[llvm] [LV] Fix MVE regression from #132190 (PR #141736)

Sam Tebbs via llvm-commits llvm-commits at lists.llvm.org
Thu May 29 06:59:13 PDT 2025


https://github.com/SamTebbs33 updated https://github.com/llvm/llvm-project/pull/141736

>From f79a4676b3276ba57dd049c55ebb221707c57157 Mon Sep 17 00:00:00 2001
From: Sam Tebbs <samuel.tebbs at arm.com>
Date: Wed, 28 May 2025 10:23:09 +0100
Subject: [PATCH 1/3] [LV] Fix MVE regression from #132190

Register pressure was only considered if the vector bandwidth was being
maximised (chosen either by the target or user options), but #132190
inadvertently caused high pressure VFs to be pruned even when max
bandwidth wasn't enabled. This PR returns to the previous behaviour.
---
 .../Transforms/Vectorize/LoopVectorize.cpp    | 27 ++++++++++++++-----
 1 file changed, 21 insertions(+), 6 deletions(-)

diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index 2fe59a464457f..ad3cbc6cd1e42 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -959,6 +959,10 @@ class LoopVectorizationCostModel {
     return expectedCost(UserVF).isValid();
   }
 
+  /// \return True if maximizing vector bandwidth is enabled by the target or
+  /// user options.
+  bool useMaxBandwidth(TargetTransformInfo::RegisterKind RegKind);
+
   /// \return The size (in bits) of the smallest and widest types in the code
   /// that needs to be vectorized. We ignore values that remain scalar such as
   /// 64 bit loop indices.
@@ -3944,6 +3948,14 @@ LoopVectorizationCostModel::computeMaxVF(ElementCount UserVF, unsigned UserIC) {
   return FixedScalableVFPair::getNone();
 }
 
+bool LoopVectorizationCostModel::useMaxBandwidth(
+    TargetTransformInfo::RegisterKind RegKind) {
+  return MaximizeBandwidth || (MaximizeBandwidth.getNumOccurrences() == 0 &&
+                               (TTI.shouldMaximizeVectorBandwidth(RegKind) ||
+                                (UseWiderVFIfCallVariantsPresent &&
+                                 Legal->hasVectorCallVariants())));
+}
+
 ElementCount LoopVectorizationCostModel::getMaximizedVFForTarget(
     unsigned MaxTripCount, unsigned SmallestType, unsigned WidestType,
     ElementCount MaxSafeVF, bool FoldTailByMasking) {
@@ -4009,10 +4021,7 @@ ElementCount LoopVectorizationCostModel::getMaximizedVFForTarget(
       ComputeScalableMaxVF ? TargetTransformInfo::RGK_ScalableVector
                            : TargetTransformInfo::RGK_FixedWidthVector;
   ElementCount MaxVF = MaxVectorElementCount;
-  if (MaximizeBandwidth ||
-      (MaximizeBandwidth.getNumOccurrences() == 0 &&
-       (TTI.shouldMaximizeVectorBandwidth(RegKind) ||
-        (UseWiderVFIfCallVariantsPresent && Legal->hasVectorCallVariants())))) {
+  if (useMaxBandwidth(RegKind)) {
     auto MaxVectorElementCountMaxBW = ElementCount::get(
         llvm::bit_floor(WidestRegister.getKnownMinValue() / SmallestType),
         ComputeScalableMaxVF);
@@ -4384,7 +4393,10 @@ VectorizationFactor LoopVectorizationPlanner::selectVectorizationFactor() {
 
       /// Don't consider the VF if it exceeds the number of registers for the
       /// target.
-      if (RU.exceedsMaxNumRegs(TTI))
+      if (CM.useMaxBandwidth(VF.isScalable()
+                                 ? TargetTransformInfo::RGK_ScalableVector
+                                 : TargetTransformInfo::RGK_FixedWidthVector) &&
+          RU.exceedsMaxNumRegs(TTI))
         continue;
 
       InstructionCost C = CM.expectedCost(VF);
@@ -7458,7 +7470,10 @@ VectorizationFactor LoopVectorizationPlanner::computeBestVF() {
       InstructionCost Cost = cost(*P, VF);
       VectorizationFactor CurrentFactor(VF, Cost, ScalarCost);
 
