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Vectorization Factor clarification

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173691 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Renato Golin 2013-01-28 16:02:45 +00:00
parent 647c66e24d
commit 237f09db09
1 changed files with 24 additions and 17 deletions
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41
lib/Transforms/Vectorize/LoopVectorize.cpp
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@ -516,14 +516,18 @@ public:
const TargetTransformInfo &TTI)
: TheLoop(L), SE(SE), LI(LI), Legal(Legal), TTI(TTI) {}
/// Information about vectorization costs
struct VectorizationFactor {
unsigned Width; // Vector width with best cost
unsigned Cost; // Cost of the loop with that width
};
/// \return The most profitable vectorization factor and the cost of that VF.
/// This method checks every power of two up to VF. If UserVF is not ZERO
/// then this vectorization factor will be selected if vectorization is
/// possible.
std::pair<unsigned, unsigned>
selectVectorizationFactor(bool OptForSize, unsigned UserVF);
VectorizationFactor selectVectorizationFactor(bool OptForSize, unsigned UserVF);
/// \returns The size (in bits) of the widest type in the code that
/// \return The size (in bits) of the widest type in the code that
/// needs to be vectorized. We ignore values that remain scalar such as
/// 64 bit loop indices.
unsigned getWidestType();
@ -633,24 +637,23 @@ struct LoopVectorize : public LoopPass {
}
// Select the optimal vectorization factor.
std::pair<unsigned, unsigned> VFPair;
VFPair = CM.selectVectorizationFactor(OptForSize, VectorizationFactor);
LoopVectorizationCostModel::VectorizationFactor VF;
VF = CM.selectVectorizationFactor(OptForSize, VectorizationFactor);
// Select the unroll factor.
unsigned UF = CM.selectUnrollFactor(OptForSize, VectorizationUnroll,
VFPair.first, VFPair.second);
unsigned VF = VFPair.first;
VF.Width, VF.Cost);
if (VF == 1) {
if (VF.Width == 1) {
DEBUG(dbgs() << "LV: Vectorization is possible but not beneficial.\n");
return false;
}
DEBUG(dbgs() << "LV: Found a vectorizable loop ("<< VF << ") in "<<
DEBUG(dbgs() << "LV: Found a vectorizable loop ("<< VF.Width << ") in "<<
F->getParent()->getModuleIdentifier()<<"\n");
DEBUG(dbgs() << "LV: Unroll Factor is " << UF << "\n");
// If we decided that it is *legal* to vectorizer the loop then do it.
InnerLoopVectorizer LB(L, SE, LI, DT, DL, VF, UF);
InnerLoopVectorizer LB(L, SE, LI, DT, DL, VF.Width, UF);
LB.vectorize(&LVL);
DEBUG(verifyFunction(*L->getHeader()->getParent()));
@ -2675,12 +2678,14 @@ bool LoopVectorizationLegality::hasComputableBounds(Value *Ptr) {
return AR->isAffine();
}
std::pair<unsigned, unsigned>
LoopVectorizationCostModel::VectorizationFactor
LoopVectorizationCostModel::selectVectorizationFactor(bool OptForSize,
unsigned UserVF) {
// Width 1 means no vectorize
VectorizationFactor Factor = { 1U, 0U };
if (OptForSize && Legal->getRuntimePointerCheck()->Need) {
DEBUG(dbgs() << "LV: Aborting. Runtime ptr check is required in Os.\n");
return std::make_pair(1U, 0U);
return Factor;
}
// Find the trip count.
@ -2708,7 +2713,7 @@ LoopVectorizationCostModel::selectVectorizationFactor(bool OptForSize,
// If we are unable to calculate the trip count then don't try to vectorize.
if (TC < 2) {
DEBUG(dbgs() << "LV: Aborting. A tail loop is required in Os.\n");
return std::make_pair(1U, 0U);
return Factor;
}
// Find the maximum SIMD width that can fit within the trip count.
@ -2721,7 +2726,7 @@ LoopVectorizationCostModel::selectVectorizationFactor(bool OptForSize,
// zero then we require a tail.
if (VF < 2) {
DEBUG(dbgs() << "LV: Aborting. A tail loop is required in Os.\n");
return std::make_pair(1U, 0U);
return Factor;
}
}
@ -2729,7 +2734,8 @@ LoopVectorizationCostModel::selectVectorizationFactor(bool OptForSize,
assert(isPowerOf2_32(UserVF) && "VF needs to be a power of two");
DEBUG(dbgs() << "LV: Using user VF "<<UserVF<<".\n");
return std::make_pair(UserVF, 0U);
Factor.Width = UserVF;
return Factor;
}
float Cost = expectedCost(1);
@ -2749,8 +2755,9 @@ LoopVectorizationCostModel::selectVectorizationFactor(bool OptForSize,
}
DEBUG(dbgs() << "LV: Selecting VF = : "<< Width << ".\n");
unsigned LoopCost = VF * Cost;
return std::make_pair(Width, LoopCost);
Factor.Width = Width;
Factor.Cost = Width * Cost;
return Factor;
}
unsigned LoopVectorizationCostModel::getWidestType() {