 60 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

344
lib/CodeGen/BranchFolding.cpp
View File

@ -32,6 +32,7 @@
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/STLExtras.h"
#include <algorithm>
@ -48,10 +49,16 @@ TailMergeThreshold("tail-merge-threshold",
cl::desc("Max number of predecessors to consider tail merging"),
cl::init(150), cl::Hidden);
// Heuristic for tail merging (and, inversely, tail duplication).
// TODO: This should be replaced with a target query.
static cl::opt<unsigned>
TailMergeSize("tail-merge-size",
cl::desc("Min number of instructions to consider tail merging"),
cl::init(3), cl::Hidden);
char BranchFolderPass::ID = 0;
FunctionPass *llvm::createBranchFoldingPass(bool DefaultEnableTailMerge) {
Pass *llvm::createBranchFoldingPass(bool DefaultEnableTailMerge) {
return new BranchFolderPass(DefaultEnableTailMerge);
}
@ -442,6 +449,25 @@ static bool MergeCompare(const std::pair<unsigned,MachineBasicBlock*> &p,
}
}
/// CountTerminators - Count the number of terminators in the given
/// block and set I to the position of the first non-terminator, if there
/// is one, or MBB->end() otherwise.
static unsigned CountTerminators(MachineBasicBlock *MBB,
MachineBasicBlock::iterator &I) {
I = MBB->end();
unsigned NumTerms = 0;
for (;;) {
if (I == MBB->begin()) {
I = MBB->end();
break;
}
--I;
if (!I->getDesc().isTerminator()) break;
++NumTerms;
}
return NumTerms;
}
/// ProfitableToMerge - Check if two machine basic blocks have a common tail
/// and decide if it would be profitable to merge those tails. Return the
/// length of the common tail and iterators to the first common instruction
@ -451,16 +477,35 @@ static bool ProfitableToMerge(MachineBasicBlock *MBB1,
unsigned minCommonTailLength,
unsigned &CommonTailLen,
MachineBasicBlock::iterator &I1,
MachineBasicBlock::iterator &I2) {
MachineBasicBlock::iterator &I2,
MachineBasicBlock *SuccBB,
MachineBasicBlock *PredBB) {
CommonTailLen = ComputeCommonTailLength(MBB1, MBB2, I1, I2);
MachineFunction *MF = MBB1->getParent();
if (CommonTailLen >= minCommonTailLength)
return true;
if (CommonTailLen == 0)
return false;
// It's almost always profitable to merge any number of non-terminator
// instructions with the block that falls through into the common successor.
if (MBB1 == PredBB || MBB2 == PredBB) {
MachineBasicBlock::iterator I;
unsigned NumTerms = CountTerminators(MBB1 == PredBB ? MBB2 : MBB1, I);
if (CommonTailLen > NumTerms)
return true;
}
// If both blocks have an unconditional branch temporarily stripped out,
// treat that as an additional common instruction.
if (MBB1 != PredBB && MBB2 != PredBB &&
!MBB1->back().getDesc().isBarrier() &&
!MBB2->back().getDesc().isBarrier())
--minCommonTailLength;
// Check if the common tail is long enough to be worthwhile.
if (CommonTailLen >= minCommonTailLength)
return true;
// If we are optimizing for code size, 1 instruction in common is enough if
// we don't have to split a block. At worst we will be replacing a
// fallthrough into the common tail with a branch, which at worst breaks
@ -483,7 +528,9 @@ static bool ProfitableToMerge(MachineBasicBlock *MBB1,
/// those blocks appear in MergePotentials (where they are not necessarily
/// consecutive).
unsigned BranchFolder::ComputeSameTails(unsigned CurHash,
unsigned minCommonTailLength) {
unsigned minCommonTailLength,
MachineBasicBlock *SuccBB,
MachineBasicBlock *PredBB) {
unsigned maxCommonTailLength = 0U;
SameTails.clear();
MachineBasicBlock::iterator TrialBBI1, TrialBBI2;
@ -495,7 +542,8 @@ unsigned BranchFolder::ComputeSameTails(unsigned CurHash,
for (MPIterator I = prior(CurMPIter); I->first == CurHash ; --I) {
unsigned CommonTailLen;
if (ProfitableToMerge(CurMPIter->second, I->second, minCommonTailLength,
CommonTailLen, TrialBBI1, TrialBBI2)) {
CommonTailLen, TrialBBI1, TrialBBI2,
SuccBB, PredBB)) {
if (CommonTailLen > maxCommonTailLength) {
SameTails.clear();
maxCommonTailLength = CommonTailLen;
@ -581,16 +629,62 @@ unsigned BranchFolder::CreateCommonTailOnlyBlock(MachineBasicBlock *&PredBB,
// The lone predecessor of Succ that falls through into Succ,
// if any, is given in PredBB.
bool BranchFolder::TryMergeBlocks(MachineBasicBlock *SuccBB,
MachineBasicBlock* PredBB) {
bool BranchFolder::TryTailMergeBlocks(MachineBasicBlock *SuccBB,
MachineBasicBlock* PredBB) {
bool MadeChange = false;
// It doesn't make sense to save a single instruction since tail merging
// will add a jump.
