Sam Tebbs c858bf620c
Reland "[LoopVectorizer] Add support for partial reductions" (#120721)
This re-lands the reverted #92418 

When the VF is small enough so that dividing the VF by the scaling
factor results in 1, the reduction phi execution thinks the VF is scalar
and sets the reduction's output as a scalar value, tripping assertions
expecting a vector value. The latest commit in this PR fixes that by
using `State.VF` in the scalar check, rather than the divided VF.

---------

Co-authored-by: Nicholas Guy <nicholas.guy@arm.com>
2024-12-24 12:08:17 +00:00

343 lines
12 KiB
C++

//===- VPlanAnalysis.cpp - Various Analyses working on VPlan ----*- C++ -*-===//
//
// 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 "VPlanAnalysis.h"
#include "VPlan.h"
#include "VPlanCFG.h"
#include "VPlanDominatorTree.h"
#include "llvm/ADT/TypeSwitch.h"
#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/PatternMatch.h"
#include "llvm/Support/GenericDomTreeConstruction.h"
using namespace llvm;
#define DEBUG_TYPE "vplan"
Type *VPTypeAnalysis::inferScalarTypeForRecipe(const VPBlendRecipe *R) {
Type *ResTy = inferScalarType(R->getIncomingValue(0));
for (unsigned I = 1, E = R->getNumIncomingValues(); I != E; ++I) {
VPValue *Inc = R->getIncomingValue(I);
assert(inferScalarType(Inc) == ResTy &&
"different types inferred for different incoming values");
CachedTypes[Inc] = ResTy;
}
return ResTy;
}
Type *VPTypeAnalysis::inferScalarTypeForRecipe(const VPInstruction *R) {
// Set the result type from the first operand, check if the types for all
// other operands match and cache them.
auto SetResultTyFromOp = [this, R]() {
Type *ResTy = inferScalarType(R->getOperand(0));
for (unsigned Op = 1; Op != R->getNumOperands(); ++Op) {
VPValue *OtherV = R->getOperand(Op);
assert(inferScalarType(OtherV) == ResTy &&
"different types inferred for different operands");
CachedTypes[OtherV] = ResTy;
}
return ResTy;
};
unsigned Opcode = R->getOpcode();
if (Instruction::isBinaryOp(Opcode) || Instruction::isUnaryOp(Opcode))
return SetResultTyFromOp();
switch (Opcode) {
case Instruction::Select: {
Type *ResTy = inferScalarType(R->getOperand(1));
VPValue *OtherV = R->getOperand(2);
assert(inferScalarType(OtherV) == ResTy &&
"different types inferred for different operands");
CachedTypes[OtherV] = ResTy;
return ResTy;
}
case Instruction::ICmp:
case VPInstruction::ActiveLaneMask:
return inferScalarType(R->getOperand(1));
case VPInstruction::ComputeReductionResult: {
auto *PhiR = cast<VPReductionPHIRecipe>(R->getOperand(0));
auto *OrigPhi = cast<PHINode>(PhiR->getUnderlyingValue());
return OrigPhi->getType();
}
case VPInstruction::ExplicitVectorLength:
return Type::getIntNTy(Ctx, 32);
case VPInstruction::FirstOrderRecurrenceSplice:
case VPInstruction::Not:
case VPInstruction::ResumePhi:
return SetResultTyFromOp();
case VPInstruction::ExtractFromEnd: {
Type *BaseTy = inferScalarType(R->getOperand(0));
if (auto *VecTy = dyn_cast<VectorType>(BaseTy))
return VecTy->getElementType();
return BaseTy;
}
case VPInstruction::LogicalAnd:
return IntegerType::get(Ctx, 1);
case VPInstruction::PtrAdd:
// Return the type based on the pointer argument (i.e. first operand).
return inferScalarType(R->getOperand(0));
case VPInstruction::BranchOnCond:
case VPInstruction::BranchOnCount:
return Type::getVoidTy(Ctx);
default:
break;
}
// Type inference not implemented for opcode.
LLVM_DEBUG({
dbgs() << "LV: Found unhandled opcode for: ";
R->getVPSingleValue()->dump();
});
llvm_unreachable("Unhandled opcode!");
}
Type *VPTypeAnalysis::inferScalarTypeForRecipe(const VPWidenRecipe *R) {
unsigned Opcode = R->getOpcode();
if (Instruction::isBinaryOp(Opcode) || Instruction::isShift(Opcode) ||
Instruction::isBitwiseLogicOp(Opcode)) {
Type *ResTy = inferScalarType(R->getOperand(0));
assert(ResTy == inferScalarType(R->getOperand(1)) &&
"types for both operands must match for binary op");
