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[LV][VPlan] Prevent calculate cost for skiped instructions in precomputeCosts(). (llvm#127966)
Skip calculating instruction costs for exit conditions in precomputeCosts() when it should be skipped. Reported from: llvm#115744 (comment) Godbolt for reduced test cases: https://godbolt.org/z/fr4YMeqcv (cherry picked from commit 8009c1f)
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‎llvm/lib/Transforms/Vectorize/LoopVectorize.cpp‎

Lines changed: 3 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -7239,7 +7239,7 @@ LoopVectorizationPlanner::precomputeCosts(VPlan &Plan, ElementCount VF,
72397239
// Collect all exit conditions.
72407240
for (BasicBlock *EB : Exiting) {
72417241
auto *Term = dyn_cast<BranchInst>(EB->getTerminator());
7242-
if (!Term)
7242+
if (!Term || CostCtx.skipCostComputation(Term, VF.isVector()))
72437243
continue;
72447244
if (auto *CondI = dyn_cast<Instruction>(Term->getOperand(0))) {
72457245
ExitInstrs.insert(CondI);
@@ -7259,7 +7259,8 @@ LoopVectorizationPlanner::precomputeCosts(VPlan &Plan, ElementCount VF,
72597259
Cost += CondICost;
72607260
for (Value *Op : CondI->operands()) {
72617261
auto *OpI = dyn_cast<Instruction>(Op);
7262-
if (!OpI || any_of(OpI->users(), [&ExitInstrs, this](User *U) {
7262+
if (!OpI || CostCtx.skipCostComputation(OpI, VF.isVector()) ||
7263+
any_of(OpI->users(), [&ExitInstrs, this](User *U) {
72637264
return OrigLoop->contains(cast<Instruction>(U)->getParent()) &&
72647265
!ExitInstrs.contains(cast<Instruction>(U));
72657266
}))

‎llvm/test/Transforms/LoopVectorize/X86/cost-model.ll‎

Lines changed: 124 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1211,6 +1211,130 @@ exit:
12111211
ret i32 %or
12121212
}
12131213

1214+
; Check if the vplan-based cost model select same VF to the legacy cost model.
1215+
; Reduced from: https://github.com/llvm/llvm-project/issues/115744#issuecomment-2670479463
1216+
define i32 @g(i64 %n) {
1217+
; CHECK-LABEL: @g(
1218+
; CHECK-NEXT: iter.check:
1219+
; CHECK-NEXT: [[TMP0:%.*]] = trunc i64 [[N:%.*]] to i32
1220+
; CHECK-NEXT: [[TMP1:%.*]] = add i32 [[TMP0]], 1
1221+
; CHECK-NEXT: [[MIN_ITERS_CHECK:%.*]] = icmp ult i32 [[TMP1]], 4
1222+
; CHECK-NEXT: br i1 [[MIN_ITERS_CHECK]], label [[VEC_EPILOG_SCALAR_PH:%.*]], label [[VECTOR_SCEVCHECK:%.*]]
