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[InstCombine] canonicalize insert+splat to/from element 0 of vector

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We recognize a splat from element 0 in (VectorUtils) llvm::getSplatValue()
and also in ShuffleVectorInst::isZeroEltSplatMask(), so this converts
to that form for better matching.

The backend generically turns these patterns into build_vector,
so there should be no codegen difference.

llvm-svn: 365342
This commit is contained in:
Sanjay Patel 2019-07-08 16:26:48 +00:00
parent 2163f094d4
commit 136e9c5044
2 changed files with 72 additions and 6 deletions
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38
lib/Transforms/InstCombine/InstCombineVectorOps.cpp
View File

@ -1346,6 +1346,41 @@ static Instruction *foldSelectShuffleWith1Binop(ShuffleVectorInst &Shuf) {
return NewBO;
}
/// If we have an insert of a scalar to a non-zero element of an undefined
/// vector and then shuffle that value, that's the same as inserting to the zero
/// element and shuffling. Splatting from the zero element is recognized as the
/// canonical form of splat.
static Instruction *canonicalizeInsertSplat(ShuffleVectorInst &Shuf,
InstCombiner::BuilderTy &Builder) {
Value *Op0 = Shuf.getOperand(0), *Op1 = Shuf.getOperand(1);
Constant *Mask = Shuf.getMask();
Value *X;
uint64_t IndexC;
// Match a shuffle that is a splat to a non-zero element.
if (!match(Op0, m_OneUse(m_InsertElement(m_Undef(), m_Value(X),
m_ConstantInt(IndexC)))) ||
!match(Op1, m_Undef()) || match(Mask, m_ZeroInt()) || IndexC == 0)
return nullptr;
// Insert into element 0 of an undef vector.
UndefValue *UndefVec = UndefValue::get(Shuf.getType());
Constant *Zero = Builder.getInt32(0);
Value *NewIns = Builder.CreateInsertElement(UndefVec, X, Zero);
// Splat from element 0. Any mask element that is undefined remains undefined.
// For example:
// shuf (inselt undef, X, 2), undef, <2,2,undef>
// --> shuf (inselt undef, X, 0), undef, <0,0,undef>
unsigned NumMaskElts = Shuf.getType()->getVectorNumElements();
SmallVector<Constant *, 16> NewMask(NumMaskElts, Zero);
for (unsigned i = 0; i != NumMaskElts; ++i)
if (isa<UndefValue>(Mask->getAggregateElement(i)))
NewMask[i] = Mask->getAggregateElement(i);
return new ShuffleVectorInst(NewIns, UndefVec, ConstantVector::get(NewMask));
}
/// Try to fold shuffles that are the equivalent of a vector select.
static Instruction *foldSelectShuffle(ShuffleVectorInst &Shuf,
InstCombiner::BuilderTy &Builder,
@ -1714,6 +1749,9 @@ Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
return &SVI;
}
if (Instruction *I = canonicalizeInsertSplat(SVI, Builder))
return I;
if (Instruction *I = foldSelectShuffle(SVI, Builder, DL))
return I;

