llvm-6502/lib/Target/PowerPC/PPCTargetTransformInfo.cpp
Bill Schmidt 0f58dbae4a Refine fix to bug 15041.
Thanks to help from Nadav and Hal, I have a more reasonable (and even
correct!) approach.  This specifically penalizes the insertelement
and extractelement operations for the performance hit that will occur
on PowerPC processors.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174725 91177308-0d34-0410-b5e6-96231b3b80d8
2013-02-08 18:19:17 +00:00

237 lines
7.9 KiB
C++

//===-- PPCTargetTransformInfo.cpp - PPC specific TTI pass ----------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
/// \file
/// This file implements a TargetTransformInfo analysis pass specific to the
/// PPC target machine. It uses the target's detailed information to provide
/// more precise answers to certain TTI queries, while letting the target
/// independent and default TTI implementations handle the rest.
///
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "ppctti"
#include "PPC.h"
#include "PPCTargetMachine.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/Support/Debug.h"
#include "llvm/Target/TargetLowering.h"
#include "llvm/Target/CostTable.h"
using namespace llvm;
// Declare the pass initialization routine locally as target-specific passes
// don't havve a target-wide initialization entry point, and so we rely on the
// pass constructor initialization.
namespace llvm {
void initializePPCTTIPass(PassRegistry &);
}
namespace {
class PPCTTI : public ImmutablePass, public TargetTransformInfo {
const PPCTargetMachine *TM;
const PPCSubtarget *ST;
const PPCTargetLowering *TLI;
/// Estimate the overhead of scalarizing an instruction. Insert and Extract
/// are set if the result needs to be inserted and/or extracted from vectors.
unsigned getScalarizationOverhead(Type *Ty, bool Insert, bool Extract) const;
public:
PPCTTI() : ImmutablePass(ID), TM(0), ST(0), TLI(0) {
llvm_unreachable("This pass cannot be directly constructed");
}
PPCTTI(const PPCTargetMachine *TM)
: ImmutablePass(ID), TM(TM), ST(TM->getSubtargetImpl()),
TLI(TM->getTargetLowering()) {
initializePPCTTIPass(*PassRegistry::getPassRegistry());
}
virtual void initializePass() {
pushTTIStack(this);
}
virtual void finalizePass() {
popTTIStack();
}
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
TargetTransformInfo::getAnalysisUsage(AU);
}
/// Pass identification.
static char ID;
/// Provide necessary pointer adjustments for the two base classes.
virtual void *getAdjustedAnalysisPointer(const void *ID) {
if (ID == &TargetTransformInfo::ID)
return (TargetTransformInfo*)this;
return this;
}
/// \name Scalar TTI Implementations
/// @{
virtual PopcntSupportKind getPopcntSupport(unsigned TyWidth) const;
/// @}
/// \name Vector TTI Implementations
/// @{
virtual unsigned getNumberOfRegisters(bool Vector) const;
virtual unsigned getRegisterBitWidth(bool Vector) const;
virtual unsigned getMaximumUnrollFactor() const;
virtual unsigned getArithmeticInstrCost(unsigned Opcode, Type *Ty) const;
virtual unsigned getShuffleCost(ShuffleKind Kind, Type *Tp,
int Index, Type *SubTp) const;
virtual unsigned getCastInstrCost(unsigned Opcode, Type *Dst,
Type *Src) const;
virtual unsigned getCmpSelInstrCost(unsigned Opcode, Type *ValTy,
Type *CondTy) const;
virtual unsigned getVectorInstrCost(unsigned Opcode, Type *Val,
unsigned Index) const;
virtual unsigned getMemoryOpCost(unsigned Opcode, Type *Src,
unsigned Alignment,
unsigned AddressSpace) const;
/// @}
};
} // end anonymous namespace
INITIALIZE_AG_PASS(PPCTTI, TargetTransformInfo, "ppctti",
"PPC Target Transform Info", true, true, false)
char PPCTTI::ID = 0;
ImmutablePass *
llvm::createPPCTargetTransformInfoPass(const PPCTargetMachine *TM) {
return new PPCTTI(TM);
}
//===----------------------------------------------------------------------===//
//
// PPC cost model.
