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Fix several areas in LSR to do a better job keeping the main

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LSRInstance data structures up to date. This fixes some
pessimizations caused by stale data which will be exposed
in an upcoming change.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@112440 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2010-08-29 16:32:54 +00:00
parent 4aa5c2e90f
commit 25608f7f4b
1 changed files with 106 additions and 50 deletions
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156
lib/Transforms/Scalar/LoopStrengthReduce.cpp
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@ -113,6 +113,7 @@ class RegUseTracker {
public:
void CountRegister(const SCEV *Reg, size_t LUIdx);
void DropRegister(const SCEV *Reg, size_t LUIdx);
void DropUse(size_t LUIdx, size_t NewLUIdx);
void DropUse(size_t LUIdx);
bool isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const;
@ -151,6 +152,24 @@ RegUseTracker::DropRegister(const SCEV *Reg, size_t LUIdx) {
RSD.UsedByIndices.reset(LUIdx);
}
/// DropUse - Clear out reference by use LUIdx, and prepare for use NewLUIdx
/// to be swapped into LUIdx's position.
void
RegUseTracker::DropUse(size_t LUIdx, size_t NewLUIdx) {
// Remove the use index from every register's use list.
for (RegUsesTy::iterator I = RegUsesMap.begin(), E = RegUsesMap.end();
I != E; ++I) {
SmallBitVector &UsedByIndices = I->second.UsedByIndices;
UsedByIndices.resize(std::max(UsedByIndices.size(), NewLUIdx + 1));
if (LUIdx < UsedByIndices.size()) {
UsedByIndices[LUIdx] = UsedByIndices[NewLUIdx];
UsedByIndices.reset(NewLUIdx);
} else
UsedByIndices.reset(LUIdx);
}
}
/// DropUse - Clear out reference by use LUIdx.
void
RegUseTracker::DropUse(size_t LUIdx) {
// Remove the use index from every register's use list.
@ -1334,7 +1353,9 @@ class LSRInstance {
UseMapDenseMapInfo> UseMapTy;
UseMapTy UseMap;
bool reconcileNewOffset(LSRUse &LU, int64_t NewOffset, bool HasBaseReg,
bool reconcileNewOffset(LSRUse &LU,
int64_t NewMinOffset, int64_t NewMaxOffset,
bool HasBaseReg,
LSRUse::KindType Kind, const Type *AccessTy);
std::pair<size_t, int64_t> getUse(const SCEV *&Expr,
@ -1343,7 +1364,8 @@ class LSRInstance {
void DeleteUse(LSRUse &LU);
LSRUse *FindUseWithSimilarFormula(const Formula &F, const LSRUse &OrigLU);
LSRUse *FindUseWithSimilarFormula(const Formula &F, const LSRUse &OrigLU,
int64_t &NewBaseOffs);
public:
void InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
@ -1843,11 +1865,13 @@ LSRInstance::OptimizeLoopTermCond() {
/// at the given offset and other details. If so, update the use and
/// return true.
bool
LSRInstance::reconcileNewOffset(LSRUse &LU, int64_t NewOffset, bool HasBaseReg,
LSRInstance::reconcileNewOffset(LSRUse &LU,
int64_t NewMinOffset, int64_t NewMaxOffset,
bool HasBaseReg,
LSRUse::KindType Kind, const Type *AccessTy) {
int64_t NewMinOffset = LU.MinOffset;
int64_t NewMaxOffset = LU.MaxOffset;
const Type *NewAccessTy = AccessTy;
int64_t ResultMinOffset = LU.MinOffset;
int64_t ResultMaxOffset = LU.MaxOffset;
const Type *ResultAccessTy = AccessTy;
// Check for a mismatched kind. It's tempting to collapse mismatched kinds to
// something conservative, however this can pessimize in the case that one of
@ -1855,29 +1879,27 @@ LSRInstance::reconcileNewOffset(LSRUse &LU, int64_t NewOffset, bool HasBaseReg,
if (LU.Kind != Kind)
return false;
// Conservatively assume HasBaseReg is true for now.
if (NewOffset < LU.MinOffset) {
if (!isAlwaysFoldable(LU.MaxOffset - NewOffset, 0, HasBaseReg,
if (NewMinOffset < LU.MinOffset) {
if (!isAlwaysFoldable(LU.MaxOffset - NewMinOffset, 0, HasBaseReg,
Kind, AccessTy, TLI))
return false;
NewMinOffset = NewOffset;
} else if (NewOffset > LU.MaxOffset) {
if (!isAlwaysFoldable(NewOffset - LU.MinOffset, 0, HasBaseReg,
ResultMinOffset = NewMinOffset;
} else if (NewMaxOffset > LU.MaxOffset) {
if (!isAlwaysFoldable(NewMaxOffset - LU.MinOffset, 0, HasBaseReg,
Kind, AccessTy, TLI))
return false;
NewMaxOffset = NewOffset;
ResultMaxOffset = NewMaxOffset;
}
// Check for a mismatched access type, and fall back conservatively as needed.
