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indvars: fixed IV cloning in -disable-iv-rewrite mode with associated

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cleanup and overdue test cases.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@132038 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Andrew Trick
2011-05-25 04:42:22 +00:00
parent 47268164f3
commit 03d3d3b361
3 changed files with 330 additions and 52 deletions
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166
lib/Transforms/Scalar/IndVarSimplify.cpp
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@ -67,6 +67,9 @@ STATISTIC(NumWidened , "Number of indvars widened");
STATISTIC(NumInserted, "Number of canonical indvars added");
STATISTIC(NumReplaced, "Number of exit values replaced");
STATISTIC(NumLFTR , "Number of loop exit tests replaced");
STATISTIC(NumElimExt , "Number of IV sign/zero extends eliminated");
STATISTIC(NumElimRem , "Number of IV remainder operations eliminated");
STATISTIC(NumElimCmp , "Number of IV comparisons eliminated");
// DisableIVRewrite mode currently affects IVUsers, so is defined in libAnalysis
// and referenced here.
@ -117,9 +120,6 @@ namespace {
PHINode *IVPhi);
void RewriteNonIntegerIVs(Loop *L);
bool canExpandBackedgeTakenCount(Loop *L,
const SCEV *BackedgeTakenCount);
ICmpInst *LinearFunctionTestReplace(Loop *L, const SCEV *BackedgeTakenCount,
PHINode *IndVar,
SCEVExpander &Rewriter);
@ -200,9 +200,8 @@ bool IndVarSimplify::isValidRewrite(Value *FromVal, Value *ToVal) {
/// canExpandBackedgeTakenCount - Return true if this loop's backedge taken
/// count expression can be safely and cheaply expanded into an instruction
/// sequence that can be used by LinearFunctionTestReplace.
bool IndVarSimplify::
canExpandBackedgeTakenCount(Loop *L,
const SCEV *BackedgeTakenCount) {
static bool canExpandBackedgeTakenCount(Loop *L, ScalarEvolution *SE) {
const SCEV *BackedgeTakenCount = SE->getBackedgeTakenCount(L);
if (isa<SCEVCouldNotCompute>(BackedgeTakenCount) ||
BackedgeTakenCount->isZero())
return false;
@ -235,6 +234,36 @@ canExpandBackedgeTakenCount(Loop *L,
return true;
}
/// getBackedgeIVType - Get the widest type used by the loop test after peeking
/// through Truncs.
///
/// TODO: Unnecessary once LinearFunctionTestReplace is removed.
static const Type *getBackedgeIVType(Loop *L) {
if (!L->getExitingBlock())
return 0;
// Can't rewrite non-branch yet.
BranchInst *BI = dyn_cast<BranchInst>(L->getExitingBlock()->getTerminator());
if (!BI)
return 0;
ICmpInst *Cond = dyn_cast<ICmpInst>(BI->getCondition());
if (!Cond)
return 0;
const Type *Ty = 0;
for(User::op_iterator OI = Cond->op_begin(), OE = Cond->op_end();
OI != OE; ++OI) {
assert((!Ty || Ty == (*OI)->getType()) && "bad icmp operand types");
TruncInst *Trunc = dyn_cast<TruncInst>(*OI);
if (!Trunc)
continue;
return Trunc->getSrcTy();
}
return Ty;
}
/// LinearFunctionTestReplace - This method rewrites the exit condition of the
/// loop to be a canonical != comparison against the incremented loop induction
/// variable. This pass is able to rewrite the exit tests of any loop where the
@ -245,7 +274,7 @@ LinearFunctionTestReplace(Loop *L,
const SCEV *BackedgeTakenCount,
PHINode *IndVar,
SCEVExpander &Rewriter) {
assert(canExpandBackedgeTakenCount(L, BackedgeTakenCount) && "precondition");
assert(canExpandBackedgeTakenCount(L, SE) && "precondition");
BranchInst *BI = cast<BranchInst>(L->getExitingBlock()->getTerminator());
// If the exiting block is not the same as the backedge block, we must compare
@ -536,12 +565,12 @@ public:
bool CreateWideIV(SCEVExpander &Rewriter);
protected:
const SCEVAddRecExpr *GetWideRecurrence(Instruction *NarrowUse);
Instruction *CloneIVUser(Instruction *NarrowUse,
Instruction *NarrowDef,
Instruction *WideDef);
const SCEVAddRecExpr *GetWideRecurrence(Instruction *NarrowUse);
Instruction *WidenIVUse(Instruction *NarrowUse,
Instruction *NarrowDef,
Instruction *WideDef);
@ -594,24 +623,10 @@ void IndVarSimplify::SimplifyIVUsers(SCEVExpander &Rewriter) {
}
}
// GetWideRecurrence - Is this instruction potentially interesting from IVUsers'
// perspective after widening it's type? In other words, can the extend be
// safely hoisted out of the loop with SCEV reducing the value to a recurrence
// on the same loop. If so, return the sign or zero extended
// recurrence. Otherwise return NULL.
const SCEVAddRecExpr *WidenIV::GetWideRecurrence(Instruction *NarrowUse) {
if (!SE->isSCEVable(NarrowUse->getType()))
return 0;
const SCEV *NarrowExpr = SE->getSCEV(NarrowUse);
const SCEV *WideExpr = IsSigned ?
