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//===-- X86ShuffleDecodeConstantPool.cpp - X86 shuffle decode -------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// Define several functions to decode x86 specific shuffle semantics using
// constants from the constant pool.
//
//===----------------------------------------------------------------------===//
#include "Utils/X86ShuffleDecode.h"
#include "llvm/ADT/APInt.h"
#include "llvm/IR/Constants.h"
//===----------------------------------------------------------------------===//
// Vector Mask Decoding
//===----------------------------------------------------------------------===//
namespace llvm {
static bool extractConstantMask(const Constant *C, unsigned MaskEltSizeInBits,
APInt &UndefElts,
SmallVectorImpl<uint64_t> &RawMask) {
// It is not an error for shuffle masks to not be a vector of
// MaskEltSizeInBits because the constant pool uniques constants by their
// bit representation.
// e.g. the following take up the same space in the constant pool:
// i128 -170141183420855150465331762880109871104
//
// <2 x i64> <i64 -9223372034707292160, i64 -9223372034707292160>
//
// <4 x i32> <i32 -2147483648, i32 -2147483648,
// i32 -2147483648, i32 -2147483648>
Type *CstTy = C->getType();
if (!CstTy->isVectorTy())
return false;
Type *CstEltTy = CstTy->getVectorElementType();
if (!CstEltTy->isIntegerTy())
return false;
unsigned CstSizeInBits = CstTy->getPrimitiveSizeInBits();
unsigned CstEltSizeInBits = CstTy->getScalarSizeInBits();
unsigned NumCstElts = CstTy->getVectorNumElements();
assert((CstSizeInBits % MaskEltSizeInBits) == 0 &&
"Unaligned shuffle mask size");
unsigned NumMaskElts = CstSizeInBits / MaskEltSizeInBits;
UndefElts = APInt(NumMaskElts, 0);
RawMask.resize(NumMaskElts, 0);
// Fast path - if the constants match the mask size then copy direct.
if (MaskEltSizeInBits == CstEltSizeInBits) {
assert(NumCstElts == NumMaskElts && "Unaligned shuffle mask size");
for (unsigned i = 0; i != NumMaskElts; ++i) {
Constant *COp = C->getAggregateElement(i);
if (!COp || (!isa<UndefValue>(COp) && !isa<ConstantInt>(COp)))
return false;
if (isa<UndefValue>(COp)) {
UndefElts.setBit(i);
RawMask[i] = 0;
continue;
}
auto *Elt = cast<ConstantInt>(COp);
RawMask[i] = Elt->getValue().getZExtValue();
}
return true;
}
// Extract all the undef/constant element data and pack into single bitsets.
APInt UndefBits(CstSizeInBits, 0);
APInt MaskBits(CstSizeInBits, 0);
for (unsigned i = 0; i != NumCstElts; ++i) {
Constant *COp = C->getAggregateElement(i);
if (!COp || (!isa<UndefValue>(COp) && !isa<ConstantInt>(COp)))
return false;
unsigned BitOffset = i * CstEltSizeInBits;
if (isa<UndefValue>(COp)) {
UndefBits.setBits(BitOffset, BitOffset + CstEltSizeInBits);
continue;
}
MaskBits.insertBits(cast<ConstantInt>(COp)->getValue(), BitOffset);
}
// Now extract the undef/constant bit data into the raw shuffle masks.
for (unsigned i = 0; i != NumMaskElts; ++i) {
unsigned BitOffset = i * MaskEltSizeInBits;
APInt EltUndef = UndefBits.extractBits(MaskEltSizeInBits, BitOffset);
// Only treat the element as UNDEF if all bits are UNDEF, otherwise
// treat it as zero.
if (EltUndef.isAllOnesValue()) {
UndefElts.setBit(i);
RawMask[i] = 0;
continue;
}
APInt EltBits = MaskBits.extractBits(MaskEltSizeInBits, BitOffset);
RawMask[i] = EltBits.getZExtValue();
}
return true;
}
void DecodePSHUFBMask(const Constant *C, unsigned Width,
SmallVectorImpl<int> &ShuffleMask) {
assert((Width == 128 || Width == 256 || Width == 512) &&
C->getType()->getPrimitiveSizeInBits() >= Width &&
"Unexpected vector size.");
// The shuffle mask requires a byte vector.
