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merge consecutive stores of extracted vector elements (PR21711)

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This is a 2nd try at the same optimization as http://reviews.llvm.org/D6698. 
That patch was checked in at r224611, but reverted at r225031 because it
caused a failure outside of the regression tests.

The cause of the crash was not recognizing consecutive stores that have mixed
source values (loads and vector element extracts), so this patch adds a check
to bail out if any store value is not coming from a vector element extract.

This patch also refactors the shared logic of the constant source and vector
extracted elements source cases into a helper function.

Differential Revision: http://reviews.llvm.org/D6850
 


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226845 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Sanjay Patel 2015-01-22 18:21:26 +00:00
parent 5196540da1
commit 05d5e213c4
2 changed files with 221 additions and 92 deletions
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254
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View File

@ -363,6 +363,28 @@ namespace {
/// chain (aliasing node.)
SDValue FindBetterChain(SDNode *N, SDValue Chain);
/// Holds a pointer to an LSBaseSDNode as well as information on where it
/// is located in a sequence of memory operations connected by a chain.
struct MemOpLink {
MemOpLink (LSBaseSDNode *N, int64_t Offset, unsigned Seq):
MemNode(N), OffsetFromBase(Offset), SequenceNum(Seq) { }
// Ptr to the mem node.
LSBaseSDNode *MemNode;
// Offset from the base ptr.
int64_t OffsetFromBase;
// What is the sequence number of this mem node.
// Lowest mem operand in the DAG starts at zero.
unsigned SequenceNum;
};
/// This is a helper function for MergeConsecutiveStores. When the source
/// elements of the consecutive stores are all constants or all extracted
/// vector elements, try to merge them into one larger store.
/// \return True if a merged store was created.
bool MergeStoresOfConstantsOrVecElts(SmallVectorImpl<MemOpLink> &StoreNodes,
EVT MemVT, unsigned NumElem,
bool IsConstantSrc, bool UseVector);
/// Merge consecutive store operations into a wide store.
/// This optimization uses wide integers or vectors when possible.
/// \return True if some memory operations were changed.
@ -9706,19 +9728,116 @@ struct BaseIndexOffset {
}
};
/// Holds a pointer to an LSBaseSDNode as well as information on where it
/// is located in a sequence of memory operations connected by a chain.
struct MemOpLink {
MemOpLink (LSBaseSDNode *N, int64_t Offset, unsigned Seq):
MemNode(N), OffsetFromBase(Offset), SequenceNum(Seq) { }
// Ptr to the mem node.
LSBaseSDNode *MemNode;
// Offset from the base ptr.
int64_t OffsetFromBase;
// What is the sequence number of this mem node.
// Lowest mem operand in the DAG starts at zero.
unsigned SequenceNum;
};
bool DAGCombiner::MergeStoresOfConstantsOrVecElts(
SmallVectorImpl<MemOpLink> &StoreNodes, EVT MemVT,
unsigned NumElem, bool IsConstantSrc, bool UseVector) {
// Make sure we have something to merge.
if (NumElem < 2)
return false;
int64_t ElementSizeBytes = MemVT.getSizeInBits() / 8;
LSBaseSDNode *FirstInChain = StoreNodes[0].MemNode;
unsigned EarliestNodeUsed = 0;
for (unsigned i=0; i < NumElem; ++i) {
// Find a chain for the new wide-store operand. Notice that some
// of the store nodes that we found may not be selected for inclusion
// in the wide store. The chain we use needs to be the chain of the
// earliest store node which is *used* and replaced by the wide store.
if (StoreNodes[i].SequenceNum > StoreNodes[EarliestNodeUsed].SequenceNum)
EarliestNodeUsed = i;
}
// The earliest Node in the DAG.
LSBaseSDNode *EarliestOp = StoreNodes[EarliestNodeUsed].MemNode;
SDLoc DL(StoreNodes[0].MemNode);
SDValue StoredVal;
if (UseVector) {
// Find a legal type for the vector store.
EVT Ty = EVT::getVectorVT(*DAG.getContext(), MemVT, NumElem);
assert(TLI.isTypeLegal(Ty) && "Illegal vector store");