1223+
; CHECK: vector.scevcheck:
1224+
; CHECK-NEXT: [[TMP2:%.*]] = icmp ugt i64 [[N]], 4294967295
1225+
; CHECK-NEXT: br i1 [[TMP2]], label [[VEC_EPILOG_SCALAR_PH]], label [[VECTOR_MAIN_LOOP_ITER_CHECK:%.*]]
1226+
; CHECK: vector.main.loop.iter.check:
1227+
; CHECK-NEXT: [[MIN_ITERS_CHECK1:%.*]] = icmp ult i32 [[TMP1]], 16
1228+
; CHECK-NEXT: br i1 [[MIN_ITERS_CHECK1]], label [[VEC_EPILOG_PH:%.*]], label [[VECTOR_PH:%.*]]
1229+
; CHECK: vector.ph:
1230+
; CHECK-NEXT: [[N_MOD_VF:%.*]] = urem i32 [[TMP1]], 16
1231+
; CHECK-NEXT: [[N_VEC:%.*]] = sub i32 [[TMP1]], [[N_MOD_VF]]
1232+
; CHECK-NEXT: [[BROADCAST_SPLATINSERT:%.*]] = insertelement <4 x i64> poison, i64 [[N]], i64 0
1233+
; CHECK-NEXT: [[BROADCAST_SPLAT:%.*]] = shufflevector <4 x i64> [[BROADCAST_SPLATINSERT]], <4 x i64> poison, <4 x i32> zeroinitializer
1234+
; CHECK-NEXT: br label [[VECTOR_BODY:%.*]]
1235+
; CHECK: vector.body:
1236+
; CHECK-NEXT: [[INDEX:%.*]] = phi i32 [ 0, [[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], [[VECTOR_BODY]] ]
1237+
; CHECK-NEXT: [[VEC_IND:%.*]] = phi <4 x i32> [ <i32 0, i32 1, i32 2, i32 3>, [[VECTOR_PH]] ], [ [[VEC_IND_NEXT:%.*]], [[VECTOR_BODY]] ]
1238+
; CHECK-NEXT: [[VEC_PHI:%.*]] = phi <4 x i32> [ zeroinitializer, [[VECTOR_PH]] ], [ [[TMP15:%.*]], [[VECTOR_BODY]] ]
1239+
; CHECK-NEXT: [[VEC_PHI2:%.*]] = phi <4 x i32> [ zeroinitializer, [[VECTOR_PH]] ], [ [[TMP16:%.*]], [[VECTOR_BODY]] ]
1240+
; CHECK-NEXT: [[VEC_PHI3:%.*]] = phi <4 x i32> [ zeroinitializer, [[VECTOR_PH]] ], [ [[TMP17:%.*]], [[VECTOR_BODY]] ]
1241+
; CHECK-NEXT: [[VEC_PHI4:%.*]] = phi <4 x i32> [ zeroinitializer, [[VECTOR_PH]] ], [ [[TMP18:%.*]], [[VECTOR_BODY]] ]
1242+
; CHECK-NEXT: [[STEP_ADD:%.*]] = add <4 x i32> [[VEC_IND]], splat (i32 4)
1243+
; CHECK-NEXT: [[STEP_ADD_2:%.*]] = add <4 x i32> [[STEP_ADD]], splat (i32 4)
1244+
; CHECK-NEXT: [[STEP_ADD_3:%.*]] = add <4 x i32> [[STEP_ADD_2]], splat (i32 4)
1245+
; CHECK-NEXT: [[TMP3:%.*]] = zext <4 x i32> [[VEC_IND]] to <4 x i64>
1246+
; CHECK-NEXT: [[TMP4:%.*]] = zext <4 x i32> [[STEP_ADD]] to <4 x i64>
1247+
; CHECK-NEXT: [[TMP5:%.*]] = zext <4 x i32> [[STEP_ADD_2]] to <4 x i64>
1248+
; CHECK-NEXT: [[TMP6:%.*]] = zext <4 x i32> [[STEP_ADD_3]] to <4 x i64>
1249+