// FIXME: Ask the target to provide the threshold?
unsigned minCommonTailLength = (SuccBB ? 1 : 2) + 1;
// Except for the special cases below, tail-merge if there are at least
// this many instructions in common.
unsigned minCommonTailLength = TailMergeSize;
DEBUG(errs() << "\nTryMergeBlocks " << MergePotentials.size() << '\n');
// If there's a successor block, there are some cases which don't require
// new branching and as such are very likely to be profitable.
if (SuccBB) {
if (SuccBB->pred_size() == MergePotentials.size() &&
!MergePotentials[0].second->empty()) {
// If all the predecessors have at least one tail instruction in common,
// merging is very likely to be a win since it won't require an increase
// in static branches, and it will decrease the static instruction count.
bool AllPredsMatch = true;
MachineBasicBlock::iterator FirstNonTerm;
unsigned MinNumTerms = CountTerminators(MergePotentials[0].second,
FirstNonTerm);
if (FirstNonTerm != MergePotentials[0].second->end()) {
for (unsigned i = 1, e = MergePotentials.size(); i != e; ++i) {
MachineBasicBlock::iterator OtherFirstNonTerm;
unsigned NumTerms = CountTerminators(MergePotentials[0].second,
OtherFirstNonTerm);
if (NumTerms < MinNumTerms)
MinNumTerms = NumTerms;
if (OtherFirstNonTerm == MergePotentials[i].second->end() ||
OtherFirstNonTerm->isIdenticalTo(FirstNonTerm)) {
AllPredsMatch = false;
break;
}
}
// If they all have an instruction in common, do any amount of merging.
if (AllPredsMatch)
minCommonTailLength = MinNumTerms + 1;
}
}
}
DEBUG(errs() << "\nTryTailMergeBlocks: ";
for (unsigned i = 0, e = MergePotentials.size(); i != e; ++i)
errs() << "BB#" << MergePotentials[i].second->getNumber()
<< (i == e-1 ? "" : ", ");
errs() << "\n";
if (SuccBB) {
errs() << " with successor BB#" << SuccBB->getNumber() << '\n';
if (PredBB)
errs() << " which has fall-through from BB#"
<< PredBB->getNumber() << "\n";
}
errs() << "Looking for common tails of at least "
<< minCommonTailLength << " instruction"
<< (minCommonTailLength == 1 ? "" : "s") << '\n';
);
// Sort by hash value so that blocks with identical end sequences sort
// together.
@ -603,7 +697,8 @@ bool BranchFolder::TryMergeBlocks(MachineBasicBlock *SuccBB,
// Build SameTails, identifying the set of blocks with this hash code
// and with the maximum number of instructions in common.
unsigned maxCommonTailLength = ComputeSameTails(CurHash,
minCommonTailLength);
minCommonTailLength,
SuccBB, PredBB);
// If we didn't find any pair that has at least minCommonTailLength
// instructions in common, remove all blocks with this hash code and retry.
@ -621,27 +716,35 @@ bool BranchFolder::TryMergeBlocks(MachineBasicBlock *SuccBB,
unsigned int commonTailIndex, i;
for (commonTailIndex=SameTails.size(), i=0; i<SameTails.size(); i++) {
MachineBasicBlock *MBB = SameTails[i].first->second;
if (MBB->begin() == SameTails[i].second && MBB != EntryBB) {
if (MBB == EntryBB)
continue;
if (MBB == PredBB) {
commonTailIndex = i;
if (MBB == PredBB)
break;
break;
}
if (MBB->begin() == SameTails[i].second)
commonTailIndex = i;
}
if (commonTailIndex == SameTails.size()) {
if (commonTailIndex == SameTails.size() ||
(SameTails[commonTailIndex].first->second == PredBB &&
SameTails[commonTailIndex].first->second->begin() !=
SameTails[i].second)) {
// None of the blocks consist entirely of the common tail.
// Split a block so that one does.
commonTailIndex = CreateCommonTailOnlyBlock(PredBB, maxCommonTailLength);
commonTailIndex = CreateCommonTailOnlyBlock(PredBB, maxCommonTailLength);
}
MachineBasicBlock *MBB = SameTails[commonTailIndex].first->second;
// MBB is common tail. Adjust all other BB's to jump to this one.
// Traversal must be forwards so erases work.
