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//===-- RISCVTargetTransformInfo.cpp - RISC-V specific TTI ----------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
#include "RISCVTargetTransformInfo.h"
#include "MCTargetDesc/RISCVMatInt.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/CodeGen/BasicTTIImpl.h"
#include "llvm/CodeGen/TargetLowering.h"
using namespace llvm;
#define DEBUG_TYPE "riscvtti"
InstructionCost RISCVTTIImpl::getIntImmCost(const APInt &Imm, Type *Ty,
TTI::TargetCostKind CostKind) {
assert(Ty->isIntegerTy() &&
"getIntImmCost can only estimate cost of materialising integers");
// We have a Zero register, so 0 is always free.
if (Imm == 0)
return TTI::TCC_Free;
// Otherwise, we check how many instructions it will take to materialise.
const DataLayout &DL = getDataLayout();
return RISCVMatInt::getIntMatCost(Imm, DL.getTypeSizeInBits(Ty),
getST()->is64Bit());
}
InstructionCost RISCVTTIImpl::getIntImmCostInst(unsigned Opcode, unsigned Idx,
const APInt &Imm, Type *Ty,
TTI::TargetCostKind CostKind,
Instruction *Inst) {
assert(Ty->isIntegerTy() &&
"getIntImmCost can only estimate cost of materialising integers");
// We have a Zero register, so 0 is always free.
if (Imm == 0)
return TTI::TCC_Free;
// Some instructions in RISC-V can take a 12-bit immediate. Some of these are
// commutative, in others the immediate comes from a specific argument index.
bool Takes12BitImm = false;
unsigned ImmArgIdx = ~0U;
switch (Opcode) {
case Instruction::GetElementPtr:
// Never hoist any arguments to a GetElementPtr. CodeGenPrepare will
// split up large offsets in GEP into better parts than ConstantHoisting
// can.
return TTI::TCC_Free;
case Instruction::Add:
case Instruction::And:
case Instruction::Or:
case Instruction::Xor:
case Instruction::Mul:
Takes12BitImm = true;
break;
case Instruction::Sub:
case Instruction::Shl:
case Instruction::LShr:
case Instruction::AShr:
Takes12BitImm = true;
ImmArgIdx = 1;
break;
default:
break;
}
if (Takes12BitImm) {
// Check immediate is the correct argument...
if (Instruction::isCommutative(Opcode) || Idx == ImmArgIdx) {
// ... and fits into the 12-bit immediate.
if (Imm.getMinSignedBits() <= 64 &&
getTLI()->isLegalAddImmediate(Imm.getSExtValue())) {
return TTI::TCC_Free;
}
}
// Otherwise, use the full materialisation cost.
return getIntImmCost(Imm, Ty, CostKind);
}
// By default, prevent hoisting.
return TTI::TCC_Free;
}
InstructionCost
RISCVTTIImpl::getIntImmCostIntrin(Intrinsic::ID IID, unsigned Idx,
const APInt &Imm, Type *Ty,
TTI::TargetCostKind CostKind) {
// Prevent hoisting in unknown cases.
return TTI::TCC_Free;
}
TargetTransformInfo::PopcntSupportKind
RISCVTTIImpl::getPopcntSupport(unsigned TyWidth) {
assert(isPowerOf2_32(TyWidth) && "Ty width must be power of 2");
return ST->hasStdExtZbb() ? TTI::PSK_FastHardware : TTI::PSK_Software;
}
bool RISCVTTIImpl::shouldExpandReduction(const IntrinsicInst *II) const {
// Currently, the ExpandReductions pass can't expand scalable-vector
// reductions, but we still request expansion as RVV doesn't support certain
// reductions and the SelectionDAG can't legalize them either.
switch (II->getIntrinsicID()) {
default:
return false;
// These reductions have no equivalent in RVV
case Intrinsic::vector_reduce_mul:
case Intrinsic::vector_reduce_fmul:
// The fmin and fmax intrinsics are not currently supported due to a
// discrepancy between the LLVM semantics and the RVV 0.10 ISA behaviour with
// regards to signaling NaNs: the vector fmin/fmax reduction intrinsics match
// the behaviour minnum/maxnum intrinsics, whereas the vfredmin/vfredmax
// instructions match the vfmin/vfmax instructions which match the equivalent
// scalar fmin/fmax instructions as defined in 2.2 F/D/Q extension (see
// https://bugs.llvm.org/show_bug.cgi?id=27363).
// This behaviour is likely fixed in version 2.3 of the RISC-V F/D/Q
// extension, where fmin/fmax behave like minnum/maxnum, but until then the
// intrinsics are left unsupported.
case Intrinsic::vector_reduce_fmax:
case Intrinsic::vector_reduce_fmin:
return true;
}
}
Optional<unsigned> RISCVTTIImpl::getMaxVScale() const {
// There is no assumption of the maximum vector length in V specification.
// We use the value specified by users as the maximum vector length.
// This function will use the assumed maximum vector length to get the
// maximum vscale for LoopVectorizer.
// If users do not specify the maximum vector length, we have no way to
// know whether the LoopVectorizer is safe to do or not.
// We only consider to use single vector register (LMUL = 1) to vectorize.
unsigned MaxVectorSizeInBits = ST->getMaxRVVVectorSizeInBits();
if (ST->hasStdExtV() && MaxVectorSizeInBits != 0)
return MaxVectorSizeInBits / RISCV::RVVBitsPerBlock;
return BaseT::getMaxVScale();
}
InstructionCost RISCVTTIImpl::getGatherScatterOpCost(
unsigned Opcode, Type *DataTy, const Value *Ptr, bool VariableMask,
Align Alignment, TTI::TargetCostKind CostKind, const Instruction *I) {
if (CostKind != TTI::TCK_RecipThroughput)
return BaseT::getGatherScatterOpCost(Opcode, DataTy, Ptr, VariableMask,
Alignment, CostKind, I);
if ((Opcode == Instruction::Load &&
!isLegalMaskedGather(DataTy, Align(Alignment))) ||
(Opcode == Instruction::Store &&
!isLegalMaskedScatter(DataTy, Align(Alignment))))
return BaseT::getGatherScatterOpCost(Opcode, DataTy, Ptr, VariableMask,
Alignment, CostKind, I);
// FIXME: Only supporting fixed vectors for now.
if (!isa<FixedVectorType>(DataTy))
return BaseT::getGatherScatterOpCost(Opcode, DataTy, Ptr, VariableMask,
Alignment, CostKind, I);
auto *VTy = cast<FixedVectorType>(DataTy);
unsigned NumLoads = VTy->getNumElements();
InstructionCost MemOpCost =
getMemoryOpCost(Opcode, VTy->getElementType(), Alignment, 0, CostKind, I);
return NumLoads * MemOpCost;
}
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