; CHECK-NEXT: [[TMP7:%.*]] = icmp eq <4 x i64> [[BROADCAST_SPLAT]], [[TMP3]]
1250+
; CHECK-NEXT: [[TMP8:%.*]] = icmp eq <4 x i64> [[BROADCAST_SPLAT]], [[TMP4]]
1251+
; CHECK-NEXT: [[TMP9:%.*]] = icmp eq <4 x i64> [[BROADCAST_SPLAT]], [[TMP5]]
1252+
; CHECK-NEXT: [[TMP10:%.*]] = icmp eq <4 x i64> [[BROADCAST_SPLAT]], [[TMP6]]
1253+
; CHECK-NEXT: [[TMP11:%.*]] = select <4 x i1> [[TMP7]], <4 x i32> zeroinitializer, <4 x i32> splat (i32 2)
1254+
; CHECK-NEXT: [[TMP12:%.*]] = select <4 x i1> [[TMP8]], <4 x i32> zeroinitializer, <4 x i32> splat (i32 2)
1255+
; CHECK-NEXT: [[TMP13:%.*]] = select <4 x i1> [[TMP9]], <4 x i32> zeroinitializer, <4 x i32> splat (i32 2)
1256+
; CHECK-NEXT: [[TMP14:%.*]] = select <4 x i1> [[TMP10]], <4 x i32> zeroinitializer, <4 x i32> splat (i32 2)
1257+
; CHECK-NEXT: [[TMP15]] = or <4 x i32> [[TMP11]], [[VEC_PHI]]
1258+
; CHECK-NEXT: [[TMP16]] = or <4 x i32> [[TMP12]], [[VEC_PHI2]]
1259+
; CHECK-NEXT: [[TMP17]] = or <4 x i32> [[TMP13]], [[VEC_PHI3]]
1260+
; CHECK-NEXT: [[TMP18]] = or <4 x i32> [[TMP14]], [[VEC_PHI4]]
1261+
; CHECK-NEXT: [[INDEX_NEXT]] = add nuw i32 [[INDEX]], 16
1262+
; CHECK-NEXT: [[VEC_IND_NEXT]] = add <4 x i32> [[STEP_ADD_3]], splat (i32 4)
1263+
; CHECK-NEXT: [[TMP19:%.*]] = icmp eq i32 [[INDEX_NEXT]], [[N_VEC]]
1264+
; CHECK-NEXT: br i1 [[TMP19]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop [[LOOP30:![0-9]+]]
1265+
; CHECK: middle.block:
1266+
; CHECK-NEXT: [[BIN_RDX:%.*]] = or <4 x i32> [[TMP16]], [[TMP15]]
1267+
; CHECK-NEXT: [[BIN_RDX5:%.*]] = or <4 x i32> [[TMP17]], [[BIN_RDX]]
1268+
; CHECK-NEXT: [[BIN_RDX6:%.*]] = or <4 x i32> [[TMP18]], [[BIN_RDX5]]
1269+
; CHECK-NEXT: [[TMP20:%.*]] = call i32 @llvm.vector.reduce.or.v4i32(<4 x i32> [[BIN_RDX6]])
1270+
; CHECK-NEXT: [[CMP_N:%.*]] = icmp eq i32 [[TMP1]], [[N_VEC]]
1271+
; CHECK-NEXT: br i1 [[CMP_N]], label [[EXIT:%.*]], label [[VEC_EPILOG_ITER_CHECK:%.*]]
1272+
; CHECK: vec.epilog.iter.check:
1273+
; CHECK-NEXT: [[N_VEC_REMAINING:%.*]] = sub i32 [[TMP1]], [[N_VEC]]
1274+
; CHECK-NEXT: [[MIN_EPILOG_ITERS_CHECK:%.*]] = icmp ult i32 [[N_VEC_REMAINING]], 4
1275+
; CHECK-NEXT: br i1 [[MIN_EPILOG_ITERS_CHECK]], label [[VEC_EPILOG_SCALAR_PH]], label [[VEC_EPILOG_PH]]
1276+
; CHECK: vec.epilog.ph:
1277+
; CHECK-NEXT: [[BC_RESUME_VAL:%.*]] = phi i32 [ [[N_VEC]], [[VEC_EPILOG_ITER_CHECK]] ], [ 0, [[VECTOR_MAIN_LOOP_ITER_CHECK]] ]
