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Implement a basic cost model for vector and scalar instructions. 

llvm-svn: 166642
This commit is contained in:
Nadav Rotem 2012-10-24 23:47:38 +00:00
parent b636875196
commit 4a87683a41
6 changed files with 168 additions and 23 deletions
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2
llvm/include/llvm/Target/TargetLowering.h
View File

@ -1958,6 +1958,7 @@ private:
ValueTypeActionImpl ValueTypeActions;
public:
LegalizeKind
getTypeConversion(LLVMContext &Context, EVT VT) const {
// If this is a simple type, use the ComputeRegisterProp mechanism.
@ -2074,6 +2075,7 @@ private:
return LegalizeKind(TypeSplitVector, NVT);
}
private:
std::vector<std::pair<EVT, const TargetRegisterClass*> > AvailableRegClasses;
/// TargetDAGCombineArray - Targets can specify ISD nodes that they would

5
llvm/include/llvm/Target/TargetTransformImpl.h
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@ -16,6 +16,7 @@
#define LLVM_TARGET_TARGET_TRANSFORMATION_IMPL_H
#include "llvm/TargetTransformInfo.h"
#include "llvm/CodeGen/ValueTypes.h"
namespace llvm {
@ -51,6 +52,10 @@ class VectorTargetTransformImpl : public VectorTargetTransformInfo {
private:
const TargetLowering *TLI;
/// Estimate the cost of type-legalization and the legalized type.
std::pair<unsigned, EVT>
getTypeLegalizationCost(LLVMContext &C, EVT Ty) const;
public:
explicit VectorTargetTransformImpl(const TargetLowering *TL) : TLI(TL) {}