// TODO: Be less conservative when the type is similar and can use the same
// addressing modes.
if (Kind == LSRUse::Address && AccessTy != LU.AccessTy)
NewAccessTy = Type::getVoidTy(AccessTy->getContext());
ResultAccessTy = Type::getVoidTy(AccessTy->getContext());
// Update the use.
LU.MinOffset = NewMinOffset;
LU.MaxOffset = NewMaxOffset;
LU.AccessTy = NewAccessTy;
if (NewOffset != LU.Offsets.back())
LU.Offsets.push_back(NewOffset);
LU.MinOffset = ResultMinOffset;
LU.MaxOffset = ResultMaxOffset;
LU.AccessTy = ResultAccessTy;
return true;
}
@ -1902,9 +1924,12 @@ LSRInstance::getUse(const SCEV *&Expr,
// A use already existed with this base.
size_t LUIdx = P.first->second;
LSRUse &LU = Uses[LUIdx];
if (reconcileNewOffset(LU, Offset, /*HasBaseReg=*/true, Kind, AccessTy))
if (reconcileNewOffset(LU, Offset, Offset,
/*HasBaseReg=*/true, Kind, AccessTy)) {
LU.Offsets.push_back(Offset);
// Reuse this use.
return std::make_pair(LUIdx, Offset);
}
}
// Create a new use.
@ -1913,11 +1938,7 @@ LSRInstance::getUse(const SCEV *&Expr,
Uses.push_back(LSRUse(Kind, AccessTy));
LSRUse &LU = Uses[LUIdx];
// We don't need to track redundant offsets, but we don't need to go out
// of our way here to avoid them.
if (LU.Offsets.empty() || Offset != LU.Offsets.back())
LU.Offsets.push_back(Offset);
LU.Offsets.push_back(Offset);
LU.MinOffset = Offset;
LU.MaxOffset = Offset;
return std::make_pair(LUIdx, Offset);
@ -1925,8 +1946,12 @@ LSRInstance::getUse(const SCEV *&Expr,
/// DeleteUse - Delete the given use from the Uses list.
void LSRInstance::DeleteUse(LSRUse &LU) {
if (&LU != &Uses.back())
if (&LU != &Uses.back()) {
std::swap(LU, Uses.back());
RegUses.DropUse(&LU - Uses.begin(), Uses.size() - 1);
} else {
RegUses.DropUse(&LU - Uses.begin());
}
Uses.pop_back();
}
@ -1934,8 +1959,9 @@ void LSRInstance::DeleteUse(LSRUse &LU) {
/// a formula that has the same registers as the given formula.
LSRUse *
LSRInstance::FindUseWithSimilarFormula(const Formula &OrigF,
const LSRUse &OrigLU) {
// Search all uses for the formula. This could be more clever.
const LSRUse &OrigLU,
int64_t &NewBaseOffs) {
// Search all uses for a formula similar to OrigF. This could be more clever.
for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
LSRUse &LU = Uses[LUIdx];
// Check whether this use is close enough to OrigLU, to see whether it's
@ -1958,8 +1984,15 @@ LSRInstance::FindUseWithSimilarFormula(const Formula &OrigF,
F.ScaledReg == OrigF.ScaledReg &&
F.AM.BaseGV == OrigF.AM.BaseGV &&
F.AM.Scale == OrigF.AM.Scale) {
if (F.AM.BaseOffs == 0)
// Ok, all the registers and symbols matched. Check to see if the
// immediate looks nicer than our old one.
if (OrigF.AM.BaseOffs == INT64_MIN ||
(F.AM.BaseOffs != INT64_MIN &&
abs64(F.AM.BaseOffs) < abs64(OrigF.AM.BaseOffs))) {
// Looks good. Take it.
NewBaseOffs = F.AM.BaseOffs;
return &LU;
}
// This is the formula where all the registers and symbols matched;
// there aren't going to be any others. Since we declined it, we
// can skip the rest of the formulae and procede to the next LSRUse.
@ -2600,6 +2633,17 @@ struct WorkItem {
WorkItem(size_t LI, int64_t I, const SCEV *R)
: LUIdx(LI), Imm(I), OrigReg(R) {}
bool operator==(const WorkItem &that) const {
return LUIdx == that.LUIdx && Imm == that.Imm && OrigReg == that.OrigReg;
}
bool operator<(const WorkItem &that) const {
if (LUIdx != that.LUIdx)
return LUIdx < that.LUIdx;
if (Imm != that.Imm)
return Imm < that.Imm;
return OrigReg < that.OrigReg;
}
void print(raw_ostream &OS) const;
void dump() const;
};
@ -2639,8 +2683,7 @@ void LSRInstance::GenerateCrossUseConstantOffsets() {
// Now examine each set of registers with the same base value. Build up
// a list of work to do and do the work in a separate step so that we're
// not adding formulae and register counts while we're searching.