1278+
; CHECK-NEXT: [[BC_MERGE_RDX:%.*]] = phi i32 [ [[TMP20]], [[VEC_EPILOG_ITER_CHECK]] ], [ 0, [[VECTOR_MAIN_LOOP_ITER_CHECK]] ]
1279+
; CHECK-NEXT: [[N_MOD_VF7:%.*]] = urem i32 [[TMP1]], 4
1280+
; CHECK-NEXT: [[N_VEC8:%.*]] = sub i32 [[TMP1]], [[N_MOD_VF7]]
1281+
; CHECK-NEXT: [[DOTSPLATINSERT:%.*]] = insertelement <4 x i32> poison, i32 [[BC_RESUME_VAL]], i64 0
1282+
; CHECK-NEXT: [[DOTSPLAT:%.*]] = shufflevector <4 x i32> [[DOTSPLATINSERT]], <4 x i32> poison, <4 x i32> zeroinitializer
1283+
; CHECK-NEXT: [[INDUCTION:%.*]] = add <4 x i32> [[DOTSPLAT]], <i32 0, i32 1, i32 2, i32 3>
1284+
; CHECK-NEXT: [[TMP21:%.*]] = insertelement <4 x i32> zeroinitializer, i32 [[BC_MERGE_RDX]], i32 0
1285+
; CHECK-NEXT: [[BROADCAST_SPLATINSERT13:%.*]] = insertelement <4 x i64> poison, i64 [[N]], i64 0
1286+
; CHECK-NEXT: [[BROADCAST_SPLAT14:%.*]] = shufflevector <4 x i64> [[BROADCAST_SPLATINSERT13]], <4 x i64> poison, <4 x i32> zeroinitializer
1287+
; CHECK-NEXT: br label [[VEC_EPILOG_VECTOR_BODY:%.*]]
1288+
; CHECK: vec.epilog.vector.body:
1289+
; CHECK-NEXT: [[INDEX9:%.*]] = phi i32 [ [[BC_RESUME_VAL]], [[VEC_EPILOG_PH]] ], [ [[INDEX_NEXT15:%.*]], [[VEC_EPILOG_VECTOR_BODY]] ]
1290+
; CHECK-NEXT: [[VEC_IND10:%.*]] = phi <4 x i32> [ [[INDUCTION]], [[VEC_EPILOG_PH]] ], [ [[VEC_IND_NEXT11:%.*]], [[VEC_EPILOG_VECTOR_BODY]] ]
1291+
; CHECK-NEXT: [[VEC_PHI12:%.*]] = phi <4 x i32> [ [[TMP21]], [[VEC_EPILOG_PH]] ], [ [[TMP25:%.*]], [[VEC_EPILOG_VECTOR_BODY]] ]
1292+
; CHECK-NEXT: [[TMP22:%.*]] = zext <4 x i32> [[VEC_IND10]] to <4 x i64>
1293+
; CHECK-NEXT: [[TMP23:%.*]] = icmp eq <4 x i64> [[BROADCAST_SPLAT14]], [[TMP22]]
1294+
; CHECK-NEXT: [[TMP24:%.*]] = select <4 x i1> [[TMP23]], <4 x i32> zeroinitializer, <4 x i32> splat (i32 2)
1295+
; CHECK-NEXT: [[TMP25]] = or <4 x i32> [[TMP24]], [[VEC_PHI12]]
1296+
; CHECK-NEXT: [[INDEX_NEXT15]] = add nuw i32 [[INDEX9]], 4
1297+
; CHECK-NEXT: [[VEC_IND_NEXT11]] = add <4 x i32> [[VEC_IND10]], splat (i32 4)
1298+
; CHECK-NEXT: [[TMP26:%.*]] = icmp eq i32 [[INDEX_NEXT15]], [[N_VEC8]]
1299+
; CHECK-NEXT: br i1 [[TMP26]], label [[VEC_EPILOG_MIDDLE_BLOCK:%.*]], label [[VEC_EPILOG_VECTOR_BODY]], !llvm.loop [[LOOP31:![0-9]+]]
1300+
; CHECK: vec.epilog.middle.block:
1301+
