aboutsummaryrefslogtreecommitdiff
path: root/llvm/lib/Analysis/LoopAccessAnalysis.cpp
diff options
context:
space:
mode:
Diffstat (limited to 'llvm/lib/Analysis/LoopAccessAnalysis.cpp')
-rw-r--r--llvm/lib/Analysis/LoopAccessAnalysis.cpp166
1 files changed, 28 insertions, 138 deletions
diff --git a/llvm/lib/Analysis/LoopAccessAnalysis.cpp b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
index dd98270..018861a 100644
--- a/llvm/lib/Analysis/LoopAccessAnalysis.cpp
+++ b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
@@ -21,7 +21,6 @@
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SmallVector.h"
-#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/AliasSetTracker.h"
#include "llvm/Analysis/LoopAnalysisManager.h"
@@ -71,8 +70,6 @@ using namespace llvm::PatternMatch;
#define DEBUG_TYPE "loop-accesses"
-STATISTIC(HistogramsDetected, "Number of Histograms detected");
-
static cl::opt<unsigned, true>
VectorizationFactor("force-vector-width", cl::Hidden,
cl::desc("Sets the SIMD width. Zero is autoselect."),
@@ -735,23 +732,6 @@ public:
return UnderlyingObjects;
}
- /// Find Histogram counts that match high-level code in loops:
- /// \code
- /// buckets[indices[i]]+=step;
- /// \endcode
- ///
- /// It matches a pattern starting from \p HSt, which Stores to the 'buckets'
- /// array the computed histogram. It uses a BinOp to sum all counts, storing
- /// them using a loop-variant index Load from the 'indices' input array.
- ///
- /// On successful matches it updates the STATISTIC 'HistogramsDetected',
- /// regardless of hardware support. When there is support, it additionally
- /// stores the BinOp/Load pairs in \p HistogramCounts, as well the pointers
- /// used to update histogram in \p HistogramPtrs.
- void findHistograms(StoreInst *HSt, Loop *TheLoop,
- SmallVectorImpl<HistogramInfo> &Histograms,
- SmallPtrSetImpl<const Value *> &HistogramPtrs);
-
private:
typedef MapVector<MemAccessInfo, SmallSetVector<Type *, 1>> PtrAccessMap;
@@ -1718,7 +1698,6 @@ MemoryDepChecker::Dependence::isSafeForVectorization(DepType Type) {
case NoDep:
case Forward:
case BackwardVectorizable:
- case Histogram:
return VectorizationSafetyStatus::Safe;
case Unknown:
@@ -1739,7 +1718,6 @@ bool MemoryDepChecker::Dependence::isBackward() const {
case ForwardButPreventsForwarding:
case Unknown:
case IndirectUnsafe:
- case Histogram:
return false;
case BackwardVectorizable:
@@ -1751,7 +1729,7 @@ bool MemoryDepChecker::Dependence::isBackward() const {
}
bool MemoryDepChecker::Dependence::isPossiblyBackward() const {
- return isBackward() || Type == Unknown || Type == Histogram;
+ return isBackward() || Type == Unknown;
}
bool MemoryDepChecker::Dependence::isForward() const {
@@ -1766,7 +1744,6 @@ bool MemoryDepChecker::Dependence::isForward() const {
case Backward:
case BackwardVectorizableButPreventsForwarding:
case IndirectUnsafe:
- case Histogram:
return false;
}
llvm_unreachable("unexpected DepType!");
@@ -1936,8 +1913,8 @@ std::variant<MemoryDepChecker::Dependence::DepType,
MemoryDepChecker::getDependenceDistanceStrideAndSize(
const AccessAnalysis::MemAccessInfo &A, Instruction *AInst,
const AccessAnalysis::MemAccessInfo &B, Instruction *BInst,
- const DenseMap<Value *, SmallVector<const Value *, 16>> &UnderlyingObjects,
- const SmallPtrSetImpl<const Value *> &HistogramPtrs) {
+ const DenseMap<Value *, SmallVector<const Value *, 16>>
+ &UnderlyingObjects) {
auto &DL = InnermostLoop->getHeader()->getDataLayout();
auto &SE = *PSE.getSE();
auto [APtr, AIsWrite] = A;
@@ -1955,12 +1932,6 @@ MemoryDepChecker::getDependenceDistanceStrideAndSize(
BPtr->getType()->getPointerAddressSpace())
return MemoryDepChecker::Dependence::Unknown;
- // Ignore Histogram count updates as they are handled by the Intrinsic. This
- // happens when the same pointer is first used to read from and then is used
- // to write to.