CachedTypes[R->getOperand(1)] = ResTy;
return ResTy;
}
switch (Opcode) {
case Instruction::ICmp:
case Instruction::FCmp:
return IntegerType::get(Ctx, 1);
case Instruction::FNeg:
case Instruction::Freeze:
return inferScalarType(R->getOperand(0));
default:
break;
}
// Type inference not implemented for opcode.
LLVM_DEBUG({
dbgs() << "LV: Found unhandled opcode for: ";
R->getVPSingleValue()->dump();
});
llvm_unreachable("Unhandled opcode!");
}
Type *VPTypeAnalysis::inferScalarTypeForRecipe(const VPWidenCallRecipe *R) {
auto &CI = *cast<CallInst>(R->getUnderlyingInstr());
return CI.getType();
}
Type *VPTypeAnalysis::inferScalarTypeForRecipe(const VPWidenMemoryRecipe *R) {
assert((isa<VPWidenLoadRecipe, VPWidenLoadEVLRecipe>(R)) &&
"Store recipes should not define any values");
return cast<LoadInst>(&R->getIngredient())->getType();
}
Type *VPTypeAnalysis::inferScalarTypeForRecipe(const VPWidenSelectRecipe *R) {
Type *ResTy = inferScalarType(R->getOperand(1));
VPValue *OtherV = R->getOperand(2);
assert(inferScalarType(OtherV) == ResTy &&
"different types inferred for different operands");
CachedTypes[OtherV] = ResTy;
return ResTy;
}
Type *VPTypeAnalysis::inferScalarTypeForRecipe(const VPReplicateRecipe *R) {
unsigned Opcode = R->getUnderlyingInstr()->getOpcode();
if (Instruction::isBinaryOp(Opcode) || Instruction::isShift(Opcode) ||
Instruction::isBitwiseLogicOp(Opcode)) {
Type *ResTy = inferScalarType(R->getOperand(0));
assert(ResTy == inferScalarType(R->getOperand(1)) &&
"inferred types for operands of binary op don't match");
CachedTypes[R->getOperand(1)] = ResTy;
return ResTy;
}
if (Instruction::isCast(Opcode))
return R->getUnderlyingInstr()->getType();
switch (Opcode) {
case Instruction::Call: {
unsigned CallIdx = R->getNumOperands() - (R->isPredicated() ? 2 : 1);
return cast<Function>(R->getOperand(CallIdx)->getLiveInIRValue())
->getReturnType();
}
case Instruction::Select: {
Type *ResTy = inferScalarType(R->getOperand(1));
assert(ResTy == inferScalarType(R->getOperand(2)) &&
"inferred types for operands of select op don't match");
CachedTypes[R->getOperand(2)] = ResTy;
return ResTy;
}
case Instruction::ICmp:
case Instruction::FCmp:
return IntegerType::get(Ctx, 1);
case Instruction::Alloca:
case Instruction::ExtractValue:
return R->getUnderlyingInstr()->getType();
case Instruction::Freeze:
case Instruction::FNeg:
case Instruction::GetElementPtr:
return inferScalarType(R->getOperand(0));
case Instruction::Load:
return cast<LoadInst>(R->getUnderlyingInstr())->getType();
case Instruction::Store:
// FIXME: VPReplicateRecipes with store opcodes still define a result
// VPValue, so we need to handle them here. Remove the code here once this
// is modeled accurately in VPlan.
return Type::getVoidTy(Ctx);
default:
break;
}
// Type inference not implemented for opcode.
LLVM_DEBUG({
dbgs() << "LV: Found unhandled opcode for: ";
R->getVPSingleValue()->dump();
});
llvm_unreachable("Unhandled opcode");
}
Type *VPTypeAnalysis::inferScalarType(const VPValue *V) {
if (Type *CachedTy = CachedTypes.lookup(V))
return CachedTy;
if (V->isLiveIn()) {
if (auto *IRValue = V->getLiveInIRValue())
return IRValue->getType();
// All VPValues without any underlying IR value (like the vector trip count
// or the backedge-taken count) have the same type as the canonical IV.
return CanonicalIVTy;
}
Type *ResultTy =
TypeSwitch<const VPRecipeBase *, Type *>(V->getDefiningRecipe())
.Case<VPActiveLaneMaskPHIRecipe, VPCanonicalIVPHIRecipe,
VPFirstOrderRecurrencePHIRecipe, VPReductionPHIRecipe,
VPWidenPointerInductionRecipe, VPEVLBasedIVPHIRecipe,
VPScalarPHIRecipe>([this](const auto *R) {
// Handle header phi recipes, except VPWidenIntOrFpInduction
// which needs special handling due it being possibly truncated.
// TODO: consider inferring/caching type of siblings, e.g.,
// backedge value, here and in cases below.
