From 995fd47944f471e985e34d7da8c0667059decbac Mon Sep 17 00:00:00 2001 From: Florian Hahn Date: Sat, 12 Apr 2025 20:05:37 +0100 Subject: [PATCH] [LAA] Make sure MaxVF for Store-Load forward safe dep distances is pow2. MaxVF computed in couldPreventStoreLoadFowrard may not be a power of 2, as CommonStride may not be a power-of-2. This can cause crashes after 78777a20. Use bit_floor to make sure it is a suitable power-of-2. Fixes https://github.com/llvm/llvm-project/issues/134696. --- llvm/lib/Analysis/LoopAccessAnalysis.cpp | 3 +- .../LoopVectorize/RISCV/safe-dep-distance.ll | 63 +++++++++++++++++++ 2 files changed, 65 insertions(+), 1 deletion(-) diff --git a/llvm/lib/Analysis/LoopAccessAnalysis.cpp b/llvm/lib/Analysis/LoopAccessAnalysis.cpp index a37ed5c706bd..0cb1332eb337 100644 --- a/llvm/lib/Analysis/LoopAccessAnalysis.cpp +++ b/llvm/lib/Analysis/LoopAccessAnalysis.cpp @@ -1781,7 +1781,8 @@ bool MemoryDepChecker::couldPreventStoreLoadForward(uint64_t Distance, MaxStoreLoadForwardSafeDistanceInBits && MaxVFWithoutSLForwardIssuesPowerOf2 != VectorizerParams::MaxVectorWidth * TypeByteSize) { - uint64_t MaxVF = MaxVFWithoutSLForwardIssuesPowerOf2 / CommonStride; + uint64_t MaxVF = + bit_floor(MaxVFWithoutSLForwardIssuesPowerOf2 / CommonStride); uint64_t MaxVFInBits = MaxVF * TypeByteSize * 8; MaxStoreLoadForwardSafeDistanceInBits = std::min(MaxStoreLoadForwardSafeDistanceInBits, MaxVFInBits); diff --git a/llvm/test/Transforms/LoopVectorize/RISCV/safe-dep-distance.ll b/llvm/test/Transforms/LoopVectorize/RISCV/safe-dep-distance.ll index ee9cb446183a..3cba3de13b03 100644 --- a/llvm/test/Transforms/LoopVectorize/RISCV/safe-dep-distance.ll +++ b/llvm/test/Transforms/LoopVectorize/RISCV/safe-dep-distance.ll @@ -256,3 +256,66 @@ loop: exit: ret void } + +@a = external global [10 x [12 x i16]] + +; Test case for https://github.com/llvm/llvm-project/issues/134696. +define void @safe_load_store_distance_not_pow_of_2(i64 %N) { +; CHECK-LABEL: @safe_load_store_distance_not_pow_of_2( +; CHECK-NEXT: entry: +; CHECK-NEXT: [[UMIN:%.*]] = call i64 @llvm.umin.i64(i64 [[N:%.*]], i64 1) +; CHECK-NEXT: [[TMP0:%.*]] = sub i64 [[N]], [[UMIN]] +; CHECK-NEXT: [[TMP1:%.*]] = udiv i64 [[TMP0]], 3 +; CHECK-NEXT: [[TMP2:%.*]] = add i64 [[UMIN]], [[TMP1]] +; CHECK-NEXT: [[TMP3:%.*]] = add i64 [[TMP2]], 1 +; CHECK-NEXT: [[MIN_ITERS_CHECK:%.*]] = icmp ule i64 [[TMP3]], 8 +; CHECK-NEXT: br i1 [[MIN_ITERS_CHECK]], label [[SCALAR_PH:%.*]], label [[VECTOR_PH:%.