- if (!AIsWrite && BIsWrite && APtr == BPtr && HistogramPtrs.contains(APtr))
- return MemoryDepChecker::Dependence::Histogram;
-
int64_t StrideAPtr =
getPtrStride(PSE, ATy, APtr, InnermostLoop, SymbolicStrides, true)
.value_or(0);
@@ -2037,14 +2008,14 @@ MemoryDepChecker::getDependenceDistanceStrideAndSize(
MemoryDepChecker::Dependence::DepType MemoryDepChecker::isDependent(
const MemAccessInfo &A, unsigned AIdx, const MemAccessInfo &B,
unsigned BIdx,
- const DenseMap<Value *, SmallVector<const Value *, 16>> &UnderlyingObjects,
- const SmallPtrSetImpl<const Value *> &HistogramPtrs) {
+ const DenseMap<Value *, SmallVector<const Value *, 16>>
+ &UnderlyingObjects) {
assert(AIdx < BIdx && "Must pass arguments in program order");
// Get the dependence distance, stride, type size and what access writes for
// the dependence between A and B.
auto Res = getDependenceDistanceStrideAndSize(
- A, InstMap[AIdx], B, InstMap[BIdx], UnderlyingObjects, HistogramPtrs);
+ A, InstMap[AIdx], B, InstMap[BIdx], UnderlyingObjects);
if (std::holds_alternative<Dependence::DepType>(Res))
return std::get<Dependence::DepType>(Res);
@@ -2280,8 +2251,8 @@ MemoryDepChecker::Dependence::DepType MemoryDepChecker::isDependent(
bool MemoryDepChecker::areDepsSafe(
DepCandidates &AccessSets, MemAccessInfoList &CheckDeps,
- const DenseMap<Value *, SmallVector<const Value *, 16>> &UnderlyingObjects,
- const SmallPtrSetImpl<const Value *> &HistogramPtrs) {
+ const DenseMap<Value *, SmallVector<const Value *, 16>>
+ &UnderlyingObjects) {
MinDepDistBytes = -1;
SmallPtrSet<MemAccessInfo, 8> Visited;
@@ -2324,9 +2295,8 @@ bool MemoryDepChecker::areDepsSafe(
if (*I1 > *I2)
std::swap(A, B);
- Dependence::DepType Type =
- isDependent(*A.first, A.second, *B.first, B.second,
- UnderlyingObjects, HistogramPtrs);
+ Dependence::DepType Type = isDependent(*A.first, A.second, *B.first,
+ B.second, UnderlyingObjects);
mergeInStatus(Dependence::isSafeForVectorization(Type));
// Gather dependences unless we accumulated MaxDependences
@@ -2377,8 +2347,7 @@ const char *MemoryDepChecker::Dependence::DepName[] = {
"ForwardButPreventsForwarding",
"Backward",
"BackwardVectorizable",
- "BackwardVectorizableButPreventsForwarding",
- "Histogram"};
+ "BackwardVectorizableButPreventsForwarding"};
void MemoryDepChecker::Dependence::print(
raw_ostream &OS, unsigned Depth,
@@ -2426,9 +2395,9 @@ bool LoopAccessInfo::canAnalyzeLoop() {
return true;
}
-LoopAccessInfo::VecMemPossible
-LoopAccessInfo::analyzeLoop(AAResults *AA, LoopInfo *LI,
- const TargetLibraryInfo *TLI, DominatorTree *DT) {
+bool LoopAccessInfo::analyzeLoop(AAResults *AA, LoopInfo *LI,
+ const TargetLibraryInfo *TLI,
+ DominatorTree *DT) {
// Holds the Load and Store instructions.
SmallVector<LoadInst *, 16> Loads;
SmallVector<StoreInst *, 16> Stores;
@@ -2468,7 +2437,7 @@ LoopAccessInfo::analyzeLoop(AAResults *AA, LoopInfo *LI,
// With both a non-vectorizable memory instruction and a convergent
// operation, found in this loop, no reason to continue the search.
if (HasComplexMemInst && HasConvergentOp)
- return CantVec;
+ return false;
// Avoid hitting recordAnalysis multiple times.
if (HasComplexMemInst)
@@ -2544,7 +2513,7 @@ LoopAccessInfo::analyzeLoop(AAResults *AA, LoopInfo *LI,
} // Next block.
if (HasComplexMemInst)
- return CantVec;
+ return false;
// Now we have two lists that hold the loads and the stores.