-      if (RU.exceedsMaxNumRegs(TTI)) {
+      if (CM.useMaxBandwidth(VF.isScalable()
+                                 ? TargetTransformInfo::RGK_ScalableVector
+                                 : TargetTransformInfo::RGK_FixedWidthVector) &&
+          RU.exceedsMaxNumRegs(TTI)) {
         LLVM_DEBUG(dbgs() << "LV(REG): Not considering vector loop of width "
                           << VF << " because it uses too many registers\n");
         continue;

>From a4a0728f7436ab84a7bcb0c82e539545d7a62454 Mon Sep 17 00:00:00 2001
From: Samuel Tebbs <samuel.tebbs at arm.com>
Date: Thu, 29 May 2025 13:46:02 +0100
Subject: [PATCH 2/3] Add test

---
 .../ARM/mve-reg-pressure-vmla.ll              | 147 ++++++++++++++++++
 1 file changed, 147 insertions(+)
 create mode 100644 llvm/test/Transforms/LoopVectorize/ARM/mve-reg-pressure-vmla.ll

diff --git a/llvm/test/Transforms/LoopVectorize/ARM/mve-reg-pressure-vmla.ll b/llvm/test/Transforms/LoopVectorize/ARM/mve-reg-pressure-vmla.ll
new file mode 100644
index 0000000000000..667022e0470e4
--- /dev/null
+++ b/llvm/test/Transforms/LoopVectorize/ARM/mve-reg-pressure-vmla.ll
@@ -0,0 +1,147 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --filter-out-after "^scalar.ph:" --version 5
+; RUN: opt -passes=loop-vectorize < %s -S -o - | FileCheck %s
+
+source_filename = "<source>"
+target datalayout = "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64"
+target triple = "thumbv8.1m.main-unknown-none-eabihf"
+
+; Even though it has high register pressure, this example should still vectorise since the mul+add chains become VMLAs.
+
+define void @fn(i32 noundef %n, ptr %in, ptr %out) #0 {
+; CHECK-LABEL: define void @fn(
+; CHECK-SAME: i32 noundef [[N:%.*]], ptr [[IN:%.*]], ptr [[OUT:%.*]]) #[[ATTR0:[0-9]+]] {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    [[CMP46_NOT:%.*]] = icmp eq i32 [[N]], 0
+; CHECK-NEXT:    br i1 [[CMP46_NOT]], [[FOR_COND_CLEANUP:label %.*]], label %[[FOR_BODY_PREHEADER:.*]]
+; CHECK:       [[FOR_BODY_PREHEADER]]:
+; CHECK-NEXT:    br i1 false, label %[[SCALAR_PH:.*]], label %[[VECTOR_MEMCHECK:.*]]
+; CHECK:       [[VECTOR_MEMCHECK]]:
+; CHECK-NEXT:    [[TMP0:%.*]] = mul i32 [[N]], 3
+; CHECK-NEXT:    [[SCEVGEP:%.*]] = getelementptr i8, ptr [[OUT]], i32 [[TMP0]]
+; CHECK-NEXT:    [[SCEVGEP1:%.*]] = getelementptr i8, ptr [[IN]], i32 [[TMP0]]
+; CHECK-NEXT:    [[BOUND0:%.*]] = icmp ult ptr [[OUT]], [[SCEVGEP1]]
+; CHECK-NEXT:    [[BOUND1:%.*]] = icmp ult ptr [[IN]], [[SCEVGEP]]
+; CHECK-NEXT:    [[FOUND_CONFLICT:%.*]] = and i1 [[BOUND0]], [[BOUND1]]