SE->getSignExtendExpr(NarrowExpr, WideType) :
SE->getZeroExtendExpr(NarrowExpr, WideType);
const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(WideExpr);
if (!AddRec || AddRec->getLoop() != L)
return 0;
return AddRec;
static Value *getExtend( Value *NarrowOper, const Type *WideType,
bool IsSigned, IRBuilder<> &Builder) {
return IsSigned ? Builder.CreateSExt(NarrowOper, WideType) :
Builder.CreateZExt(NarrowOper, WideType);
}
/// CloneIVUser - Instantiate a wide operation to replace a narrow
@ -636,36 +651,51 @@ Instruction *WidenIV::CloneIVUser(Instruction *NarrowUse,
case Instruction::AShr:
DEBUG(dbgs() << "Cloning IVUser: " << *NarrowUse << "\n");
IRBuilder<> Builder(NarrowUse);
// Replace NarrowDef operands with WideDef. Otherwise, we don't know
// anything about the narrow operand yet so must insert a [sz]ext. It is
// probably loop invariant and will be folded or hoisted. If it actually
// comes from a widened IV, it should be removed during a future call to
// WidenIVUse.
Value *LHS = (NarrowUse->getOperand(0) == NarrowDef) ? WideDef :
getExtend(NarrowUse->getOperand(0), WideType, IsSigned, Builder);
Value *RHS = (NarrowUse->getOperand(1) == NarrowDef) ? WideDef :
getExtend(NarrowUse->getOperand(1), WideType, IsSigned, Builder);
BinaryOperator *NarrowBO = cast<BinaryOperator>(NarrowUse);
BinaryOperator *WideBO = BinaryOperator::Create(NarrowBO->getOpcode(),
NarrowBO->getOperand(0),
NarrowBO->getOperand(1),
LHS, RHS,
NarrowBO->getName());
IRBuilder<> Builder(NarrowUse);
Builder.Insert(WideBO);
if (NarrowBO->hasNoUnsignedWrap()) WideBO->setHasNoUnsignedWrap();
if (NarrowBO->hasNoSignedWrap()) WideBO->setHasNoSignedWrap();
for (unsigned i = 0; i < NarrowBO->getNumOperands(); ++i) {
Value *NarrowOper = NarrowBO->getOperand(i);
if (NarrowOper == NarrowDef) {
WideBO->setOperand(i, WideDef);
continue;
}
// We don't know anything about the other operand here so must insert a
// [sz]ext. It is probably loop invariant and will be folded or
// hoisted. If it actually comes from a widened IV, it should be removed
// during a future call to WidenIVUse.
IRBuilder<> Builder(NarrowUse);
Value *Extend = IsSigned ?
Builder.CreateSExt(NarrowOper, WideType) :
Builder.CreateZExt(NarrowOper, WideType);
WideBO->setOperand(i, Extend);
}
return WideBO;
}
llvm_unreachable(0);
}
// GetWideRecurrence - Is this instruction potentially interesting from IVUsers'
// perspective after widening it's type? In other words, can the extend be
// safely hoisted out of the loop with SCEV reducing the value to a recurrence
// on the same loop. If so, return the sign or zero extended
// recurrence. Otherwise return NULL.
const SCEVAddRecExpr *WidenIV::GetWideRecurrence(Instruction *NarrowUse) {
if (!SE->isSCEVable(NarrowUse->getType()))
return 0;
const SCEV *NarrowExpr = SE->getSCEV(NarrowUse);
const SCEV *WideExpr = IsSigned ?
SE->getSignExtendExpr(NarrowExpr, WideType) :
SE->getZeroExtendExpr(NarrowExpr, WideType);
const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(WideExpr);
if (!AddRec || AddRec->getLoop() != L)
return 0;
return AddRec;
}
/// WidenIVUse - Determine whether an individual user of the narrow IV can be
/// widened. If so, return the wide clone of the user.
