//===----------------------------------------------------------------------===//
//
// This file defines the cost model analysis. It provides a very basic cost
-// estimation for LLVM-IR. The cost result can be thought of as cycles, but it
-// is really unit-less. The estimated cost is ment to be used for comparing
-// alternatives.
+// estimation for LLVM-IR. This analysis uses the services of the codegen
+// to approximate the cost of any IR instruction when lowered to machine
+// instructions. The cost results are unit-less and the cost number represents
+// the throughput of the machine assuming that all loads hit the cache, all
+// branches are predicted, etc. The cost numbers can be added in order to
+// compare two or more transformation alternatives.
//
//===----------------------------------------------------------------------===//
-#define CM_NAME "cost-model"
-#define DEBUG_TYPE CM_NAME
+#include "llvm/ADT/STLExtras.h"
#include "llvm/Analysis/Passes.h"
-#include "llvm/Function.h"
-#include "llvm/Instructions.h"
+#include "llvm/Analysis/TargetTransformInfo.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Value.h"
#include "llvm/Pass.h"
+#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
-#include "llvm/TargetTransformInfo.h"
-#include "llvm/Value.h"
using namespace llvm;
+#define CM_NAME "cost-model"
+#define DEBUG_TYPE CM_NAME
+
+static cl::opt<bool> EnableReduxCost("costmodel-reduxcost", cl::init(false),
+ cl::Hidden,
+ cl::desc("Recognize reduction patterns."));
+
namespace {
class CostModelAnalysis : public FunctionPass {
public:
static char ID; // Class identification, replacement for typeinfo
- CostModelAnalysis() : FunctionPass(ID), F(0), VTTI(0) {
+ CostModelAnalysis() : FunctionPass(ID), F(nullptr), TTI(nullptr) {
initializeCostModelAnalysisPass(
*PassRegistry::getPassRegistry());
}
/// Returns -1 if the cost is unknown.
/// Note, this method does not cache the cost calculation and it
/// can be expensive in some cases.
- unsigned getInstructionCost(Instruction *I) const;
+ unsigned getInstructionCost(const Instruction *I) const;
private:
- virtual void getAnalysisUsage(AnalysisUsage &AU) const;
- virtual bool runOnFunction(Function &F);
- virtual void print(raw_ostream &OS, const Module*) const;
+ void getAnalysisUsage(AnalysisUsage &AU) const override;
+ bool runOnFunction(Function &F) override;
+ void print(raw_ostream &OS, const Module*) const override;
/// The function that we analyze.
Function *F;
- /// Vector target information.
- const VectorTargetTransformInfo *VTTI;
+ /// Target information.
+ const TargetTransformInfo *TTI;
};
} // End of anonymous namespace
bool
CostModelAnalysis::runOnFunction(Function &F) {
this->F = &F;
-
- // Target information.
- TargetTransformInfo *TTI;
- TTI = getAnalysisIfAvailable<TargetTransformInfo>();
- if (TTI)
- VTTI = TTI->getVectorTargetTransformInfo();
+ auto *TTIWP = getAnalysisIfAvailable<TargetTransformInfoWrapperPass>();
+ TTI = TTIWP ? &TTIWP->getTTI(F) : nullptr;
return false;
}
-unsigned CostModelAnalysis::getInstructionCost(Instruction *I) const {
- if (!VTTI)
+static bool isReverseVectorMask(SmallVectorImpl<int> &Mask) {
+ for (unsigned i = 0, MaskSize = Mask.size(); i < MaskSize; ++i)
+ if (Mask[i] > 0 && Mask[i] != (int)(MaskSize - 1 - i))
+ return false;
+ return true;
+}
+
+static bool isAlternateVectorMask(SmallVectorImpl<int> &Mask) {
+ bool isAlternate = true;
+ unsigned MaskSize = Mask.size();
+
+ // Example: shufflevector A, B, <0,5,2,7>
+ for (unsigned i = 0; i < MaskSize && isAlternate; ++i) {
+ if (Mask[i] < 0)
+ continue;
+ isAlternate = Mask[i] == (int)((i & 1) ? MaskSize + i : i);
+ }
+
+ if (isAlternate)
+ return true;
+
+ isAlternate = true;
+ // Example: shufflevector A, B, <4,1,6,3>
+ for (unsigned i = 0; i < MaskSize && isAlternate; ++i) {
+ if (Mask[i] < 0)
+ continue;
+ isAlternate = Mask[i] == (int)((i & 1) ? i : MaskSize + i);
+ }
+
+ return isAlternate;
+}
+
+static TargetTransformInfo::OperandValueKind getOperandInfo(Value *V) {
+ TargetTransformInfo::OperandValueKind OpInfo =
+ TargetTransformInfo::OK_AnyValue;
+
+ // Check for a splat of a constant or for a non uniform vector of constants.