if (IsConstantSrc) {
// A vector store with a constant source implies that the constant is
// zero; we only handle merging stores of constant zeros because the zero
// can be materialized without a load.
// It may be beneficial to loosen this restriction to allow non-zero
// store merging.
StoredVal = DAG.getConstant(0, Ty);
} else {
SmallVector<SDValue, 8> Ops;
for (unsigned i = 0; i < NumElem ; ++i) {
StoreSDNode *St = cast<StoreSDNode>(StoreNodes[i].MemNode);
SDValue Val = St->getValue();
// All of the operands of a BUILD_VECTOR must have the same type.
if (Val.getValueType() != MemVT)
return false;
Ops.push_back(Val);
}
// Build the extracted vector elements back into a vector.
StoredVal = DAG.getNode(ISD::BUILD_VECTOR, DL, Ty, Ops);
}
} else {
// We should always use a vector store when merging extracted vector
// elements, so this path implies a store of constants.
assert(IsConstantSrc && "Merged vector elements should use vector store");
unsigned StoreBW = NumElem * ElementSizeBytes * 8;
APInt StoreInt(StoreBW, 0);
// Construct a single integer constant which is made of the smaller
// constant inputs.
bool IsLE = TLI.isLittleEndian();
for (unsigned i = 0; i < NumElem ; ++i) {
unsigned Idx = IsLE ? (NumElem - 1 - i) : i;
StoreSDNode *St = cast<StoreSDNode>(StoreNodes[Idx].MemNode);
SDValue Val = St->getValue();
StoreInt <<= ElementSizeBytes*8;
if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Val)) {
StoreInt |= C->getAPIntValue().zext(StoreBW);
} else if (ConstantFPSDNode *C = dyn_cast<ConstantFPSDNode>(Val)) {
StoreInt |= C->getValueAPF().bitcastToAPInt().zext(StoreBW);
} else {
llvm_unreachable("Invalid constant element type");
}
}
// Create the new Load and Store operations.
EVT StoreTy = EVT::getIntegerVT(*DAG.getContext(), StoreBW);
StoredVal = DAG.getConstant(StoreInt, StoreTy);
}
SDValue NewStore = DAG.getStore(EarliestOp->getChain(), DL, StoredVal,
FirstInChain->getBasePtr(),
FirstInChain->getPointerInfo(),
false, false,
FirstInChain->getAlignment());
// Replace the first store with the new store
CombineTo(EarliestOp, NewStore);
// Erase all other stores.
for (unsigned i = 0; i < NumElem ; ++i) {
if (StoreNodes[i].MemNode == EarliestOp)
continue;
StoreSDNode *St = cast<StoreSDNode>(StoreNodes[i].MemNode);
// ReplaceAllUsesWith will replace all uses that existed when it was
// called, but graph optimizations may cause new ones to appear. For
// example, the case in pr14333 looks like
//
// St's chain -> St -> another store -> X
//
// And the only difference from St to the other store is the chain.
// When we change it's chain to be St's chain they become identical,
// get CSEed and the net result is that X is now a use of St.
// Since we know that St is redundant, just iterate.
while (!St->use_empty())
DAG.ReplaceAllUsesWith(SDValue(St, 0), St->getChain());
deleteAndRecombine(St);
}
return true;
}
bool DAGCombiner::MergeConsecutiveStores(StoreSDNode* St) {
EVT MemVT = St->getMemoryVT();
@ -9731,11 +9850,14 @@ bool DAGCombiner::MergeConsecutiveStores(StoreSDNode* St) {
return false;
// Perform an early exit check. Do not bother looking at stored values that
// are not constants or loads.
// are not constants, loads, or extracted vector elements.
SDValue StoredVal = St->getValue();
bool IsLoadSrc = isa<LoadSDNode>(StoredVal);
if (!isa<ConstantSDNode>(StoredVal) && !isa<ConstantFPSDNode>(StoredVal) &&
!IsLoadSrc)
bool IsConstantSrc = isa<ConstantSDNode>(StoredVal) ||
isa<ConstantFPSDNode>(StoredVal);
bool IsExtractVecEltSrc = (StoredVal.getOpcode() == ISD::EXTRACT_VECTOR_ELT);
if (!IsConstantSrc && !IsLoadSrc && !IsExtractVecEltSrc)
return false;
// Only look at ends of store sequences.
@ -9877,7 +9999,7 @@ bool DAGCombiner::MergeConsecutiveStores(StoreSDNode* St) {
LSBaseSDNode *FirstInChain = StoreNodes[0].MemNode;
// Store the constants into memory as one consecutive store.
if (!IsLoadSrc) {
if (IsConstantSrc) {
unsigned LastLegalType = 0;
unsigned LastLegalVectorType = 0;
bool NonZero = false;