Instruction *WidenIV::WidenIVUse(Instruction *NarrowUse,
@ -682,9 +712,32 @@ Instruction *WidenIV::WidenIVUse(Instruction *NarrowUse,
// Our raison d'etre! Eliminate sign and zero extension.
if (IsSigned ? isa<SExtInst>(NarrowUse) : isa<ZExtInst>(NarrowUse)) {
NarrowUse->replaceAllUsesWith(WideDef);
DeadInsts.push_back(NarrowUse);
Value *NewDef = WideDef;
if (NarrowUse->getType() != WideType) {
unsigned CastWidth = SE->getTypeSizeInBits(NarrowUse->getType());
unsigned IVWidth = SE->getTypeSizeInBits(WideType);
if (CastWidth < IVWidth) {
// The cast isn't as wide as the IV, so insert a Trunc.
IRBuilder<> Builder(NarrowUse);
NewDef = Builder.CreateTrunc(WideDef, NarrowUse->getType());
}
else {
// A wider extend was hidden behind a narrower one. This may induce
// another round of IV widening in which the intermediate IV becomes
// dead. It should be very rare.
DEBUG(dbgs() << "INDVARS: New IV " << *WidePhi
<< " not wide enough to subsume " << *NarrowUse << "\n");
NarrowUse->replaceUsesOfWith(NarrowDef, WideDef);
NewDef = NarrowUse;
}
}
if (NewDef != NarrowUse) {
DEBUG(dbgs() << "INDVARS: eliminating " << *NarrowUse
<< " replaced by " << *WideDef << "\n");
++NumElimExt;
NarrowUse->replaceAllUsesWith(NewDef);
DeadInsts.push_back(NarrowUse);
}
// Now that the extend is gone, expose it's uses to IVUsers for potential
// further simplification within SimplifyIVUsers.
IU->AddUsersIfInteresting(WideDef, WidePhi);
@ -698,7 +751,7 @@ Instruction *WidenIV::WidenIVUse(Instruction *NarrowUse,
// follow it. Instead insert a Trunc to kill off the original use,
// eventually isolating the original narrow IV so it can be removed.
IRBuilder<> Builder(NarrowUse);
Value *Trunc = Builder.CreateTrunc(WideDef, NarrowUse->getType());
Value *Trunc = Builder.CreateTrunc(WideDef, NarrowDef->getType());
NarrowUse->replaceUsesOfWith(NarrowDef, Trunc);
return 0;
}
@ -834,6 +887,7 @@ void IndVarSimplify::EliminateIVComparison(ICmpInst *ICmp, Value *IVOperand) {
return;
DEBUG(dbgs() << "INDVARS: Eliminated comparison: " << *ICmp << '\n');
++NumElimCmp;
Changed = true;
DeadInsts.push_back(ICmp);
}
@ -888,6 +942,7 @@ void IndVarSimplify::EliminateIVRemainder(BinaryOperator *Rem,
IU->AddUsersIfInteresting(I, IVPhi);
DEBUG(dbgs() << "INDVARS: Simplified rem: " << *Rem << '\n');
++NumElimRem;
Changed = true;
DeadInsts.push_back(Rem);
}
@ -940,13 +995,20 @@ bool IndVarSimplify::runOnLoop(Loop *L, LPPassManager &LPM) {
// a canonical induction variable should be inserted.
const Type *LargestType = 0;
bool NeedCannIV = false;
bool ExpandBECount = canExpandBackedgeTakenCount(L, BackedgeTakenCount);
bool ExpandBECount = canExpandBackedgeTakenCount(L, SE);
if (ExpandBECount) {
// If we have a known trip count and a single exit block, we'll be
// rewriting the loop exit test condition below, which requires a
// canonical induction variable.
NeedCannIV = true;
const Type *Ty = BackedgeTakenCount->getType();
if (DisableIVRewrite) {
// In this mode, SimplifyIVUsers may have already widened the IV used by
// the backedge test and inserted a Trunc on the compare's operand. Get
// the wider type to avoid creating a redundant narrow IV only used by the
// loop test.
LargestType = getBackedgeIVType(L);
}
if (!LargestType ||
SE->getTypeSizeInBits(Ty) >
SE->getTypeSizeInBits(LargestType))
@ -1002,7 +1064,7 @@ bool IndVarSimplify::runOnLoop(Loop *L, LPPassManager &LPM) {
// using it. We can currently only handle loops with a single exit.
ICmpInst *NewICmp = 0;
if (ExpandBECount) {
assert(canExpandBackedgeTakenCount(L, BackedgeTakenCount) &&
assert(canExpandBackedgeTakenCount(L, SE) &&
"canonical IV disrupted BackedgeTaken expansion");
assert(NeedCannIV &&
"LinearFunctionTestReplace requires a canonical induction variable");