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When inserting expressions for post-increment users which contain

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loop-variant components, adds must be inserted after the increment.
Keep track of the increment position for this case, and insert
these adds in the correct location.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@94110 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2010-01-21 23:01:22 +00:00
parent 940bd3e236
commit eca35b76ce
1 changed files with 32 additions and 17 deletions
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49
lib/Transforms/Scalar/LoopStrengthReduce.cpp
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@ -619,7 +619,8 @@ public:
bool InsertFormula(const Formula &F);
void Rewrite(Loop *L, SCEVExpander &Rewriter,
void Rewrite(Loop *L, Instruction *IVIncInsertPos,
SCEVExpander &Rewriter,
SmallVectorImpl<WeakVH> &DeadInsts,
ScalarEvolution &SE, DominatorTree &DT,
Pass *P) const;
@ -628,8 +629,8 @@ public:
void dump() const;
private:
Value *Expand(BasicBlock::iterator IP,
Loop *L, SCEVExpander &Rewriter,
Value *Expand(BasicBlock::iterator IP, Loop *L, Instruction *IVIncInsertPos,
SCEVExpander &Rewriter,
SmallVectorImpl<WeakVH> &DeadInsts,
ScalarEvolution &SE, DominatorTree &DT) const;
};
@ -809,7 +810,8 @@ static BasicBlock *getImmediateDominator(BasicBlock *BB, DominatorTree &DT) {
}
Value *LSRUse::Expand(BasicBlock::iterator IP,
Loop *L, SCEVExpander &Rewriter,
Loop *L, Instruction *IVIncInsertPos,
SCEVExpander &Rewriter,
SmallVectorImpl<WeakVH> &DeadInsts,
ScalarEvolution &SE, DominatorTree &DT) const {
// Then, collect some instructions which we will remain dominated by when
@ -885,8 +887,13 @@ Value *LSRUse::Expand(BasicBlock::iterator IP,
// If we're expanding for a post-inc user for the add-rec's loop, make the
// post-inc adjustment.
if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Reg))
if (AR->getLoop() == PostIncLoop)
if (AR->getLoop() == PostIncLoop) {
Reg = SE.getAddExpr(Reg, AR->getStepRecurrence(SE));
// If the user is inside the loop, insert the code after the increment
// so that it is dominated by its operand.
if (L->contains(UserInst))
IP = IVIncInsertPos;
}
Ops.push_back(SE.getUnknown(Rewriter.expandCodeFor(Reg, 0, IP)));
}
@ -988,7 +995,8 @@ Value *LSRUse::Expand(BasicBlock::iterator IP,
/// Rewrite - Emit instructions for the leading candidate expression for this
/// LSRUse (this is called "expanding"), and update the UserInst to reference
/// the newly expanded value.
void LSRUse::Rewrite(Loop *L, SCEVExpander &Rewriter,
void LSRUse::Rewrite(Loop *L, Instruction *IVIncInsertPos,
SCEVExpander &Rewriter,
SmallVectorImpl<WeakVH> &DeadInsts,
ScalarEvolution &SE, DominatorTree &DT,
Pass *P) const {
@ -1029,8 +1037,8 @@ void LSRUse::Rewrite(Loop *L, SCEVExpander &Rewriter,
if (!Pair.second)
PN->setIncomingValue(i, Pair.first->second);
else {
Value *FullV = Expand(BB->getTerminator(),
L, Rewriter, DeadInsts, SE, DT);
Value *FullV = Expand(BB->getTerminator(), L, IVIncInsertPos,
Rewriter, DeadInsts, SE, DT);
// If this is reuse-by-noop-cast, insert the noop cast.
if (FullV->getType() != OpTy)
@ -1045,7 +1053,8 @@ void LSRUse::Rewrite(Loop *L, SCEVExpander &Rewriter,
}
}
} else {
Value *FullV = Expand(UserInst, L, Rewriter, DeadInsts, SE, DT);
Value *FullV = Expand(UserInst, L, IVIncInsertPos,
Rewriter, DeadInsts, SE, DT);
// If this is reuse-by-noop-cast, insert the noop cast.
if (FullV->getType() != OpTy) {
@ -1381,6 +1390,12 @@ class LSRInstance {
Loop *const L;
bool Changed;
/// IVIncInsertPos - This is the insert position that the current loop's
/// induction variable increment should be placed. In simple loops, this is
/// the latch block's terminator. But in more complicated cases, this is
/// a position which will dominate all the in-loop post-increment users.
