[llvm] [LV] Incorporate trip counts into selection of scalable VFs (PR #80926)

Florian Hahn via llvm-commits llvm-commits at lists.llvm.org
Wed Feb 14 06:47:46 PST 2024


================
@@ -8,50 +8,51 @@ define void @clamped_tc_8(ptr nocapture %dst, i32 %n, i64 %val){
 ; CHECK-NEXT:    br i1 false, label [[SCALAR_PH:%.*]], label [[VECTOR_PH:%.*]]
 ; CHECK:       vector.ph:
 ; CHECK-NEXT:    [[TMP0:%.*]] = call i64 @llvm.vscale.i64()
-; CHECK-NEXT:    [[TMP1:%.*]] = mul i64 [[TMP0]], 8
+; CHECK-NEXT:    [[TMP1:%.*]] = mul i64 [[TMP0]], 4
 ; CHECK-NEXT:    [[TMP2:%.*]] = call i64 @llvm.vscale.i64()
-; CHECK-NEXT:    [[TMP3:%.*]] = mul i64 [[TMP2]], 8
+; CHECK-NEXT:    [[TMP3:%.*]] = mul i64 [[TMP2]], 4
 ; CHECK-NEXT:    [[TMP4:%.*]] = sub i64 [[TMP3]], 1
 ; CHECK-NEXT:    [[N_RND_UP:%.*]] = add i64 8, [[TMP4]]
 ; CHECK-NEXT:    [[N_MOD_VF:%.*]] = urem i64 [[N_RND_UP]], [[TMP1]]
 ; CHECK-NEXT:    [[N_VEC:%.*]] = sub i64 [[N_RND_UP]], [[N_MOD_VF]]
 ; CHECK-NEXT:    [[IND_END:%.*]] = getelementptr i8, ptr [[DST]], i64 [[N_VEC]]
 ; CHECK-NEXT:    [[TMP5:%.*]] = call i64 @llvm.vscale.i64()
-; CHECK-NEXT:    [[TMP6:%.*]] = mul i64 [[TMP5]], 8
+; CHECK-NEXT:    [[TMP6:%.*]] = mul i64 [[TMP5]], 4
 ; CHECK-NEXT:    [[TMP7:%.*]] = call i64 @llvm.vscale.i64()
-; CHECK-NEXT:    [[TMP8:%.*]] = mul i64 [[TMP7]], 8
+; CHECK-NEXT:    [[TMP8:%.*]] = mul i64 [[TMP7]], 4
 ; CHECK-NEXT:    [[TMP9:%.*]] = sub i64 8, [[TMP8]]
 ; CHECK-NEXT:    [[TMP10:%.*]] = icmp ugt i64 8, [[TMP8]]
 ; CHECK-NEXT:    [[TMP11:%.*]] = select i1 [[TMP10]], i64 [[TMP9]], i64 0
-; CHECK-NEXT:    [[ACTIVE_LANE_MASK_ENTRY:%.*]] = call <vscale x 8 x i1> @llvm.get.active.lane.mask.nxv8i1.i64(i64 0, i64 8)
-; CHECK-NEXT:    [[TMP12:%.*]] = call <vscale x 8 x i64> @llvm.experimental.stepvector.nxv8i64()
-; CHECK-NEXT:    [[TMP13:%.*]] = add <vscale x 8 x i64> [[TMP12]], zeroinitializer
-; CHECK-NEXT:    [[TMP14:%.*]] = mul <vscale x 8 x i64> [[TMP13]], shufflevector (<vscale x 8 x i64> insertelement (<vscale x 8 x i64> poison, i64 1, i64 0), <vscale x 8 x i64> poison, <vscale x 8 x i32> zeroinitializer)
-; CHECK-NEXT:    [[INDUCTION:%.*]] = add <vscale x 8 x i64> zeroinitializer, [[TMP14]]
+; CHECK-NEXT:    [[ACTIVE_LANE_MASK_ENTRY:%.*]] = call <vscale x 4 x i1> @llvm.get.active.lane.mask.nxv4i1.i64(i64 0, i64 8)
+; CHECK-NEXT:    [[TMP12:%.*]] = call <vscale x 4 x i64> @llvm.experimental.stepvector.nxv4i64()
+; CHECK-NEXT:    [[TMP13:%.*]] = add <vscale x 4 x i64> [[TMP12]], zeroinitializer
+; CHECK-NEXT:    [[TMP14:%.*]] = mul <vscale x 4 x i64> [[TMP13]], shufflevector (<vscale x 4 x i64> insertelement (<vscale x 4 x i64> poison, i64 1, i64 0), <vscale x 4 x i64> poison, <vscale x 4 x i32> zeroinitializer)