+; CHECK-NEXT:    br i1 [[FOUND_CONFLICT]], 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:    br label %[[VECTOR_BODY:.*]]
+; CHECK:       [[VECTOR_BODY]]:
+; CHECK-NEXT:    [[INDEX:%.*]] = phi i32 [ 0, %[[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], %[[VECTOR_BODY]] ]
+; CHECK-NEXT:    [[POINTER_PHI:%.*]] = phi ptr [ [[IN]], %[[VECTOR_PH]] ], [ [[PTR_IND:%.*]], %[[VECTOR_BODY]] ]
+; CHECK-NEXT:    [[POINTER_PHI2:%.*]] = phi ptr [ [[OUT]], %[[VECTOR_PH]] ], [ [[PTR_IND3:%.*]], %[[VECTOR_BODY]] ]
+; CHECK-NEXT:    [[VECTOR_GEP:%.*]] = getelementptr i8, ptr [[POINTER_PHI]], <4 x i32> <i32 0, i32 3, i32 6, i32 9>
+; CHECK-NEXT:    [[VECTOR_GEP4:%.*]] = getelementptr i8, ptr [[POINTER_PHI2]], <4 x i32> <i32 0, i32 3, i32 6, i32 9>
+; CHECK-NEXT:    [[ACTIVE_LANE_MASK:%.*]] = call <4 x i1> @llvm.get.active.lane.mask.v4i1.i32(i32 [[INDEX]], i32 [[N]])
+; CHECK-NEXT:    [[TMP1:%.*]] = getelementptr inbounds nuw i8, <4 x ptr> [[VECTOR_GEP]], i32 1
+; CHECK-NEXT:    [[WIDE_MASKED_GATHER:%.*]] = call <4 x i8> @llvm.masked.gather.v4i8.v4p0(<4 x ptr> [[VECTOR_GEP]], i32 1, <4 x i1> [[ACTIVE_LANE_MASK]], <4 x i8> poison), !alias.scope [[META0:![0-9]+]]
+; CHECK-NEXT:    [[TMP2:%.*]] = getelementptr inbounds nuw i8, <4 x ptr> [[VECTOR_GEP]], i32 2
+; CHECK-NEXT:    [[WIDE_MASKED_GATHER5:%.*]] = call <4 x i8> @llvm.masked.gather.v4i8.v4p0(<4 x ptr> [[TMP1]], i32 1, <4 x i1> [[ACTIVE_LANE_MASK]], <4 x i8> poison), !alias.scope [[META0]]
+; CHECK-NEXT:    [[WIDE_MASKED_GATHER6:%.*]] = call <4 x i8> @llvm.masked.gather.v4i8.v4p0(<4 x ptr> [[TMP2]], i32 1, <4 x i1> [[ACTIVE_LANE_MASK]], <4 x i8> poison), !alias.scope [[META0]]
+; CHECK-NEXT:    [[TMP3:%.*]] = zext <4 x i8> [[WIDE_MASKED_GATHER]] to <4 x i32>
+; CHECK-NEXT:    [[TMP4:%.*]] = mul nuw nsw <4 x i32> [[TMP3]], splat (i32 19595)
+; CHECK-NEXT:    [[TMP5:%.*]] = zext <4 x i8> [[WIDE_MASKED_GATHER5]] to <4 x i32>
+; CHECK-NEXT:    [[TMP6:%.*]] = mul nuw nsw <4 x i32> [[TMP5]], splat (i32 38470)
+; CHECK-NEXT:    [[TMP7:%.*]] = zext <4 x i8> [[WIDE_MASKED_GATHER6]] to <4 x i32>
+; CHECK-NEXT:    [[TMP8:%.*]] = mul nuw nsw <4 x i32> [[TMP7]], splat (i32 7471)
+; CHECK-NEXT:    [[TMP9:%.*]] = add nuw nsw <4 x i32> [[TMP4]], splat (i32 32768)
+; CHECK-NEXT:    [[TMP10:%.*]] = add nuw nsw <4 x i32> [[TMP9]], [[TMP6]]
+; CHECK-NEXT:    [[TMP11:%.*]] = add nuw nsw <4 x i32> [[TMP10]], [[TMP8]]
+; CHECK-NEXT:    [[TMP12:%.*]] = lshr <4 x i32> [[TMP11]], splat (i32 16)
+; CHECK-NEXT:    [[TMP13:%.*]] = trunc <4 x i32> [[TMP12]] to <4 x i8>
+; CHECK-NEXT:    [[TMP14:%.*]] = mul nuw nsw <4 x i32> [[TMP3]], splat (i32 32767)