+ if (isa<ConstantVector>(V) || isa<ConstantDataVector>(V)) {
+ OpInfo = TargetTransformInfo::OK_NonUniformConstantValue;
+ if (cast<Constant>(V)->getSplatValue() != nullptr)
+ OpInfo = TargetTransformInfo::OK_UniformConstantValue;
+ }
+
+ return OpInfo;
+}
+
+static bool matchPairwiseShuffleMask(ShuffleVectorInst *SI, bool IsLeft,
+ unsigned Level) {
+ // We don't need a shuffle if we just want to have element 0 in position 0 of
+ // the vector.
+ if (!SI && Level == 0 && IsLeft)
+ return true;
+ else if (!SI)
+ return false;
+
+ SmallVector<int, 32> Mask(SI->getType()->getVectorNumElements(), -1);
+
+ // Build a mask of 0, 2, ... (left) or 1, 3, ... (right) depending on whether
+ // we look at the left or right side.
+ for (unsigned i = 0, e = (1 << Level), val = !IsLeft; i != e; ++i, val += 2)
+ Mask[i] = val;
+
+ SmallVector<int, 16> ActualMask = SI->getShuffleMask();
+ return Mask == ActualMask;
+}
+
+static bool matchPairwiseReductionAtLevel(const BinaryOperator *BinOp,
+ unsigned Level, unsigned NumLevels) {
+ // Match one level of pairwise operations.
+ // %rdx.shuf.0.0 = shufflevector <4 x float> %rdx, <4 x float> undef,
+ // <4 x i32> <i32 0, i32 2 , i32 undef, i32 undef>
+ // %rdx.shuf.0.1 = shufflevector <4 x float> %rdx, <4 x float> undef,
+ // <4 x i32> <i32 1, i32 3, i32 undef, i32 undef>
+ // %bin.rdx.0 = fadd <4 x float> %rdx.shuf.0.0, %rdx.shuf.0.1
+ if (BinOp == nullptr)
+ return false;
+
+ assert(BinOp->getType()->isVectorTy() && "Expecting a vector type");
+
+ unsigned Opcode = BinOp->getOpcode();
+ Value *L = BinOp->getOperand(0);
+ Value *R = BinOp->getOperand(1);
+
+ ShuffleVectorInst *LS = dyn_cast<ShuffleVectorInst>(L);
+ if (!LS && Level)
+ return false;
+ ShuffleVectorInst *RS = dyn_cast<ShuffleVectorInst>(R);
+ if (!RS && Level)
+ return false;
+
+ // On level 0 we can omit one shufflevector instruction.
+ if (!Level && !RS && !LS)
+ return false;
+
+ // Shuffle inputs must match.
+ Value *NextLevelOpL = LS ? LS->getOperand(0) : nullptr;
+ Value *NextLevelOpR = RS ? RS->getOperand(0) : nullptr;
+ Value *NextLevelOp = nullptr;
+ if (NextLevelOpR && NextLevelOpL) {
+ // If we have two shuffles their operands must match.
+ if (NextLevelOpL != NextLevelOpR)
+ return false;
+
+ NextLevelOp = NextLevelOpL;
+ } else if (Level == 0 && (NextLevelOpR || NextLevelOpL)) {
+ // On the first level we can omit the shufflevector <0, undef,...>. So the
+ // input to the other shufflevector <1, undef> must match with one of the
+ // inputs to the current binary operation.
+ // Example:
+ // %NextLevelOpL = shufflevector %R, <1, undef ...>
+ // %BinOp = fadd %NextLevelOpL, %R
+ if (NextLevelOpL && NextLevelOpL != R)
+ return false;
+ else if (NextLevelOpR && NextLevelOpR != L)
+ return false;
+
+ NextLevelOp = NextLevelOpL ? R : L;
+ } else
+ return false;
+
+ // Check that the next levels binary operation exists and matches with the
+ // current one.
+ BinaryOperator *NextLevelBinOp = nullptr;
+ if (Level + 1 != NumLevels) {
+ if (!(NextLevelBinOp = dyn_cast<BinaryOperator>(NextLevelOp)))
+ return false;
+ else if (NextLevelBinOp->getOpcode() != Opcode)
+ return false;
+ }
+
+ // Shuffle mask for pairwise operation must match.
