[llvm] LAA: improve code in a couple of routines (NFC) (PR #108092)
Ramkumar Ramachandra via llvm-commits
llvm-commits at lists.llvm.org
Thu Nov 28 03:53:19 PST 2024
https://github.com/artagnon updated https://github.com/llvm/llvm-project/pull/108092
>From aa7f6b92862ca5faa50afde81a24e4cb9868a197 Mon Sep 17 00:00:00 2001
From: Ramkumar Ramachandra <ramkumar.ramachandra at codasip.com>
Date: Tue, 10 Sep 2024 22:17:17 +0100
Subject: [PATCH 1/3] LAA: improve code in a couple of routines (NFC)
---
llvm/lib/Analysis/LoopAccessAnalysis.cpp | 33 ++++++++++--------------
1 file changed, 14 insertions(+), 19 deletions(-)
diff --git a/llvm/lib/Analysis/LoopAccessAnalysis.cpp b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
index 907bb7875dc807..c5b671886646c0 100644
--- a/llvm/lib/Analysis/LoopAccessAnalysis.cpp
+++ b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
@@ -1978,13 +1978,12 @@ MemoryDepChecker::getDependenceDistanceStrideAndSize(
<< " Sink induction step: " << StrideBPtrInt << "\n");
// At least Src or Sink are loop invariant and the other is strided or
// invariant. We can generate a runtime check to disambiguate the accesses.
- if (StrideAPtrInt == 0 || StrideBPtrInt == 0)
+ if (!StrideAPtrInt || !StrideBPtrInt)
return MemoryDepChecker::Dependence::Unknown;
// Both Src and Sink have a constant stride, check if they are in the same
// direction.
- if ((StrideAPtrInt > 0 && StrideBPtrInt < 0) ||
- (StrideAPtrInt < 0 && StrideBPtrInt > 0)) {
+ if (StrideAPtrInt > 0 != StrideBPtrInt > 0) {
LLVM_DEBUG(
dbgs() << "Pointer access with strides in different directions\n");
return MemoryDepChecker::Dependence::Unknown;
@@ -2040,19 +2039,16 @@ MemoryDepChecker::isDependent(const MemAccessInfo &A, unsigned AIdx,
*Dist, MaxStride, TypeByteSize))
return Dependence::NoDep;
- const SCEVConstant *C = dyn_cast<SCEVConstant>(Dist);
+ const SCEVConstant *ConstDist = dyn_cast<SCEVConstant>(Dist);
// Attempt to prove strided accesses independent.
- if (C) {
- const APInt &Val = C->getAPInt();
- int64_t Distance = Val.getSExtValue();
+ if (ConstDist) {
+ int64_t Distance = std::abs(ConstDist->getAPInt().getSExtValue());
// If the distance between accesses and their strides are known constants,
// check whether the accesses interlace each other.
- if (std::abs(Distance) > 0 && CommonStride && *CommonStride > 1 &&
- HasSameSize &&
- areStridedAccessesIndependent(std::abs(Distance), *CommonStride,
- TypeByteSize)) {
+ if (Distance > 0 && CommonStride && CommonStride > 1 && HasSameSize &&
+ areStridedAccessesIndependent(Distance, *CommonStride, TypeByteSize)) {
LLVM_DEBUG(dbgs() << "LAA: Strided accesses are independent\n");
return Dependence::NoDep;
}
@@ -2085,7 +2081,7 @@ MemoryDepChecker::isDependent(const MemAccessInfo &A, unsigned AIdx,
// forward dependency will allow vectorization using any width.
