[llvm] 28be3f8 - [LAA] Cache pointer bounds expansions (NFCI).
Florian Hahn via llvm-commits
llvm-commits at lists.llvm.org
Thu Jul 4 02:00:38 PDT 2024
Author: Florian Hahn
Date: 2024-07-04T10:00:05+01:00
New Revision: 28be3f8ac51e62610f8e78b411adf05a2365dff7
URL: https://github.com/llvm/llvm-project/commit/28be3f8ac51e62610f8e78b411adf05a2365dff7
DIFF: https://github.com/llvm/llvm-project/commit/28be3f8ac51e62610f8e78b411adf05a2365dff7.diff
LOG: [LAA] Cache pointer bounds expansions (NFCI).
This avoids expanding the same bounds multiple times, which helps reduce
the compile-time impact of removing the restrictions added in
234cc40adc6, notably -0.06% on stage1-O3 and -0.05% on both
stage1-ReleaseThinLTO and stage1-ReleaseLTO-g.
https://llvm-compile-time-tracker.com/compare.php?from=8b9ebc4bb86cf0979e05908cbb04336f2d01dda5&to=fabd36f96c31e47ea72653f5a404feaadfc7b5b5&stat=instructions:u
Added:
Modified:
llvm/include/llvm/Analysis/LoopAccessAnalysis.h
llvm/lib/Analysis/LoopAccessAnalysis.cpp
Removed:
################################################################################
diff --git a/llvm/include/llvm/Analysis/LoopAccessAnalysis.h b/llvm/include/llvm/Analysis/LoopAccessAnalysis.h
index 7a54fe55014be..c74e76604e786 100644
--- a/llvm/include/llvm/Analysis/LoopAccessAnalysis.h
+++ b/llvm/include/llvm/Analysis/LoopAccessAnalysis.h
@@ -269,6 +269,11 @@ class MemoryDepChecker {
const Loop *getInnermostLoop() const { return InnermostLoop; }
+ DenseMap<const SCEV *, std::pair<const SCEV *, const SCEV *>> &
+ getPointerBounds() {
+ return PointerBounds;
+ }
+
private:
/// A wrapper around ScalarEvolution, used to add runtime SCEV checks, and
/// applies dynamic knowledge to simplify SCEV expressions and convert them
@@ -327,6 +332,10 @@ class MemoryDepChecker {
/// backwards-vectorizable or unknown (triggering a runtime check).
unsigned MaxTargetVectorWidthInBits = 0;
+ /// Mapping of SCEV expressions to their expanded pointer bounds (pair of
+ /// start and end pointer expressions).
+ DenseMap<const SCEV *, std::pair<const SCEV *, const SCEV *>> PointerBounds;
+
/// Check whether there is a plausible dependence between the two
/// accesses.
///
diff --git a/llvm/lib/Analysis/LoopAccessAnalysis.cpp b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
index 38bf6d8160aa9..f132e45540525 100644
--- a/llvm/lib/Analysis/LoopAccessAnalysis.cpp
+++ b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
@@ -203,11 +203,18 @@ RuntimeCheckingPtrGroup::RuntimeCheckingPtrGroup(
///
/// There is no conflict when the intervals are disjoint:
/// NoConflict = (P2.Start >= P1.End) || (P1.Start >= P2.End)
-static std::pair<const SCEV *, const SCEV *>
-getStartAndEndForAccess(const Loop *Lp, const SCEV *PtrExpr, Type *AccessTy,
- PredicatedScalarEvolution &PSE) {
+static std::pair<const SCEV *, const SCEV *> getStartAndEndForAccess(
+ const Loop *Lp, const SCEV *PtrExpr, Type *AccessTy,
+ PredicatedScalarEvolution &PSE,
+ DenseMap<const SCEV *, std::pair<const SCEV *, const SCEV *>>
+ &PointerBounds) {
ScalarEvolution *SE = PSE.getSE();
+ auto [Iter, Ins] = PointerBounds.insert(
+ {PtrExpr, {SE->getCouldNotCompute(), SE->getCouldNotCompute()}});
+ if (!Ins)
+ return Iter->second;
+
const SCEV *ScStart;
const SCEV *ScEnd;
@@ -244,7 +251,8 @@ getStartAndEndForAccess(const Loop *Lp, const SCEV *PtrExpr, Type *AccessTy,
const SCEV *EltSizeSCEV = SE->getStoreSizeOfExpr(IdxTy, AccessTy);
ScEnd = SE->getAddExpr(ScEnd, EltSizeSCEV);
- return {ScStart, ScEnd};
+ Iter->second = {ScStart, ScEnd};
+ return Iter->second;
}
/// Calculate Start and End points of memory access using
@@ -254,8 +262,8 @@ void RuntimePointerChecking::insert(Loop *Lp, Value *Ptr, const SCEV *PtrExpr,
unsigned DepSetId, unsigned ASId,
PredicatedScalarEvolution &PSE,
bool NeedsFreeze) {
- const auto &[ScStart, ScEnd] =
- getStartAndEndForAccess(Lp, PtrExpr, AccessTy, PSE);
+ const auto &[ScStart, ScEnd] = getStartAndEndForAccess(
+ Lp, PtrExpr, AccessTy, PSE, DC.getPointerBounds());
assert(!isa<SCEVCouldNotCompute>(ScStart) &&
!isa<SCEVCouldNotCompute>(ScEnd) &&
"must be able to compute both start and end expressions");
@@ -1964,10 +1972,9 @@ MemoryDepChecker::getDependenceDistanceStrideAndSize(
if (SE.isLoopInvariant(Src, InnermostLoop) ||
SE.isLoopInvariant(Sink, InnermostLoop)) {
const auto &[SrcStart, SrcEnd] =
- getStartAndEndForAccess(InnermostLoop, Src, ATy, PSE);
+ getStartAndEndForAccess(InnermostLoop, Src, ATy, PSE, PointerBounds);
const auto &[SinkStart, SinkEnd] =
- getStartAndEndForAccess(InnermostLoop, Sink, BTy, PSE);
-
+ getStartAndEndForAccess(InnermostLoop, Sink, BTy, PSE, PointerBounds);
if (!isa<SCEVCouldNotCompute>(SrcStart) &&
!isa<SCEVCouldNotCompute>(SrcEnd) &&
!isa<SCEVCouldNotCompute>(SinkStart) &&
More information about the llvm-commits
mailing list