SmallVector<WorkItem, 32> WorkItems;
SmallSet<std::pair<size_t, int64_t>, 32> UniqueItems;
SmallSetVector<WorkItem, 32> WorkItems;
for (SmallVectorImpl<const SCEV *>::const_iterator I = Sequence.begin(),
E = Sequence.end(); I != E; ++I) {
const SCEV *Reg = *I;
@ -2683,10 +2726,10 @@ void LSRInstance::GenerateCrossUseConstantOffsets() {
// Compute the difference between the two.
int64_t Imm = (uint64_t)JImm - M->first;
for (int LUIdx = UsedByIndices.find_first(); LUIdx != -1;
LUIdx = UsedByIndices.find_next(LUIdx))
LUIdx = UsedByIndices.find_next(LUIdx)) {
// Make a memo of this use, offset, and register tuple.
if (UniqueItems.insert(std::make_pair(LUIdx, Imm)))
WorkItems.push_back(WorkItem(LUIdx, Imm, OrigReg));
WorkItems.insert(WorkItem(LUIdx, Imm, OrigReg));
}
}
}
}
@ -2694,7 +2737,6 @@ void LSRInstance::GenerateCrossUseConstantOffsets() {
Map.clear();
Sequence.clear();
UsedByIndicesMap.clear();
UniqueItems.clear();
// Now iterate through the worklist and add new formulae.
for (SmallVectorImpl<WorkItem>::const_iterator I = WorkItems.begin(),
@ -2991,8 +3033,12 @@ void LSRInstance::NarrowSearchSpaceByCollapsingUnrolledCode() {
E = LU.Formulae.end(); I != E; ++I) {
const Formula &F = *I;
if (F.AM.BaseOffs != 0 && F.AM.Scale == 0) {
if (LSRUse *LUThatHas = FindUseWithSimilarFormula(F, LU)) {
if (reconcileNewOffset(*LUThatHas, F.AM.BaseOffs,
int64_t NewBaseOffs;
if (LSRUse *LUThatHas = FindUseWithSimilarFormula(F, LU,
NewBaseOffs)) {
if (reconcileNewOffset(*LUThatHas,
F.AM.BaseOffs + LU.MinOffset - NewBaseOffs,
F.AM.BaseOffs + LU.MaxOffset - NewBaseOffs,
/*HasBaseReg=*/false,
LU.Kind, LU.AccessTy)) {
DEBUG(dbgs() << " Deleting use "; LU.print(dbgs());
@ -3000,6 +3046,30 @@ void LSRInstance::NarrowSearchSpaceByCollapsingUnrolledCode() {
LUThatHas->AllFixupsOutsideLoop &= LU.AllFixupsOutsideLoop;
// Update the relocs to reference the new use.
// Do this first so that MinOffset and MaxOffset are updated
// before we begin to determine which formulae to delete.
for (SmallVectorImpl<LSRFixup>::iterator I = Fixups.begin(),
E = Fixups.end(); I != E; ++I) {
LSRFixup &Fixup = *I;
if (Fixup.LUIdx == LUIdx) {
Fixup.LUIdx = LUThatHas - &Uses.front();
Fixup.Offset += F.AM.BaseOffs - NewBaseOffs;
DEBUG(dbgs() << "New fixup has offset "
<< Fixup.Offset << '\n');
LUThatHas->Offsets.push_back(Fixup.Offset);
if (Fixup.Offset > LUThatHas->MaxOffset)
LUThatHas->MaxOffset = Fixup.Offset;
if (Fixup.Offset < LUThatHas->MinOffset)
LUThatHas->MinOffset = Fixup.Offset;
}
// DeleteUse will do a swap+pop_back, so if this fixup is
// now pointing to the last LSRUse, update it to point to the
// position it'll be swapped to.
if (Fixup.LUIdx == NumUses-1)
Fixup.LUIdx = LUIdx;
}
// Delete formulae from the new use which are no longer legal.
bool Any = false;
for (size_t i = 0, e = LUThatHas->Formulae.size(); i != e; ++i) {
@ -3018,20 +3088,6 @@ void LSRInstance::NarrowSearchSpaceByCollapsingUnrolledCode() {
if (Any)
LUThatHas->RecomputeRegs(LUThatHas - &Uses.front(), RegUses);
// Update the relocs to reference the new use.
for (SmallVectorImpl<LSRFixup>::iterator I = Fixups.begin(),
E = Fixups.end(); I != E; ++I) {
LSRFixup &Fixup = *I;
if (Fixup.LUIdx == LUIdx) {
Fixup.LUIdx = LUThatHas - &Uses.front();
Fixup.Offset += F.AM.BaseOffs;
DEBUG(dbgs() << "New fixup has offset "
<< Fixup.Offset << '\n');
}
if (Fixup.LUIdx == NumUses-1)
Fixup.LUIdx = LUIdx;
}
// Delete the old use.
DeleteUse(LU);
--LUIdx;