*]] +; CHECK: vector.ph: +; CHECK-NEXT: [[N_MOD_VF:%.*]] = urem i64 [[TMP3]], 8 +; CHECK-NEXT: [[TMP4:%.*]] = icmp eq i64 [[N_MOD_VF]], 0 +; CHECK-NEXT: [[TMP5:%.*]] = select i1 [[TMP4]], i64 8, i64 [[N_MOD_VF]] +; CHECK-NEXT: [[N_VEC:%.*]] = sub i64 [[TMP3]], [[TMP5]] +; CHECK-NEXT: [[TMP6:%.*]] = mul i64 [[N_VEC]], 3 +; CHECK-NEXT: br label [[VECTOR_BODY:%.*]] +; CHECK: vector.body: +; CHECK-NEXT: [[INDEX:%.*]] = phi i64 [ 0, [[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], [[VECTOR_BODY]] ] +; CHECK-NEXT: [[VEC_IND:%.*]] = phi <8 x i64> [ , [[VECTOR_PH]] ], [ [[VEC_IND_NEXT:%.*]], [[VECTOR_BODY]] ] +; CHECK-NEXT: [[TMP7:%.*]] = getelementptr [10 x [12 x i16]], ptr @a, i64 0, i64 8, <8 x i64> [[VEC_IND]] +; CHECK-NEXT: call void @llvm.masked.scatter.v8i16.v8p0(<8 x i16> zeroinitializer, <8 x ptr> [[TMP7]], i32 2, <8 x i1> splat (i1 true)) +; CHECK-NEXT: [[INDEX_NEXT]] = add nuw i64 [[INDEX]], 8 +; CHECK-NEXT: [[VEC_IND_NEXT]] = add <8 x i64> [[VEC_IND]], splat (i64 24) +; CHECK-NEXT: [[TMP8:%.*]] = icmp eq i64 [[INDEX_NEXT]], [[N_VEC]] +; CHECK-NEXT: br i1 [[TMP8]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop [[LOOP10:![0-9]+]] +; CHECK: middle.block: +; CHECK-NEXT: br label [[SCALAR_PH]] +; CHECK: scalar.ph: +; CHECK-NEXT: [[BC_RESUME_VAL:%.*]] = phi i64 [ [[TMP6]], [[MIDDLE_BLOCK]] ], [ 0, [[ENTRY:%.*]] ] +; CHECK-NEXT: br label [[LOOP:%.*]] +; CHECK: loop: +; CHECK-NEXT: [[IV:%.*]] = phi i64 [ [[BC_RESUME_VAL]], [[SCALAR_PH]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ] +; CHECK-NEXT: [[GEP:%.*]] = getelementptr [10 x [12 x i16]], ptr @a, i64 0, i64 0, i64 [[IV]] +; CHECK-NEXT: [[TMP9:%.*]] = load i16, ptr [[GEP]], align 2 +; CHECK-NEXT: [[GEP_OFF:%.*]] = getelementptr [10 x [12 x i16]], ptr @a, i64 0, i64 8, i64 [[IV]] +; CHECK-NEXT: store i16 0, ptr [[GEP_OFF]], align 2 +; CHECK-NEXT: [[IV_NEXT]] = add nsw i64 [[IV]], 3 +; CHECK-NEXT: [[CMP:%.*]] = icmp ult i64 [[IV]], [[N]] +; CHECK-NEXT: br i1 [[CMP]], label [[LOOP]], label [[EXIT:%.*]], !llvm.loop [[LOOP11:![0-9]+]] +; CHECK: exit: +; CHECK-NEXT: ret void +; +entry: + br label %loop + +loop: + %iv = phi i64 [ 0, %entry ], [ %iv.next, %loop ] + %gep = getelementptr [10 x [12 x i16]], ptr @a, i64 0, i64 0, i64 %iv + %1 = load i16, ptr %gep, align 2 + %gep.off = getelementptr [10 x [12 x i16]], ptr @a, i64 0, i64 8, i64 %iv + store i16 0, ptr %gep.off, align 2 + %iv.next = add nsw i64 %iv, 3 + %cmp = icmp ult i64 %iv, %N + br i1 %cmp, label %loop, label %exit + +exit: + ret void +}