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[InstCombine] allow shuffle+binop canonicalization with widening shuffles 

This lines up with the behavior of an existing transform where if both 
operands of the binop are shuffled, we allow moving the binop before the 
shuffle regardless of whether the shuffle changes the size of the vector.

llvm-svn: 340787
This commit is contained in:
Sanjay Patel 2018-08-27 22:41:44 +00:00
parent 20d7892143
commit 42d31c20a8
2 changed files with 22 additions and 12 deletions
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18
llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
View File

@ -1393,7 +1393,10 @@ Instruction *InstCombiner::foldShuffledBinop(BinaryOperator &Inst) {
if (match(&Inst, m_c_BinOp(
m_OneUse(m_ShuffleVector(m_Value(V1), m_Undef(), m_Constant(Mask))),
m_Constant(C))) &&
V1->getType() == Inst.getType()) {
V1->getType()->getVectorNumElements() <= VWidth) {
assert(Inst.getType()->getScalarType() == V1->getType()->getScalarType() &&
"Shuffle should not change scalar type");
unsigned V1Width = V1->getType()->getVectorNumElements();
// Find constant NewC that has property:
// shuffle(NewC, ShMask) = C
// If such constant does not exist (example: ShMask=<0,0> and C=<1,2>)
@ -1402,14 +1405,21 @@ Instruction *InstCombiner::foldShuffledBinop(BinaryOperator &Inst) {
SmallVector<int, 16> ShMask;
ShuffleVectorInst::getShuffleMask(Mask, ShMask);
SmallVector<Constant *, 16>
NewVecC(VWidth, UndefValue::get(C->getType()->getScalarType()));
NewVecC(V1Width, UndefValue::get(C->getType()->getScalarType()));
bool MayChange = true;
for (unsigned I = 0; I < VWidth; ++I) {
if (ShMask[I] >= 0) {
assert(ShMask[I] < (int)VWidth);
assert(ShMask[I] < (int)VWidth && "Not expecting narrowing shuffle");
Constant *CElt = C->getAggregateElement(I);
Constant *NewCElt = NewVecC[ShMask[I]];
if (!CElt || (!isa<UndefValue>(NewCElt) && NewCElt != CElt)) {
// Bail out if:
// 1. The constant vector contains a constant expression.
// 2. The shuffle needs an element of the constant vector that can't
// be mapped to a new constant vector.
// 3. This is a widening shuffle that copies elements of V1 into the
// extended elements (extending with undef is allowed).
if (!CElt || (!isa<UndefValue>(NewCElt) && NewCElt != CElt) ||
I >= V1Width) {
MayChange = false;
break;
}

16
llvm/test/Transforms/InstCombine/vec_shuffle.ll
View File

@ -474,12 +474,12 @@ define <2 x float> @fmul_const_invalid_constant(<2 x float> %v) {
ret <2 x float> %r
}
; TODO: Reduce the width of the binop by moving it ahead of a shuffle.
; Reduce the width of the binop by moving it ahead of a shuffle.
define <4 x i8> @widening_shuffle_add_1(<2 x i8> %x) {
; CHECK-LABEL: @widening_shuffle_add_1(
; CHECK-NEXT: [[WIDEX:%.*]] = shufflevector <2 x i8> [[X:%.*]], <2 x i8> undef, <4 x i32> <i32 0, i32 1, i32 undef, i32 undef>
; CHECK-NEXT: [[R:%.*]] = add <4 x i8> [[WIDEX]], <i8 42, i8 43, i8 44, i8 45>
; CHECK-NEXT: [[TMP1:%.*]] = add <2 x i8> [[X:%.*]], <i8 42, i8 43>
; CHECK-NEXT: [[R:%.*]] = shufflevector <2 x i8> [[TMP1]], <2 x i8> undef, <4 x i32> <i32 0, i32 1, i32 undef, i32 undef>
; CHECK-NEXT: ret <4 x i8> [[R]]
;
%widex = shufflevector <2 x i8> %x, <2 x i8> undef, <4 x i32> <i32 0, i32 1, i32 undef, i32 undef>
@ -487,12 +487,12 @@ define <4 x i8> @widening_shuffle_add_1(<2 x i8> %x) {
ret <4 x i8> %r
}
; TODO: Reduce the width of the binop by moving it ahead of a shuffle.
; Reduce the width of the binop by moving it ahead of a shuffle.
define <4 x i8> @widening_shuffle_add_2(<2 x i8> %x) {
; CHECK-LABEL: @widening_shuffle_add_2(
; CHECK-NEXT: [[WIDEX:%.*]] = shufflevector <2 x i8> [[X:%.*]], <2 x i8> undef, <4 x i32> <i32 1, i32 0, i32 undef, i32 undef>
; CHECK-NEXT: [[R:%.*]] = add <4 x i8> [[WIDEX]], <i8 42, i8 43, i8 44, i8 45>
; CHECK-NEXT: [[TMP1:%.*]] = add <2 x i8> [[X:%.*]], <i8 43, i8 42>
; CHECK-NEXT: [[R:%.*]] = shufflevector <2 x i8> [[TMP1]], <2 x i8> undef, <4 x i32> <i32 1, i32 0, i32 undef, i32 undef>
; CHECK-NEXT: ret <4 x i8> [[R]]
;
%widex = shufflevector <2 x i8> %x, <2 x i8> undef, <4 x i32> <i32 1, i32 0, i32 undef, i32 undef>
@ -500,7 +500,7 @@ define <4 x i8> @widening_shuffle_add_2(<2 x i8> %x) {
ret <4 x i8> %r
}
; Widening shuffles have the same mask/constant constraint as non-size-changing shuffles.
; Negative test - widening shuffles have the same mask/constant constraint as non-size-changing shuffles.
define <4 x i8> @widening_shuffle_add_invalid_constant(<2 x i8> %x) {
; CHECK-LABEL: @widening_shuffle_add_invalid_constant(
@ -513,7 +513,7 @@ define <4 x i8> @widening_shuffle_add_invalid_constant(<2 x i8> %x) {
ret <4 x i8> %r
}
; And widening shuffles have an additional constraint - they must not extend with anything but undefs.
; Negative test - widening shuffles have an additional constraint: they must not extend with anything but undefs.
define <4 x i8> @widening_shuffle_add_invalid_mask(<2 x i8> %x) {
; CHECK-LABEL: @widening_shuffle_add_invalid_mask(