+ if (matchPairwiseShuffleMask(LS, true, Level)) {
+ if (!matchPairwiseShuffleMask(RS, false, Level))
+ return false;
+ } else if (matchPairwiseShuffleMask(RS, true, Level)) {
+ if (!matchPairwiseShuffleMask(LS, false, Level))
+ return false;
+ } else
+ return false;
+
+ if (++Level == NumLevels)
+ return true;
+
+ // Match next level.
+ return matchPairwiseReductionAtLevel(NextLevelBinOp, Level, NumLevels);
+}
+
+static bool matchPairwiseReduction(const ExtractElementInst *ReduxRoot,
+ unsigned &Opcode, Type *&Ty) {
+ if (!EnableReduxCost)
+ return false;
+
+ // Need to extract the first element.
+ ConstantInt *CI = dyn_cast<ConstantInt>(ReduxRoot->getOperand(1));
+ unsigned Idx = ~0u;
+ if (CI)
+ Idx = CI->getZExtValue();
+ if (Idx != 0)
+ return false;
+
+ BinaryOperator *RdxStart = dyn_cast<BinaryOperator>(ReduxRoot->getOperand(0));
+ if (!RdxStart)
+ return false;
+
+ Type *VecTy = ReduxRoot->getOperand(0)->getType();
+ unsigned NumVecElems = VecTy->getVectorNumElements();
+ if (!isPowerOf2_32(NumVecElems))
+ return false;
+
+ // We look for a sequence of shuffle,shuffle,add triples like the following
+ // that builds a pairwise reduction tree.
+ //
+ // (X0, X1, X2, X3)
+ // (X0 + X1, X2 + X3, undef, undef)
+ // ((X0 + X1) + (X2 + X3), undef, undef, undef)
+ //
+ // %rdx.shuf.0.0 = shufflevector <4 x float> %rdx, <4 x float> undef,
+ // <4 x i32> <i32 0, i32 2 , i32 undef, i32 undef>
+ // %rdx.shuf.0.1 = shufflevector <4 x float> %rdx, <4 x float> undef,
+ // <4 x i32> <i32 1, i32 3, i32 undef, i32 undef>
+ // %bin.rdx.0 = fadd <4 x float> %rdx.shuf.0.0, %rdx.shuf.0.1
+ // %rdx.shuf.1.0 = shufflevector <4 x float> %bin.rdx.0, <4 x float> undef,
+ // <4 x i32> <i32 0, i32 undef, i32 undef, i32 undef>
+ // %rdx.shuf.1.1 = shufflevector <4 x float> %bin.rdx.0, <4 x float> undef,
+ // <4 x i32> <i32 1, i32 undef, i32 undef, i32 undef>
+ // %bin.rdx8 = fadd <4 x float> %rdx.shuf.1.0, %rdx.shuf.1.1
+ // %r = extractelement <4 x float> %bin.rdx8, i32 0
+ if (!matchPairwiseReductionAtLevel(RdxStart, 0, Log2_32(NumVecElems)))
+ return false;
+
+ Opcode = RdxStart->getOpcode();
+ Ty = VecTy;
+
+ return true;
+}
+
+static std::pair<Value *, ShuffleVectorInst *>
+getShuffleAndOtherOprd(BinaryOperator *B) {
+
+ Value *L = B->getOperand(0);
+ Value *R = B->getOperand(1);
+ ShuffleVectorInst *S = nullptr;
+
+ if ((S = dyn_cast<ShuffleVectorInst>(L)))
+ return std::make_pair(R, S);
+
+ S = dyn_cast<ShuffleVectorInst>(R);
+ return std::make_pair(L, S);
+}
+
+static bool matchVectorSplittingReduction(const ExtractElementInst *ReduxRoot,
+ unsigned &Opcode, Type *&Ty) {
+ if (!EnableReduxCost)
+ return false;
+
+ // Need to extract the first element.
+ ConstantInt *CI = dyn_cast<ConstantInt>(ReduxRoot->getOperand(1));
+ unsigned Idx = ~0u;
+ if (CI)
+ Idx = CI->getZExtValue();
+ if (Idx != 0)
+ return false;
+
+ BinaryOperator *RdxStart = dyn_cast<BinaryOperator>(ReduxRoot->getOperand(0));
+ if (!RdxStart)
+ return false;
+ unsigned RdxOpcode = RdxStart->getOpcode();
+
+ Type *VecTy = ReduxRoot->getOperand(0)->getType();
+ unsigned NumVecElems = VecTy->getVectorNumElements();
+ if (!isPowerOf2_32(NumVecElems))
+ return false;
+
+ // We look for a sequence of shuffles and adds like the following matching one
+ // fadd, shuffle vector pair at a time.
