Index: llvm/lib/Analysis/ScalarEvolution.cpp =================================================================== --- llvm/lib/Analysis/ScalarEvolution.cpp +++ llvm/lib/Analysis/ScalarEvolution.cpp @@ -1176,6 +1176,14 @@ return getTruncateOrZeroExtend(SZ->getOperand(), Ty, Depth + 1); if (Depth > MaxCastDepth) { + // Return zero if truncating to known zeros. Since we're already at maximum + // desired recursion depth, only do this for unknown SCEV's. + if (const SCEVUnknown *U = dyn_cast(Op)) { + uint32_t MinTrailingZeros = GetMinTrailingZeros(Op); + if (MinTrailingZeros >= getTypeSizeInBits(Ty)) + return getZero(Ty); + } + SCEV *S = new (SCEVAllocator) SCEVTruncateExpr(ID.Intern(SCEVAllocator), Op, Ty); UniqueSCEVs.InsertNode(S, IP); @@ -1222,6 +1230,11 @@ return getAddRecExpr(Operands, AddRec->getLoop(), SCEV::FlagAnyWrap); } + // Return zero if truncating to known zeros. + uint32_t MinTrailingZeros = GetMinTrailingZeros(Op); + if (MinTrailingZeros >= getTypeSizeInBits(Ty)) + return getZero(Ty); + // The cast wasn't folded; create an explicit cast node. We can reuse // the existing insert position since if we get here, we won't have // made any changes which would invalidate it. Index: llvm/test/Analysis/ScalarEvolution/trunc-simplify.ll =================================================================== --- llvm/test/Analysis/ScalarEvolution/trunc-simplify.ll +++ llvm/test/Analysis/ScalarEvolution/trunc-simplify.ll @@ -24,3 +24,25 @@ %c = trunc i32 %b to i8 ret i8 %c } + +; Check that we truncate to zero values assumed to have at least as many +; trailing zeros as the target type. +; CHECK-LABEL: @trunc_to_assumed_zeros +define i8 @trunc_to_assumed_zeros(i32* %p) { + %a = load i32, i32* %p + %and = and i32 %a, 255 + %cmp = icmp eq i32 %and, 0 + tail call void @llvm.assume(i1 %cmp) + ; CHECK: %c + ; CHECK-NEXT: --> 0 + %c = trunc i32 %a to i8 + ; CHECK: %d + ; CHECK-NEXT: --> false + %d = trunc i32 %a to i1 + ; CHECK: %e + ; CHECK-NEXT: --> (trunc i32 %a to i16) + %e = trunc i32 %a to i16 + ret i8 %c +} + +declare void @llvm.assume(i1 noundef) nofree nosync nounwind willreturn Index: llvm/test/Transforms/LoopVectorize/dont-fold-tail-for-assumed-divisible-TC.ll =================================================================== --- llvm/test/Transforms/LoopVectorize/dont-fold-tail-for-assumed-divisible-TC.ll +++ llvm/test/Transforms/LoopVectorize/dont-fold-tail-for-assumed-divisible-TC.ll @@ -3,7 +3,7 @@ target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128" -; TODO: Make sure the loop is vectorized under -Os without folding its tail based on +; Make sure the loop is vectorized under -Os without folding its tail based on ; its trip-count's lower bits assumed to be zero. define dso_local void @assumeAlignedTC(i32* noalias nocapture %A, i32* %p) optsize { @@ -13,57 +13,28 @@ ; CHECK-NEXT: [[AND:%.