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//===--------- X86InterleavedAccess.cpp ----------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===--------------------------------------------------------------------===//
///
/// \file
/// This file contains the X86 implementation of the interleaved accesses
/// optimization generating X86-specific instructions/intrinsics for
/// interleaved access groups.
///
//===--------------------------------------------------------------------===//
#include "X86ISelLowering.h"
#include "X86TargetMachine.h"
using namespace llvm;
/// \brief This class holds necessary information to represent an interleaved
/// access group and supports utilities to lower the group into
/// X86-specific instructions/intrinsics.
/// E.g. A group of interleaving access loads (Factor = 2; accessing every
/// other element)
/// %wide.vec = load <8 x i32>, <8 x i32>* %ptr
/// %v0 = shuffle <8 x i32> %wide.vec, <8 x i32> undef, <0, 2, 4, 6>
/// %v1 = shuffle <8 x i32> %wide.vec, <8 x i32> undef, <1, 3, 5, 7>
class X86InterleavedAccessGroup {
/// \brief Reference to the wide-load instruction of an interleaved access
/// group.
Instruction *const Inst;
/// \brief Reference to the shuffle(s), consumer(s) of the (load) 'Inst'.
ArrayRef<ShuffleVectorInst *> Shuffles;
/// \brief Reference to the starting index of each user-shuffle.
ArrayRef<unsigned> Indices;
/// \brief Reference to the interleaving stride in terms of elements.
const unsigned Factor;
/// \brief Reference to the underlying target.
const X86Subtarget &Subtarget;
const DataLayout &DL;
IRBuilder<> &Builder;
/// \brief Breaks down a vector \p 'Inst' of N elements into \p NumSubVectors
/// sub vectors of type \p T. Returns true and the sub-vectors in
/// \p DecomposedVectors if it decomposes the Inst, returns false otherwise.
bool decompose(Instruction *Inst, unsigned NumSubVectors, VectorType *T,
SmallVectorImpl<Instruction *> &DecomposedVectors);
/// \brief Performs matrix transposition on a 4x4 matrix \p InputVectors and
/// returns the transposed-vectors in \p TransposedVectors.
/// E.g.
/// InputVectors:
/// In-V0 = p1, p2, p3, p4
/// In-V1 = q1, q2, q3, q4
/// In-V2 = r1, r2, r3, r4
/// In-V3 = s1, s2, s3, s4
/// OutputVectors:
/// Out-V0 = p1, q1, r1, s1
/// Out-V1 = p2, q2, r2, s2
/// Out-V2 = p3, q3, r3, s3
/// Out-V3 = P4, q4, r4, s4
void transpose_4x4(ArrayRef<Instruction *> InputVectors,
SmallVectorImpl<Value *> &TrasposedVectors);
public:
/// In order to form an interleaved access group X86InterleavedAccessGroup
/// requires a wide-load instruction \p 'I', a group of interleaved-vectors
/// \p Shuffs, reference to the first indices of each interleaved-vector
/// \p 'Ind' and the interleaving stride factor \p F. In order to generate
/// X86-specific instructions/intrinsics it also requires the underlying
/// target information \p STarget.
explicit X86InterleavedAccessGroup(Instruction *I,
ArrayRef<ShuffleVectorInst *> Shuffs,
ArrayRef<unsigned> Ind,
const unsigned F,
const X86Subtarget &STarget,
IRBuilder<> &B)
: Inst(I), Shuffles(Shuffs), Indices(Ind), Factor(F), Subtarget(STarget),
DL(Inst->getModule()->getDataLayout()), Builder(B) {}
/// \brief Returns true if this interleaved access group can be lowered into
/// x86-specific instructions/intrinsics, false otherwise.
bool isSupported() const;
/// \brief Lowers this interleaved access group into X86-specific
/// instructions/intrinsics.
bool lowerIntoOptimizedSequence();
};
bool X86InterleavedAccessGroup::isSupported() const {
VectorType *ShuffleVecTy = Shuffles[0]->getType();
uint64_t ShuffleVecSize = DL.getTypeSizeInBits(ShuffleVecTy);
Type *ShuffleEltTy = ShuffleVecTy->getVectorElementType();
if (DL.getTypeSizeInBits(Inst->getType()) < Factor * ShuffleVecSize)
return false;
// Currently, lowering is supported for 64 bits on AVX.