+; CHECK-NEXT:    [[TMP15:%.*]] = mul nuw <4 x i32> [[TMP5]], splat (i32 16762097)
+; CHECK-NEXT:    [[TMP16:%.*]] = mul nuw <4 x i32> [[TMP7]], splat (i32 16759568)
+; CHECK-NEXT:    [[TMP17:%.*]] = add nuw nsw <4 x i32> [[TMP14]], splat (i32 32768)
+; CHECK-NEXT:    [[TMP18:%.*]] = add nuw <4 x i32> [[TMP17]], [[TMP15]]
+; CHECK-NEXT:    [[TMP19:%.*]] = add <4 x i32> [[TMP18]], [[TMP16]]
+; CHECK-NEXT:    [[TMP20:%.*]] = lshr <4 x i32> [[TMP19]], splat (i32 16)
+; CHECK-NEXT:    [[TMP21:%.*]] = trunc <4 x i32> [[TMP20]] to <4 x i8>
+; CHECK-NEXT:    [[TMP22:%.*]] = mul nuw nsw <4 x i32> [[TMP3]], splat (i32 13282)
+; CHECK-NEXT:    [[TMP23:%.*]] = mul nuw <4 x i32> [[TMP5]], splat (i32 16744449)
+; CHECK-NEXT:    [[TMP24:%.*]] = mul nuw nsw <4 x i32> [[TMP7]], splat (i32 19485)
+; CHECK-NEXT:    [[TMP25:%.*]] = add nuw nsw <4 x i32> [[TMP22]], splat (i32 32768)
+; CHECK-NEXT:    [[TMP26:%.*]] = add nuw <4 x i32> [[TMP25]], [[TMP23]]
+; CHECK-NEXT:    [[TMP27:%.*]] = add nuw <4 x i32> [[TMP26]], [[TMP24]]
+; CHECK-NEXT:    [[TMP28:%.*]] = lshr <4 x i32> [[TMP27]], splat (i32 16)
+; CHECK-NEXT:    [[TMP29:%.*]] = trunc <4 x i32> [[TMP28]] to <4 x i8>
+; CHECK-NEXT:    [[TMP30:%.*]] = getelementptr inbounds nuw i8, <4 x ptr> [[VECTOR_GEP4]], i32 1
+; CHECK-NEXT:    call void @llvm.masked.scatter.v4i8.v4p0(<4 x i8> [[TMP13]], <4 x ptr> [[VECTOR_GEP4]], i32 1, <4 x i1> [[ACTIVE_LANE_MASK]]), !alias.scope [[META3:![0-9]+]], !noalias [[META0]]
+; CHECK-NEXT:    [[TMP31:%.*]] = getelementptr inbounds nuw i8, <4 x ptr> [[VECTOR_GEP4]], i32 2
+; CHECK-NEXT:    call void @llvm.masked.scatter.v4i8.v4p0(<4 x i8> [[TMP21]], <4 x ptr> [[TMP30]], i32 1, <4 x i1> [[ACTIVE_LANE_MASK]]), !alias.scope [[META3]], !noalias [[META0]]
+; CHECK-NEXT:    call void @llvm.masked.scatter.v4i8.v4p0(<4 x i8> [[TMP29]], <4 x ptr> [[TMP31]], i32 1, <4 x i1> [[ACTIVE_LANE_MASK]]), !alias.scope [[META3]], !noalias [[META0]]
+; CHECK-NEXT:    [[INDEX_NEXT]] = add i32 [[INDEX]], 4
+; CHECK-NEXT:    [[PTR_IND]] = getelementptr i8, ptr [[POINTER_PHI]], i32 12
+; CHECK-NEXT:    [[PTR_IND3]] = getelementptr i8, ptr [[POINTER_PHI2]], i32 12
+; CHECK-NEXT:    [[TMP32:%.*]] = icmp eq i32 [[INDEX_NEXT]], [[N_VEC]]
+; CHECK-NEXT:    br i1 [[TMP32]], label %[[MIDDLE_BLOCK:.*]], label %[[VECTOR_BODY]], !llvm.loop [[LOOP5:![0-9]+]]
+; CHECK:       [[MIDDLE_BLOCK]]:
+; CHECK-NEXT:    br [[FOR_COND_CLEANUP_LOOPEXIT:label %.*]]
+; CHECK:       [[SCALAR_PH]]:
+;
+entry:
+  %cmp46.not = icmp eq i32 %n, 0
+  br i1 %cmp46.not, label %for.cond.cleanup, label %for.body.preheader
+
+for.body.preheader:                               ; preds = %entry
