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[InstCombine] fold extract subvector of bitcast insertelt 

This is visible in the original example from:
https://llvm.org/PR50055
(but this change doesn't solve the bug)

https://alive2.llvm.org/ce/z/vM_Yq-
This commit is contained in:
Sanjay Patel 2021-05-10 17:20:10 -04:00
parent 8a74cc139d
commit 5577e86691
2 changed files with 18 additions and 9 deletions
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13
llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
View File

@ -2080,13 +2080,22 @@ static Instruction *narrowVectorSelect(ShuffleVectorInst &Shuf,
return SelectInst::Create(NarrowCond, NarrowX, NarrowY);
}
/// Try to combine 2 shuffles into 1 shuffle by concatenating a shuffle mask.
/// Try to fold an extract subvector operation.
static Instruction *foldIdentityExtractShuffle(ShuffleVectorInst &Shuf) {
Value *Op0 = Shuf.getOperand(0), *Op1 = Shuf.getOperand(1);
if (!Shuf.isIdentityWithExtract() || !match(Op1, m_Undef()))
return nullptr;
Value *X, *Y;
// Check if we are extracting all bits of an inserted scalar:
// extract-subvec (bitcast (inselt ?, X, 0) --> bitcast X to subvec type
Value *X;
if (match(Op0, m_BitCast(m_InsertElt(m_Value(), m_Value(X), m_Zero()))) &&
X->getType()->getPrimitiveSizeInBits() ==
Shuf.getType()->getPrimitiveSizeInBits())
return new BitCastInst(X, Shuf.getType());
// Try to combine 2 shuffles into 1 shuffle by concatenating a shuffle mask.
Value *Y;
ArrayRef<int> Mask;
if (!match(Op0, m_Shuffle(m_Value(X), m_Value(Y), m_Mask(Mask))))
return nullptr;

14
llvm/test/Transforms/InstCombine/shufflevec-bitcast.ll
View File

@ -170,9 +170,7 @@ define <16 x i8> @shuf_bitcast_operand_cannot_widen_undef(<4 x i32> %x) {
define <2 x i4> @shuf_bitcast_insert(<2 x i8> %v, i8 %x) {
; CHECK-LABEL: @shuf_bitcast_insert(
; CHECK-NEXT: [[I:%.*]] = insertelement <2 x i8> poison, i8 [[X:%.*]], i32 0
; CHECK-NEXT: [[B:%.*]] = bitcast <2 x i8> [[I]] to <4 x i4>
; CHECK-NEXT: [[R:%.*]] = shufflevector <4 x i4> [[B]], <4 x i4> undef, <2 x i32> <i32 0, i32 1>
; CHECK-NEXT: [[R:%.*]] = bitcast i8 [[X:%.*]] to <2 x i4>
; CHECK-NEXT: ret <2 x i4> [[R]]
;
%i = insertelement <2 x i8> %v, i8 %x, i32 0
@ -185,8 +183,7 @@ define <2 x i4> @shuf_bitcast_inserti_use1(<2 x i8> %v, i8 %x, <2 x i8>* %p) {
; CHECK-LABEL: @shuf_bitcast_inserti_use1(
; CHECK-NEXT: [[I:%.*]] = insertelement <2 x i8> [[V:%.*]], i8 [[X:%.*]], i32 0
; CHECK-NEXT: store <2 x i8> [[I]], <2 x i8>* [[P:%.*]], align 2
; CHECK-NEXT: [[B:%.*]] = bitcast <2 x i8> [[I]] to <4 x i4>
; CHECK-NEXT: [[R:%.*]] = shufflevector <4 x i4> [[B]], <4 x i4> undef, <2 x i32> <i32 0, i32 1>
; CHECK-NEXT: [[R:%.*]] = bitcast i8 [[X]] to <2 x i4>
; CHECK-NEXT: ret <2 x i4> [[R]]
;
%i = insertelement <2 x i8> %v, i8 %x, i32 0
@ -199,10 +196,9 @@ define <2 x i4> @shuf_bitcast_inserti_use1(<2 x i8> %v, i8 %x, <2 x i8>* %p) {
define <2 x i4> @shuf_bitcast_insert_use2(<2 x i8> %v, i8 %x, <4 x i4>* %p) {
; CHECK-LABEL: @shuf_bitcast_insert_use2(
; CHECK-NEXT: [[I:%.*]] = insertelement <2 x i8> [[V:%.*]], i8 [[X:%.*]], i32 0
; CHECK-NEXT: [[B:%.*]] = bitcast <2 x i8> [[I]] to <4 x i4>
; CHECK-NEXT: [[TMP1:%.*]] = bitcast <4 x i4>* [[P:%.*]] to <2 x i8>*
; CHECK-NEXT: store <2 x i8> [[I]], <2 x i8>* [[TMP1]], align 4
; CHECK-NEXT: [[R:%.*]] = shufflevector <4 x i4> [[B]], <4 x i4> undef, <2 x i32> <i32 0, i32 1>
; CHECK-NEXT: [[R:%.*]] = bitcast i8 [[X]] to <2 x i4>
; CHECK-NEXT: ret <2 x i4> [[R]]
;
%i = insertelement <2 x i8> %v, i8 %x, i32 0
@ -212,6 +208,8 @@ define <2 x i4> @shuf_bitcast_insert_use2(<2 x i8> %v, i8 %x, <4 x i4>* %p) {
ret <2 x i4> %r
}
; negative test - but demanded elements reduces this.
define <2 x i4> @shuf_bitcast_insert_wrong_index(<2 x i8> %v, i8 %x) {
; CHECK-LABEL: @shuf_bitcast_insert_wrong_index(
; CHECK-NEXT: [[B:%.*]] = bitcast <2 x i8> [[V:%.*]] to <4 x i4>
@ -224,6 +222,8 @@ define <2 x i4> @shuf_bitcast_insert_wrong_index(<2 x i8> %v, i8 %x) {
ret <2 x i4> %r
}
; negative test
define <3 x i4> @shuf_bitcast_wrong_size(<2 x i8> %v, i8 %x) {
; CHECK-LABEL: @shuf_bitcast_wrong_size(
; CHECK-NEXT: [[I:%.*]] = insertelement <2 x i8> [[V:%.*]], i8 [[X:%.*]], i32 0