129
llvm/lib/Target/TargetTransformImpl.cpp
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@ -9,6 +9,7 @@
#include "llvm/Target/TargetTransformImpl.h"
#include "llvm/Target/TargetLowering.h"
#include <utility>
using namespace llvm;
@ -53,11 +54,131 @@ unsigned ScalarTargetTransformImpl::getJumpBufSize() const {
// Calls used by the vectorizers.
//
//===----------------------------------------------------------------------===//
int InstructionOpcodeToISD(unsigned Opcode) {
static const int OpToISDTbl[] = {
/*Instruction::Ret */ 0, // Opcode numbering start at #1.
/*Instruction::Br */ 0,
/*Instruction::Switch */ 0,
/*Instruction::IndirectBr */ 0,
/*Instruction::Invoke */ 0,
/*Instruction::Resume */ 0,
/*Instruction::Unreachable */ 0,
/*Instruction::Add */ ISD::ADD,
/*Instruction::FAdd */ ISD::FADD,
/*Instruction::Sub */ ISD::SUB,
/*Instruction::FSub */ ISD::FSUB,
/*Instruction::Mul */ ISD::MUL,
/*Instruction::FMul */ ISD::FMUL,
/*Instruction::UDiv */ ISD::UDIV,
/*Instruction::SDiv */ ISD::UDIV,
/*Instruction::FDiv */ ISD::FDIV,
/*Instruction::URem */ ISD::UREM,
/*Instruction::SRem */ ISD::SREM,
/*Instruction::FRem */ ISD::FREM,
/*Instruction::Shl */ ISD::SHL,
/*Instruction::LShr */ ISD::SRL,
/*Instruction::AShr */ ISD::SRA,
/*Instruction::And */ ISD::AND,
/*Instruction::Or */ ISD::OR,
/*Instruction::Xor */ ISD::XOR,
/*Instruction::Alloca */ 0,
/*Instruction::Load */ ISD::LOAD,
/*Instruction::Store */ ISD::STORE,
/*Instruction::GetElementPtr */ 0,
/*Instruction::Fence */ 0,
/*Instruction::AtomicCmpXchg */ 0,
/*Instruction::AtomicRMW */ 0,
/*Instruction::Trunc */ ISD::TRUNCATE,
/*Instruction::ZExt */ ISD::ZERO_EXTEND,
/*Instruction::SExt */ ISD::SEXTLOAD,
/*Instruction::FPToUI */ ISD::FP_TO_UINT,
/*Instruction::FPToSI */ ISD::FP_TO_SINT,
/*Instruction::UIToFP */ ISD::UINT_TO_FP,
/*Instruction::SIToFP */ ISD::SINT_TO_FP,
/*Instruction::FPTrunc */ ISD::FP_ROUND,
/*Instruction::FPExt */ ISD::FP_EXTEND,
/*Instruction::PtrToInt */ ISD::BITCAST,
/*Instruction::IntToPtr */ ISD::BITCAST,
/*Instruction::BitCast */ ISD::BITCAST,
/*Instruction::ICmp */ ISD::SETCC,
/*Instruction::FCmp */ ISD::SETCC,
/*Instruction::PHI */ 0,
/*Instruction::Call */ 0,
/*Instruction::Select */ ISD::SELECT,
/*Instruction::UserOp1 */ 0,
/*Instruction::UserOp2 */ 0,
/*Instruction::VAArg */ 0,
/*Instruction::ExtractElement*/ ISD::EXTRACT_VECTOR_ELT,
/*Instruction::InsertElement */ ISD::INSERT_VECTOR_ELT,
/*Instruction::ShuffleVector */ ISD::VECTOR_SHUFFLE,
/*Instruction::ExtractValue */ ISD::MERGE_VALUES,
/*Instruction::InsertValue */ ISD::MERGE_VALUES,
/*Instruction::LandingPad */ 0};
assert((Instruction::Ret == 1) && (Instruction::LandingPad == 58) &&
"Instruction order had changed");
// Opcode numbering starts at #1 but the table starts at #0, so we subtract
// one from the opcode number.
return OpToISDTbl[Opcode - 1];
}
std::pair<unsigned, EVT>
VectorTargetTransformImpl::getTypeLegalizationCost(LLVMContext &C,
EVT Ty) const {
unsigned Cost = 1;
// We keep legalizing the type until we find a legal kind. We assume that
// the only operation that costs anything is the split. After splitting
// we need to handle two types.
while (true) {
TargetLowering::LegalizeKind LK = TLI->getTypeConversion(C, Ty);
if (LK.first == TargetLowering::TypeLegal)
return std::make_pair(Cost, LK.second);
if (LK.first == TargetLowering::TypeSplitVector)
Cost *= 2;
// Keep legalizing the type.
Ty = LK.second;
}
}
unsigned
VectorTargetTransformImpl::getInstrCost(unsigned Opcode, Type *Ty1,
Type *Ty2) const {
return 1;
// Check if any of the operands are vector operands.
int ISD = InstructionOpcodeToISD(Opcode);
// Selects on vectors are actually vector selects.
if (ISD == ISD::SELECT) {
assert(Ty2 && "Ty2 must hold the select type");
if (Ty2->isVectorTy())
ISD = ISD::VSELECT;
}
// If we don't have any information about this instruction assume it costs 1.
if (ISD == 0)
return 1;
assert(Ty1 && "We need to have at least one type");
// From this stage we look at the legalized type.
std::pair<unsigned, EVT> LT =
getTypeLegalizationCost(Ty1->getContext(), TLI->getValueType(Ty1));
if (TLI->isOperationLegalOrCustom(ISD, LT.second)) {
// The operation is legal. Assume it costs 1. Multiply
// by the type-legalization overhead.
return LT.first * 1;
}
unsigned NumElem =
(LT.second.isVector() ? LT.second.getVectorNumElements() : 1);
// We will probably scalarize this instruction. Assume that the cost is the
// number of the vector elements.
return LT.first * NumElem * 1;
}
unsigned
@ -69,5 +190,9 @@ unsigned
VectorTargetTransformImpl::getMemoryOpCost(unsigned Opcode, Type *Src,
unsigned Alignment,
unsigned AddressSpace) const {
return 1;
// From this stage we look at the legalized type.
std::pair<unsigned, EVT> LT =
getTypeLegalizationCost(Src->getContext(), TLI->getValueType(Src));
// Assume that all loads of legal types cost 1.
return LT.first;
}

2
llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
View File

@ -185,7 +185,7 @@ void PassManagerBuilder::populateModulePassManager(PassManagerBase &MPM) {
MPM.add(createLoopIdiomPass()); // Recognize idioms like memset.
MPM.add(createLoopDeletionPass()); // Delete dead loops
if (Vectorize) {
if (Vectorize || true) {
MPM.add(createLoopVectorizePass());
MPM.add(createLICMPass());
}