DEBUG(errs() << "\nUsing common tail BB#" << MBB->getNumber() << " for ");
for (unsigned int i=0; i<SameTails.size(); ++i) {
DEBUG(errs() << "\nUsing common tail in BB#" << MBB->getNumber()
<< " for ");
for (unsigned int i=0, e = SameTails.size(); i != e; ++i) {
if (commonTailIndex == i)
continue;
DEBUG(errs() << "BB#" << SameTails[i].first->second->getNumber() << ", ");
DEBUG(errs() << "BB#" << SameTails[i].first->second->getNumber()
<< (i == e-1 ? "" : ", "));
// Hack the end off BB i, making it jump to BB commonTailIndex instead.
ReplaceTailWithBranchTo(SameTails[i].second, MBB);
// BB i is no longer a predecessor of SuccBB; remove it from the worklist.
@ -671,7 +774,7 @@ bool BranchFolder::TailMergeBlocks(MachineFunction &MF) {
// See if we can do any tail merging on those.
if (MergePotentials.size() < TailMergeThreshold &&
MergePotentials.size() >= 2)
MadeChange |= TryMergeBlocks(NULL, NULL);
MadeChange |= TryTailMergeBlocks(NULL, NULL);
// Look at blocks (IBB) with multiple predecessors (PBB).
// We change each predecessor to a canonical form, by
@ -692,7 +795,8 @@ bool BranchFolder::TailMergeBlocks(MachineFunction &MF) {
// a compile-time infinite loop repeatedly doing and undoing the same
// transformations.)
for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) {
for (MachineFunction::iterator I = next(MF.begin()), E = MF.end();
I != E; ++I) {
if (I->pred_size() >= 2 && I->pred_size() < TailMergeThreshold) {
SmallPtrSet<MachineBasicBlock *, 8> UniquePreds;
MachineBasicBlock *IBB = I;
@ -754,13 +858,13 @@ bool BranchFolder::TailMergeBlocks(MachineFunction &MF) {
}
}
if (MergePotentials.size() >= 2)
MadeChange |= TryMergeBlocks(I, PredBB);
MadeChange |= TryTailMergeBlocks(IBB, PredBB);
// Reinsert an unconditional branch if needed.
// The 1 below can occur as a result of removing blocks in TryMergeBlocks.
PredBB = prior(I); // this may have been changed in TryMergeBlocks
// The 1 below can occur as a result of removing blocks in TryTailMergeBlocks.
PredBB = prior(I); // this may have been changed in TryTailMergeBlocks
if (MergePotentials.size() == 1 &&
MergePotentials.begin()->second != PredBB)
FixTail(MergePotentials.begin()->second, I, TII);
FixTail(MergePotentials.begin()->second, IBB, TII);
}
}
return MadeChange;
@ -813,9 +917,17 @@ bool BranchFolder::CanFallThrough(MachineBasicBlock *CurBB,
if (!CurBB->isSuccessor(Fallthrough))
return false;
// If we couldn't analyze the branch, assume it could fall through.
if (BranchUnAnalyzable) return true;
// If we couldn't analyze the branch, examine the last instruction.
// If the block doesn't end in a known control barrier, assume fallthrough
// is possible. The isPredicable check is needed because this code can be
// called during IfConversion, where an instruction which is normally a
// Barrier is predicated and thus no longer an actual control barrier. This
// is over-conservative though, because if an instruction isn't actually
// predicated we could still treat it like a barrier.
if (BranchUnAnalyzable)
return CurBB->empty() || !CurBB->back().getDesc().isBarrier() ||
CurBB->back().getDesc().isPredicable();
// If there is no branch, control always falls through.
if (TBB == 0) return true;
@ -870,11 +982,108 @@ static bool IsBetterFallthrough(MachineBasicBlock *MBB1,
return MBB2I->getDesc().isCall() && !MBB1I->getDesc().isCall();
}
/// TailDuplicate - MBB unconditionally branches to SuccBB. If it is profitable,
/// duplicate SuccBB's contents in MBB to eliminate the branch.
bool BranchFolder::TailDuplicate(MachineBasicBlock *TailBB,
bool PrevFallsThrough,
MachineFunction &MF) {
// Don't try to tail-duplicate single-block loops.
if (TailBB->isSuccessor(TailBB))
return false;
// Don't tail-duplicate a block which will soon be folded into its successor.
if (TailBB->succ_size() == 1 &&
TailBB->succ_begin()[0]->pred_size() == 1)
return false;
// Duplicate up to one less that the tail-merge threshold, so that we don't
// get into an infinite loop between duplicating and merging. When optimizing
// for size, duplicate only one, because one branch instruction can be
// eliminated to compensate for the duplication.
unsigned MaxDuplicateCount =
MF.getFunction()->hasFnAttr(Attribute::OptimizeForSize) ?