*]] = and i32 [[N]], 3 ; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[AND]], 0 ; CHECK-NEXT: tail call void @llvm.assume(i1 [[CMP]]) -; CHECK-NEXT: br i1 false, label [[SCALAR_PH:%.*]], label [[VECTOR_PH:%.*]] +; CHECK-NEXT: [[MIN_ITERS_CHECK:%.*]] = icmp ult i32 [[N]], 4 +; CHECK-NEXT: br i1 [[MIN_ITERS_CHECK]], label [[SCALAR_PH:%.*]], label [[VECTOR_PH:%.*]] ; CHECK: vector.ph: -; CHECK-NEXT: [[N_RND_UP:%.*]] = add i32 [[N]], 3 -; CHECK-NEXT: [[N_MOD_VF:%.*]] = urem i32 [[N_RND_UP]], 4 -; CHECK-NEXT: [[N_VEC:%.*]] = sub i32 [[N_RND_UP]], [[N_MOD_VF]] -; CHECK-NEXT: [[TRIP_COUNT_MINUS_1:%.*]] = sub i32 [[N]], 1 -; CHECK-NEXT: [[BROADCAST_SPLATINSERT:%.*]] = insertelement <4 x i32> poison, i32 [[TRIP_COUNT_MINUS_1]], i32 0 -; CHECK-NEXT: [[BROADCAST_SPLAT:%.*]] = shufflevector <4 x i32> [[BROADCAST_SPLATINSERT]], <4 x i32> poison, <4 x i32> zeroinitializer +; CHECK-NEXT: [[N_MOD_VF:%.*]] = urem i32 [[N]], 4 +; CHECK-NEXT: [[N_VEC:%.*]] = sub i32 [[N]], [[N_MOD_VF]] ; CHECK-NEXT: br label [[VECTOR_BODY:%.*]] ; CHECK: vector.body: -; CHECK-NEXT: [[INDEX:%.*]] = phi i32 [ 0, [[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], [[PRED_STORE_CONTINUE6:%.*]] ] -; CHECK-NEXT: [[VEC_IND:%.*]] = phi <4 x i32> [ , [[VECTOR_PH]] ], [ [[VEC_IND_NEXT:%.*]], [[PRED_STORE_CONTINUE6]] ] -; CHECK-NEXT: [[TMP0:%.*]] = icmp ule <4 x i32> [[VEC_IND]], [[BROADCAST_SPLAT]] -; CHECK-NEXT: [[TMP1:%.*]] = extractelement <4 x i1> [[TMP0]], i32 0 -; CHECK-NEXT: br i1 [[TMP1]], label [[PRED_STORE_IF:%.*]], label [[PRED_STORE_CONTINUE:%.*]] -; CHECK: pred.store.if: -; CHECK-NEXT: [[TMP2:%.*]] = add i32 [[INDEX]], 0 -; CHECK-NEXT: [[TMP3:%.*]] = getelementptr inbounds i32, i32* [[A:%.*]], i32 [[TMP2]] -; CHECK-NEXT: store i32 13, i32* [[TMP3]], align 1 -; CHECK-NEXT: br label [[PRED_STORE_CONTINUE]] -; CHECK: pred.store.continue: -; CHECK-NEXT: [[TMP4:%.*]] = extractelement <4 x i1> [[TMP0]], i32 1 -; CHECK-NEXT: br i1 [[TMP4]], label [[PRED_STORE_IF1:%.*]], label [[PRED_STORE_CONTINUE2:%.*]] -; CHECK: pred.store.if1: -; CHECK-NEXT: [[TMP5:%.*]] = add i32 [[INDEX]], 1 -; CHECK-NEXT: [[TMP6:%.*]] = getelementptr inbounds i32, i32* [[A]], i32 [[TMP5]] -; CHECK-NEXT: store i32 13, i32* [[TMP6]], align 1 -; CHECK-NEXT: br label [[PRED_STORE_CONTINUE2]] -; CHECK: pred.store.continue2: -; CHECK-NEXT: [[TMP7:%.