49
llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
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@ -300,10 +300,10 @@ private:
class LoopVectorizationCostModel {
public:
/// C'tor.
LoopVectorizationCostModel(Loop *Lp, ScalarEvolution *Se, DataLayout *Dl,
LoopVectorizationCostModel(Loop *Lp, ScalarEvolution *Se,
LoopVectorizationLegality *Leg,
const VectorTargetTransformInfo *Vtti):
TheLoop(Lp), SE(Se), DL(Dl), Legal(Leg), VTTI(Vtti) { }
TheLoop(Lp), SE(Se), Legal(Leg), VTTI(Vtti) { }
/// Returns the most profitable vectorization factor for the loop that is
/// smaller or equal to the VF argument. This method checks every power
@ -325,8 +325,7 @@ private:
Loop *TheLoop;
/// Scev analysis.
ScalarEvolution *SE;
/// DataLayout analysis.
DataLayout *DL;
/// Vectorization legality.
LoopVectorizationLegality *Legal;
/// Vector target information.
@ -372,7 +371,7 @@ struct LoopVectorize : public LoopPass {
if (TTI)
VTTI = TTI->getVectorTargetTransformInfo();
// Use the cost model.
LoopVectorizationCostModel CM(L, SE, DL, &LVL, VTTI);
LoopVectorizationCostModel CM(L, SE, &LVL, VTTI);
VF = CM.findBestVectorizationFactor();
if (VF == 1) {
@ -1432,11 +1431,12 @@ unsigned LoopVectorizationCostModel::expectedCost(unsigned VF) {
// For each instruction in the old loop.
for (BasicBlock::iterator it = BB->begin(), e = BB->end(); it != e; ++it) {
Instruction *Inst = it;
Cost += getInstructionCost(Inst, VF);
unsigned C = getInstructionCost(Inst, VF);
Cost += C;
DEBUG(dbgs() << "LV: Found an estimated cost of "<< C <<" for VF "<< VF <<
" For instruction: "<< *Inst << "\n");
}
// Return the cost divided by VF, because we will be executing
// less iterations of the vector form.
return Cost;
}
@ -1444,11 +1444,13 @@ unsigned
LoopVectorizationCostModel::getInstructionCost(Instruction *I, unsigned VF) {
assert(VTTI && "Invalid vector target transformation info");
switch (I->getOpcode()) {
case Instruction::GetElementPtr:
return 0;
case Instruction::Br: {
return VTTI->getInstrCost(I->getOpcode());
}
case Instruction::PHI:
// PHIs are handled the same as the binary instructions below.
return 0;
case Instruction::Add:
case Instruction::FAdd:
case Instruction::Sub:
@ -1493,11 +1495,17 @@ LoopVectorizationCostModel::getInstructionCost(Instruction *I, unsigned VF) {
// Scalarized stores.
if (!Legal->isConsecutiveGep(SI->getPointerOperand())) {
unsigned Cost = 0;
unsigned ExtCost = VTTI->getInstrCost(Instruction::ExtractElement, VTy);
// The cost of extracting from the vector value.
Cost += VF * ExtCost;
if (VF != 1) {
unsigned ExtCost = VTTI->getInstrCost(Instruction::ExtractElement,
VTy);
// The cost of extracting from the value vector and pointer vector.
Cost += VF * (ExtCost * 2);
}
// The cost of the scalar stores.
Cost += VF * VTTI->getInstrCost(I->getOpcode(), VTy->getScalarType());
Cost += VF * VTTI->getMemoryOpCost(I->getOpcode(),
VTy->getScalarType(),
SI->getAlignment(),
SI->getPointerAddressSpace());
return Cost;
}
@ -1512,11 +1520,18 @@ LoopVectorizationCostModel::getInstructionCost(Instruction *I, unsigned VF) {
// Scalarized loads.
if (!Legal->isConsecutiveGep(LI->getPointerOperand())) {
unsigned Cost = 0;
unsigned InCost = VTTI->getInstrCost(Instruction::InsertElement, VTy);
// The cost of inserting the loaded value into the result vector.
Cost += VF * InCost;
if (VF != 1) {
unsigned InCost = VTTI->getInstrCost(Instruction::InsertElement, VTy);
unsigned ExCost = VTTI->getInstrCost(Instruction::ExtractValue, VTy);
// The cost of inserting the loaded value into the result vector, and
// extracting from a vector of pointers.
Cost += VF * (InCost + ExCost);
}
// The cost of the scalar stores.
Cost += VF * VTTI->getInstrCost(I->getOpcode(), VTy->getScalarType());
Cost += VF * VTTI->getMemoryOpCost(I->getOpcode(), VTy->getScalarType(),
LI->getAlignment(),
LI->getPointerAddressSpace());
return Cost;
}

4
llvm/test/Transforms/LoopVectorize/cost-model.ll
View File

@ -8,10 +8,8 @@ target triple = "x86_64-apple-macosx10.8.0"
@d = common global [2048 x i32] zeroinitializer, align 16
@a = common global [2048 x i32] zeroinitializer, align 16
; At this point the cost model is pretty bad and we are vectorizing the code below.
; TODO: This code should not be vectorized on x86.
;CHECK: cost_model_1
;CHECK: <4 x i32>
;CHECK-NOT: <4 x i32>
;CHECK: ret void
define void @cost_model_1() nounwind uwtable noinline ssp {
entry: