return new ShuffleVectorInst(X, Y, ConstantVector::get(NewMask));
}
-/// Try to replace a shuffle with an insertelement.
+/// Try to replace a shuffle with an insertelement or try to replace a shuffle
+/// operand with the operand of an insertelement.
static Instruction *foldShuffleWithInsert(ShuffleVectorInst &Shuf) {
Value *V0 = Shuf.getOperand(0), *V1 = Shuf.getOperand(1);
SmallVector<int, 16> Mask = Shuf.getShuffleMask();
if (NumElts != (int)(V0->getType()->getVectorNumElements()))
return nullptr;
+ // This is a specialization of a fold in SimplifyDemandedVectorElts. We may
+ // not be able to handle it there if the insertelement has >1 use.
+ // If the shuffle has an insertelement operand but does not choose the
+ // inserted scalar element from that value, then we can replace that shuffle
+ // operand with the source vector of the insertelement.
+ Value *X;
+ uint64_t IdxC;
+ if (match(V0, m_InsertElement(m_Value(X), m_Value(), m_ConstantInt(IdxC)))) {
+ // shuf (inselt X, ?, IdxC), ?, Mask --> shuf X, ?, Mask
+ if (none_of(Mask, [IdxC](int MaskElt) { return MaskElt == (int)IdxC; })) {
+ Shuf.setOperand(0, X);
+ return &Shuf;
+ }
+ }
+ if (match(V1, m_InsertElement(m_Value(X), m_Value(), m_ConstantInt(IdxC)))) {
+ // Offset the index constant by the vector width because we are checking for
+ // accesses to the 2nd vector input of the shuffle.
+ IdxC += NumElts;
+ // shuf ?, (inselt X, ?, IdxC), Mask --> shuf ?, X, Mask
+ if (none_of(Mask, [IdxC](int MaskElt) { return MaskElt == (int)IdxC; })) {
+ Shuf.setOperand(1, X);
+ return &Shuf;
+ }
+ }
+
// shuffle (insert ?, Scalar, IndexC), V1, Mask --> insert V1, Scalar, IndexC'
auto isShufflingScalarIntoOp1 = [&](Value *&Scalar, ConstantInt *&IndexC) {
// We need an insertelement with a constant index.
; CHECK-LABEL: @insert_undemanded_element_op0(
; CHECK-NEXT: [[INS:%.*]] = insertelement <4 x float> [[X:%.*]], float 4.200000e+01, i32 3
; CHECK-NEXT: call void @use(<4 x float> [[INS]])
-; CHECK-NEXT: [[S:%.*]] = shufflevector <4 x float> [[INS]], <4 x float> [[Y:%.*]], <4 x i32> <i32 0, i32 7, i32 1, i32 4>
+; CHECK-NEXT: [[S:%.*]] = shufflevector <4 x float> [[X]], <4 x float> [[Y:%.*]], <4 x i32> <i32 0, i32 7, i32 1, i32 4>
; CHECK-NEXT: ret <4 x float> [[S]]
;
%ins = insertelement <4 x float> %x, float 42.0, i32 3
; CHECK-LABEL: @insert_undemanded_element_op1(
; CHECK-NEXT: [[INS:%.*]] = insertelement <4 x float> [[X:%.*]], float 4.200000e+01, i32 3
; CHECK-NEXT: call void @use(<4 x float> [[INS]])
-; CHECK-NEXT: [[S:%.*]] = shufflevector <4 x float> [[Y:%.*]], <4 x float> [[INS]], <4 x i32> <i32 3, i32 2, i32 1, i32 4>
+; CHECK-NEXT: [[S:%.*]] = shufflevector <4 x float> [[Y:%.*]], <4 x float> [[X]], <4 x i32> <i32 3, i32 2, i32 1, i32 4>
; CHECK-NEXT: ret <4 x float> [[S]]
;
%ins = insertelement <4 x float> %x, float 42.0, i32 3
ret <4 x float> %s
}
+; Negative test - shuffle chooses the inserted constant.
+
define <4 x float> @insert_demanded_element_op0(<4 x float> %x, <4 x float> %y) {
; CHECK-LABEL: @insert_demanded_element_op0(
; CHECK-NEXT: [[INS:%.*]] = insertelement <4 x float> [[X:%.*]], float 4.200000e+01, i32 3
ret <4 x float> %s
}
+; Negative test - shuffle chooses the inserted constant.
+
define <4 x float> @insert_demanded_element_op1(<4 x float> %x, <4 x float> %y) {
; CHECK-LABEL: @insert_demanded_element_op1(
; CHECK-NEXT: [[INS:%.*]] = insertelement <4 x float> [[X:%.*]], float 4.300000e+01, i32 3