diff --git a/llvm/lib/Transforms/Scalar/LoopInterchange.cpp b/llvm/lib/Transforms/Scalar/LoopInterchange.cpp index 61b86d2aecef0..b3dcd182fbf29 100644 --- a/llvm/lib/Transforms/Scalar/LoopInterchange.cpp +++ b/llvm/lib/Transforms/Scalar/LoopInterchange.cpp @@ -1141,17 +1141,15 @@ LoopInterchangeProfitability::isProfitablePerLoopCacheAnalysis( if (OuterLoopIt == CostMap.end()) return std::nullopt; + if (CC->getLoopCost(*OuterLoop) == CC->getLoopCost(*InnerLoop)) + return std::nullopt; unsigned InnerIndex = InnerLoopIt->second; unsigned OuterIndex = OuterLoopIt->second; LLVM_DEBUG(dbgs() << "InnerIndex = " << InnerIndex << ", OuterIndex = " << OuterIndex << "\n"); - if (InnerIndex < OuterIndex) - return std::optional(true); assert(InnerIndex != OuterIndex && "CostMap should assign unique " "numbers to each loop"); - if (CC->getLoopCost(*OuterLoop) == CC->getLoopCost(*InnerLoop)) - return std::nullopt; - return std::optional(false); + return std::optional(InnerIndex < OuterIndex); } std::optional diff --git a/llvm/test/Transforms/LoopInterchange/profitability-redundant-interchange.ll b/llvm/test/Transforms/LoopInterchange/profitability-redundant-interchange.ll new file mode 100644 index 0000000000000..ceea36ae7bc4a --- /dev/null +++ b/llvm/test/Transforms/LoopInterchange/profitability-redundant-interchange.ll @@ -0,0 +1,81 @@ +; RUN: opt < %s -passes=loop-interchange -cache-line-size=1 -pass-remarks-output=%t -disable-output \ +; RUN: -verify-dom-info -verify-loop-info +; RUN: FileCheck -input-file %t %s + + +; Test that loop-interchange doesn't undo its own transoformation. This is +; the case when the cost computed by CacheCost is the same for the loop of `j` +; and `k`. +; +; #define N 4 +; int a[N*N][N*N][N*N]; +; void f() { +; for (int i = 0; i < N; i++) +; for (int j = 1; j < 2*N; j++) +; for (int k = 1; k < 2*N; k++) +; a[i][k+1][j-1] -= a[i+N-1][k][j]; +; } + +; CHECK: --- !Passed +; CHECK-NEXT: Pass: loop-interchange +; CHECK-NEXT: Name: Interchanged +; CHECK-NEXT: Function: f +; CHECK-NEXT: Args: +; CHECK-NEXT: - String: Loop interchanged with enclosing loop. +; CHECK-NEXT: ... +; CHECK-NEXT: --- !Missed +; CHECK-NEXT: Pass: loop-interchange +; CHECK-NEXT: Name: Dependence +; CHECK-NEXT: Function: f +; CHECK-NEXT: Args: +; CHECK-NEXT: - String: Cannot interchange loops due to dependences. +; CHECK-NEXT: ... +; CHECK-NEXT: --- !Missed +; CHECK-NEXT: Pass: loop-interchange +; CHECK-NEXT: Name: InterchangeNotProfitable +; CHECK-NEXT: Function: f +; CHECK-NEXT: Args: +; CHECK-NEXT: - String: Interchanging loops is not considered to improve cache locality nor vectorization. +; CHECK-NEXT: ... + +@a = dso_local local_unnamed_addr global [16 x [16 x [16 x i32]]] zeroinitializer, align 4 + +define dso_local void @f() { +entry: + br label %for.cond1.preheader + +for.cond1.preheader: + %indvars.iv46 = phi i64 [ 0, %entry ], [ %indvars.iv.next47, %for.cond.cleanup3 ] + %0 = add nuw nsw i64 %indvars.iv46, 3 + br label %for.cond5.preheader + +for.cond5.preheader: + %indvars.iv41 = phi i64 [ 1, %for.cond1.preheader ], [ %indvars.iv.next42, %for.cond.cleanup7 ] + %1 = add nsw i64 %indvars.iv41, -1 + br label %for.body8 + +for.cond.cleanup3: + %indvars.iv.next47 = add nuw nsw i64 %indvars.iv46, 1 + %exitcond50 = icmp ne i64 %indvars.iv.next47, 4 + br i1 %exitcond50, label %for.cond1.preheader, label %for.cond.cleanup + +for.cond.cleanup7: + %indvars.iv.next42 = add nuw nsw i64 %indvars.iv41, 1 + %exitcond45 = icmp ne i64 %indvars.iv.next42, 8 + br i1 %exitcond45, label %for.cond5.preheader, label %for.cond.cleanup3 + +for.body8: + %indvars.iv = phi i64 [ 1, %for.cond5.preheader ], [ %indvars.iv.next, %for.body8 ] + %arrayidx12 = getelementptr inbounds nuw [16 x [16 x [16 x i32]]], ptr @a, i64 0, i64 %0, i64 %indvars.iv, i64 %indvars.iv41 + %2 = load i32, ptr %arrayidx12, align 4 + %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1 + %arrayidx20 = getelementptr inbounds [16 x [16 x [16 x i32]]], ptr @a, i64 0, i64 %indvars.iv46, i64 %indvars.iv.next, i64 %1 + %3 = load i32, ptr %arrayidx20, align 4 + %sub21 = sub nsw i32 %3, %2 + store i32 %sub21, ptr %arrayidx20, align 4 + %exitcond = icmp ne i64 %indvars.iv.next, 8 + br i1 %exitcond, label %for.body8, label %for.cond.cleanup7 + +for.cond.cleanup: + ret void +}