+ //
+ // %rdx.shuf = shufflevector <4 x float> %rdx, <4 x float> undef,
+ // <4 x i32> <i32 2, i32 3, i32 undef, i32 undef>
+ // %bin.rdx = fadd <4 x float> %rdx, %rdx.shuf
+ // %rdx.shuf7 = shufflevector <4 x float> %bin.rdx, <4 x float> undef,
+ // <4 x i32> <i32 1, i32 undef, i32 undef, i32 undef>
+ // %bin.rdx8 = fadd <4 x float> %bin.rdx, %rdx.shuf7
+ // %r = extractelement <4 x float> %bin.rdx8, i32 0
+
+ unsigned MaskStart = 1;
+ Value *RdxOp = RdxStart;
+ SmallVector<int, 32> ShuffleMask(NumVecElems, 0);
+ unsigned NumVecElemsRemain = NumVecElems;
+ while (NumVecElemsRemain - 1) {
+ // Check for the right reduction operation.
+ BinaryOperator *BinOp;
+ if (!(BinOp = dyn_cast<BinaryOperator>(RdxOp)))
+ return false;
+ if (BinOp->getOpcode() != RdxOpcode)
+ return false;
+
+ Value *NextRdxOp;
+ ShuffleVectorInst *Shuffle;
+ std::tie(NextRdxOp, Shuffle) = getShuffleAndOtherOprd(BinOp);
+
+ // Check the current reduction operation and the shuffle use the same value.
+ if (Shuffle == nullptr)
+ return false;
+ if (Shuffle->getOperand(0) != NextRdxOp)
+ return false;
+
+ // Check that shuffle masks matches.
+ for (unsigned j = 0; j != MaskStart; ++j)
+ ShuffleMask[j] = MaskStart + j;
+ // Fill the rest of the mask with -1 for undef.
+ std::fill(&ShuffleMask[MaskStart], ShuffleMask.end(), -1);
+
+ SmallVector<int, 16> Mask = Shuffle->getShuffleMask();
+ if (ShuffleMask != Mask)
+ return false;
+
+ RdxOp = NextRdxOp;
+ NumVecElemsRemain /= 2;
+ MaskStart *= 2;
+ }
+
+ Opcode = RdxOpcode;
+ Ty = VecTy;
+ return true;
+}
+
+unsigned CostModelAnalysis::getInstructionCost(const Instruction *I) const {
+ if (!TTI)
return -1;
switch (I->getOpcode()) {
+ case Instruction::GetElementPtr:
+ return TTI->getUserCost(I);
+
case Instruction::Ret:
case Instruction::PHI:
case Instruction::Br: {
- return VTTI->getCFInstrCost(I->getOpcode());
+ return TTI->getCFInstrCost(I->getOpcode());
}
case Instruction::Add:
case Instruction::FAdd:
case Instruction::And:
case Instruction::Or:
case Instruction::Xor: {
- return VTTI->getArithmeticInstrCost(I->getOpcode(), I->getType());
+ TargetTransformInfo::OperandValueKind Op1VK =
+ getOperandInfo(I->getOperand(0));
+ TargetTransformInfo::OperandValueKind Op2VK =
+ getOperandInfo(I->getOperand(1));
+ return TTI->getArithmeticInstrCost(I->getOpcode(), I->getType(), Op1VK,
+ Op2VK);
}
case Instruction::Select: {
- SelectInst *SI = cast<SelectInst>(I);
+ const SelectInst *SI = cast<SelectInst>(I);
Type *CondTy = SI->getCondition()->getType();
- return VTTI->getCmpSelInstrCost(I->getOpcode(), I->getType(), CondTy);
+ return TTI->getCmpSelInstrCost(I->getOpcode(), I->getType(), CondTy);
}
case Instruction::ICmp:
case Instruction::FCmp: {
Type *ValTy = I->getOperand(0)->getType();
- return VTTI->getCmpSelInstrCost(I->getOpcode(), ValTy);
+ return TTI->getCmpSelInstrCost(I->getOpcode(), ValTy);
}
case Instruction::Store: {
- StoreInst *SI = cast<StoreInst>(I);
+ const StoreInst *SI = cast<StoreInst>(I);
Type *ValTy = SI->getValueOperand()->getType();
- return VTTI->getMemoryOpCost(I->getOpcode(), ValTy,
+ return TTI->getMemoryOpCost(I->getOpcode(), ValTy,
SI->getAlignment(),
SI->getPointerAddressSpace());
}
case Instruction::Load: {
- LoadInst *LI = cast<LoadInst>(I);
- return VTTI->getMemoryOpCost(I->getOpcode(), I->getType(),
