[LV][VPlan] Implement VPlan-based cost for exit condition. #125640
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@llvm/pr-subscribers-llvm-transforms @llvm/pr-subscribers-vectorizers Author: Elvis Wang (ElvisWang123) ChangesThis patch tried to model the cost of exit conditions through vplan-based cost model.
The branch instruction is already implemented by the VPRegionBlock so we only need to calculate the cost of icmp. If the VF is same as the trip count of the loop, the cost of the BranchOnCount is free. There are some tests changes for following reasons.
Patch is 76.32 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/125640.diff 14 Files Affected:
diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index 29f3940ed6fa7a..49159ad40fafc7 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -7238,45 +7238,6 @@ LoopVectorizationPlanner::precomputeCosts(VPlan &Plan, ElementCount VF,
}
}
- /// Compute the cost of all exiting conditions of the loop using the legacy
- /// cost model. This is to match the legacy behavior, which adds the cost of
- /// all exit conditions. Note that this over-estimates the cost, as there will
- /// be a single condition to control the vector loop.
- SmallVector<BasicBlock *> Exiting;
- CM.TheLoop->getExitingBlocks(Exiting);
- SetVector<Instruction *> ExitInstrs;
- // Collect all exit conditions.
- for (BasicBlock *EB : Exiting) {
- auto *Term = dyn_cast<BranchInst>(EB->getTerminator());
- if (!Term)
- continue;
- if (auto *CondI = dyn_cast<Instruction>(Term->getOperand(0))) {
- ExitInstrs.insert(CondI);
- }
- }
- // Compute the cost of all instructions only feeding the exit conditions.
- for (unsigned I = 0; I != ExitInstrs.size(); ++I) {
- Instruction *CondI = ExitInstrs[I];
- if (!OrigLoop->contains(CondI) ||
- !CostCtx.SkipCostComputation.insert(CondI).second)
- continue;
- InstructionCost CondICost = CostCtx.getLegacyCost(CondI, VF);
- LLVM_DEBUG({
- dbgs() << "Cost of " << CondICost << " for VF " << VF
- << ": exit condition instruction " << *CondI << "\n";
- });
- Cost += CondICost;
- for (Value *Op : CondI->operands()) {
- auto *OpI = dyn_cast<Instruction>(Op);
- if (!OpI || any_of(OpI->users(), [&ExitInstrs, this](User *U) {
- return OrigLoop->contains(cast<Instruction>(U)->getParent()) &&
- !ExitInstrs.contains(cast<Instruction>(U));
- }))
- continue;
- ExitInstrs.insert(OpI);
- }
- }
-
// The legacy cost model has special logic to compute the cost of in-loop
// reductions, which may be smaller than the sum of all instructions involved
// in the reduction.
diff --git a/llvm/lib/Transforms/Vectorize/VPlan.h b/llvm/lib/Transforms/Vectorize/VPlan.h
index db45ad8aadbbe3..a46a5af6151f8b 100644
--- a/llvm/lib/Transforms/Vectorize/VPlan.h
+++ b/llvm/lib/Transforms/Vectorize/VPlan.h
@@ -1318,10 +1318,7 @@ class VPInstruction : public VPRecipeWithIRFlags,
/// Return the cost of this VPInstruction.
InstructionCost computeCost(ElementCount VF,
- VPCostContext &Ctx) const override {
- // TODO: Compute accurate cost after retiring the legacy cost model.
- return 0;
- }
+ VPCostContext &Ctx) const override;
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
/// Print the VPInstruction to \p O.
diff --git a/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp b/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
index aa5f92b235555e..6b80fda76d0f19 100644
--- a/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
+++ b/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
@@ -823,6 +823,29 @@ bool VPInstruction::onlyFirstPartUsed(const VPValue *Op) const {
llvm_unreachable("switch should return");
}
+InstructionCost VPInstruction::computeCost(ElementCount VF,
+ VPCostContext &Ctx) const {
+ Type *ValTy = Ctx.Types.inferScalarType(getOperand(0));
+
+ switch (getOpcode()) {
+ case VPInstruction::BranchOnCount: {
+ // BranchOnCount will genearte icmp_eq + br instructions and the
+ // cost of branch will be calculated in VPRegionBlock.
+ // If the vector loop only executed once, ignore the cost of the cmp.