APInt UndefElts;
SmallVector<uint64_t, 64> RawMask;
if (!extractConstantMask(C, 8, UndefElts, RawMask))
return;
unsigned NumElts = Width / 8;
assert((NumElts == 16 || NumElts == 32 || NumElts == 64) &&
"Unexpected number of vector elements.");
for (unsigned i = 0; i != NumElts; ++i) {
if (UndefElts[i]) {
ShuffleMask.push_back(SM_SentinelUndef);
continue;
}
uint64_t Element = RawMask[i];
// If the high bit (7) of the byte is set, the element is zeroed.
if (Element & (1 << 7))
ShuffleMask.push_back(SM_SentinelZero);
else {
// For AVX vectors with 32 bytes the base of the shuffle is the 16-byte
// lane of the vector we're inside.
unsigned Base = i & ~0xf;
// Only the least significant 4 bits of the byte are used.
int Index = Base + (Element & 0xf);
ShuffleMask.push_back(Index);
}
}
}
void DecodeVPERMILPMask(const Constant *C, unsigned ElSize, unsigned Width,
SmallVectorImpl<int> &ShuffleMask) {
assert((Width == 128 || Width == 256 || Width == 512) &&
C->getType()->getPrimitiveSizeInBits() >= Width &&
"Unexpected vector size.");
assert((ElSize == 32 || ElSize == 64) && "Unexpected vector element size.");
// The shuffle mask requires elements the same size as the target.
APInt UndefElts;
SmallVector<uint64_t, 16> RawMask;
if (!extractConstantMask(C, ElSize, UndefElts, RawMask))
return;
unsigned NumElts = Width / ElSize;
unsigned NumEltsPerLane = 128 / ElSize;
assert((NumElts == 2 || NumElts == 4 || NumElts == 8 || NumElts == 16) &&
"Unexpected number of vector elements.");
for (unsigned i = 0; i != NumElts; ++i) {
if (UndefElts[i]) {
ShuffleMask.push_back(SM_SentinelUndef);
continue;
}
int Index = i & ~(NumEltsPerLane - 1);
uint64_t Element = RawMask[i];
if (ElSize == 64)
Index += (Element >> 1) & 0x1;
else
Index += Element & 0x3;
ShuffleMask.push_back(Index);
}
}
void DecodeVPERMIL2PMask(const Constant *C, unsigned M2Z, unsigned ElSize,
unsigned Width,
SmallVectorImpl<int> &ShuffleMask) {
Type *MaskTy = C->getType();
unsigned MaskTySize = MaskTy->getPrimitiveSizeInBits();
(void)MaskTySize;
assert((MaskTySize == 128 || MaskTySize == 256) &&
Width >= MaskTySize && "Unexpected vector size.");
// The shuffle mask requires elements the same size as the target.
APInt UndefElts;
SmallVector<uint64_t, 8> RawMask;
if (!extractConstantMask(C, ElSize, UndefElts, RawMask))
return;
unsigned NumElts = Width / ElSize;
unsigned NumEltsPerLane = 128 / ElSize;
assert((NumElts == 2 || NumElts == 4 || NumElts == 8) &&
"Unexpected number of vector elements.");
for (unsigned i = 0; i != NumElts; ++i) {
if (UndefElts[i]) {
ShuffleMask.push_back(SM_SentinelUndef);
continue;
}
// VPERMIL2 Operation.
// Bits[3] - Match Bit.
// Bits[2:1] - (Per Lane) PD Shuffle Mask.
// Bits[2:0] - (Per Lane) PS Shuffle Mask.
uint64_t Selector = RawMask[i];
unsigned MatchBit = (Selector >> 3) & 0x1;
// M2Z[0:1] MatchBit
// 0Xb X Source selected by Selector index.
// 10b 0 Source selected by Selector index.
// 10b 1 Zero.
// 11b 0 Zero.
