[llvm-commits] [llvm] r94110 - /llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp
Dan Gohman
gohman at apple.com
Thu Jan 21 15:01:23 PST 2010
Author: djg
Date: Thu Jan 21 17:01:22 2010
New Revision: 94110
URL: http://llvm.org/viewvc/llvm-project?rev=94110&view=rev
Log:
When inserting expressions for post-increment users which contain
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.
Modified:
llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp
Modified: llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp?rev=94110&r1=94109&r2=94110&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp Thu Jan 21 17:01:22 2010
@@ -619,7 +619,8 @@
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 @@
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 @@
}
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 @@
// 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 @@
/// 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 @@
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 @@
}
}
} 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 @@
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 @@
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 @@
/// 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 @@
/// 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 @@
: 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 @@
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 @@
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 @@
"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;
}
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