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[LSV] Insert stores at the right point.

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Summary:
Previously, the insertion point for stores was the last instruction in
Chain *before calling getVectorizablePrefixEndIdx*.  Thus if
getVectorizablePrefixEndIdx didn't return Chain.size(), we still would
insert at the last instruction in Chain.

This patch changes our internal API a bit in an attempt to make it less
prone to this sort of error.  As a result, we end up recalculating the
Chain's boundary instructions, but I think worrying about the speed hit
of this is a premature optimization right now.

Reviewers: asbirlea, tstellarAMD

Subscribers: mzolotukhin, arsenm, llvm-commits

Differential Revision: https://reviews.llvm.org/D22534

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@276056 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Justin Lebar
2016-07-19 23:19:20 +00:00
parent abcf9144a5
commit 85ee7e9487
2 changed files with 57 additions and 32 deletions
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58
lib/Transforms/Vectorize/LoadStoreVectorizer.cpp
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@@ -104,13 +104,12 @@ private:
std::pair<ArrayRef<Value *>, ArrayRef<Value *>>
splitOddVectorElts(ArrayRef<Value *> Chain, unsigned ElementSizeBits);
/// Checks for instructions which may affect the memory accessed
/// in the chain between \p From and \p To. Returns Index, where
/// \p Chain[0, Index) is the largest vectorizable chain prefix.
/// The elements of \p Chain should be all loads or all stores.
unsigned getVectorizablePrefixEndIdx(ArrayRef<Value *> Chain,
BasicBlock::iterator From,
BasicBlock::iterator To);
/// Finds the largest prefix of Chain that's vectorizable, checking for
/// intervening instructions which may affect the memory accessed by the
/// instructions within Chain.
///
/// The elements of \p Chain must be all loads or all stores.
ArrayRef<Value *> getVectorizablePrefix(ArrayRef<Value *> Chain);
/// Collects load and store instructions to vectorize.
std::pair<ValueListMap, ValueListMap> collectInstructions(BasicBlock *BB);
@@ -424,14 +423,12 @@ Vectorizer::splitOddVectorElts(ArrayRef<Value *> Chain,
return std::make_pair(Chain.slice(0, NumLeft), Chain.slice(NumLeft));
}
unsigned Vectorizer::getVectorizablePrefixEndIdx(ArrayRef<Value *> Chain,
BasicBlock::iterator From,
BasicBlock::iterator To) {
ArrayRef<Value *> Vectorizer::getVectorizablePrefix(ArrayRef<Value *> Chain) {
SmallVector<std::pair<Value *, unsigned>, 16> MemoryInstrs;
SmallVector<std::pair<Value *, unsigned>, 16> ChainInstrs;
unsigned InstrIdx = 0;
for (Instruction &I : make_range(From, To)) {
for (Instruction &I : make_range(getBoundaryInstrs(Chain))) {
++InstrIdx;
if (isa<LoadInst>(I) || isa<StoreInst>(I)) {
if (!is_contained(Chain, &I))
@@ -445,7 +442,7 @@ unsigned Vectorizer::getVectorizablePrefixEndIdx(ArrayRef<Value *> Chain,
}
assert(Chain.size() == ChainInstrs.size() &&
"All instructions in the Chain must exist in [From, To).");
"All instrs in Chain must be within range getBoundaryInstrs(Chain).");
unsigned ChainIdx = 0;
for (auto EntryChain : ChainInstrs) {
@@ -487,12 +484,12 @@ unsigned Vectorizer::getVectorizablePrefixEndIdx(ArrayRef<Value *> Chain,
<< " " << *Ptr1 << '\n';
});
return ChainIdx;
return Chain.slice(0, ChainIdx);
}
}
ChainIdx++;
}
return Chain.size();
return Chain;
}
std::pair<ValueListMap, ValueListMap>
@@ -694,22 +691,20 @@ bool Vectorizer::vectorizeStoreChain(
return false;
}
BasicBlock::iterator First, Last;
std::tie(First, Last) = getBoundaryInstrs(Chain);
unsigned StopChain = getVectorizablePrefixEndIdx(Chain, First, Last);
if (StopChain == 0) {
ArrayRef<Value *> NewChain = getVectorizablePrefix(Chain);
if (NewChain.empty()) {
// There exists a side effect instruction, no vectorization possible.
InstructionsProcessed->insert(Chain.begin(), Chain.end());
return false;
}
if (StopChain == 1) {
if (NewChain.size() == 1) {
// Failed after the first instruction. Discard it and try the smaller chain.
InstructionsProcessed->insert(Chain.front());
InstructionsProcessed->insert(NewChain.front());
return false;
}
// Update Chain to the valid vectorizable subchain.
Chain = Chain.slice(0, StopChain);
Chain = NewChain;
ChainSize = Chain.size();
// Store size should be 1B, 2B or multiple of 4B.
@@ -773,7 +768,8 @@ bool Vectorizer::vectorizeStoreChain(
}
}
// Set insert point.
BasicBlock::iterator First, Last;
std::tie(First, Last) = getBoundaryInstrs(Chain);
Builder.SetInsertPoint(&*Last);
Value *Vec = UndefValue::get(VecTy);
@@ -849,22 +845,20 @@ bool Vectorizer::vectorizeLoadChain(
return false;
}
BasicBlock::iterator First, Last;
std::tie(First, Last) = getBoundaryInstrs(Chain);
unsigned StopChain = getVectorizablePrefixEndIdx(Chain, First, Last);
if (StopChain == 0) {
ArrayRef<Value *> NewChain = getVectorizablePrefix(Chain);
if (NewChain.empty()) {
// There exists a side effect instruction, no vectorization possible.
InstructionsProcessed->insert(Chain.begin(), Chain.end());
return false;
}
if (StopChain == 1) {
if (NewChain.size() == 1) {
// Failed after the first instruction. Discard it and try the smaller chain.
InstructionsProcessed->insert(Chain.front());
InstructionsProcessed->insert(NewChain.front());
return false;
}
// Update Chain to the valid vectorizable subchain.
Chain = Chain.slice(0, StopChain);
Chain = NewChain;
ChainSize = Chain.size();
// Load size should be 1B, 2B or multiple of 4B.
@@ -927,7 +921,11 @@ bool Vectorizer::vectorizeLoadChain(
V->dump();
});
// Set insert point.
// getVectorizablePrefix already computed getBoundaryInstrs. The value of
// Last may have changed since then, but the value of First won't have. If it
// matters, we could compute getBoundaryInstrs only once and reuse it here.
BasicBlock::iterator First, Last;
std::tie(First, Last) = getBoundaryInstrs(Chain);
Builder.SetInsertPoint(&*First);
Value *Bitcast =