@ -9926,85 +10048,33 @@ bool DAGCombiner::MergeConsecutiveStores(StoreSDNode* St) {
bool UseVector = (LastLegalVectorType > LastLegalType) && !NoVectors;
unsigned NumElem = UseVector ? LastLegalVectorType : LastLegalType;
// Make sure we have something to merge.
if (NumElem < 2)
return false;
return MergeStoresOfConstantsOrVecElts(StoreNodes, MemVT, NumElem,
true, UseVector);
}
unsigned EarliestNodeUsed = 0;
for (unsigned i=0; i < NumElem; ++i) {
// Find a chain for the new wide-store operand. Notice that some
// of the store nodes that we found may not be selected for inclusion
// in the wide store. The chain we use needs to be the chain of the
// earliest store node which is *used* and replaced by the wide store.
if (StoreNodes[i].SequenceNum > StoreNodes[EarliestNodeUsed].SequenceNum)
EarliestNodeUsed = i;
}
// The earliest Node in the DAG.
LSBaseSDNode *EarliestOp = StoreNodes[EarliestNodeUsed].MemNode;
SDLoc DL(StoreNodes[0].MemNode);
SDValue StoredVal;
if (UseVector) {
// When extracting multiple vector elements, try to store them
// in one vector store rather than a sequence of scalar stores.
if (IsExtractVecEltSrc) {
unsigned NumElem = 0;
for (unsigned i = 0; i < LastConsecutiveStore + 1; ++i) {
StoreSDNode *St = cast<StoreSDNode>(StoreNodes[i].MemNode);
SDValue StoredVal = St->getValue();
// This restriction could be loosened.
// Bail out if any stored values are not elements extracted from a vector.
// It should be possible to handle mixed sources, but load sources need
// more careful handling (see the block of code below that handles
// consecutive loads).
if (StoredVal.getOpcode() != ISD::EXTRACT_VECTOR_ELT)
return false;
// Find a legal type for the vector store.
EVT Ty = EVT::getVectorVT(*DAG.getContext(), MemVT, NumElem);
assert(TLI.isTypeLegal(Ty) && "Illegal vector store");
StoredVal = DAG.getConstant(0, Ty);
} else {
unsigned StoreBW = NumElem * ElementSizeBytes * 8;
APInt StoreInt(StoreBW, 0);
// Construct a single integer constant which is made of the smaller
// constant inputs.
bool IsLE = TLI.isLittleEndian();
for (unsigned i = 0; i < NumElem ; ++i) {
unsigned Idx = IsLE ?(NumElem - 1 - i) : i;
StoreSDNode *St = cast<StoreSDNode>(StoreNodes[Idx].MemNode);
SDValue Val = St->getValue();
StoreInt<<=ElementSizeBytes*8;
if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Val)) {
StoreInt|=C->getAPIntValue().zext(StoreBW);
} else if (ConstantFPSDNode *C = dyn_cast<ConstantFPSDNode>(Val)) {
StoreInt|= C->getValueAPF().bitcastToAPInt().zext(StoreBW);
} else {
llvm_unreachable("Invalid constant element type");
}
}
// Create the new Load and Store operations.
EVT StoreTy = EVT::getIntegerVT(*DAG.getContext(), StoreBW);
StoredVal = DAG.getConstant(StoreInt, StoreTy);
EVT Ty = EVT::getVectorVT(*DAG.getContext(), MemVT, i+1);
if (TLI.isTypeLegal(Ty))
NumElem = i + 1;
}
SDValue NewStore = DAG.getStore(EarliestOp->getChain(), DL, StoredVal,
FirstInChain->getBasePtr(),
FirstInChain->getPointerInfo(),
false, false,
FirstInChain->getAlignment());
// Replace the first store with the new store
CombineTo(EarliestOp, NewStore);
// Erase all other stores.
for (unsigned i = 0; i < NumElem ; ++i) {
if (StoreNodes[i].MemNode == EarliestOp)
continue;
StoreSDNode *St = cast<StoreSDNode>(StoreNodes[i].MemNode);
// ReplaceAllUsesWith will replace all uses that existed when it was
// called, but graph optimizations may cause new ones to appear. For
// example, the case in pr14333 looks like
//
// St's chain -> St -> another store -> X
//
// And the only difference from St to the other store is the chain.
// When we change it's chain to be St's chain they become identical,
// get CSEed and the net result is that X is now a use of St.
// Since we know that St is redundant, just iterate.
while (!St->use_empty())
DAG.ReplaceAllUsesWith(SDValue(St, 0), St->getChain());
deleteAndRecombine(St);
}
return true;
return MergeStoresOfConstantsOrVecElts(StoreNodes, MemVT, NumElem,
false, true);
}
// Below we handle the case of multiple consecutive stores that

