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[InstCombine] allow bitcast to/from FP for vector insert/extract transform

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This is a follow-up to rL343482 / D52439.
This was a pattern that initially caused the commit to be reverted because
the transform requires a bitcast as shown here.

llvm-svn: 343794
This commit is contained in:
Sanjay Patel 2018-10-04 16:25:05 +00:00
parent 9c6205b103
commit fd5c125b13
3 changed files with 53 additions and 17 deletions
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35
lib/Transforms/InstCombine/InstCombineVectorOps.cpp
View File

@ -189,9 +189,7 @@ static Instruction *foldBitcastExtElt(ExtractElementInst &Ext,
// If the source elements are wider than the destination, try to shift and
// truncate a subset of scalar bits of an insert op.
// TODO: This is limited to integer types, but we could bitcast to/from FP.
if (NumSrcElts < NumElts && SrcTy->getScalarType()->isIntegerTy() &&
DestTy->getScalarType()->isIntegerTy()) {
if (NumSrcElts < NumElts) {
Value *Scalar;
uint64_t InsIndexC;
if (!match(X, m_InsertElement(m_Value(), m_Value(Scalar),
@ -220,13 +218,42 @@ static Instruction *foldBitcastExtElt(ExtractElementInst &Ext,
unsigned Chunk = ExtIndexC % NarrowingRatio;
if (IsBigEndian)
Chunk = NarrowingRatio - 1 - Chunk;
unsigned ShAmt = Chunk * DestTy->getPrimitiveSizeInBits();
// Bail out if this is an FP vector to FP vector sequence. That would take
// more instructions than we started with unless there is no shift, and it
// may not be handled as well in the backend.
bool NeedSrcBitcast = SrcTy->getScalarType()->isFloatingPointTy();
bool NeedDestBitcast = DestTy->isFloatingPointTy();
if (NeedSrcBitcast && NeedDestBitcast)
return nullptr;
unsigned SrcWidth = SrcTy->getScalarSizeInBits();
unsigned DestWidth = DestTy->getPrimitiveSizeInBits();
unsigned ShAmt = Chunk * DestWidth;
// TODO: This limitation is more strict than necessary. We could sum the
// number of new instructions and subtract the number eliminated to know if
// we can proceed.
if (!X->hasOneUse() || !Ext.getVectorOperand()->hasOneUse())
if (NeedSrcBitcast || NeedDestBitcast)
return nullptr;
if (NeedSrcBitcast) {
Type *SrcIntTy = IntegerType::getIntNTy(Scalar->getContext(), SrcWidth);
Scalar = Builder.CreateBitCast(Scalar, SrcIntTy);
}
if (ShAmt) {
// Bail out if we could end with more instructions than we started with.
if (!Ext.getVectorOperand()->hasOneUse())
return nullptr;
Scalar = Builder.CreateLShr(Scalar, ShAmt);
}
if (NeedDestBitcast) {
Type *DestIntTy = IntegerType::getIntNTy(Scalar->getContext(), DestWidth);
return new BitCastInst(Builder.CreateTrunc(Scalar, DestIntTy), DestTy);
}
return new TruncInst(Scalar, DestTy);
}

5
test/Transforms/InstCombine/AMDGPU/amdgcn-demanded-vector-elts.ll
View File

@ -299,9 +299,8 @@ define i32 @extract0_bitcast_buffer_load_format_v4f32(i32 %arg) #0 {
; CHECK-LABEL: @extract_lo16_0_bitcast_buffer_load_format_v4f32(
; CHECK-NEXT: %tmp = call float @llvm.amdgcn.buffer.load.format.f32(<4 x i32> undef, i32 %arg, i32 16, i1 false, i1 false)
; CHECK-NEXT: %1 = insertelement <4 x float> undef, float %tmp, i64 0
; CHECK-NEXT: %tmp1 = bitcast <4 x float> %1 to <8 x i16>
; CHECK-NEXT: %tmp2 = extractelement <8 x i16> %tmp1, i32 0
; CHECK-NEXT: %1 = bitcast float %tmp to i32
; CHECK-NEXT: %tmp2 = trunc i32 %1 to i16
; CHECK-NEXT: ret i16 %tmp2
define i16 @extract_lo16_0_bitcast_buffer_load_format_v4f32(i32 %arg) #0 {
%tmp = call <4 x float> @llvm.amdgcn.buffer.load.format.v4f32(<4 x i32> undef, i32 %arg, i32 16, i1 false, i1 false) #3

30
test/Transforms/InstCombine/extractelement.ll
View File

@ -164,11 +164,16 @@ define i8 @bitcasted_inselt_wide_source_uses(i32 %x) {
}
define float @bitcasted_inselt_to_FP(i64 %x) {
; ANY-LABEL: @bitcasted_inselt_to_FP(
; ANY-NEXT: [[I:%.*]] = insertelement <2 x i64> undef, i64 [[X:%.*]], i32 0
; ANY-NEXT: [[B:%.*]] = bitcast <2 x i64> [[I]] to <4 x float>
; ANY-NEXT: [[R:%.*]] = extractelement <4 x float> [[B]], i32 1
; ANY-NEXT: ret float [[R]]
; LE-LABEL: @bitcasted_inselt_to_FP(
; LE-NEXT: [[TMP1:%.*]] = lshr i64 [[X:%.*]], 32
; LE-NEXT: [[TMP2:%.*]] = trunc i64 [[TMP1]] to i32
; LE-NEXT: [[R:%.*]] = bitcast i32 [[TMP2]] to float
; LE-NEXT: ret float [[R]]
;
; BE-LABEL: @bitcasted_inselt_to_FP(
; BE-NEXT: [[TMP1:%.*]] = trunc i64 [[X:%.*]] to i32
; BE-NEXT: [[R:%.*]] = bitcast i32 [[TMP1]] to float
; BE-NEXT: ret float [[R]]
;
%i = insertelement <2 x i64> undef, i64 %x, i32 0
%b = bitcast <2 x i64> %i to <4 x float>
@ -210,11 +215,16 @@ define float @bitcasted_inselt_to_FP_uses2(i128 %x) {
}
define i32 @bitcasted_inselt_from_FP(double %x) {
; ANY-LABEL: @bitcasted_inselt_from_FP(
; ANY-NEXT: [[I:%.*]] = insertelement <2 x double> undef, double [[X:%.*]], i32 0
; ANY-NEXT: [[B:%.*]] = bitcast <2 x double> [[I]] to <4 x i32>
; ANY-NEXT: [[R:%.*]] = extractelement <4 x i32> [[B]], i32 1
; ANY-NEXT: ret i32 [[R]]
; LE-LABEL: @bitcasted_inselt_from_FP(
; LE-NEXT: [[TMP1:%.*]] = bitcast double [[X:%.*]] to i64
; LE-NEXT: [[TMP2:%.*]] = lshr i64 [[TMP1]], 32
; LE-NEXT: [[R:%.*]] = trunc i64 [[TMP2]] to i32
; LE-NEXT: ret i32 [[R]]
;
; BE-LABEL: @bitcasted_inselt_from_FP(
; BE-NEXT: [[TMP1:%.*]] = bitcast double [[X:%.*]] to i64
; BE-NEXT: [[R:%.*]] = trunc i64 [[TMP1]] to i32
; BE-NEXT: ret i32 [[R]]
;
%i = insertelement <2 x double> undef, double %x, i32 0
%b = bitcast <2 x double> %i to <4 x i32>