+  br label %for.body
+
+for.cond.cleanup.loopexit:                        ; preds = %for.body
+  br label %for.cond.cleanup
+
+for.cond.cleanup:                                 ; preds = %for.cond.cleanup.loopexit, %entry
+  ret void
+
+for.body:                                         ; preds = %for.body.preheader, %for.body
+  %in.addr.049 = phi ptr [ %incdec.ptr2, %for.body ], [ %in, %for.body.preheader ]
+  %out.addr.048 = phi ptr [ %incdec.ptr34, %for.body ], [ %out, %for.body.preheader ]
+  %i.047 = phi i32 [ %inc, %for.body ], [ 0, %for.body.preheader ]
+  %incdec.ptr = getelementptr inbounds nuw i8, ptr %in.addr.049, i32 1
+  %0 = load i8, ptr %in.addr.049, align 1
+  %incdec.ptr1 = getelementptr inbounds nuw i8, ptr %in.addr.049, i32 2
+  %1 = load i8, ptr %incdec.ptr, align 1
+  %incdec.ptr2 = getelementptr inbounds nuw i8, ptr %in.addr.049, i32 3
+  %2 = load i8, ptr %incdec.ptr1, align 1
+  %conv = zext i8 %0 to i32
+  %mul = mul nuw nsw i32 %conv, 19595
+  %conv3 = zext i8 %1 to i32
+  %mul4 = mul nuw nsw i32 %conv3, 38470
+  %conv5 = zext i8 %2 to i32
+  %mul6 = mul nuw nsw i32 %conv5, 7471
+  %add = add nuw nsw i32 %mul, 32768
+  %add7 = add nuw nsw i32 %add, %mul4
+  %add8 = add nuw nsw i32 %add7, %mul6
+  %shr = lshr i32 %add8, 16
+  %conv9 = trunc nuw i32 %shr to i8
+  %mul11 = mul nuw nsw i32 %conv, 32767
+  %mul13 = mul nuw i32 %conv3, 16762097
+  %mul16 = mul nuw i32 %conv5, 16759568
+  %add14 = add nuw nsw i32 %mul11, 32768
+  %add17 = add nuw i32 %add14, %mul13
+  %add18 = add i32 %add17, %mul16
+  %shr19 = lshr i32 %add18, 16
+  %conv20 = trunc i32 %shr19 to i8
+  %mul22 = mul nuw nsw i32 %conv, 13282
+  %mul24 = mul nuw i32 %conv3, 16744449
+  %mul27 = mul nuw nsw i32 %conv5, 19485
+  %add25 = add nuw nsw i32 %mul22, 32768
+  %add28 = add nuw i32 %add25, %mul24
+  %add29 = add nuw i32 %add28, %mul27
+  %shr30 = lshr i32 %add29, 16
+  %conv31 = trunc i32 %shr30 to i8
+  %incdec.ptr32 = getelementptr inbounds nuw i8, ptr %out.addr.048, i32 1
+  store i8 %conv9, ptr %out.addr.048, align 1
+  %incdec.ptr33 = getelementptr inbounds nuw i8, ptr %out.addr.048, i32 2
+  store i8 %conv20, ptr %incdec.ptr32, align 1
+  %incdec.ptr34 = getelementptr inbounds nuw i8, ptr %out.addr.048, i32 3
+  store i8 %conv31, ptr %incdec.ptr33, align 1
+  %inc = add nuw i32 %i.047, 1
+  %exitcond.not = icmp eq i32 %inc, %n
+  br i1 %exitcond.not, label %for.cond.cleanup.loopexit, label %for.body, !llvm.loop !7
+}
+
+attributes #0 = { nofree norecurse nosync nounwind memory(argmem: readwrite) "target-features"="+mve" }
+
+!7 = !{!"llvm.loop.mustprogress"}

