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Revert "[SLP] add another bailout for load-combine patterns"
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It caused asserts building Chromium, see discussion on
https://reviews.llvm.org/D78997

This reverts commit 86dfbc6.
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@zmodem
zmodem committed May 7, 2020
1 parent 666c61d commit c54c6ee
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Showing 2 changed files with 33 additions and 75 deletions.
36 changes: 5 additions & 31 deletions llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
View file
Expand Up @@ -666,15 +666,6 @@ class BoUpSLP {
/// may not be necessary.
bool isLoadCombineReductionCandidate(unsigned ReductionOpcode) const;

/// Assume that a vector of stores of bitwise-or/shifted/zexted loaded values
/// can be load combined in the backend. Load combining may not be allowed in
/// the IR optimizer, so we do not want to alter the pattern. For example,
/// partially transforming a scalar bswap() pattern into vector code is
/// effectively impossible for the backend to undo.
/// TODO: If load combining is allowed in the IR optimizer, this analysis
/// may not be necessary.
bool isLoadCombineCandidate() const;

OptimizationRemarkEmitter *getORE() { return ORE; }

/// This structure holds any data we need about the edges being traversed
Expand Down Expand Up @@ -3682,8 +3673,8 @@ bool BoUpSLP::isFullyVectorizableTinyTree() const {
return true;
}

static bool isLoadCombineCandidateImpl(Value *Root, unsigned NumElts,
TargetTransformInfo *TTI) {
static bool isLoadCombineCandidate(Value *Root, unsigned NumElts,
TargetTransformInfo *TTI) {
// Look past the root to find a source value. Arbitrarily follow the
// path through operand 0 of any 'or'. Also, peek through optional
// shift-left-by-constant.
Expand All @@ -3692,9 +3683,9 @@ static bool isLoadCombineCandidateImpl(Value *Root, unsigned NumElts,
match(ZextLoad, m_Shl(m_Value(), m_Constant())))
ZextLoad = cast<BinaryOperator>(ZextLoad)->getOperand(0);

// Check if the input is an extended load of the required or/shift expression.
// Check if the input is an extended load.
Value *LoadPtr;
if (ZextLoad == Root || !match(ZextLoad, m_ZExt(m_Load(m_Value(LoadPtr)))))
if (!match(ZextLoad, m_ZExt(m_Load(m_Value(LoadPtr)))))
return false;

// Require that the total load bit width is a legal integer type.
Expand All @@ -3719,20 +3710,7 @@ bool BoUpSLP::isLoadCombineReductionCandidate(unsigned RdxOpcode) const {

unsigned NumElts = VectorizableTree[0]->Scalars.size();
Value *FirstReduced = VectorizableTree[0]->Scalars[0];
return isLoadCombineCandidateImpl(FirstReduced, NumElts, TTI);
}

bool BoUpSLP::isLoadCombineCandidate() const {
// Peek through a final sequence of stores and check if all operations are
// likely to be load-combined.
unsigned NumElts = VectorizableTree[0]->Scalars.size();
for (Value *Scalar : VectorizableTree[0]->Scalars) {
Value *X;
if (!match(Scalar, m_Store(m_Value(X), m_Value())) ||
!isLoadCombineCandidateImpl(X, NumElts, TTI))
return false;
}
return true;
return isLoadCombineCandidate(FirstReduced, NumElts, TTI);
}

bool BoUpSLP::isTreeTinyAndNotFullyVectorizable() const {
Expand Down Expand Up @@ -5780,8 +5758,6 @@ bool SLPVectorizerPass::vectorizeStoreChain(ArrayRef<Value *> Chain, BoUpSLP &R,
}
if (R.isTreeTinyAndNotFullyVectorizable())
return false;
if (R.isLoadCombineCandidate())
return false;

R.computeMinimumValueSizes();

Expand Down Expand Up @@ -6034,8 +6010,6 @@ bool SLPVectorizerPass::tryToVectorizeList(ArrayRef<Value *> VL, BoUpSLP &R,
}
if (R.isTreeTinyAndNotFullyVectorizable())
continue;
if (R.isLoadCombineCandidate())
return false;