//
//===----------------------------------------------------------------------===//
PPCTTI::PopcntSupportKind PPCTTI::getPopcntSupport(unsigned TyWidth) const {
assert(isPowerOf2_32(TyWidth) && "Ty width must be power of 2");
// FIXME: PPC currently does not have custom popcnt lowering even though
// there is hardware support. Once this is fixed, update this function
// to reflect the real capabilities of the hardware.
return PSK_Software;
}
unsigned PPCTTI::getNumberOfRegisters(bool Vector) const {
if (Vector && !ST->hasAltivec())
return 0;
return 32;
}
unsigned PPCTTI::getRegisterBitWidth(bool Vector) const {
if (Vector) {
if (ST->hasAltivec()) return 128;
return 0;
}
if (ST->isPPC64())
return 64;
return 32;
}
unsigned PPCTTI::getMaximumUnrollFactor() const {
unsigned Directive = ST->getDarwinDirective();
// The 440 has no SIMD support, but floating-point instructions
// have a 5-cycle latency, so unroll by 5x for latency hiding.
if (Directive == PPC::DIR_440)
return 5;
// The A2 has no SIMD support, but floating-point instructions
// have a 6-cycle latency, so unroll by 6x for latency hiding.
if (Directive == PPC::DIR_A2)
return 6;
// FIXME: For lack of any better information, do no harm...
if (Directive == PPC::DIR_E500mc || Directive == PPC::DIR_E5500)
return 1;
// For most things, modern systems have two execution units (and
// out-of-order execution).
return 2;
}
unsigned PPCTTI::getArithmeticInstrCost(unsigned Opcode, Type *Ty) const {
assert(TLI->InstructionOpcodeToISD(Opcode) && "Invalid opcode");
// Fallback to the default implementation.
return TargetTransformInfo::getArithmeticInstrCost(Opcode, Ty);
}
unsigned PPCTTI::getShuffleCost(ShuffleKind Kind, Type *Tp, int Index,
Type *SubTp) const {
return TargetTransformInfo::getShuffleCost(Kind, Tp, Index, SubTp);
}
unsigned PPCTTI::getCastInstrCost(unsigned Opcode, Type *Dst, Type *Src) const {
assert(TLI->InstructionOpcodeToISD(Opcode) && "Invalid opcode");
return TargetTransformInfo::getCastInstrCost(Opcode, Dst, Src);
}
unsigned PPCTTI::getCmpSelInstrCost(unsigned Opcode, Type *ValTy,
Type *CondTy) const {
return TargetTransformInfo::getCmpSelInstrCost(Opcode, ValTy, CondTy);
}
unsigned PPCTTI::getVectorInstrCost(unsigned Opcode, Type *Val,
unsigned Index) const {
assert(Val->isVectorTy() && "This must be a vector type");
int ISD = TLI->InstructionOpcodeToISD(Opcode);
assert(ISD && "Invalid opcode");
// Estimated cost of a load-hit-store delay. This was obtained
// experimentally as a minimum needed to prevent unprofitable
// vectorization for the paq8p benchmark. It may need to be
// raised further if other unprofitable cases remain.
unsigned LHSPenalty = 12;
// Vector element insert/extract with Altivec is very expensive,
// because they require store and reload with the attendant
// processor stall for load-hit-store. Until VSX is available,
// these need to be estimated as very costly.
if (ISD == ISD::EXTRACT_VECTOR_ELT ||
ISD == ISD::INSERT_VECTOR_ELT)
return LHSPenalty +
TargetTransformInfo::getVectorInstrCost(Opcode, Val, Index);
return TargetTransformInfo::getVectorInstrCost(Opcode, Val, Index);
}
unsigned PPCTTI::getMemoryOpCost(unsigned Opcode, Type *Src, unsigned Alignment,
unsigned AddressSpace) const {
// Legalize the type.
std::pair<unsigned, MVT> LT = TLI->getTypeLegalizationCost(Src);
assert((Opcode == Instruction::Load || Opcode == Instruction::Store) &&
"Invalid Opcode");
// Each load/store unit costs 1.
unsigned Cost = LT.first * 1;
// PPC in general does not support unaligned loads and stores. They'll need
// to be decomposed based on the alignment factor.
unsigned SrcBytes = LT.second.getStoreSize();
if (SrcBytes && Alignment && Alignment < SrcBytes)
Cost *= (SrcBytes/Alignment);
return Cost;
}