+; CHECK-NEXT:    [[INDUCTION:%.*]] = add <vscale x 4 x i64> zeroinitializer, [[TMP14]]
 ; CHECK-NEXT:    [[TMP15:%.*]] = call i64 @llvm.vscale.i64()
-; CHECK-NEXT:    [[TMP16:%.*]] = mul i64 [[TMP15]], 8
+; CHECK-NEXT:    [[TMP16:%.*]] = mul i64 [[TMP15]], 4
 ; CHECK-NEXT:    [[TMP17:%.*]] = mul i64 1, [[TMP16]]
-; CHECK-NEXT:    [[DOTSPLATINSERT:%.*]] = insertelement <vscale x 8 x i64> poison, i64 [[TMP17]], i64 0
-; CHECK-NEXT:    [[DOTSPLAT:%.*]] = shufflevector <vscale x 8 x i64> [[DOTSPLATINSERT]], <vscale x 8 x i64> poison, <vscale x 8 x i32> zeroinitializer
-; CHECK-NEXT:    [[BROADCAST_SPLATINSERT:%.*]] = insertelement <vscale x 8 x i64> poison, i64 [[VAL]], i64 0
-; CHECK-NEXT:    [[BROADCAST_SPLAT:%.*]] = shufflevector <vscale x 8 x i64> [[BROADCAST_SPLATINSERT]], <vscale x 8 x i64> poison, <vscale x 8 x i32> zeroinitializer
+; CHECK-NEXT:    [[DOTSPLATINSERT:%.*]] = insertelement <vscale x 4 x i64> poison, i64 [[TMP17]], i64 0
+; CHECK-NEXT:    [[DOTSPLAT:%.*]] = shufflevector <vscale x 4 x i64> [[DOTSPLATINSERT]], <vscale x 4 x i64> poison, <vscale x 4 x i32> zeroinitializer
+; CHECK-NEXT:    [[BROADCAST_SPLATINSERT:%.*]] = insertelement <vscale x 4 x i64> poison, i64 [[VAL]], i64 0
+; CHECK-NEXT:    [[BROADCAST_SPLAT:%.*]] = shufflevector <vscale x 4 x i64> [[BROADCAST_SPLATINSERT]], <vscale x 4 x i64> poison, <vscale x 4 x i32> zeroinitializer
 ; CHECK-NEXT:    br label [[VECTOR_BODY:%.*]]
 ; CHECK:       vector.body:
 ; CHECK-NEXT:    [[INDEX:%.*]] = phi i64 [ 0, [[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], [[VECTOR_BODY]] ]
-; CHECK-NEXT:    [[ACTIVE_LANE_MASK:%.*]] = phi <vscale x 8 x i1> [ [[ACTIVE_LANE_MASK_ENTRY]], [[VECTOR_PH]] ], [ [[ACTIVE_LANE_MASK_NEXT:%.*]], [[VECTOR_BODY]] ]
-; CHECK-NEXT:    [[VEC_IND:%.*]] = phi <vscale x 8 x i64> [ [[INDUCTION]], [[VECTOR_PH]] ], [ [[VEC_IND_NEXT:%.*]], [[VECTOR_BODY]] ]
+; CHECK-NEXT:    [[ACTIVE_LANE_MASK:%.*]] = phi <vscale x 4 x i1> [ [[ACTIVE_LANE_MASK_ENTRY]], [[VECTOR_PH]] ], [ [[ACTIVE_LANE_MASK_NEXT:%.*]], [[VECTOR_BODY]] ]
+; CHECK-NEXT:    [[VEC_IND:%.*]] = phi <vscale x 4 x i64> [ [[INDUCTION]], [[VECTOR_PH]] ], [ [[VEC_IND_NEXT:%.*]], [[VECTOR_BODY]] ]
 ; CHECK-NEXT:    [[TMP18:%.*]] = add i64 [[INDEX]], 0
 ; CHECK-NEXT:    [[NEXT_GEP:%.*]] = getelementptr i8, ptr [[DST]], i64 [[TMP18]]
-; CHECK-NEXT:    [[TMP19:%.*]] = shl nuw nsw <vscale x 8 x i64> [[VEC_IND]], shufflevector (<vscale x 8 x i64> insertelement (<vscale x 8 x i64> poison, i64 3, i64 0), <vscale x 8 x i64> poison, <vscale x 8 x i32> zeroinitializer)