1 : (TailMergeSize - 1);
// Check the instructions in the block to determine whether tail-duplication
// is invalid or unlikely to be unprofitable.
unsigned i = 0;
bool HasCall = false;
for (MachineBasicBlock::iterator I = TailBB->begin();
I != TailBB->end(); ++I, ++i) {
// Non-duplicable things shouldn't be tail-duplicated.
if (I->getDesc().isNotDuplicable()) return false;
// Don't duplicate more than the threshold.
if (i == MaxDuplicateCount) return false;
// Remember if we saw a call.
if (I->getDesc().isCall()) HasCall = true;
}
// Heuristically, don't tail-duplicate calls if it would expand code size,
// as it's less likely to be worth the extra cost.
if (i > 1 && HasCall)
return false;
// Iterate through all the unique predecessors and tail-duplicate this
// block into them, if possible. Copying the list ahead of time also
// avoids trouble with the predecessor list reallocating.
bool Changed = false;
SmallSetVector<MachineBasicBlock *, 8> Preds(TailBB->pred_begin(),
TailBB->pred_end());
for (SmallSetVector<MachineBasicBlock *, 8>::iterator PI = Preds.begin(),
PE = Preds.end(); PI != PE; ++PI) {
MachineBasicBlock *PredBB = *PI;
assert(TailBB != PredBB &&
"Single-block loop should have been rejected earlier!");
if (PredBB->succ_size() > 1) continue;
MachineBasicBlock *PredTBB, *PredFBB;
SmallVector<MachineOperand, 4> PredCond;
if (TII->AnalyzeBranch(*PredBB, PredTBB, PredFBB, PredCond, true))
continue;
if (!PredCond.empty())
continue;
// EH edges are ignored by AnalyzeBranch.
if (PredBB->succ_size() != 1)
continue;
// Don't duplicate into a fall-through predecessor unless its the
// only predecessor.
if (&*next(MachineFunction::iterator(PredBB)) == TailBB &&
PrevFallsThrough &&
TailBB->pred_size() != 1)
continue;
DEBUG(errs() << "\nTail-duplicating into PredBB: " << *PredBB
<< "From Succ: " << *TailBB);
// Remove PredBB's unconditional branch.
TII->RemoveBranch(*PredBB);
// Clone the contents of TailBB into PredBB.
for (MachineBasicBlock::iterator I = TailBB->begin(), E = TailBB->end();
I != E; ++I) {
MachineInstr *NewMI = MF.CloneMachineInstr(I);
PredBB->insert(PredBB->end(), NewMI);
}
// Update the CFG.
PredBB->removeSuccessor(PredBB->succ_begin());
assert(PredBB->succ_empty() &&
"TailDuplicate called on block with multiple successors!");
for (MachineBasicBlock::succ_iterator I = TailBB->succ_begin(),
E = TailBB->succ_end(); I != E; ++I)
PredBB->addSuccessor(*I);
Changed = true;
}
return Changed;
}
/// OptimizeBlock - Analyze and optimize control flow related to the specified
/// block. This is never called on the entry block.
bool BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
bool MadeChange = false;
MachineFunction &MF = *MBB->getParent();
ReoptimizeBlock:
MachineFunction::iterator FallThrough = MBB;
++FallThrough;
@ -927,16 +1136,36 @@ bool BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
TII->InsertBranch(PrevBB, PriorTBB, 0, PriorCond);
MadeChange = true;
++NumBranchOpts;
return OptimizeBlock(MBB);
goto ReoptimizeBlock;
}
// If the previous block unconditionally falls through to this block and
// this block has no other predecessors, move the contents of this block
// into the prior block. This doesn't usually happen when SimplifyCFG
// has been used, but it can happen tail duplication eliminates all the
// non-branch predecessors of a block leaving only the fall-through edge.
// This has to check PrevBB->succ_size() because EH edges are ignored by
// AnalyzeBranch.
if (PriorCond.empty() && !PriorTBB && MBB->pred_size() == 1 &&
PrevBB.succ_size() == 1 &&
!MBB->hasAddressTaken()) {
DEBUG(errs() << "\nMerging into block: " << PrevBB
<< "From MBB: " << *MBB);
PrevBB.splice(PrevBB.end(), MBB, MBB->begin(), MBB->end());
PrevBB.removeSuccessor(PrevBB.succ_begin());;
assert(PrevBB.succ_empty());
PrevBB.transferSuccessors(MBB);
MadeChange = true;
return MadeChange;
}
// If the previous branch *only* branches to *this* block (conditional or
// not) remove the branch.