// Next, we find the pointers that they use.
@@ -2553,7 +2522,7 @@ LoopAccessInfo::analyzeLoop(AAResults *AA, LoopInfo *LI,
// care if the pointers are *restrict*.
if (!Stores.size()) {
LLVM_DEBUG(dbgs() << "LAA: Found a read-only loop!\n");
- return NormalVec;
+ return true;
}
MemoryDepChecker::DepCandidates DependentAccesses;
@@ -2606,7 +2575,7 @@ LoopAccessInfo::analyzeLoop(AAResults *AA, LoopInfo *LI,
LLVM_DEBUG(
dbgs() << "LAA: A loop annotated parallel, ignore memory dependency "
<< "checks.\n");
- return NormalVec;
+ return true;
}
for (LoadInst *LD : Loads) {
@@ -2653,16 +2622,13 @@ LoopAccessInfo::analyzeLoop(AAResults *AA, LoopInfo *LI,
// other reads in this loop then is it safe to vectorize.
if (NumReadWrites == 1 && NumReads == 0) {
LLVM_DEBUG(dbgs() << "LAA: Found a write-only loop!\n");
- return NormalVec;
+ return true;
}
// Build dependence sets and check whether we need a runtime pointer bounds
// check.
Accesses.buildDependenceSets();
- for (StoreInst *ST : Stores)
- Accesses.findHistograms(ST, TheLoop, Histograms, HistogramPtrs);
-
// Find pointers with computable bounds. We are going to use this information
// to place a runtime bound check.
Value *UncomputablePtr = nullptr;
@@ -2675,7 +2641,7 @@ LoopAccessInfo::analyzeLoop(AAResults *AA, LoopInfo *LI,
<< "cannot identify array bounds";
LLVM_DEBUG(dbgs() << "LAA: We can't vectorize because we can't find "
<< "the array bounds.\n");
- return CantVec;
+ return false;
}
LLVM_DEBUG(
@@ -2684,9 +2650,9 @@ LoopAccessInfo::analyzeLoop(AAResults *AA, LoopInfo *LI,
bool DepsAreSafe = true;
if (Accesses.isDependencyCheckNeeded()) {
LLVM_DEBUG(dbgs() << "LAA: Checking memory dependencies\n");
- DepsAreSafe = DepChecker->areDepsSafe(
- DependentAccesses, Accesses.getDependenciesToCheck(),
- Accesses.getUnderlyingObjects(), HistogramPtrs);
+ DepsAreSafe = DepChecker->areDepsSafe(DependentAccesses,
+ Accesses.getDependenciesToCheck(),
+ Accesses.getUnderlyingObjects());
if (!DepsAreSafe && DepChecker->shouldRetryWithRuntimeCheck()) {
LLVM_DEBUG(dbgs() << "LAA: Retrying with memory checks\n");
@@ -2708,7 +2674,7 @@ LoopAccessInfo::analyzeLoop(AAResults *AA, LoopInfo *LI,
recordAnalysis("CantCheckMemDepsAtRunTime", I)
<< "cannot check memory dependencies at runtime";
LLVM_DEBUG(dbgs() << "LAA: Can't vectorize with memory checks\n");
- return CantVec;
+ return false;
}
DepsAreSafe = true;
}
@@ -2719,7 +2685,7 @@ LoopAccessInfo::analyzeLoop(AAResults *AA, LoopInfo *LI,
<< "cannot add control dependency to convergent operation";
LLVM_DEBUG(dbgs() << "LAA: We can't vectorize because a runtime check "
"would be needed with a convergent operation\n");
- return CantVec;
+ return false;
}
if (DepsAreSafe) {
@@ -2727,11 +2693,11 @@ LoopAccessInfo::analyzeLoop(AAResults *AA, LoopInfo *LI,
dbgs() << "LAA: No unsafe dependent memory operations in loop. We"
<< (PtrRtChecking->Need ? "" : " don't")
<< " need runtime memory checks.\n");
- return Histograms.empty() ? NormalVec : HistogramVec;
+ return true;
}
emitUnsafeDependenceRemark();
- return CantVec;
+ return false;
}
void LoopAccessInfo::emitUnsafeDependenceRemark() {
@@ -2791,9 +2757,6 @@ void LoopAccessInfo::emitUnsafeDependenceRemark() {
case MemoryDepChecker::Dependence::Unknown:
R << "\nUnknown data dependence.";
break;
- case MemoryDepChecker::Dependence::Histogram:
- R << "\nHistogram data dependence.";
- break;
}
if (Instruction *I = Dep.getSource(getDepChecker())) {
@@ -3065,7 +3028,7 @@ LoopAccessInfo::LoopAccessInfo(Loop *L, ScalarEvolution *SE,
}
void LoopAccessInfo::print(raw_ostream &OS, unsigned Depth) const {
- if (CanVecMem != CantVec) {
+ if (CanVecMem) {
OS.indent(Depth) << "Memory dependences are safe";
const MemoryDepChecker &DC = getDepChecker();
if (!DC.isSafeForAnyVectorWidth())
@@ -3138,79 +3101,6 @@ void LoopAccessInfoManager::clear() {
LoopAccessInfoMap.erase(L);
}
-void AccessAnalysis::findHistograms(
- StoreInst *HSt, Loop *TheLoop, SmallVectorImpl<HistogramInfo> &Histograms,
- SmallPtrSetImpl<const Value *> &HistogramPtrs) {
-
- // Store value must come from a Binary Operation.