R.computeMinimumValueSizes();
int Cost = R.getTreeCost() - UserCost;
Expand Down
72 changes: 28 additions & 44 deletions llvm/test/Transforms/SLPVectorizer/X86/bad-reduction.ll
View file
Expand Up @@ -393,50 +393,34 @@ define void @PR39538(i8* %t0, i32* %t1) {
; CHECK-NEXT: [[T63:%.*]] = load i8, i8* [[T62]], align 1
; CHECK-NEXT: [[T68:%.*]] = load i8, i8* [[T67]], align 1
; CHECK-NEXT: [[T73:%.*]] = load i8, i8* [[T72]], align 1
; CHECK-NEXT: [[T4:%.*]] = zext i8 [[T3]] to i32
; CHECK-NEXT: [[T8:%.*]] = zext i8 [[T7]] to i32
; CHECK-NEXT: [[T13:%.*]] = zext i8 [[T12]] to i32
; CHECK-NEXT: [[T18:%.*]] = zext i8 [[T17]] to i32
; CHECK-NEXT: [[T22:%.*]] = zext i8 [[T21]] to i32
; CHECK-NEXT: [[T26:%.*]] = zext i8 [[T25]] to i32
; CHECK-NEXT: [[T31:%.*]] = zext i8 [[T30]] to i32
; CHECK-NEXT: [[T36:%.*]] = zext i8 [[T35]] to i32
; CHECK-NEXT: [[T41:%.*]] = zext i8 [[T40]] to i32
; CHECK-NEXT: [[T45:%.*]] = zext i8 [[T44]] to i32
; CHECK-NEXT: [[T50:%.*]] = zext i8 [[T49]] to i32
; CHECK-NEXT: [[T55:%.*]] = zext i8 [[T54]] to i32
; CHECK-NEXT: [[T60:%.*]] = zext i8 [[T59]] to i32
; CHECK-NEXT: [[T64:%.*]] = zext i8 [[T63]] to i32
; CHECK-NEXT: [[T69:%.*]] = zext i8 [[T68]] to i32
; CHECK-NEXT: [[T74:%.*]] = zext i8 [[T73]] to i32
; CHECK-NEXT: [[T5:%.*]] = shl nuw i32 [[T4]], 24
; CHECK-NEXT: [[T23:%.*]] = shl nuw i32 [[T22]], 24
; CHECK-NEXT: [[T42:%.*]] = shl nuw i32 [[T41]], 24
; CHECK-NEXT: [[T61:%.*]] = shl nuw i32 [[T60]], 24
; CHECK-NEXT: [[T9:%.*]] = shl nuw nsw i32 [[T8]], 16
; CHECK-NEXT: [[T27:%.*]] = shl nuw nsw i32 [[T26]], 16
; CHECK-NEXT: [[T46:%.*]] = shl nuw nsw i32 [[T45]], 16
; CHECK-NEXT: [[T65:%.*]] = shl nuw nsw i32 [[T64]], 16
; CHECK-NEXT: [[T14:%.*]] = shl nuw nsw i32 [[T13]], 8
; CHECK-NEXT: [[T32:%.*]] = shl nuw nsw i32 [[T31]], 8
; CHECK-NEXT: [[T51:%.*]] = shl nuw nsw i32 [[T50]], 8
; CHECK-NEXT: [[T70:%.*]] = shl nuw nsw i32 [[T69]], 8
; CHECK-NEXT: [[T10:%.*]] = or i32 [[T9]], [[T5]]
; CHECK-NEXT: [[T15:%.*]] = or i32 [[T10]], [[T14]]
; CHECK-NEXT: [[T19:%.*]] = or i32 [[T15]], [[T18]]
; CHECK-NEXT: [[T28:%.*]] = or i32 [[T27]], [[T23]]
; CHECK-NEXT: [[T33:%.*]] = or i32 [[T28]], [[T32]]
; CHECK-NEXT: [[T37:%.*]] = or i32 [[T33]], [[T36]]
; CHECK-NEXT: [[T47:%.*]] = or i32 [[T46]], [[T42]]
; CHECK-NEXT: [[T52:%.*]] = or i32 [[T47]], [[T51]]
; CHECK-NEXT: [[T56:%.*]] = or i32 [[T52]], [[T55]]
; CHECK-NEXT: [[T66:%.*]] = or i32 [[T65]], [[T61]]
; CHECK-NEXT: [[T71:%.*]] = or i32 [[T66]], [[T70]]
; CHECK-NEXT: [[T75:%.*]] = or i32 [[T71]], [[T74]]