// 11b 1 Source selected by Selector index.
if ((M2Z & 0x2) != 0u && MatchBit != (M2Z & 0x1)) {
ShuffleMask.push_back(SM_SentinelZero);
continue;
}
int Index = i & ~(NumEltsPerLane - 1);
if (ElSize == 64)
Index += (Selector >> 1) & 0x1;
else
Index += Selector & 0x3;
int Src = (Selector >> 2) & 0x1;
Index += Src * NumElts;
ShuffleMask.push_back(Index);
}
}
void DecodeVPPERMMask(const Constant *C, unsigned Width,
SmallVectorImpl<int> &ShuffleMask) {
Type *MaskTy = C->getType();
unsigned MaskTySize = MaskTy->getPrimitiveSizeInBits();
(void)MaskTySize;
assert(Width == 128 && Width >= MaskTySize && "Unexpected vector size.");
// The shuffle mask requires a byte vector.
APInt UndefElts;
SmallVector<uint64_t, 16> RawMask;
if (!extractConstantMask(C, 8, UndefElts, RawMask))
return;
unsigned NumElts = Width / 8;
assert(NumElts == 16 && "Unexpected number of vector elements.");
for (unsigned i = 0; i != NumElts; ++i) {
if (UndefElts[i]) {
ShuffleMask.push_back(SM_SentinelUndef);
continue;
}
// VPPERM Operation
// Bits[4:0] - Byte Index (0 - 31)
// Bits[7:5] - Permute Operation
//
// Permute Operation:
// 0 - Source byte (no logical operation).
// 1 - Invert source byte.
// 2 - Bit reverse of source byte.
// 3 - Bit reverse of inverted source byte.
// 4 - 00h (zero - fill).
// 5 - FFh (ones - fill).
// 6 - Most significant bit of source byte replicated in all bit positions.
// 7 - Invert most significant bit of source byte and replicate in all bit
// positions.
uint64_t Element = RawMask[i];
uint64_t Index = Element & 0x1F;
uint64_t PermuteOp = (Element >> 5) & 0x7;
if (PermuteOp == 4) {
ShuffleMask.push_back(SM_SentinelZero);
continue;
}
if (PermuteOp != 0) {
ShuffleMask.clear();
return;
}
ShuffleMask.push_back((int)Index);
}
}
void DecodeVPERMVMask(const Constant *C, unsigned ElSize, unsigned Width,
SmallVectorImpl<int> &ShuffleMask) {
assert((Width == 128 || Width == 256 || Width == 512) &&
C->getType()->getPrimitiveSizeInBits() >= Width &&
"Unexpected vector size.");
assert((ElSize == 8 || ElSize == 16 || ElSize == 32 || ElSize == 64) &&
"Unexpected vector element size.");
// The shuffle mask requires elements the same size as the target.
APInt UndefElts;
SmallVector<uint64_t, 64> RawMask;
if (!extractConstantMask(C, ElSize, UndefElts, RawMask))
return;
unsigned NumElts = Width / ElSize;
for (unsigned i = 0; i != NumElts; ++i) {
if (UndefElts[i]) {
ShuffleMask.push_back(SM_SentinelUndef);
continue;
}
int Index = RawMask[i] & (NumElts - 1);
ShuffleMask.push_back(Index);
}
}
void DecodeVPERMV3Mask(const Constant *C, unsigned ElSize, unsigned Width,
SmallVectorImpl<int> &ShuffleMask) {
assert((Width == 128 || Width == 256 || Width == 512) &&
C->getType()->getPrimitiveSizeInBits() >= Width &&
"Unexpected vector size.");
assert((ElSize == 8 || ElSize == 16 || ElSize == 32 || ElSize == 64) &&
"Unexpected vector element size.");
// The shuffle mask requires elements the same size as the target.
APInt UndefElts;
SmallVector<uint64_t, 64> RawMask;
if (!extractConstantMask(C, ElSize, UndefElts, RawMask))
return;
unsigned NumElts = Width / ElSize;
for (unsigned i = 0; i != NumElts; ++i) {
if (UndefElts[i]) {
ShuffleMask.push_back(SM_SentinelUndef);
continue;
}
int Index = RawMask[i] & (NumElts*2 - 1);
ShuffleMask.push_back(Index);
}
}
} // llvm namespace