>From d6837fe64352588a9b664f69bafa7a0907aaeb5b Mon Sep 17 00:00:00 2001
From: Samuel Tebbs <samuel.tebbs at arm.com>
Date: Thu, 29 May 2025 14:23:23 +0100
Subject: [PATCH 3/3] Only compute reg usage if needed

---
 .../Transforms/Vectorize/LoopVectorize.cpp    | 24 ++++++++---
 .../LoopVectorize/RISCV/reg-usage-bf16.ll     |  3 +-
 .../LoopVectorize/RISCV/reg-usage-f16.ll      |  6 +--
 .../LoopVectorize/RISCV/reg-usage.ll          | 40 ++++++++-----------
 4 files changed, 37 insertions(+), 36 deletions(-)

diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index ad3cbc6cd1e42..49bacc239f034 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -4385,8 +4385,14 @@ VectorizationFactor LoopVectorizationPlanner::selectVectorizationFactor() {
   for (auto &P : VPlans) {
     ArrayRef<ElementCount> VFs(P->vectorFactors().begin(),
                                P->vectorFactors().end());
-    auto RUs = ::calculateRegisterUsage(*P, VFs, TTI, CM.ValuesToIgnore);
-    for (auto [VF, RU] : zip_equal(VFs, RUs)) {
+
+    SmallVector<LoopVectorizationCostModel::RegisterUsage, 8> RUs;
+    if (CM.useMaxBandwidth(TargetTransformInfo::RGK_ScalableVector) ||
+        CM.useMaxBandwidth(TargetTransformInfo::RGK_FixedWidthVector))
+      RUs = ::calculateRegisterUsage(*P, VFs, TTI, CM.ValuesToIgnore);
+
+    for (unsigned I = 0; I < VFs.size(); I++) {
+      ElementCount VF = VFs[I];
       // The cost for scalar VF=1 is already calculated, so ignore it.
       if (VF.isScalar())
         continue;
@@ -4396,7 +4402,7 @@ VectorizationFactor LoopVectorizationPlanner::selectVectorizationFactor() {
       if (CM.useMaxBandwidth(VF.isScalable()
                                  ? TargetTransformInfo::RGK_ScalableVector
                                  : TargetTransformInfo::RGK_FixedWidthVector) &&
-          RU.exceedsMaxNumRegs(TTI))
+          RUs[I].exceedsMaxNumRegs(TTI))
         continue;
 
       InstructionCost C = CM.expectedCost(VF);
@@ -7447,8 +7453,14 @@ VectorizationFactor LoopVectorizationPlanner::computeBestVF() {
   for (auto &P : VPlans) {
     ArrayRef<ElementCount> VFs(P->vectorFactors().begin(),
                                P->vectorFactors().end());
-    auto RUs = ::calculateRegisterUsage(*P, VFs, TTI, CM.ValuesToIgnore);
-    for (auto [VF, RU] : zip_equal(VFs, RUs)) {
+
+    SmallVector<LoopVectorizationCostModel::RegisterUsage, 8> RUs;
+    if (CM.useMaxBandwidth(TargetTransformInfo::RGK_ScalableVector) ||
+        CM.useMaxBandwidth(TargetTransformInfo::RGK_FixedWidthVector))
+      RUs = ::calculateRegisterUsage(*P, VFs, TTI, CM.ValuesToIgnore);
+
+    for (unsigned I = 0; I < VFs.size(); I++) {
+      ElementCount VF = VFs[I];
       if (VF.isScalar())
         continue;
       if (!ForceVectorization && !willGenerateVectors(*P, VF, TTI)) {
@@ -7473,7 +7485,7 @@ VectorizationFactor LoopVectorizationPlanner::computeBestVF() {
       if (CM.useMaxBandwidth(VF.isScalable()
                                  ? TargetTransformInfo::RGK_ScalableVector
                                  : TargetTransformInfo::RGK_FixedWidthVector) &&
-          RU.exceedsMaxNumRegs(TTI)) {
+          RUs[I].exceedsMaxNumRegs(TTI)) {
         LLVM_DEBUG(dbgs() << "LV(REG): Not considering vector loop of width "
                           << VF << " because it uses too many registers\n");
         continue;
diff --git a/llvm/test/Transforms/LoopVectorize/RISCV/reg-usage-bf16.ll b/llvm/test/Transforms/LoopVectorize/RISCV/reg-usage-bf16.ll
index 8de1beea8e57e..9c89c998a1c3e 100644
--- a/llvm/test/Transforms/LoopVectorize/RISCV/reg-usage-bf16.ll
+++ b/llvm/test/Transforms/LoopVectorize/RISCV/reg-usage-bf16.ll
@@ -3,8 +3,7 @@
 
 define void @add(ptr noalias nocapture readonly %src1, ptr noalias nocapture readonly %src2, i32 signext %size, ptr noalias nocapture writeonly %result) {
 ; CHECK-LABEL: add
-; CHECK:       LV(REG): VF = 8
-; CHECK-NEXT:  LV(REG): Found max usage: 2 item
+; CHECK:  LV(REG): Found max usage: 2 item
 ; CHECK-NEXT:  LV(REG): RegisterClass: RISCV::GPRRC, 3 registers
 ; CHECK-NEXT:  LV(REG): RegisterClass: RISCV::VRRC, 4 registers
 ; CHECK-NEXT:  LV(REG): Found invariant usage: 1 item
diff --git a/llvm/test/Transforms/LoopVectorize/RISCV/reg-usage-f16.ll b/llvm/test/Transforms/LoopVectorize/RISCV/reg-usage-f16.ll
index 2005e82e9f27a..54124aa3e3f59 100644
--- a/llvm/test/Transforms/LoopVectorize/RISCV/reg-usage-f16.ll
+++ b/llvm/test/Transforms/LoopVectorize/RISCV/reg-usage-f16.ll
@@ -4,14 +4,12 @@
 