return inferScalarType(R->getStartValue());
})
.Case<VPWidenIntOrFpInductionRecipe, VPDerivedIVRecipe>(
[](const auto *R) { return R->getScalarType(); })
.Case<VPReductionRecipe, VPPredInstPHIRecipe, VPWidenPHIRecipe,
VPScalarIVStepsRecipe, VPWidenGEPRecipe, VPVectorPointerRecipe,
VPReverseVectorPointerRecipe, VPWidenCanonicalIVRecipe,
VPPartialReductionRecipe>([this](const VPRecipeBase *R) {
return inferScalarType(R->getOperand(0));
})
.Case<VPBlendRecipe, VPInstruction, VPWidenRecipe, VPWidenEVLRecipe,
VPReplicateRecipe, VPWidenCallRecipe, VPWidenMemoryRecipe,
VPWidenSelectRecipe>(
[this](const auto *R) { return inferScalarTypeForRecipe(R); })
.Case<VPWidenIntrinsicRecipe>([](const VPWidenIntrinsicRecipe *R) {
return R->getResultType();
})
.Case<VPInterleaveRecipe>([V](const VPInterleaveRecipe *R) {
// TODO: Use info from interleave group.
return V->getUnderlyingValue()->getType();
})
.Case<VPWidenCastRecipe>(
[](const VPWidenCastRecipe *R) { return R->getResultType(); })
.Case<VPScalarCastRecipe>(
[](const VPScalarCastRecipe *R) { return R->getResultType(); })
.Case<VPExpandSCEVRecipe>([](const VPExpandSCEVRecipe *R) {
return R->getSCEV()->getType();
})
.Case<VPReductionRecipe>([this](const auto *R) {
return inferScalarType(R->getChainOp());
});
assert(ResultTy && "could not infer type for the given VPValue");
CachedTypes[V] = ResultTy;
return ResultTy;
}
void llvm::collectEphemeralRecipesForVPlan(
VPlan &Plan, DenseSet<VPRecipeBase *> &EphRecipes) {
// First, collect seed recipes which are operands of assumes.
SmallVector<VPRecipeBase *> Worklist;
for (VPBasicBlock *VPBB : VPBlockUtils::blocksOnly<VPBasicBlock>(
vp_depth_first_deep(Plan.getVectorLoopRegion()->getEntry()))) {
for (VPRecipeBase &R : *VPBB) {
auto *RepR = dyn_cast<VPReplicateRecipe>(&R);
if (!RepR || !match(RepR->getUnderlyingInstr(),
PatternMatch::m_Intrinsic<Intrinsic::assume>()))
continue;
Worklist.push_back(RepR);
EphRecipes.insert(RepR);
}
}
// Process operands of candidates in worklist and add them to the set of
// ephemeral recipes, if they don't have side-effects and are only used by
// other ephemeral recipes.
while (!Worklist.empty()) {
VPRecipeBase *Cur = Worklist.pop_back_val();
for (VPValue *Op : Cur->operands()) {
auto *OpR = Op->getDefiningRecipe();
if (!OpR || OpR->mayHaveSideEffects() || EphRecipes.contains(OpR))
continue;
if (any_of(Op->users(), [EphRecipes](VPUser *U) {
auto *UR = dyn_cast<VPRecipeBase>(U);
return !UR || !EphRecipes.contains(UR);
}))
continue;
EphRecipes.insert(OpR);
Worklist.push_back(OpR);
}
}
}
template void DomTreeBuilder::Calculate<DominatorTreeBase<VPBlockBase, false>>(
DominatorTreeBase<VPBlockBase, false> &DT);
bool VPDominatorTree::properlyDominates(const VPRecipeBase *A,
const VPRecipeBase *B) {
if (A == B)
return false;
auto LocalComesBefore = [](const VPRecipeBase *A, const VPRecipeBase *B) {
for (auto &R : *A->getParent()) {
if (&R == A)
return true;
if (&R == B)
return false;
}
llvm_unreachable("recipe not found");
};
const VPBlockBase *ParentA = A->getParent();
const VPBlockBase *ParentB = B->getParent();
if (ParentA == ParentB)
return LocalComesBefore(A, B);
#ifndef NDEBUG
auto GetReplicateRegion = [](VPRecipeBase *R) -> VPRegionBlock * {
auto *Region = dyn_cast_or_null<VPRegionBlock>(R->getParent()->getParent());
if (Region && Region->isReplicator()) {
assert(Region->getNumSuccessors() == 1 &&
Region->getNumPredecessors() == 1 && "Expected SESE region!");
assert(R->getParent()->size() == 1 &&
"A recipe in an original replicator region must be the only "
"recipe in its block");
return Region;
}
return nullptr;
};
assert(!GetReplicateRegion(const_cast<VPRecipeBase *>(A)) &&
"No replicate regions expected at this point");
assert(!GetReplicateRegion(const_cast<VPRecipeBase *>(B)) &&
"No replicate regions expected at this point");
#endif
return Base::properlyDominates(ParentA, ParentB);
}