Instruction *IVIncInsertPos;
/// CurrentArbitraryRegIndex - To ensure a deterministic ordering, assign an
/// arbitrary index value to each register as a sort tie breaker.
unsigned CurrentArbitraryRegIndex;
@ -1409,7 +1424,7 @@ class LSRInstance {
const SCEV* &CondStride);
ICmpInst *OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse);
bool StrideMightBeShared(const SCEV* Stride);
bool OptimizeLoopTermCond(Instruction *&IVIncInsertPos);
bool OptimizeLoopTermCond();
LSRUse &getNewUse() {
Uses.push_back(LSRUse());
@ -1761,7 +1776,7 @@ bool LSRInstance::StrideMightBeShared(const SCEV* Stride) {
/// OptimizeLoopTermCond - Change loop terminating condition to use the
/// postinc iv when possible.
bool
LSRInstance::OptimizeLoopTermCond(Instruction *&IVIncInsertPos) {
LSRInstance::OptimizeLoopTermCond() {
SmallPtrSet<Instruction *, 4> PostIncs;
BasicBlock *LatchBlock = L->getLoopLatch();
@ -2101,6 +2116,7 @@ void LSRInstance::GenerateReassociationReuse(LSRUse &LU, unsigned LUIdx,
/// loop-dominating registers added into a single register.
void LSRInstance::GenerateCombinationReuse(LSRUse &LU, unsigned LUIdx,
Formula Base) {
// This method is only intersting on a plurality of registers.
if (Base.BaseRegs.size() <= 1) return;
Formula F = Base;
@ -2453,7 +2469,8 @@ LSRInstance::LSRInstance(const TargetLowering *tli, Loop *l, Pass *P)
: IU(P->getAnalysis<IVUsers>()),
SE(P->getAnalysis<ScalarEvolution>()),
DT(P->getAnalysis<DominatorTree>()),
TLI(tli), L(l), Changed(false), CurrentArbitraryRegIndex(0), MaxNumRegs(0) {
TLI(tli), L(l), Changed(false), IVIncInsertPos(0),
CurrentArbitraryRegIndex(0), MaxNumRegs(0) {
// If LoopSimplify form is not available, stay out of trouble.
if (!L->isLoopSimplifyForm()) return;
@ -2474,8 +2491,7 @@ LSRInstance::LSRInstance(const TargetLowering *tli, Loop *l, Pass *P)
OptimizeShadowIV();
// Change loop terminating condition to use the postinc iv when possible.
Instruction *IVIncInsertPos;
Changed |= OptimizeLoopTermCond(IVIncInsertPos);
Changed |= OptimizeLoopTermCond();
for (SmallVectorImpl<const SCEV *>::const_iterator SIter =
IU.StrideOrder.begin(), SEnd = IU.StrideOrder.end();
@ -2555,8 +2571,7 @@ LSRInstance::LSRInstance(const TargetLowering *tli, Loop *l, Pass *P)
Factors.insert(-1);
}
// Ok, now enumerate all the different formulae we can find to compute
// the value for this expression.
// Set up the initial formula for this use.
LU.InsertInitialFormula(S, L, SE, DT);
CountRegisters(LU.Formulae.back(), Uses.size() - 1);
}
@ -2688,7 +2703,7 @@ LSRInstance::LSRInstance(const TargetLowering *tli, Loop *l, Pass *P)
"Illegal formula generated!"));
// Expand the new code and update the user.
I->Rewrite(L, Rewriter, DeadInsts, SE, DT, P);
I->Rewrite(L, IVIncInsertPos, Rewriter, DeadInsts, SE, DT, P);
Changed = true;
}