-; CHECK-NEXT:    [[TMP20:%.*]] = lshr <vscale x 8 x i64> [[BROADCAST_SPLAT]], [[TMP19]]
-; CHECK-NEXT:    [[TMP21:%.*]] = trunc <vscale x 8 x i64> [[TMP20]] to <vscale x 8 x i8>
+; CHECK-NEXT:    [[TMP19:%.*]] = shl nuw nsw <vscale x 4 x i64> [[VEC_IND]], shufflevector (<vscale x 4 x i64> insertelement (<vscale x 4 x i64> poison, i64 3, i64 0), <vscale x 4 x i64> poison, <vscale x 4 x i32> zeroinitializer)
+; CHECK-NEXT:    [[TMP20:%.*]] = lshr <vscale x 4 x i64> [[BROADCAST_SPLAT]], [[TMP19]]
+; CHECK-NEXT:    [[TMP21:%.*]] = trunc <vscale x 4 x i64> [[TMP20]] to <vscale x 4 x i8>
 ; CHECK-NEXT:    [[TMP22:%.*]] = getelementptr i8, ptr [[NEXT_GEP]], i32 0
-; CHECK-NEXT:    call void @llvm.masked.store.nxv8i8.p0(<vscale x 8 x i8> [[TMP21]], ptr [[TMP22]], i32 1, <vscale x 8 x i1> [[ACTIVE_LANE_MASK]])
+; CHECK-NEXT:    call void @llvm.masked.store.nxv4i8.p0(<vscale x 4 x i8> [[TMP21]], ptr [[TMP22]], i32 1, <vscale x 4 x i1> [[ACTIVE_LANE_MASK]])
 ; CHECK-NEXT:    [[INDEX_NEXT]] = add i64 [[INDEX]], [[TMP6]]
-; CHECK-NEXT:    [[ACTIVE_LANE_MASK_NEXT]] = call <vscale x 8 x i1> @llvm.get.active.lane.mask.nxv8i1.i64(i64 [[INDEX]], i64 [[TMP11]])
-; CHECK-NEXT:    [[VEC_IND_NEXT]] = add <vscale x 8 x i64> [[VEC_IND]], [[DOTSPLAT]]
-; CHECK-NEXT:    [[TMP23:%.*]] = xor <vscale x 8 x i1> [[ACTIVE_LANE_MASK_NEXT]], shufflevector (<vscale x 8 x i1> insertelement (<vscale x 8 x i1> poison, i1 true, i64 0), <vscale x 8 x i1> poison, <vscale x 8 x i32> zeroinitializer)
-; CHECK-NEXT:    br i1 true, label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop [[LOOP0:![0-9]+]]
+; CHECK-NEXT:    [[ACTIVE_LANE_MASK_NEXT]] = call <vscale x 4 x i1> @llvm.get.active.lane.mask.nxv4i1.i64(i64 [[INDEX]], i64 [[TMP11]])
+; CHECK-NEXT:    [[TMP23:%.*]] = xor <vscale x 4 x i1> [[ACTIVE_LANE_MASK_NEXT]], shufflevector (<vscale x 4 x i1> insertelement (<vscale x 4 x i1> poison, i1 true, i64 0), <vscale x 4 x i1> poison, <vscale x 4 x i32> zeroinitializer)
+; CHECK-NEXT:    [[VEC_IND_NEXT]] = add <vscale x 4 x i64> [[VEC_IND]], [[DOTSPLAT]]
+; CHECK-NEXT:    [[TMP24:%.*]] = extractelement <vscale x 4 x i1> [[TMP23]], i32 0
+; CHECK-NEXT:    br i1 [[TMP24]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop [[LOOP0:![0-9]+]]
----------------
fhahn wrote:

The simplification is handled here: https://github.com/llvm/llvm-project/blob/main/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp#L612

Looks like this needs to be updated to account for info about the minimum value of `vscale`

https://github.com/llvm/llvm-project/pull/80926


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