+ auto TC = dyn_cast_if_present<ConstantInt>(
+ getParent()->getPlan()->getTripCount()->getUnderlyingValue());
+ if (TC && VF.isFixed() && TC->getSExtValue() == VF.getFixedValue())
+ return 0;
+ return Ctx.TTI.getCmpSelInstrCost(Instruction::ICmp, ValTy, nullptr,
+ CmpInst::ICMP_EQ, Ctx.CostKind);
+ }
+ default:
+ // TODO: Compute accurate cost after retiring the legacy cost model.
+ return 0;
+ };
+ llvm_unreachable("switch should return");
+}
+
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
void VPInstruction::dump() const {
VPSlotTracker SlotTracker(getParent()->getPlan());
diff --git a/llvm/test/Transforms/LoopVectorize/AArch64/clamped-trip-count.ll b/llvm/test/Transforms/LoopVectorize/AArch64/clamped-trip-count.ll
index 5b77ced73bce0a..b510c50450055c 100644
--- a/llvm/test/Transforms/LoopVectorize/AArch64/clamped-trip-count.ll
+++ b/llvm/test/Transforms/LoopVectorize/AArch64/clamped-trip-count.ll
@@ -8,39 +8,41 @@ define void @clamped_tc_8(ptr nocapture %dst, i32 %n, i64 %val) vscale_range(1,1
; 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]], 2
; CHECK-NEXT: [[TMP4:%.*]] = sub i64 [[TMP1]], 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: [[TMP5:%.*]] = call i64 @llvm.vscale.i64()
-; CHECK-NEXT: [[TMP6:%.*]] = mul i64 [[TMP5]], 8
+; CHECK-NEXT: [[TMP6:%.*]] = mul i64 [[TMP5]], 2
; CHECK-NEXT: [[IND_END:%.*]] = getelementptr i8, ptr [[DST]], i64 [[N_VEC]]
-; 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: [[TMP8:%.*]] = call <vscale x 8 x i64> @llvm.stepvector.nxv8i64()
-; CHECK-NEXT: [[TMP7:%.*]] = mul <vscale x 8 x i64> [[TMP8]], splat (i64 1)
-; CHECK-NEXT: [[INDUCTION:%.*]] = add <vscale x 8 x i64> zeroinitializer, [[TMP7]]
+; CHECK-NEXT: [[ACTIVE_LANE_MASK_ENTRY:%.*]] = call <vscale x 2 x i1> @llvm.get.active.lane.mask.nxv2i1.i64(i64 0, i64 8)
+; CHECK-NEXT: [[TMP8:%.*]] = call <vscale x 2 x i64> @llvm.stepvector.nxv2i64()
+; CHECK-NEXT: [[TMP7:%.*]] = mul <vscale x 2 x i64> [[TMP8]], splat (i64 1)
+; CHECK-NEXT: [[INDUCTION:%.*]] = add <vscale x 2 x i64> zeroinitializer, [[TMP7]]
; CHECK-NEXT: [[TMP12:%.*]] = mul i64 1, [[TMP6]]
-; CHECK-NEXT: [[DOTSPLATINSERT:%.*]] = insertelement <vscale x 8 x i64> poison, i64 [[TMP12]], 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 2 x i64> poison, i64 [[TMP12]], i64 0
+; CHECK-NEXT: [[DOTSPLAT:%.*]] = shufflevector <vscale x 2 x i64> [[DOTSPLATINSERT]], <vscale x 2 x i64> poison, <vscale x 2 x i32> zeroinitializer
+; CHECK-NEXT: [[BROADCAST_SPLATINSERT:%.*]] = insertelement <vscale x 2 x i64> poison, i64 [[VAL]], i64 0
+; CHECK-NEXT: [[BROADCAST_SPLAT:%.*]] = shufflevector <vscale x 2 x i64> [[BROADCAST_SPLATINSERT]], <vscale x 2 x i64> poison, <vscale x 2 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 2 x i1> [ [[ACTIVE_LANE_MASK_ENTRY]], [[VECTOR_PH]] ], [ [[ACTIVE_LANE_MASK_NEXT:%.*]], [[VECTOR_BODY]] ]
+; CHECK-NEXT: [[VEC_IND:%.*]] = phi <vscale x 2 x i64> [ [[INDUCTION]], [[VECTOR_PH]] ], [ [[VEC_IND_NEXT:%.*]], [[VECTOR_BODY]] ]
; CHECK-NEXT: [[TMP13:%.*]] = add i64 [[INDEX]], 0
; CHECK-NEXT: [[NEXT_GEP:%.*]] = getelementptr i8, ptr [[DST]], i64 [[TMP13]]
-; CHECK-NEXT: [[TMP10:%.*]] = shl nuw nsw <vscale x 8 x i64> [[VEC_IND]], splat (i64 3)
-; CHECK-NEXT: [[TMP11:%.*]] = lshr <vscale x 8 x i64> [[BROADCAST_SPLAT]], [[TMP10]]
-; CHECK-NEXT: [[TMP14:%.*]] = trunc <vscale x 8 x i64> [[TMP11]] to <vscale x 8 x i8>
+; CHECK-NEXT: [[TMP10:%.*]] = shl nuw nsw <vscale x 2 x i64> [[VEC_IND]], splat (i64 3)
+; CHECK-NEXT: [[TMP11:%.*]] = lshr <vscale x 2 x i64> [[BROADCAST_SPLAT]], [[TMP10]]
+; CHECK-NEXT: [[TMP16:%.*]] = trunc <vscale x 2 x i64> [[TMP11]] to <vscale x 2 x i8>
; CHECK-NEXT: [[TMP17:%.*]] = getelementptr i8, ptr [[NEXT_GEP]], i32 0
-; CHECK-NEXT: call void @llvm.masked.store.nxv8i8.p0(<vscale x 8 x i8> [[TMP14]], ptr [[TMP17]], i32 1, <vscale x 8 x i1> [[ACTIVE_LANE_MASK]])
+; CHECK-NEXT: call void @llvm.masked.store.nxv2i8.p0(<vscale x 2 x i8> [[TMP16]], ptr [[TMP17]], i32 1, <vscale x 2 x i1> [[ACTIVE_LANE_MASK]])
; CHECK-NEXT: [[INDEX_NEXT]] = add i64 [[INDEX]], [[TMP6]]
-; CHECK-NEXT: [[VEC_IND_NEXT]] = add <vscale x 8 x i64> [[VEC_IND]], [[DOTSPLAT]]
-; CHECK-NEXT: [[ACTIVE_LANE_MASK_NEXT]] = call <vscale x 8 x i1> @llvm.get.active.lane.mask.nxv8i1.i64(i64 [[INDEX_NEXT]], i64 8)
-; 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 2 x i1> @llvm.get.active.lane.mask.nxv2i1.i64(i64 [[INDEX_NEXT]], i64 8)
+; CHECK-NEXT: [[TMP14:%.*]] = xor <vscale x 2 x i1> [[ACTIVE_LANE_MASK_NEXT]], splat (i1 true)
+; CHECK-NEXT: [[VEC_IND_NEXT]] = add <vscale x 2 x i64> [[VEC_IND]], [[DOTSPLAT]]
+; CHECK-NEXT: [[TMP15:%.*]] = extractelement <vscale x 2 x i1> [[TMP14]], i32 0
+; CHECK-NEXT: br i1 [[TMP15]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop [[LOOP0:![0-9]+]]
; CHECK: middle.block:
; CHECK-NEXT: br i1 true, label [[FOR_COND_CLEANUP:%.*]], label [[SCALAR_PH]]
; CHECK: scalar.ph:
@@ -94,39 +96,41 @@ define void @clamped_tc_max_8(ptr nocapture %dst, i32 %n, i64 %val) vscale_range
; 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]], 2
; CHECK-NEXT: [[TMP4:%.*]] = sub i64 [[TMP1]], 1
; CHECK-NEXT: [[N_RND_UP:%.*]] = add i64 [[WIDE_TRIP_COUNT]], [[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: [[TMP5:%.*]] = call i64 @llvm.vscale.i64()
-; CHECK-NEXT: [[TMP6:%.*]] = mul i64 [[TMP5]], 8
+; CHECK-NEXT: [[TMP6:%.*]] = mul i64 [[TMP5]], 2
; CHECK-NEXT: [[IND_END:%.*]] = getelementptr i8, ptr [[DST]], i64 [[N_VEC]]
-; CHECK-NEXT: [[ACTIVE_LANE_MASK_ENTRY:%.*]] = call <vscale x 8 x i1> @llvm.get.active.lane.mask.nxv8i1.i64(i64 0, i64 [[WIDE_TRIP_COUNT]])
-; CHECK-NEXT: [[TMP8:%.*]] = call <vscale x 8 x i64> @llvm.stepvector.nxv8i64()
-; CHECK-NEXT: [[TMP7:%.*]] = mul <vscale x 8 x i64> [[TMP8]], splat (i64 1)
-; CHECK-NEXT: [[INDUCTION:%.*]] = add <vscale x 8 x i64> zeroinitializer, [[TMP7]]
+; CHECK-NEXT: [[ACTIVE_LANE_MASK_ENTRY:%.*]] = call <vscale x 2 x i1> @llvm.get.active.lane.mask.nxv2i1.i64(i64 0, i64 [[WIDE_TRIP_COUNT]])
+; CHECK-NEXT: [[TMP8:%.*]] = call <vscale x 2 x i64> @llvm.stepvector.nxv2i64()
+; CHECK-NEXT: [[TMP7:%.*]] = mul <vscale x 2 x i64> [[TMP8]], splat (i64 1)
+; CHECK-NEXT: [[INDUCTION:%.*]] = add <vscale x 2 x i64> zeroinitializer, [[TMP7]]
; CHECK-NEXT: [[TMP12:%.*]] = mul i64 1, [[TMP6]]
-; CHECK-NEXT: [[DOTSPLATINSERT:%.*]] = insertelement <vscale x 8 x i64> poison, i64 [[TMP12]], 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 2 x i64> poison, i64 [[TMP12]], i64 0
+; CHECK-NEXT: [[DOTSPLAT:%.*]] = shufflevector <vscale x 2 x i64> [[DOTSPLATINSERT]], <vscale x 2 x i64> poison, <vscale x 2 x i32> zeroinitializer
+; CHECK-NEXT: [[BROADCAST_SPLATINSERT:%.*]] = insertelement <vscale x 2 x i64> poison, i64 [[VAL]], i64 0
+; CHECK-NEXT: [[BROADCAST_SPLAT:%.*]] = shufflevector <vscale x 2 x i64> [[BROADCAST_SPLATINSERT]], <vscale x 2 x i64> poison, <vscale x 2 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 2 x i1> [ [[ACTIVE_LANE_MASK_ENTRY]], [[VECTOR_PH]] ], [ [[ACTIVE_LANE_MASK_NEXT:%.*]], [[VECTOR_BODY]] ]
+; CHECK-NEXT: [[VEC_IND:%.*]] = phi <vscale x 2 x i64> [ [[INDUCTION]], [[VECTOR_PH]] ], [ [[VEC_IND_NEXT:%.*]], [[VECTOR_BODY]] ]
; CHECK-NEXT: [[TMP13:%.*]] = add i64 [[INDEX]], 0
; CHECK-NEXT: [[NEXT_GEP:%.*]] = getelementptr i8, ptr [[DST]], i64 [[TMP13]]
-; CHECK-NEXT: [[TMP10:%.*]] = shl nuw nsw <vscale x 8 x i64> [[VEC_IND]], splat (i64 3)
-; CHECK-NEXT: [[TMP11:%.*]] = lshr <vscale x 8 x i64> [[BROADCAST_SPLAT]], [[TMP10]]
-; CHECK-NEXT: [[TMP14:%.*]] = trunc <vscale x 8 x i64> [[TMP11]] to <vscale x 8 x i8>
+; CHECK-NEXT: [[TMP10:%.*]] = shl nuw nsw <vscale x 2 x i64> [[VEC_IND]], splat (i64 3)
+; CHECK-NEXT: [[TMP11:%.*]] = lshr <vscale x 2 x i64> [[BROADCAST_SPLAT]], [[TMP10]]
+; CHECK-NEXT: [[TMP16:%.*]] = trunc <vscale x 2 x i64> [[TMP11]] to <vscale x 2 x i8>
; CHECK-NEXT: [[TMP17:%.*]] = getelementptr i8, ptr [[NEXT_GEP]], i32 0
-; CHECK-NEXT: call void @llvm.masked.store.nxv8i8.p0(<vscale x 8 x i8> [[TMP14]], ptr [[TMP17]], i32 1, <vscale x 8 x i1> [[ACTIVE_LANE_MASK]])
+; CHECK-NEXT: call void @llvm.masked.store.nxv2i8.p0(<vscale x 2 x i8> [[TMP16]], ptr [[TMP17]], i32 1, <vscale x 2 x i1> [[ACTIVE_LANE_MASK]])
; CHECK-NEXT: [[INDEX_NEXT]] = add i64 [[INDEX]], [[TMP6]]
-; CHECK-NEXT: [[VEC_IND_NEXT]] = add <vscale x 8 x i64> [[VEC_IND]], [[DOTSPLAT]]
-; CHECK-NEXT: [[ACTIVE_LANE_MASK_NEXT]] = call <vscale x 8 x i1> @llvm.get.active.lane.mask.nxv8i1.i64(i64 [[INDEX_NEXT]], i64 [[WIDE_TRIP_COUNT]])
-; CHECK-NEXT: br i1 true, label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop [[LOOP4:![0-9]+]]
+; CHECK-NEXT: [[ACTIVE_LANE_MASK_NEXT]] = call <vscale x 2 x i1> @llvm.get.active.lane.mask.nxv2i1.i64(i64 [[INDEX_NEXT]], i64 [[WIDE_TRIP_COUNT]])
+; CHECK-NEXT: [[TMP14:%.*]] = xor <vscale x 2 x i1> [[ACTIVE_LANE_MASK_NEXT]], splat (i1 true)
+; CHECK-NEXT: [[VEC_IND_NEXT]] = add <vscale x 2 x i64> [[VEC_IND]], [[DOTSPLAT]]
+; CHECK-NEXT: [[TMP15:%.*]] = extractelement <vscale x 2 x i1> [[TMP14]], i32 0
+; CHECK-NEXT: br i1 [[TMP15]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop [[LOOP4:![0-9]+]]
; CHECK: middle.block:
; CHECK-NEXT: br i1 true, label [[FOR_COND_CLEANUP_LOOPEXIT:%.*]], label [[SCALAR_PH]]
; CHECK: scalar.ph:
diff --git a/llvm/test/Transforms/LoopVectorize/AArch64/conditional-branches-cost.ll b/llvm/test/Transforms/LoopVectorize/AArch64/conditional-branches-cost.ll
index caa98d766a8c34..0ff84e13c243d9 100644
--- a/llvm/test/Transforms/LoopVectorize/AArch64/conditional-branches-cost.ll
+++ b/llvm/test/Transforms/LoopVectorize/AArch64/conditional-branches-cost.ll
@@ -768,9 +768,20 @@ define void @multiple_exit_conditions(ptr %src, ptr noalias %dst) #1 {
; DEFAULT-LABEL: define void @multiple_exit_conditions(
; DEFAULT-SAME: ptr [[SRC:%.*]], ptr noalias [[DST:%.*]]) #[[ATTR2:[0-9]+]] {
; DEFAULT-NEXT: entry:
-; DEFAULT-NEXT: br i1 false, label [[SCALAR_PH:%.*]], label [[VECTOR_PH:%.*]]
+; DEFAULT-NEXT: [[TMP7:%.*]] = call i64 @llvm.vscale.i64()
+; DEFAULT-NEXT: [[TMP9:%.*]] = mul i64 [[TMP7]], 8
+; DEFAULT-NEXT: [[MIN_ITERS_CHECK:%.*]] = icmp ult i64 257, [[TMP9]]
+; DEFAULT-NEXT: br i1 [[MIN_ITERS_CHECK]], label [[SCALAR_PH:%.*]], label [[VECTOR_PH:%.*]]
; DEFAULT: vector.ph:
-; DEFAULT-NEXT: [[IND_END:%.*]] = getelementptr i8, ptr [[DST]], i64 2048
+; DEFAULT-NEXT: [[TMP2:%.*]] = call i64 @llvm.vscale.i64()
+; DEFAULT-NEXT: [[TMP3:%.*]] = mul i64 [[TMP2]], 8
+; DEFAULT-NEXT: [[N_MOD_VF:%.*]] = urem i64 257, [[TMP3]]
+; DEFAULT-NEXT: [[N_VEC:%.*]] = sub i64 257, [[N_MOD_VF]]
+; DEFAULT-NEXT: [[TMP10:%.*]] = call i64 @llvm.vscale.i64()
+; DEFAULT-NEXT: [[TMP5:%.*]] = mul i64 [[TMP10]], 8
+; DEFAULT-NEXT: [[TMP6:%.*]] = mul i64 [[N_VEC]], 8
+; DEFAULT-NEXT: [[IND_END:%.*]] = getelementptr i8, ptr [[DST]], i64 [[TMP6]]
+; DEFAULT-NEXT: [[TMP8:%.*]] = mul i64 [[N_VEC]], 2
; DEFAULT-NEXT: br label [[VECTOR_BODY:%.*]]
; DEFAULT: vector.body:
; DEFAULT-NEXT: [[INDEX:%.*]] = phi i64 [ 0, [[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], [[VECTOR_BODY]] ]
@@ -778,20 +789,39 @@ define void @multiple_exit_conditions(ptr %src, ptr noalias %dst) #1 {
; DEFAULT-NEXT: [[TMP0:%.*]] = add i64 [[OFFSET_IDX]], 0
; DEFAULT-NEXT: [[NEXT_GEP:%.*]] = getelementptr i8, ptr [[DST]], i64 [[TMP0]]
; DEFAULT-NEXT: [[TMP1:%.*]] = load i16, ptr [[SRC]], align 2
-; DEFAULT-NEXT: [[BROADCAST_SPLATINSERT:%.*]] = insertelement <8 x i16> poison, i16 [[TMP1]], i64 0
-; DEFAULT-NEXT: [[BROADCAST_SPLAT:%.*]] = shufflevector <8 x i16> [[BROADCAST_SPLATINSERT]], <8 x i16> poison, <8 x i32> zeroinitializer
-; DEFAULT-NEXT: [[TMP2:%.*]] = or <8 x i16> [[BROADCAST_SPLAT]], splat (i16 1)
-; DEFAULT-NEXT: [[TMP3:%.*]] = uitofp <8 x i16> [[TMP2]] to <8 x double>
+; DEFAULT-NEXT: [[BROADCAST_SPLATINSERT:%.*]] = insertelement <vscale x 2 x i16> poison, i16 [[TMP1]], i64 0
+; DEFAULT-NEXT: [[BROADCAST_SPLAT:%.*]] = shufflevector <vscale x 2 x i16> [[BROADCAST_SPLATINSERT]], <vscale x 2 x i16> poison, <vscale x 2 x i32> zeroinitializer
+; DEFAULT-NEXT: [[TMP11:%.*]] = or <vscale x 2 x i16> [[BROADCAST_SPLAT]], splat (i16 1)
+; DEFAULT-NEXT: [[TMP12:%.*]] = or <vscale x 2 x i16> [[BROADCAST_SPLAT]], splat (i16 1)
+; DEFAULT-NEXT: [[TMP13:%.*]] = or <vscale x 2 x i16> [[BROADCAST_SPLAT]], splat (i16 1)
+; DEFAULT-NEXT: [[TMP14:%.*]] = or <vscale x 2 x i16> [[BROADCAST_SPLAT]], splat (i16 1)
+; DEFAULT-NEXT: [[TMP15:%.*]] = uitofp <vscale x 2 x i16> [[TMP11]] to <vscale x 2 x double>
+; DEFAULT-NEXT: [[TMP16:%.*]] = uitofp <vscale x 2 x i16> [[TMP12]] to <vscale x 2 x double>
+; DEFAULT-NEXT: [[TMP17:%.*]] = uitofp <vscale x 2 x i16> [[TMP13]] to <vscale x 2 x double>
+; DEFAULT-NEXT: [[TMP18:%.*]] = uitofp <vscale x 2 x i16> [[TMP14]] to <vscale x 2 x double>
; DEFAULT-NEXT: [[TMP4:%.*]] = getelementptr double, ptr [[NEXT_GEP]], i32 0
-; DEFAULT-NEXT: store <8 x double> [[TMP3]], ptr [[TMP4]], align 8
-; DEFAULT-NEXT: [[INDEX_NEXT]] = add nuw i64 [[INDEX]], 8
-; DEFAULT-NEXT: [[TMP5:%.*]] = icmp eq i64 [[INDEX_NEXT]], 256
-; DEFAULT-NEXT: br i1 [[TMP5]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop [[LOOP22:![0-9]+]]
+; DEFAULT-NEXT: [[TMP20:%.*]] = call i64 @llvm.vscale.i64()
+; DEFAULT-NEXT: [[TMP21:%.*]] = mul i64 [[TMP20]], 2
+; DEFAULT-NEXT: [[TMP22:%.*]] = getelementptr double, ptr [[NEXT_GEP]], i64 [[TMP21]]
+; DEFAULT-NEXT: [[TMP23:%.*]] = call i64 @llvm.vscale.i64()
+; DEFAULT-NEXT: [[TMP24:%.*]] = mul i64 [[TMP23]], 4
+; DEFAULT-NEXT: [[TMP25:%.*]] = getelementptr double, ptr [[NEXT_GEP]], i64 [[TMP24]]
...
[truncated]
|
david-arm
reviewed
Feb 4, 2025
| Type *ValTy = Ctx.Types.inferScalarType(getOperand(0)); | ||
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| switch (getOpcode()) { | ||
| case VPInstruction::BranchOnCount: { |
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Are we guaranteed to only ever generate BranchOnCount here? I thought various vplan transforms took place that could change the terminator. For example, we might need BranchOnCond here for completeness.
I think addVPLaneMaskPhiAndUpdateExitBranch shows an example where BranchOnCond should not be free.
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It looks like there are a couple of regressions, e.g. clamped_tc_8, which are probably related. The legacy cost model for now just considers the cost of the condition, but in some cases we removed the original condition already.
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Agree that BranchOnCond will generate extractelement(vec, 0) and isn't free for all target. But after this change, the test still change because the extractelement is free under AArch64.
In clamped_tc_8 the BranchOnCount is replaced by get.active.lane.mask + not + BranchOnCond.
I've tried to implement the cost of get.active.lane.mask locally but it will impact lots of tests because the cost of this intrinsics is very expensive in AArch64 (2 * element count). And the clapmed_tc_8 will not even vectorized.
fhahn
reviewed
Feb 4, 2025
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| auto TC = dyn_cast_if_present<ConstantInt>( | ||
| getParent()->getPlan()->getTripCount()->getUnderlyingValue()); | ||
| if (TC && VF.isFixed() && TC->getSExtValue() == VF.getFixedValue()) | ||
| return 0; |
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The legacy cost model check if the vectorizer can remove the condition and it will not calculate the cost of the condition. You can find this in test fully-unrolled-costs.ll.
We can remove this after we hoist unrollByUF and optimizeForVFandUF before estimating instruction cost.
@fhahn Do you have a better method to get the original trip count here?
| Type *ValTy = Ctx.Types.inferScalarType(getOperand(0)); | ||
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| switch (getOpcode()) { | ||
| case VPInstruction::BranchOnCount: { |
There was a problem hiding this comment.
It looks like there are a couple of regressions, e.g. clamped_tc_8, which are probably related. The legacy cost model for now just considers the cost of the condition, but in some cases we removed the original condition already.
ElvisWang123
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Ping! |
This patch tried to model the cost of exit conditions through vplan-based cost model. * `BranchOnCount` will generate icmp + br. The branch instruction is already implemented by the VPRegionBlock so we only need to calculate the cost of icmp. If the VF is same as the trip count of the loop, the cost of the BranchOnCount is free. This patch is not quite NFC for following reasons. * Some of the BranchOnCount could be optimized to BranchOnCond, which is free. * Some of the instructions calculated in the exit condition in legacy cost model will be optimized out.
This patch tried to model the cost of exit conditions through vplan-based cost model. * `BranchOnCount` will generate icmp + br. The branch instruction is already implemented by the VPRegionBlock so we only need to calculate the cost of icmp. If the VF is same as the trip count of the loop, the cost of the BranchOnCount is free. This patch is not quite NFC for following reasons. * Some of the BranchOnCount could be optimized to BranchOnCond, which is free. * Some of the instructions calculated in the exit condition in legacy cost model will be optimized out.
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Gentle ping :) The potential regression of |
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Gentle Ping! :) The tests changes of |
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Ping :) |
fhahn
reviewed
Jun 23, 2025
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This patch tried to model the cost of exit conditions through vplan-based cost model.
BranchOnCountwill generate icmp + br.The branch instruction is already implemented by the VPRegionBlock so we only need to calculate the cost of icmp.
If the VF is same as the trip count of the loop, the cost of the BranchOnCount is free.
There are some tests changes for following reasons.