if (IsTrueDataDependence && EnableForwardingConflictDetection) {
- if (!C) {
+ if (!ConstDist) {
// TODO: FoundNonConstantDistanceDependence is used as a necessary
// condition to consider retrying with runtime checks. Historically, we
// did not set it when strides were different but there is no inherent
@@ -2094,8 +2090,8 @@ MemoryDepChecker::isDependent(const MemAccessInfo &A, unsigned AIdx,
return Dependence::Unknown;
}
if (!HasSameSize ||
- couldPreventStoreLoadForward(C->getAPInt().abs().getZExtValue(),
- TypeByteSize)) {
+ couldPreventStoreLoadForward(
+ ConstDist->getAPInt().abs().getZExtValue(), TypeByteSize)) {
LLVM_DEBUG(
dbgs() << "LAA: Forward but may prevent st->ld forwarding\n");
return Dependence::ForwardButPreventsForwarding;
@@ -2113,7 +2109,7 @@ MemoryDepChecker::isDependent(const MemAccessInfo &A, unsigned AIdx,
return Dependence::Unknown;
}
- if (!isa<SCEVConstant>(Dist)) {
+ if (!ConstDist) {
// Previously this case would be treated as Unknown, possibly setting
// FoundNonConstantDistanceDependence to force re-trying with runtime
// checks. Until the TODO below is addressed, set it here to preserve
@@ -2175,7 +2171,7 @@ MemoryDepChecker::isDependent(const MemAccessInfo &A, unsigned AIdx,
uint64_t MinDistanceNeeded =
TypeByteSize * *CommonStride * (MinNumIter - 1) + TypeByteSize;
if (MinDistanceNeeded > static_cast<uint64_t>(MinDistance)) {
- if (!isa<SCEVConstant>(Dist)) {
+ if (!ConstDist) {
// For non-constant distances, we checked the lower bound of the
// dependence distance and the distance may be larger at runtime (and safe
// for vectorization). Classify it as Unknown, so we re-try with runtime
@@ -2216,8 +2212,7 @@ MemoryDepChecker::isDependent(const MemAccessInfo &A, unsigned AIdx,
bool IsTrueDataDependence = (!AIsWrite && BIsWrite);
uint64_t MinDepDistBytesOld = MinDepDistBytes;
- if (IsTrueDataDependence && EnableForwardingConflictDetection &&
- isa<SCEVConstant>(Dist) &&
+ if (IsTrueDataDependence && EnableForwardingConflictDetection && ConstDist &&
couldPreventStoreLoadForward(MinDistance, TypeByteSize)) {
// Sanity check that we didn't update MinDepDistBytes when calling
// couldPreventStoreLoadForward
@@ -2235,7 +2230,7 @@ MemoryDepChecker::isDependent(const MemAccessInfo &A, unsigned AIdx,
<< " with max VF = " << MaxVF << '\n');
uint64_t MaxVFInBits = MaxVF * TypeByteSize * 8;
- if (!isa<SCEVConstant>(Dist) && MaxVFInBits < MaxTargetVectorWidthInBits) {
+ if (!ConstDist && MaxVFInBits < MaxTargetVectorWidthInBits) {
// For non-constant distances, we checked the lower bound of the dependence
// distance and the distance may be larger at runtime (and safe for
// vectorization). Classify it as Unknown, so we re-try with runtime checks.
>From 9db56bd32c53bd9c8e2be978090e3799cba3deb9 Mon Sep 17 00:00:00 2001
From: Ramkumar Ramachandra <ramkumar.ramachandra at codasip.com>
Date: Thu, 28 Nov 2024 11:41:16 +0000
Subject: [PATCH 2/3] LAA: fix nit
---
llvm/lib/Analysis/LoopAccessAnalysis.cpp | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/llvm/lib/Analysis/LoopAccessAnalysis.cpp b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
index c5b671886646c0..098ad39b6d98e2 100644
--- a/llvm/lib/Analysis/LoopAccessAnalysis.cpp
+++ b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
@@ -1983,7 +1983,7 @@ MemoryDepChecker::getDependenceDistanceStrideAndSize(
// Both Src and Sink have a constant stride, check if they are in the same
// direction.
- if (StrideAPtrInt > 0 != StrideBPtrInt > 0) {
+ if ((StrideAPtrInt > 0) != (StrideBPtrInt > 0)) {
LLVM_DEBUG(
dbgs() << "Pointer access with strides in different directions\n");
return MemoryDepChecker::Dependence::Unknown;
>From dc7cd0eee7f7770faf6b41a7c05d815cdd243630 Mon Sep 17 00:00:00 2001
From: Ramkumar Ramachandra <ramkumar.ramachandra at codasip.com>
Date: Thu, 28 Nov 2024 11:52:34 +0000
Subject: [PATCH 3/3] LAA: address review
---
llvm/lib/Analysis/LoopAccessAnalysis.cpp | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/llvm/lib/Analysis/LoopAccessAnalysis.cpp b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
index 098ad39b6d98e2..71582d5d86549b 100644
--- a/llvm/lib/Analysis/LoopAccessAnalysis.cpp
+++ b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
@@ -2043,7 +2043,7 @@ MemoryDepChecker::isDependent(const MemAccessInfo &A, unsigned AIdx,
// Attempt to prove strided accesses independent.
if (ConstDist) {
- int64_t Distance = std::abs(ConstDist->getAPInt().getSExtValue());
+ uint64_t Distance = ConstDist->getAPInt().abs().getZExtValue();
// If the distance between accesses and their strides are known constants,
// check whether the accesses interlace each other.
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