+ const LoadInst *LI = cast<LoadInst>(I);
+ return TTI->getMemoryOpCost(I->getOpcode(), I->getType(),
LI->getAlignment(),
LI->getPointerAddressSpace());
}
case Instruction::UIToFP:
case Instruction::Trunc:
case Instruction::FPTrunc:
- case Instruction::BitCast: {
+ case Instruction::BitCast:
+ case Instruction::AddrSpaceCast: {
Type *SrcTy = I->getOperand(0)->getType();
- return VTTI->getCastInstrCost(I->getOpcode(), I->getType(), SrcTy);
+ return TTI->getCastInstrCost(I->getOpcode(), I->getType(), SrcTy);
}
case Instruction::ExtractElement: {
- ExtractElementInst * EEI = cast<ExtractElementInst>(I);
+ const ExtractElementInst * EEI = cast<ExtractElementInst>(I);
ConstantInt *CI = dyn_cast<ConstantInt>(I->getOperand(1));
unsigned Idx = -1;
if (CI)
Idx = CI->getZExtValue();
- return VTTI->getVectorInstrCost(I->getOpcode(),
- EEI->getOperand(0)->getType(), Idx);
+
+ // Try to match a reduction sequence (series of shufflevector and vector
+ // adds followed by a extractelement).
+ unsigned ReduxOpCode;
+ Type *ReduxType;
+
+ if (matchVectorSplittingReduction(EEI, ReduxOpCode, ReduxType))
+ return TTI->getReductionCost(ReduxOpCode, ReduxType, false);
+ else if (matchPairwiseReduction(EEI, ReduxOpCode, ReduxType))
+ return TTI->getReductionCost(ReduxOpCode, ReduxType, true);
+
+ return TTI->getVectorInstrCost(I->getOpcode(),
+ EEI->getOperand(0)->getType(), Idx);
}
case Instruction::InsertElement: {
- InsertElementInst * IE = cast<InsertElementInst>(I);
- ConstantInt *CI = dyn_cast<ConstantInt>(IE->getOperand(2));
- unsigned Idx = -1;
- if (CI)
- Idx = CI->getZExtValue();
- return VTTI->getVectorInstrCost(I->getOpcode(),
- IE->getType(), Idx);
+ const InsertElementInst * IE = cast<InsertElementInst>(I);
+ ConstantInt *CI = dyn_cast<ConstantInt>(IE->getOperand(2));
+ unsigned Idx = -1;
+ if (CI)
+ Idx = CI->getZExtValue();
+ return TTI->getVectorInstrCost(I->getOpcode(),
+ IE->getType(), Idx);
+ }
+ case Instruction::ShuffleVector: {
+ const ShuffleVectorInst *Shuffle = cast<ShuffleVectorInst>(I);
+ Type *VecTypOp0 = Shuffle->getOperand(0)->getType();
+ unsigned NumVecElems = VecTypOp0->getVectorNumElements();
+ SmallVector<int, 16> Mask = Shuffle->getShuffleMask();
+
+ if (NumVecElems == Mask.size()) {
+ if (isReverseVectorMask(Mask))
+ return TTI->getShuffleCost(TargetTransformInfo::SK_Reverse, VecTypOp0,
+ 0, nullptr);
+ if (isAlternateVectorMask(Mask))
+ return TTI->getShuffleCost(TargetTransformInfo::SK_Alternate,
+ VecTypOp0, 0, nullptr);
+ }
+
+ return -1;
+ }
+ case Instruction::Call:
+ if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
+ SmallVector<Value *, 4> Args;
+ for (unsigned J = 0, JE = II->getNumArgOperands(); J != JE; ++J)
+ Args.push_back(II->getArgOperand(J));
+
+ return TTI->getIntrinsicInstrCost(II->getIntrinsicID(), II->getType(),
+ Args);
}
+ return -1;
default:
// We don't have any information on this instruction.
return -1;
for (Function::iterator B = F->begin(), BE = F->end(); B != BE; ++B) {
for (BasicBlock::iterator it = B->begin(), e = B->end(); it != e; ++it) {
- Instruction *Inst = it;
+ Instruction *Inst = &*it;
unsigned Cost = getInstructionCost(Inst);
if (Cost != (unsigned)-1)
OS << "Cost Model: Found an estimated cost of " << Cost;
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