if (PriorTBB == MBB && PriorFBB == 0) {
TII->RemoveBranch(PrevBB);
MadeChange = true;
++NumBranchOpts;
return OptimizeBlock(MBB);
goto ReoptimizeBlock;
}
// If the prior block branches somewhere else on the condition and here if
@ -946,7 +1175,7 @@ bool BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
TII->InsertBranch(PrevBB, PriorTBB, 0, PriorCond);
MadeChange = true;
++NumBranchOpts;
return OptimizeBlock(MBB);
goto ReoptimizeBlock;
}
// If the prior block branches here on true and somewhere else on false, and
@ -959,7 +1188,7 @@ bool BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
TII->InsertBranch(PrevBB, PriorFBB, 0, NewPriorCond);
MadeChange = true;
++NumBranchOpts;
return OptimizeBlock(MBB);
goto ReoptimizeBlock;
}
}
@ -1041,7 +1270,7 @@ bool BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
TII->InsertBranch(*MBB, CurFBB, CurTBB, NewCond);
MadeChange = true;
++NumBranchOpts;
return OptimizeBlock(MBB);
goto ReoptimizeBlock;
}
}
@ -1107,7 +1336,7 @@ bool BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
TII->InsertBranch(*PMBB, NewCurTBB, 0, NewCurCond);
MadeChange = true;
++NumBranchOpts;
PMBB->CorrectExtraCFGEdges(NewCurTBB, NewCurFBB, false);
PMBB->CorrectExtraCFGEdges(NewCurTBB, 0, false);
}
}
}
@ -1127,16 +1356,26 @@ bool BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
}
}
// Now we know that there was no fall-through into this block, check to
// see if it has a fall-through into its successor.
bool CurFallsThru = CanFallThrough(MBB, CurUnAnalyzable, CurTBB, CurFBB,
CurCond);
bool PrevFallsThru = CanFallThrough(&PrevBB, PriorUnAnalyzable,
PriorTBB, PriorFBB, PriorCond);
// If this block is small, unconditionally branched to, and does not
// fall through, tail-duplicate its instructions into its predecessors
// to eliminate a (dynamic) branch.
if (!CurFallsThru)
if (TailDuplicate(MBB, PrevFallsThru, MF)) {
MadeChange = true;
return MadeChange;
}
// If the prior block doesn't fall through into this block, and if this
// block doesn't fall through into some other block, see if we can find a
// place to move this block where a fall-through will happen.
if (!CanFallThrough(&PrevBB, PriorUnAnalyzable,
PriorTBB, PriorFBB, PriorCond)) {
// Now we know that there was no fall-through into this block, check to
// see if it has a fall-through into its successor.
bool CurFallsThru = CanFallThrough(MBB, CurUnAnalyzable, CurTBB, CurFBB,
CurCond);
if (!PrevFallsThru) {
if (!MBB->isLandingPad()) {
// Check all the predecessors of this block. If one of them has no fall
// throughs, move this block right after it.
@ -1145,7 +1384,10 @@ bool BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
// Analyze the branch at the end of the pred.
MachineBasicBlock *PredBB = *PI;
MachineFunction::iterator PredFallthrough = PredBB; ++PredFallthrough;
if (PredBB != MBB && !CanFallThrough(PredBB)
MachineBasicBlock *PredTBB, *PredFBB;
SmallVector<MachineOperand, 4> PredCond;
if (PredBB != MBB && !CanFallThrough(PredBB) &&
!TII->AnalyzeBranch(*PredBB, PredTBB, PredFBB, PredCond, true)
&& (!CurFallsThru || !CurTBB || !CurFBB)
&& (!CurFallsThru || MBB->getNumber() >= PredBB->getNumber())) {
// If the current block doesn't fall through, just move it.
@ -1165,7 +1407,7 @@ bool BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
}
MBB->moveAfter(PredBB);
MadeChange = true;
return OptimizeBlock(MBB);
goto ReoptimizeBlock;
}
}
}
@ -1182,18 +1424,22 @@ bool BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
// 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
// fallthrough to happen.
if (SuccBB != MBB && !CanFallThrough(SuccPrev) &&
if (SuccBB != MBB && &*SuccPrev != MBB &&
!CanFallThrough(SuccPrev) && !CurUnAnalyzable &&
!SuccBB->isLandingPad()) {
MBB->moveBefore(SuccBB);
MadeChange = true;
return OptimizeBlock(MBB);
goto ReoptimizeBlock;
}
}
// 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, *PrevFBB;
SmallVector<MachineOperand, 4> PrevCond;
if (FallThrough != MF.end() &&
!TII->AnalyzeBranch(PrevBB, PrevTBB, PrevFBB, PrevCond, true) &&
PrevBB.isSuccessor(FallThrough)) {
MBB->moveAfter(--MF.end());
MadeChange = true;

5
lib/CodeGen/MachineBasicBlock.cpp
View File

@ -371,10 +371,7 @@ bool MachineBasicBlock::CorrectExtraCFGEdges(MachineBasicBlock *DestA,
MachineBasicBlock::succ_iterator SI = succ_begin();
MachineBasicBlock *OrigDestA = DestA, *OrigDestB = DestB;
while (SI != succ_end()) {
if (*SI == DestA && DestA == DestB) {
DestA = DestB = 0;
++SI;
} else if (*SI == DestA) {
if (*SI == DestA) {
DestA = 0;
++SI;
} else if (*SI == DestB) {

3
test/CodeGen/Thumb2/thumb2-cbnz.ll
View File

@ -20,7 +20,8 @@ bb7: ; preds = %bb3
br i1 %a, label %bb11, label %bb9
bb9: ; preds = %bb7
; CHECK: @ BB#2:
; CHECK: cmp r0, #0
; CHECK-NEXT: cmp r0, #0
; CHECK-NEXT: cbnz
%0 = tail call arm_apcscc double @floor(double %b) nounwind readnone ; <double> [#uses=0]
br label %bb11

2
test/CodeGen/Thumb2/thumb2-ifcvt3.ll
View File

@ -23,7 +23,7 @@ bb52: ; preds = %newFuncRoot
; CHECK: movne
; CHECK: moveq
; CHECK: pop
; CHECK-NEXT: LBB1_2:
; CHECK-NEXT: LBB1_1:
%0 = load i64* @posed, align 4 ; <i64> [#uses=3]
%1 = sub i64 %0, %.reload78 ; <i64> [#uses=1]
%2 = ashr i64 %1, 1 ; <i64> [#uses=3]

10
test/CodeGen/X86/loop-blocks.ll
View File

@ -74,16 +74,16 @@ exit:
; CHECK: yet_more_involved:
; CHECK: jmp .LBB3_1
; CHECK-NEXT: align
; CHECK-NEXT: .LBB3_3:
; CHECK-NEXT: .LBB3_4:
; CHECK-NEXT: call bar99
; CHECK-NEXT: call get
; CHECK-NEXT: cmpl $2999, %eax
; CHECK-NEXT: jg .LBB3_5
; CHECK-NEXT: jg .LBB3_6
; CHECK-NEXT: call block_a_true_func
; CHECK-NEXT: jmp .LBB3_6
; CHECK-NEXT: .LBB3_5:
; CHECK-NEXT: call block_a_false_func
; CHECK-NEXT: jmp .LBB3_7
; CHECK-NEXT: .LBB3_6:
; CHECK-NEXT: call block_a_false_func
; CHECK-NEXT: .LBB3_7:
; CHECK-NEXT: call block_a_merge_func
; CHECK-NEXT: .LBB3_1:
; CHECK-NEXT: call body

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test/CodeGen/X86/tail-opts.ll Normal file
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; RUN: llc < %s -march=x86-64 -mtriple=x86_64-unknown-linux-gnu -asm-verbose=false | FileCheck %s
declare void @bar(i32)
declare void @car(i32)
declare void @dar(i32)
declare void @ear(i32)
declare void @far(i32)
declare i1 @qux()
@GHJK = global i32 0
@HABC = global i32 0
; BranchFolding should tail-merge the stores since they all precede
; direct branches to the same place.
; CHECK: tail_merge_me:
; CHECK-NOT: GHJK
; CHECK: movl $0, GHJK(%rip)
; CHECK-NEXT: movl $1, HABC(%rip)
; CHECK-NOT: GHJK
define void @tail_merge_me() nounwind {
entry:
%a = call i1 @qux()
br i1 %a, label %A, label %next
next:
%b = call i1 @qux()
br i1 %b, label %B, label %C
A:
call void @bar(i32 0)
store i32 0, i32* @GHJK
br label %M
B:
call void @car(i32 1)
store i32 0, i32* @GHJK
br label %M
C:
call void @dar(i32 2)
store i32 0, i32* @GHJK
br label %M
M:
store i32 1, i32* @HABC
%c = call i1 @qux()
br i1 %c, label %return, label %altret
return:
call void @ear(i32 1000)
ret void
altret:
call void @far(i32 1001)
ret void
}
declare i8* @choose(i8*, i8*);
; BranchFolding should tail-duplicate the indirect jump to avoid
; redundant branching.
; CHECK: tail_duplicate_me:
; CHECK: movl $0, GHJK(%rip)
; CHECK-NEXT: jmpq *%rbx
; CHECK: movl $0, GHJK(%rip)
; CHECK-NEXT: jmpq *%rbx
; CHECK: movl $0, GHJK(%rip)
; CHECK-NEXT: jmpq *%rbx
define void @tail_duplicate_me() nounwind {
entry:
%a = call i1 @qux()
%c = call i8* @choose(i8* blockaddress(@tail_duplicate_me, %return),
i8* blockaddress(@tail_duplicate_me, %altret))
br i1 %a, label %A, label %next
next:
%b = call i1 @qux()
br i1 %b, label %B, label %C
A:
call void @bar(i32 0)
store i32 0, i32* @GHJK
br label %M
B:
call void @car(i32 1)
store i32 0, i32* @GHJK
br label %M
C:
call void @dar(i32 2)
store i32 0, i32* @GHJK
br label %M
M:
indirectbr i8* %c, [label %return, label %altret]
return:
call void @ear(i32 1000)
ret void
altret:
call void @far(i32 1001)
ret void
}
; BranchFolding shouldn't try to merge the tails of two blocks
; with only a branch in common, regardless of the fallthrough situation.
; CHECK: dont_merge_oddly:
; CHECK-NOT: ret
; CHECK: ucomiss %xmm0, %xmm1
; CHECK-NEXT: jbe .LBB3_3
; CHECK-NEXT: ucomiss %xmm2, %xmm0
; CHECK-NEXT: ja .LBB3_4
; CHECK-NEXT: .LBB3_2:
; CHECK-NEXT: movb $1, %al
; CHECK-NEXT: ret
; CHECK-NEXT: .LBB3_3:
; CHECK-NEXT: ucomiss %xmm2, %xmm1
; CHECK-NEXT: jbe .LBB3_2
; CHECK-NEXT: .LBB3_4:
; CHECK-NEXT: xorb %al, %al
; CHECK-NEXT: ret
define i1 @dont_merge_oddly(float* %result) nounwind {
entry:
%tmp4 = getelementptr float* %result, i32 2
%tmp5 = load float* %tmp4, align 4
%tmp7 = getelementptr float* %result, i32 4
%tmp8 = load float* %tmp7, align 4
%tmp10 = getelementptr float* %result, i32 6
%tmp11 = load float* %tmp10, align 4
%tmp12 = fcmp olt float %tmp8, %tmp11
br i1 %tmp12, label %bb, label %bb21
bb:
%tmp23469 = fcmp olt float %tmp5, %tmp8
br i1 %tmp23469, label %bb26, label %bb30
bb21:
%tmp23 = fcmp olt float %tmp5, %tmp11
br i1 %tmp23, label %bb26, label %bb30
bb26:
ret i1 0
bb30:
ret i1 1
}
; Do any-size tail-merging when two candidate blocks will both require
; an unconditional jump to complete a two-way conditional branch.
; CHECK: c_expand_expr_stmt:
; CHECK: jmp .LBB4_7
; CHECK-NEXT: .LBB4_12:
; CHECK-NEXT: movq 8(%rax), %rax
; CHECK-NEXT: movb 16(%rax), %al
; CHECK-NEXT: cmpb $16, %al
; CHECK-NEXT: je .LBB4_6
; CHECK-NEXT: cmpb $23, %al
; CHECK-NEXT: je .LBB4_6
; CHECK-NEXT: jmp .LBB4_15
; CHECK-NEXT: .LBB4_14:
; CHECK-NEXT: cmpb $23, %bl
; CHECK-NEXT: jne .LBB4_15
; CHECK-NEXT: .LBB4_15:
%0 = type { %struct.rtx_def* }
%struct.lang_decl = type opaque
%struct.rtx_def = type { i16, i8, i8, [1 x %union.rtunion] }
%struct.tree_decl = type { [24 x i8], i8*, i32, %union.tree_node*, i32, i8, i8, i8, i8, %union.tree_node*, %union.tree_node*, %union.tree_node*, %union.tree_node*, %union.tree_node*, %union.tree_node*, %union.tree_node*, %union.tree_node*, %union.tree_node*, %struct.rtx_def*, %union..2anon, %0, %union.tree_node*, %struct.lang_decl* }
%union..2anon = type { i32 }
%union.rtunion = type { i8* }
%union.tree_node = type { %struct.tree_decl }
define fastcc void @c_expand_expr_stmt(%union.tree_node* %expr) nounwind {
entry:
%tmp4 = load i8* null, align 8 ; <i8> [#uses=3]
switch i8 %tmp4, label %bb3 [
i8 18, label %bb
]
bb: ; preds = %entry
switch i32 undef, label %bb1 [
i32 0, label %bb2.i
i32 37, label %bb.i
]
bb.i: ; preds = %bb
switch i32 undef, label %bb1 [
i32 0, label %lvalue_p.exit
]
bb2.i: ; preds = %bb
br label %bb3
lvalue_p.exit: ; preds = %bb.i
%tmp21 = load %union.tree_node** null, align 8 ; <%union.tree_node*> [#uses=3]
%tmp22 = getelementptr inbounds %union.tree_node* %tmp21, i64 0, i32 0, i32 0, i64 0 ; <i8*> [#uses=1]
%tmp23 = load i8* %tmp22, align 8 ; <i8> [#uses=1]
%tmp24 = zext i8 %tmp23 to i32 ; <i32> [#uses=1]
switch i32 %tmp24, label %lvalue_p.exit4 [
i32 0, label %bb2.i3
i32 2, label %bb.i1
]
bb.i1: ; preds = %lvalue_p.exit
%tmp25 = getelementptr inbounds %union.tree_node* %tmp21, i64 0, i32 0, i32 2 ; <i32*> [#uses=1]
%tmp26 = bitcast i32* %tmp25 to %union.tree_node** ; <%union.tree_node**> [#uses=1]
%tmp27 = load %union.tree_node** %tmp26, align 8 ; <%union.tree_node*> [#uses=2]
%tmp28 = getelementptr inbounds %union.tree_node* %tmp27, i64 0, i32 0, i32 0, i64 16 ; <i8*> [#uses=1]
%tmp29 = load i8* %tmp28, align 8 ; <i8> [#uses=1]
%tmp30 = zext i8 %tmp29 to i32 ; <i32> [#uses=1]
switch i32 %tmp30, label %lvalue_p.exit4 [
i32 0, label %bb2.i.i2
i32 2, label %bb.i.i
]
bb.i.i: ; preds = %bb.i1
%tmp34 = tail call fastcc i32 @lvalue_p(%union.tree_node* null) nounwind ; <i32> [#uses=1]
%phitmp = icmp ne i32 %tmp34, 0 ; <i1> [#uses=1]
br label %lvalue_p.exit4
bb2.i.i2: ; preds = %bb.i1
%tmp35 = getelementptr inbounds %union.tree_node* %tmp27, i64 0, i32 0, i32 0, i64 8 ; <i8*> [#uses=1]
%tmp36 = bitcast i8* %tmp35 to %union.tree_node** ; <%union.tree_node**> [#uses=1]
%tmp37 = load %union.tree_node** %tmp36, align 8 ; <%union.tree_node*> [#uses=1]
%tmp38 = getelementptr inbounds %union.tree_node* %tmp37, i64 0, i32 0, i32 0, i64 16 ; <i8*> [#uses=1]
%tmp39 = load i8* %tmp38, align 8 ; <i8> [#uses=1]
switch i8 %tmp39, label %bb2 [
i8 16, label %lvalue_p.exit4
i8 23, label %lvalue_p.exit4
]
bb2.i3: ; preds = %lvalue_p.exit
%tmp40 = getelementptr inbounds %union.tree_node* %tmp21, i64 0, i32 0, i32 0, i64 8 ; <i8*> [#uses=1]
%tmp41 = bitcast i8* %tmp40 to %union.tree_node** ; <%union.tree_node**> [#uses=1]
%tmp42 = load %union.tree_node** %tmp41, align 8 ; <%union.tree_node*> [#uses=1]
%tmp43 = getelementptr inbounds %union.tree_node* %tmp42, i64 0, i32 0, i32 0, i64 16 ; <i8*> [#uses=1]
%tmp44 = load i8* %tmp43, align 8 ; <i8> [#uses=1]
switch i8 %tmp44, label %bb2 [
i8 16, label %lvalue_p.exit4
i8 23, label %lvalue_p.exit4
]
lvalue_p.exit4: ; preds = %bb2.i3, %bb2.i3, %bb2.i.i2, %bb2.i.i2, %bb.i.i, %bb.i1, %lvalue_p.exit
%tmp45 = phi i1 [ %phitmp, %bb.i.i ], [ false, %bb2.i.i2 ], [ false, %bb2.i.i2 ], [ false, %bb.i1 ], [ false, %bb2.i3 ], [ false, %bb2.i3 ], [ false, %lvalue_p.exit ] ; <i1> [#uses=1]
%tmp46 = icmp eq i8 %tmp4, 0 ; <i1> [#uses=1]
%or.cond = or i1 %tmp45, %tmp46 ; <i1> [#uses=1]
br i1 %or.cond, label %bb2, label %bb3
bb1: ; preds = %bb2.i.i, %bb.i, %bb
%.old = icmp eq i8 %tmp4, 23 ; <i1> [#uses=1]
br i1 %.old, label %bb2, label %bb3
bb2: ; preds = %bb1, %lvalue_p.exit4, %bb2.i3, %bb2.i.i2
br label %bb3
bb3: ; preds = %bb2, %bb1, %lvalue_p.exit4, %bb2.i, %entry
%expr_addr.0 = phi %union.tree_node* [ null, %bb2 ], [ %expr, %bb2.i ], [ %expr, %entry ], [ %expr, %bb1 ], [ %expr, %lvalue_p.exit4 ] ; <%union.tree_node*> [#uses=0]
unreachable
}
declare fastcc i32 @lvalue_p(%union.tree_node* nocapture) nounwind readonly
declare fastcc %union.tree_node* @default_conversion(%union.tree_node*) nounwind