 define void @add(ptr noalias nocapture readonly %src1, ptr noalias nocapture readonly %src2, i32 signext %size, ptr noalias nocapture writeonly %result) {
 ; CHECK-LABEL: add
-; ZVFH:       LV(REG): VF = 8
-; ZVFH-NEXT:  LV(REG): Found max usage: 2 item
+; ZVFH:  LV(REG): Found max usage: 2 item
 ; ZVFH-NEXT:  LV(REG): RegisterClass: RISCV::GPRRC, 3 registers
 ; ZVFH-NEXT:  LV(REG): RegisterClass: RISCV::VRRC, 2 registers
 ; ZVFH-NEXT:  LV(REG): Found invariant usage: 1 item
 ; ZVFH-NEXT:  LV(REG): RegisterClass: RISCV::GPRRC, 1 registers
-; ZVFHMIN:       LV(REG): VF = 8
-; ZVFHMIN-NEXT:  LV(REG): Found max usage: 2 item
+; ZVFHMIN:  LV(REG): Found max usage: 2 item
 ; ZVFHMIN-NEXT:  LV(REG): RegisterClass: RISCV::GPRRC, 3 registers
 ; ZVFHMIN-NEXT:  LV(REG): RegisterClass: RISCV::VRRC, 4 registers
 ; ZVFHMIN-NEXT:  LV(REG): Found invariant usage: 1 item
diff --git a/llvm/test/Transforms/LoopVectorize/RISCV/reg-usage.ll b/llvm/test/Transforms/LoopVectorize/RISCV/reg-usage.ll
index 15665fbd9e315..d9929bc0a16da 100644
--- a/llvm/test/Transforms/LoopVectorize/RISCV/reg-usage.ll
+++ b/llvm/test/Transforms/LoopVectorize/RISCV/reg-usage.ll
@@ -28,28 +28,24 @@ define void @add(ptr noalias nocapture readonly %src1, ptr noalias nocapture rea
 ; CHECK-SCALAR-NEXT: LV(REG): RegisterClass: RISCV::FPRRC, 2 registers
 ; CHECK-SCALAR-NEXT: LV(REG): Found invariant usage: 1 item
 ; CHECK-SCALAR-NEXT: LV(REG): RegisterClass: RISCV::GPRRC, 1 registers
-; CHECK-LMUL1:       LV(REG): VF = 2
-; CHECK-LMUL1-NEXT:  LV(REG): Found max usage: 2 item
+; CHECK-LMUL1:  LV(REG): Found max usage: 2 item
 ; CHECK-LMUL1-NEXT:  LV(REG): RegisterClass: RISCV::GPRRC, 3 registers
 ; CHECK-LMUL1-NEXT:  LV(REG): RegisterClass: RISCV::VRRC, 2 registers
 ; CHECK-LMUL1-NEXT:  LV(REG): Found invariant usage: 1 item
 ; CHECK-LMUL1-NEXT:  LV(REG): RegisterClass: RISCV::GPRRC, 1 registers
-; CHECK-LMUL2:       LV(REG): VF = 4
-; CHECK-LMUL2-NEXT:  LV(REG): Found max usage: 2 item
+; CHECK-LMUL2:  LV(REG): Found max usage: 2 item
 ; CHECK-LMUL2-NEXT:  LV(REG): RegisterClass: RISCV::GPRRC, 3 registers
-; CHECK-LMUL2-NEXT:  LV(REG): RegisterClass: RISCV::VRRC, 2 registers
+; CHECK-LMUL2-NEXT:  LV(REG): RegisterClass: RISCV::VRRC, 4 registers
 ; CHECK-LMUL2-NEXT:  LV(REG): Found invariant usage: 1 item
 ; CHECK-LMUL2-NEXT:  LV(REG): RegisterClass: RISCV::GPRRC, 1 registers
-; CHECK-LMUL4:       LV(REG): VF = 8
-; CHECK-LMUL4-NEXT:  LV(REG): Found max usage: 2 item
+; CHECK-LMUL4:  LV(REG): Found max usage: 2 item
 ; CHECK-LMUL4-NEXT:  LV(REG): RegisterClass: RISCV::GPRRC, 3 registers
-; CHECK-LMUL4-NEXT:  LV(REG): RegisterClass: RISCV::VRRC, 4 registers
+; CHECK-LMUL4-NEXT:  LV(REG): RegisterClass: RISCV::VRRC, 8 registers
 ; CHECK-LMUL4-NEXT:  LV(REG): Found invariant usage: 1 item
 ; CHECK-LMUL4-NEXT:  LV(REG): RegisterClass: RISCV::GPRRC, 1 registers
-; CHECK-LMUL8:       LV(REG): VF = 16
-; CHECK-LMUL8-NEXT:  LV(REG): Found max usage: 2 item
+; CHECK-LMUL8:  LV(REG): Found max usage: 2 item
 ; CHECK-LMUL8-NEXT:  LV(REG): RegisterClass: RISCV::GPRRC, 3 registers
-; CHECK-LMUL8-NEXT:  LV(REG): RegisterClass: RISCV::VRRC, 8 registers
+; CHECK-LMUL8-NEXT:  LV(REG): RegisterClass: RISCV::VRRC, 16 registers
 ; CHECK-LMUL8-NEXT:  LV(REG): Found invariant usage: 1 item
 ; CHECK-LMUL8-NEXT:  LV(REG): RegisterClass: RISCV::GPRRC, 1 registers
 