40
test/Transforms/InstCombine/insert-extract-shuffle.ll
View File

@ -427,8 +427,8 @@ define <5 x float> @insert_not_undef_shuffle_translate_commute_lengthen(float %x
define <4 x float> @insert_nonzero_index_splat(float %x) {
; CHECK-LABEL: @insert_nonzero_index_splat(
; CHECK-NEXT: [[XV:%.*]] = insertelement <4 x float> undef, float [[X:%.*]], i32 2
; CHECK-NEXT: [[SPLAT:%.*]] = shufflevector <4 x float> [[XV]], <4 x float> undef, <4 x i32> <i32 undef, i32 2, i32 2, i32 undef>
; CHECK-NEXT: [[TMP1:%.*]] = insertelement <4 x float> undef, float [[X:%.*]], i32 0
; CHECK-NEXT: [[SPLAT:%.*]] = shufflevector <4 x float> [[TMP1]], <4 x float> undef, <4 x i32> <i32 undef, i32 0, i32 0, i32 undef>
; CHECK-NEXT: ret <4 x float> [[SPLAT]]
;
%xv = insertelement <4 x float> undef, float %x, i32 2
@ -438,8 +438,8 @@ define <4 x float> @insert_nonzero_index_splat(float %x) {
define <3 x double> @insert_nonzero_index_splat_narrow(double %x) {
; CHECK-LABEL: @insert_nonzero_index_splat_narrow(
; CHECK-NEXT: [[XV:%.*]] = insertelement <4 x double> undef, double [[X:%.*]], i32 3
; CHECK-NEXT: [[SPLAT:%.*]] = shufflevector <4 x double> [[XV]], <4 x double> undef, <3 x i32> <i32 3, i32 undef, i32 3>
; CHECK-NEXT: [[TMP1:%.*]] = insertelement <3 x double> undef, double [[X:%.*]], i32 0
; CHECK-NEXT: [[SPLAT:%.*]] = shufflevector <3 x double> [[TMP1]], <3 x double> undef, <3 x i32> <i32 0, i32 undef, i32 0>
; CHECK-NEXT: ret <3 x double> [[SPLAT]]
;
%xv = insertelement <4 x double> undef, double %x, i32 3
@ -449,8 +449,8 @@ define <3 x double> @insert_nonzero_index_splat_narrow(double %x) {
define <5 x i7> @insert_nonzero_index_splat_widen(i7 %x) {
; CHECK-LABEL: @insert_nonzero_index_splat_widen(
; CHECK-NEXT: [[XV:%.*]] = insertelement <4 x i7> undef, i7 [[X:%.*]], i32 1
; CHECK-NEXT: [[SPLAT:%.*]] = shufflevector <4 x i7> [[XV]], <4 x i7> undef, <5 x i32> <i32 undef, i32 1, i32 1, i32 undef, i32 1>
; CHECK-NEXT: [[TMP1:%.*]] = insertelement <5 x i7> undef, i7 [[X:%.*]], i32 0
; CHECK-NEXT: [[SPLAT:%.*]] = shufflevector <5 x i7> [[TMP1]], <5 x i7> undef, <5 x i32> <i32 undef, i32 0, i32 0, i32 undef, i32 0>
; CHECK-NEXT: ret <5 x i7> [[SPLAT]]
;
%xv = insertelement <4 x i7> undef, i7 %x, i32 1
@ -458,6 +458,8 @@ define <5 x i7> @insert_nonzero_index_splat_widen(i7 %x) {
ret <5 x i7> %splat
}
; Negative test - don't increase instruction count
define <4 x float> @insert_nonzero_index_splat_extra_use(float %x) {
; CHECK-LABEL: @insert_nonzero_index_splat_extra_use(
; CHECK-NEXT: [[XV:%.*]] = insertelement <4 x float> undef, float [[X:%.*]], i32 2
@ -470,3 +472,29 @@ define <4 x float> @insert_nonzero_index_splat_extra_use(float %x) {
%splat = shufflevector <4 x float> %xv, <4 x float> undef, <4 x i32> <i32 undef, i32 2, i32 2, i32 undef>
ret <4 x float> %splat
}
; Negative test - non-undef base vector
define <4 x float> @insert_nonzero_index_splat_wrong_base(float %x, <4 x float> %y) {
; CHECK-LABEL: @insert_nonzero_index_splat_wrong_base(
; CHECK-NEXT: [[XV:%.*]] = insertelement <4 x float> [[Y:%.*]], float [[X:%.*]], i32 2
; CHECK-NEXT: [[SPLAT:%.*]] = shufflevector <4 x float> [[XV]], <4 x float> undef, <4 x i32> <i32 undef, i32 2, i32 3, i32 undef>
; CHECK-NEXT: ret <4 x float> [[SPLAT]]
;
%xv = insertelement <4 x float> %y, float %x, i32 2
%splat = shufflevector <4 x float> %xv, <4 x float> undef, <4 x i32> <i32 undef, i32 2, i32 3, i32 undef>
ret <4 x float> %splat
}
; Negative test - non-constant insert index
define <4 x float> @insert_nonzero_index_splat_wrong_index(float %x, i32 %index) {
; CHECK-LABEL: @insert_nonzero_index_splat_wrong_index(
; CHECK-NEXT: [[XV:%.*]] = insertelement <4 x float> undef, float [[X:%.*]], i32 [[INDEX:%.*]]
; CHECK-NEXT: [[SPLAT:%.*]] = shufflevector <4 x float> [[XV]], <4 x float> undef, <4 x i32> <i32 undef, i32 1, i32 1, i32 undef>
; CHECK-NEXT: ret <4 x float> [[SPLAT]]
;
%xv = insertelement <4 x float> undef, float %x, i32 %index
%splat = shufflevector <4 x float> %xv, <4 x float> undef, <4 x i32> <i32 undef, i32 1, i32 1, i32 undef>
ret <4 x float> %splat
}