; CHECK-NEXT: [[TMP27:%.*]] = call i32 @llvm.vector.reduce.or.v4i32(<4 x i32> [[TMP25]])
1302+
; CHECK-NEXT: [[CMP_N16:%.*]] = icmp eq i32 [[TMP1]], [[N_VEC8]]
1303+
; CHECK-NEXT: br i1 [[CMP_N16]], label [[EXIT]], label [[VEC_EPILOG_SCALAR_PH]]
1304+
; CHECK: vec.epilog.scalar.ph:
1305+
; CHECK-NEXT: [[BC_RESUME_VAL17:%.*]] = phi i32 [ [[N_VEC8]], [[VEC_EPILOG_MIDDLE_BLOCK]] ], [ 0, [[VECTOR_SCEVCHECK]] ], [ 0, [[ITER_CHECK:%.*]] ], [ [[N_VEC]], [[VEC_EPILOG_ITER_CHECK]] ]
1306+
; CHECK-NEXT: [[BC_MERGE_RDX18:%.*]] = phi i32 [ [[TMP27]], [[VEC_EPILOG_MIDDLE_BLOCK]] ], [ 0, [[VECTOR_SCEVCHECK]] ], [ 0, [[ITER_CHECK]] ], [ [[TMP20]], [[VEC_EPILOG_ITER_CHECK]] ]
1307+
; CHECK-NEXT: br label [[LOOP:%.*]]
1308+
; CHECK: loop:
1309+
; CHECK-NEXT: [[IV:%.*]] = phi i32 [ [[BC_RESUME_VAL17]], [[VEC_EPILOG_SCALAR_PH]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
1310+
; CHECK-NEXT: [[SELECT:%.*]] = phi i32 [ [[BC_MERGE_RDX18]], [[VEC_EPILOG_SCALAR_PH]] ], [ [[SELECT_NEXT:%.*]], [[LOOP]] ]
1311+
; CHECK-NEXT: [[IV_WIDEN:%.*]] = zext i32 [[IV]] to i64
1312+
; CHECK-NEXT: [[EXITCOND:%.*]] = icmp eq i64 [[N]], [[IV_WIDEN]]
1313+
; CHECK-NEXT: [[SELECT_I:%.*]] = select i1 [[EXITCOND]], i32 0, i32 2
1314+
; CHECK-NEXT: [[SELECT_NEXT]] = or i32 [[SELECT_I]], [[SELECT]]
1315+
; CHECK-NEXT: [[IV_NEXT]] = add i32 [[IV]], 1
1316+
; CHECK-NEXT: br i1 [[EXITCOND]], label [[EXIT]], label [[LOOP]], !llvm.loop [[LOOP32:![0-9]+]]
1317+
; CHECK: exit:
1318+
; CHECK-NEXT: [[SELECT_NEXT_LCSSA:%.*]] = phi i32 [ [[SELECT_NEXT]], [[LOOP]] ], [ [[TMP20]], [[MIDDLE_BLOCK]] ], [ [[TMP27]], [[VEC_EPILOG_MIDDLE_BLOCK]] ]
1319+
; CHECK-NEXT: ret i32 [[SELECT_NEXT_LCSSA]]
1320+
;
1321+
entry:
1322+
br label %loop
1323+
1324+
loop:
1325+
%iv = phi i32 [ 0, %entry ], [ %iv.next, %loop ]
1326+
%select = phi i32 [ 0, %entry ], [ %select.next, %loop ]
1327+
%iv.widen = zext i32 %iv to i64
1328+
%exitcond = icmp eq i64 %n, %iv.widen
1329+
%select.i = select i1 %exitcond, i32 0, i32 2
1330+
%select.next = or i32 %select.i, %select
1331+
%iv.next = add i32 %iv, 1
1332+
br i1 %exitcond, label %exit, label %loop
1333+
1334+
exit:
1335+
ret i32 %select.next
1336+
}
1337+
12141338
declare void @llvm.assume(i1 noundef) #0
12151339

12161340
attributes #0 = { "target-cpu"="penryn" }

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