; CHECK-NEXT: store i32 [[T19]], i32* [[T1]], align 4
; CHECK-NEXT: store i32 [[T37]], i32* [[T38]], align 4
; CHECK-NEXT: store i32 [[T56]], i32* [[T57]], align 4
; CHECK-NEXT: store i32 [[T75]], i32* [[T76]], align 4
; CHECK-NEXT: [[TMP1:%.*]] = insertelement <4 x i8> undef, i8 [[T3]], i32 0
; CHECK-NEXT: [[TMP2:%.*]] = insertelement <4 x i8> [[TMP1]], i8 [[T21]], i32 1
; CHECK-NEXT: [[TMP3:%.*]] = insertelement <4 x i8> [[TMP2]], i8 [[T40]], i32 2
; CHECK-NEXT: [[TMP4:%.*]] = insertelement <4 x i8> [[TMP3]], i8 [[T59]], i32 3
; CHECK-NEXT: [[TMP5:%.*]] = zext <4 x i8> [[TMP4]] to <4 x i32>
; CHECK-NEXT: [[TMP6:%.*]] = insertelement <4 x i8> undef, i8 [[T7]], i32 0
; CHECK-NEXT: [[TMP7:%.*]] = insertelement <4 x i8> [[TMP6]], i8 [[T25]], i32 1
; CHECK-NEXT: [[TMP8:%.*]] = insertelement <4 x i8> [[TMP7]], i8 [[T44]], i32 2
; CHECK-NEXT: [[TMP9:%.*]] = insertelement <4 x i8> [[TMP8]], i8 [[T63]], i32 3
; CHECK-NEXT: [[TMP10:%.*]] = zext <4 x i8> [[TMP9]] to <4 x i32>
; CHECK-NEXT: [[TMP11:%.*]] = insertelement <4 x i8> undef, i8 [[T12]], i32 0
; CHECK-NEXT: [[TMP12:%.*]] = insertelement <4 x i8> [[TMP11]], i8 [[T30]], i32 1
; CHECK-NEXT: [[TMP13:%.*]] = insertelement <4 x i8> [[TMP12]], i8 [[T49]], i32 2
; CHECK-NEXT: [[TMP14:%.*]] = insertelement <4 x i8> [[TMP13]], i8 [[T68]], i32 3
; CHECK-NEXT: [[TMP15:%.*]] = zext <4 x i8> [[TMP14]] to <4 x i32>
; CHECK-NEXT: [[TMP16:%.*]] = insertelement <4 x i8> undef, i8 [[T17]], i32 0
; CHECK-NEXT: [[TMP17:%.*]] = insertelement <4 x i8> [[TMP16]], i8 [[T35]], i32 1
; CHECK-NEXT: [[TMP18:%.*]] = insertelement <4 x i8> [[TMP17]], i8 [[T54]], i32 2
; CHECK-NEXT: [[TMP19:%.*]] = insertelement <4 x i8> [[TMP18]], i8 [[T73]], i32 3
; CHECK-NEXT: [[TMP20:%.*]] = zext <4 x i8> [[TMP19]] to <4 x i32>
; CHECK-NEXT: [[TMP21:%.*]] = shl nuw <4 x i32> [[TMP5]], <i32 24, i32 24, i32 24, i32 24>
; CHECK-NEXT: [[TMP22:%.*]] = shl nuw nsw <4 x i32> [[TMP10]], <i32 16, i32 16, i32 16, i32 16>
; CHECK-NEXT: [[TMP23:%.*]] = shl nuw nsw <4 x i32> [[TMP15]], <i32 8, i32 8, i32 8, i32 8>
; CHECK-NEXT: [[TMP24:%.*]] = or <4 x i32> [[TMP22]], [[TMP21]]
; CHECK-NEXT: [[TMP25:%.*]] = or <4 x i32> [[TMP24]], [[TMP23]]
; CHECK-NEXT: [[TMP26:%.*]] = or <4 x i32> [[TMP25]], [[TMP20]]
; CHECK-NEXT: [[TMP27:%.*]] = bitcast i32* [[T1]] to <4 x i32>*
; CHECK-NEXT: store <4 x i32> [[TMP26]], <4 x i32>* [[TMP27]], align 4
; CHECK-NEXT: ret void
;
%t6 = getelementptr inbounds i8, i8* %t0, i64 1
Expand Down

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