@@ -80,21 +76,17 @@ define void @goo(ptr nocapture noundef %a, i32 noundef signext %n) {
 ; CHECK-SCALAR:      LV(REG): VF = 1
 ; CHECK-SCALAR-NEXT: LV(REG): Found max usage: 1 item
 ; CHECK-SCALAR-NEXT: LV(REG): RegisterClass: RISCV::GPRRC, 3 registers
-; CHECK-LMUL1:       LV(REG): VF = 2
-; CHECK-LMUL1-NEXT:  LV(REG): Found max usage: 2 item
-; CHECK-LMUL1-NEXT:  LV(REG): RegisterClass: RISCV::GPRRC, 3 registers
-; CHECK-LMUL1-NEXT:  LV(REG): RegisterClass: RISCV::VRRC, 2 registers
-; CHECK-LMUL2:       LV(REG): VF = 4
-; CHECK-LMUL2-NEXT:  LV(REG): Found max usage: 2 item
-; CHECK-LMUL2-NEXT:  LV(REG): RegisterClass: RISCV::GPRRC, 3 registers
+; CHECK-LMUL1:  LV(REG): Found max usage: 2 item
+; CHECK-LMUL1-NEXT:  LV(REG): RegisterClass: RISCV::GPRRC, 2 registers
+; CHECK-LMUL1-NEXT:  LV(REG): RegisterClass: RISCV::VRRC, 1 registers
+; CHECK-LMUL2:  LV(REG): Found max usage: 2 item
+; CHECK-LMUL2-NEXT:  LV(REG): RegisterClass: RISCV::GPRRC, 2 registers
 ; CHECK-LMUL2-NEXT:  LV(REG): RegisterClass: RISCV::VRRC, 2 registers
-; CHECK-LMUL4:       LV(REG): VF = 8
-; CHECK-LMUL4-NEXT:  LV(REG): Found max usage: 2 item
-; CHECK-LMUL4-NEXT:  LV(REG): RegisterClass: RISCV::GPRRC, 3 registers
+; CHECK-LMUL4:  LV(REG): Found max usage: 2 item
+; CHECK-LMUL4-NEXT:  LV(REG): RegisterClass: RISCV::GPRRC, 2 registers
 ; CHECK-LMUL4-NEXT:  LV(REG): RegisterClass: RISCV::VRRC, 4 registers
-; CHECK-LMUL8:       LV(REG): VF = 16
-; CHECK-LMUL8-NEXT:  LV(REG): Found max usage: 2 item
-; CHECK-LMUL8-NEXT:  LV(REG): RegisterClass: RISCV::GPRRC, 3 registers
+; CHECK-LMUL8:  LV(REG): Found max usage: 2 item
+; CHECK-LMUL8-NEXT:  LV(REG): RegisterClass: RISCV::GPRRC, 2 registers
 ; CHECK-LMUL8-NEXT:  LV(REG): RegisterClass: RISCV::VRRC, 8 registers
 entry:
   %cmp3 = icmp sgt i32 %n, 0



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