59
test/CodeGen/X86/MergeConsecutiveStores.ll
View File

@ -434,3 +434,62 @@ define void @loadStoreBaseIndexOffsetSextNoSex(i8* %a, i8* %b, i8* %c, i32 %n) {
; <label>:14
ret void
}
; PR21711 ( http://llvm.org/bugs/show_bug.cgi?id=21711 )
define void @merge_vec_element_store(<8 x float> %v, float* %ptr) {
%vecext0 = extractelement <8 x float> %v, i32 0
%vecext1 = extractelement <8 x float> %v, i32 1
%vecext2 = extractelement <8 x float> %v, i32 2
%vecext3 = extractelement <8 x float> %v, i32 3
%vecext4 = extractelement <8 x float> %v, i32 4
%vecext5 = extractelement <8 x float> %v, i32 5
%vecext6 = extractelement <8 x float> %v, i32 6
%vecext7 = extractelement <8 x float> %v, i32 7
%arrayidx1 = getelementptr inbounds float* %ptr, i64 1
%arrayidx2 = getelementptr inbounds float* %ptr, i64 2
%arrayidx3 = getelementptr inbounds float* %ptr, i64 3
%arrayidx4 = getelementptr inbounds float* %ptr, i64 4
%arrayidx5 = getelementptr inbounds float* %ptr, i64 5
%arrayidx6 = getelementptr inbounds float* %ptr, i64 6
%arrayidx7 = getelementptr inbounds float* %ptr, i64 7
store float %vecext0, float* %ptr, align 4
store float %vecext1, float* %arrayidx1, align 4
store float %vecext2, float* %arrayidx2, align 4
store float %vecext3, float* %arrayidx3, align 4
store float %vecext4, float* %arrayidx4, align 4
store float %vecext5, float* %arrayidx5, align 4
store float %vecext6, float* %arrayidx6, align 4
store float %vecext7, float* %arrayidx7, align 4
ret void
; CHECK-LABEL: merge_vec_element_store
; CHECK: vmovups
; CHECK-NEXT: vzeroupper
; CHECK-NEXT: retq
}
; This is a minimized test based on real code that was failing.
; We could merge stores (and loads) like this...
define void @merge_vec_element_and_scalar_load([6 x i64]* %array) {
%idx0 = getelementptr inbounds [6 x i64]* %array, i64 0, i64 0
%idx1 = getelementptr inbounds [6 x i64]* %array, i64 0, i64 1
%idx4 = getelementptr inbounds [6 x i64]* %array, i64 0, i64 4
%idx5 = getelementptr inbounds [6 x i64]* %array, i64 0, i64 5
%a0 = load i64* %idx0, align 8
store i64 %a0, i64* %idx4, align 8
%b = bitcast i64* %idx1 to <2 x i64>*
%v = load <2 x i64>* %b, align 8
%a1 = extractelement <2 x i64> %v, i32 0
store i64 %a1, i64* %idx5, align 8
ret void
; CHECK-LABEL: merge_vec_element_and_scalar_load
; CHECK: movq (%rdi), %rax
; CHECK-NEXT: movq %rax, 32(%rdi)
; CHECK-NEXT: movq 8(%rdi), %rax
; CHECK-NEXT: movq %rax, 40(%rdi)
; CHECK-NEXT: retq
}