- Instruction *HPtrInstr = nullptr;
- BinaryOperator *HBinOp = nullptr;
- if (!match(HSt, m_Store(m_BinOp(HBinOp), m_Instruction(HPtrInstr))))
- return;
-
- // BinOp must be an Add or a Sub modifying the bucket value by a
- // loop invariant amount.
- // FIXME: We assume the loop invariant term is on the RHS.
- // Fine for an immediate/constant, but maybe not a generic value?
- Value *HIncVal = nullptr;
- if (!match(HBinOp, m_Add(m_Load(m_Specific(HPtrInstr)), m_Value(HIncVal))) &&
- !match(HBinOp, m_Sub(m_Load(m_Specific(HPtrInstr)), m_Value(HIncVal))))
- return;
-
- // Make sure the increment value is loop invariant.
- if (!TheLoop->isLoopInvariant(HIncVal))
- return;
-
- // The address to store is calculated through a GEP Instruction.
- // FIXME: Support GEPs with more operands.
- GetElementPtrInst *HPtr = dyn_cast<GetElementPtrInst>(HPtrInstr);
- if (!HPtr || HPtr->getNumOperands() > 2)
- return;
-
- // Check that the index is calculated by loading from another array. Ignore
- // any extensions.
- // FIXME: Support indices from other sources that a linear load from memory?
- Value *HIdx = HPtr->getOperand(1);
- Instruction *IdxInst = nullptr;
- if (!match(HIdx, m_ZExtOrSExtOrSelf(m_Instruction(IdxInst))))
- return;
-
- // Currently restricting this to linear addressing when loading indices.
- LoadInst *VLoad = dyn_cast<LoadInst>(IdxInst);
- Value *VPtrVal;
- if (!VLoad || !match(VLoad, m_Load(m_Value(VPtrVal))))
- return;
-
- if (!isa<SCEVAddRecExpr>(PSE.getSCEV(VPtrVal)))
- return;
-
- // Ensure we'll have the same mask by checking that all parts of the histogram
- // (gather load, update, scatter store) are in the same block.
- LoadInst *IndexedLoad = cast<LoadInst>(HBinOp->getOperand(0));
- BasicBlock *LdBB = IndexedLoad->getParent();
- if (LdBB != HBinOp->getParent() || LdBB != HSt->getParent())
- return;
-
- // A histogram pointer may only alias to itself, and must only have two uses,
- // the load and the store.
- // We may be able to relax these constraints later.
- for (AliasSet &AS : AST)
- if (AS.isMustAlias() || AS.isMayAlias())
- if ((is_contained(AS.getPointers(), HPtr) && AS.size() > 1) ||
- HPtr->getNumUses() != 2)
- return;
-
- HistogramsDetected++;
-
- LLVM_DEBUG(dbgs() << "LAA: Found histogram for load: " << *IndexedLoad
- << " and store: " << *HSt << "\n");
-
- // Store the operations that make up the histogram.
- Histograms.emplace_back(IndexedLoad, HBinOp, HSt);
- // Store pointers used to write those counts in the computed histogram.
- HistogramPtrs.insert(HPtr);
-}
-
bool LoopAccessInfoManager::invalidate(
Function &F, const PreservedAnalyses &PA,
FunctionAnalysisManager::Invalidator &Inv) {
generated by cgit v1.1 at 2025-09-29 23:22:30 +0000