diff --git a/llvm/lib/Analysis/LoopAccessAnalysis.cpp b/llvm/lib/Analysis/LoopAccessAnalysis.cpp index 9193e38b573b..895c47e759fb 100644 --- a/llvm/lib/Analysis/LoopAccessAnalysis.cpp +++ b/llvm/lib/Analysis/LoopAccessAnalysis.cpp @@ -1212,8 +1212,18 @@ MemoryDepChecker::isDependent(const MemAccessInfo &A, unsigned AIdx, auto &DL = InnermostLoop->getHeader()->getModule()->getDataLayout(); unsigned TypeByteSize = DL.getTypeAllocSize(ATy); - // Negative distances are not plausible dependencies. const APInt &Val = C->getAPInt(); + int64_t Distance = Val.getSExtValue(); + unsigned Stride = std::abs(StrideAPtr); + + // Attempt to prove strided accesses independent. + if (std::abs(Distance) > 0 && Stride > 1 && ATy == BTy && + areStridedAccessesIndependent(std::abs(Distance), Stride, TypeByteSize)) { + DEBUG(dbgs() << "LAA: Strided accesses are independent\n"); + return Dependence::NoDep; + } + + // Negative distances are not plausible dependencies. if (Val.isNegative()) { bool IsTrueDataDependence = (AIsWrite && !BIsWrite); if (IsTrueDataDependence && EnableForwardingConflictDetection && @@ -1244,15 +1254,6 @@ MemoryDepChecker::isDependent(const MemAccessInfo &A, unsigned AIdx, return Dependence::Unknown; } - unsigned Distance = (unsigned) Val.getZExtValue(); - - unsigned Stride = std::abs(StrideAPtr); - if (Stride > 1 && - areStridedAccessesIndependent(Distance, Stride, TypeByteSize)) { - DEBUG(dbgs() << "LAA: Strided accesses are independent\n"); - return Dependence::NoDep; - } - // Bail out early if passed-in parameters make vectorization not feasible. unsigned ForcedFactor = (VectorizerParams::VectorizationFactor ? VectorizerParams::VectorizationFactor : 1); diff --git a/llvm/test/Analysis/LoopAccessAnalysis/independent-interleaved.ll b/llvm/test/Analysis/LoopAccessAnalysis/independent-interleaved.ll new file mode 100644 index 000000000000..1be6ee6dc707 --- /dev/null +++ b/llvm/test/Analysis/LoopAccessAnalysis/independent-interleaved.ll @@ -0,0 +1,45 @@ +; RUN: opt < %s -store-to-load-forwarding-conflict-detection=false -loop-accesses -analyze | FileCheck %s + +; This test checks that we prove the strided accesses to be independent before +; concluding that there is a forward dependence. + +; struct pair { +; int x; +; int y; +; }; +; +; int independent_interleaved(struct pair *p, int z, int n) { +; int s = 0; +; for (int i = 0; i < n; i++) { +; p[i].y = z; +; s += p[i].x; +; } +; return s; +; } + +; CHECK: for.body: +; CHECK-NOT: Forward: +; CHECK-NOT: store i32 %z, i32* %p_i.y, align 8 -> +; CHECK-NOT: %0 = load i32, i32* %p_i.x, align 8 + +%pair = type { i32, i32 } +define i32 @independent_interleaved(%pair *%p, i64 %n, i32 %z) { +entry: + br label %for.body + +for.body: + %i = phi i64 [ %i.next, %for.body ], [ 0, %entry ] + %s = phi i32 [ %1, %for.body ], [ 0, %entry ] + %p_i.x = getelementptr inbounds %pair, %pair* %p, i64 %i, i32 0 + %p_i.y = getelementptr inbounds %pair, %pair* %p, i64 %i, i32 1 + store i32 %z, i32* %p_i.y, align 8 + %0 = load i32, i32* %p_i.x, align 8 + %1 = add nsw i32 %0, %s + %i.next = add nuw nsw i64 %i, 1 + %cond = icmp slt i64 %i.next, %n + br i1 %cond, label %for.body, label %for.end + +for.end: + %2 = phi i32 [ %1, %for.body ] + ret i32 %2 +}