if (!Subtarget.hasAVX() || ShuffleVecSize != 256 ||
DL.getTypeSizeInBits(ShuffleEltTy) != 64 || Factor != 4)
return false;
return true;
}
bool X86InterleavedAccessGroup::decompose(
Instruction *VecInst, unsigned NumSubVectors, VectorType *SubVecTy,
SmallVectorImpl<Instruction *> &DecomposedVectors) {
Type *VecTy = VecInst->getType();
(void)VecTy;
assert(VecTy->isVectorTy() &&
DL.getTypeSizeInBits(VecTy) >=
DL.getTypeSizeInBits(SubVecTy) * NumSubVectors &&
"Invalid Inst-size!!!");
assert(VecTy->getVectorElementType() == SubVecTy->getVectorElementType() &&
"Element type mismatched!!!");
if (!isa<LoadInst>(VecInst))
return false;
LoadInst *LI = cast<LoadInst>(VecInst);
Type *VecBasePtrTy = SubVecTy->getPointerTo(LI->getPointerAddressSpace());
Value *VecBasePtr =
Builder.CreateBitCast(LI->getPointerOperand(), VecBasePtrTy);
// Generate N loads of T type
for (unsigned i = 0; i < NumSubVectors; i++) {
// TODO: Support inbounds GEP
Value *NewBasePtr = Builder.CreateGEP(VecBasePtr, Builder.getInt32(i));
Instruction *NewLoad =
Builder.CreateAlignedLoad(NewBasePtr, LI->getAlignment());
DecomposedVectors.push_back(NewLoad);
}
return true;
}
void X86InterleavedAccessGroup::transpose_4x4(
ArrayRef<Instruction *> Matrix,
SmallVectorImpl<Value *> &TransposedMatrix) {
assert(Matrix.size() == 4 && "Invalid matrix size");
TransposedMatrix.resize(4);
// dst = src1[0,1],src2[0,1]
uint32_t IntMask1[] = {0, 1, 4, 5};
ArrayRef<uint32_t> Mask = makeArrayRef(IntMask1, 4);
Value *IntrVec1 = Builder.CreateShuffleVector(Matrix[0], Matrix[2], Mask);
Value *IntrVec2 = Builder.CreateShuffleVector(Matrix[1], Matrix[3], Mask);
// dst = src1[2,3],src2[2,3]
uint32_t IntMask2[] = {2, 3, 6, 7};
Mask = makeArrayRef(IntMask2, 4);
Value *IntrVec3 = Builder.CreateShuffleVector(Matrix[0], Matrix[2], Mask);
Value *IntrVec4 = Builder.CreateShuffleVector(Matrix[1], Matrix[3], Mask);
// dst = src1[0],src2[0],src1[2],src2[2]
uint32_t IntMask3[] = {0, 4, 2, 6};
Mask = makeArrayRef(IntMask3, 4);
TransposedMatrix[0] = Builder.CreateShuffleVector(IntrVec1, IntrVec2, Mask);
TransposedMatrix[2] = Builder.CreateShuffleVector(IntrVec3, IntrVec4, Mask);
// dst = src1[1],src2[1],src1[3],src2[3]
uint32_t IntMask4[] = {1, 5, 3, 7};
Mask = makeArrayRef(IntMask4, 4);
TransposedMatrix[1] = Builder.CreateShuffleVector(IntrVec1, IntrVec2, Mask);
TransposedMatrix[3] = Builder.CreateShuffleVector(IntrVec3, IntrVec4, Mask);
}
// Lowers this interleaved access group into X86-specific
// instructions/intrinsics.
bool X86InterleavedAccessGroup::lowerIntoOptimizedSequence() {
SmallVector<Instruction *, 4> DecomposedVectors;
VectorType *VecTy = Shuffles[0]->getType();
// Try to generate target-sized register(/instruction).
if (!decompose(Inst, Factor, VecTy, DecomposedVectors))
return false;
SmallVector<Value *, 4> TransposedVectors;
// Perform matrix-transposition in order to compute interleaved
// results by generating some sort of (optimized) target-specific
// instructions.
transpose_4x4(DecomposedVectors, TransposedVectors);
// Now replace the unoptimized-interleaved-vectors with the
// transposed-interleaved vectors.
for (unsigned i = 0; i < Shuffles.size(); i++)
Shuffles[i]->replaceAllUsesWith(TransposedVectors[Indices[i]]);
return true;
}
// Lower interleaved load(s) into target specific instructions/
// intrinsics. Lowering sequence varies depending on the vector-types, factor,
// number of shuffles and ISA.
// Currently, lowering is supported for 4x64 bits with Factor = 4 on AVX.
bool X86TargetLowering::lowerInterleavedLoad(
LoadInst *LI, ArrayRef<ShuffleVectorInst *> Shuffles,
ArrayRef<unsigned> Indices, unsigned Factor) const {
assert(Factor >= 2 && Factor <= getMaxSupportedInterleaveFactor() &&
"Invalid interleave factor");
assert(!Shuffles.empty() && "Empty shufflevector input");
assert(Shuffles.size() == Indices.size() &&
"Unmatched number of shufflevectors and indices");
// Create an interleaved access group.
IRBuilder<> Builder(LI);
X86InterleavedAccessGroup Grp(LI, Shuffles, Indices, Factor, Subtarget,
Builder);
return Grp.isSupported() && Grp.lowerIntoOptimizedSequence();
}
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