*]] = extractelement <4 x i1> [[TMP0]], i32 2 -; CHECK-NEXT: br i1 [[TMP7]], label [[PRED_STORE_IF3:%.*]], label [[PRED_STORE_CONTINUE4:%.*]] -; CHECK: pred.store.if3: -; CHECK-NEXT: [[TMP8:%.*]] = add i32 [[INDEX]], 2 -; CHECK-NEXT: [[TMP9:%.*]] = getelementptr inbounds i32, i32* [[A]], i32 [[TMP8]] -; CHECK-NEXT: store i32 13, i32* [[TMP9]], align 1 -; CHECK-NEXT: br label [[PRED_STORE_CONTINUE4]] -; CHECK: pred.store.continue4: -; CHECK-NEXT: [[TMP10:%.*]] = extractelement <4 x i1> [[TMP0]], i32 3 -; CHECK-NEXT: br i1 [[TMP10]], label [[PRED_STORE_IF5:%.*]], label [[PRED_STORE_CONTINUE6]] -; CHECK: pred.store.if5: -; CHECK-NEXT: [[TMP11:%.*]] = add i32 [[INDEX]], 3 -; CHECK-NEXT: [[TMP12:%.*]] = getelementptr inbounds i32, i32* [[A]], i32 [[TMP11]] -; CHECK-NEXT: store i32 13, i32* [[TMP12]], align 1 -; CHECK-NEXT: br label [[PRED_STORE_CONTINUE6]] -; CHECK: pred.store.continue6: +; CHECK-NEXT: [[INDEX:%.*]] = phi i32 [ 0, [[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], [[VECTOR_BODY]] ] +; CHECK-NEXT: [[BROADCAST_SPLATINSERT:%.*]] = insertelement <4 x i32> poison, i32 [[INDEX]], i32 0 +; CHECK-NEXT: [[BROADCAST_SPLAT:%.*]] = shufflevector <4 x i32> [[BROADCAST_SPLATINSERT]], <4 x i32> poison, <4 x i32> zeroinitializer +; CHECK-NEXT: [[INDUCTION:%.*]] = add <4 x i32> [[BROADCAST_SPLAT]], +; CHECK-NEXT: [[TMP0:%.*]] = add i32 [[INDEX]], 0 +; CHECK-NEXT: [[TMP1:%.*]] = getelementptr inbounds i32, i32* [[A:%.*]], i32 [[TMP0]] +; CHECK-NEXT: [[TMP2:%.*]] = getelementptr inbounds i32, i32* [[TMP1]], i32 0 +; CHECK-NEXT: [[TMP3:%.*]] = bitcast i32* [[TMP2]] to <4 x i32>* +; CHECK-NEXT: store <4 x i32> , <4 x i32>* [[TMP3]], align 1 ; CHECK-NEXT: [[INDEX_NEXT]] = add i32 [[INDEX]], 4 -; CHECK-NEXT: [[VEC_IND_NEXT]] = add <4 x i32> [[VEC_IND]], -; CHECK-NEXT: [[TMP13:%.*]] = icmp eq i32 [[INDEX_NEXT]], [[N_VEC]] -; CHECK-NEXT: br i1 [[TMP13]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], [[LOOP0:!llvm.loop !.*]] +; CHECK-NEXT: [[TMP4:%.*]] = icmp eq i32 [[INDEX_NEXT]], [[N_VEC]] +; CHECK-NEXT: br i1 [[TMP4]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], [[LOOP0:!llvm.loop !.*]] ; CHECK: middle.block: -; CHECK-NEXT: br i1 true, label [[EXIT:%.*]], label [[SCALAR_PH]] +; CHECK-NEXT: [[CMP_N:%.*]] = icmp eq i32 [[N]], [[N_VEC]] +; CHECK-NEXT: br i1 [[CMP_N]], label [[EXIT:%.*]], label [[SCALAR_PH]] ; CHECK: scalar.ph: ; CHECK-NEXT: [[BC_RESUME_VAL:%.*]] = phi i32 [ [[N_VEC]], [[MIDDLE_BLOCK]] ], [ 0, [[ENTRY:%.*]] ] ; CHECK-NEXT: br label [[LOOP:%.*]]