Move transform to VectorCombine and update tests.

Leon Clark · Leon Clark · commit 7499a48455d1 · 2025-07-08T22:50:10.000+01:00
diff --git a/llvm/lib/Transforms/AggressiveInstCombine/AggressiveInstCombine.cpp b/llvm/lib/Transforms/AggressiveInstCombine/AggressiveInstCombine.cpp
@@ -987,94 +987,6 @@ static bool foldPatternedLoads(Instruction &I, const DataLayout &DL) {
   return true;
 }
 
-// If `I` is a load instruction, used only by shufflevector instructions with
-// poison values, attempt to shrink the load to only the lanes being used.
-static bool shrinkLoadsForBroadcast(Instruction &I) {
-  auto *OldLoad = dyn_cast<LoadInst>(&I);
-  if (!OldLoad || !OldLoad->isSimple())
-    return false;
-
-  auto *VecTy = dyn_cast<FixedVectorType>(I.getType());
-  if (!VecTy)
-    return false;
-
-  auto IsPoisonOrUndef = [](Value *V) -> bool {
-    if (auto *C = dyn_cast<Constant>(V)) {
-      return isa<PoisonValue>(C) || isa<UndefValue>(C);
-    }
-    return false;
-  };
-
-  using IndexRange = std::pair<unsigned, unsigned>;
-  auto GetIndexRangeInShuffles = [&]() -> std::optional<IndexRange> {
-    auto OutputRange = IndexRange(VecTy->getNumElements(), 0u);
-    for (auto &Use : I.uses()) {
-      // All uses must be ShuffleVector instructions.
-      auto *Shuffle = dyn_cast<ShuffleVectorInst>(Use.getUser());
-      if (!Shuffle)
-        return {};
-
-      // Get index range for value.
-      auto *Op0 = Shuffle->getOperand(0u);
-      auto *Op1 = Shuffle->getOperand(1u);
-      if (!IsPoisonOrUndef(Op1))
-        return {};
-
-      // Find the min and max indices used by the ShuffleVector instruction.
-      auto Mask = Shuffle->getShuffleMask();
-      auto *Op0Ty = cast<FixedVectorType>(Op0->getType());
-      auto NumElems = Op0Ty->getNumElements();
-
-      for (unsigned Index : Mask) {
-        if (Index < NumElems) {
-          OutputRange.first = std::min(Index, OutputRange.first);
-          OutputRange.second = std::max(Index, OutputRange.second);
-        }
-      }
-    }
-    return OutputRange;
-  };
-
-  if (auto Indices = GetIndexRangeInShuffles()) {
-    auto OldSize = VecTy->getNumElements();
-    auto NewSize = Indices->second + 1u;
-
-    if (NewSize < OldSize) {
-      auto Builder = IRBuilder(&I);
-      Builder.SetCurrentDebugLocation(I.getDebugLoc());
-
-      // Create new load of smaller vector.
-      auto *ElemTy = VecTy->getElementType();
-      auto *NewVecTy = FixedVectorType::get(ElemTy, NewSize);
-      auto *NewLoad = cast<LoadInst>(
-          Builder.CreateLoad(NewVecTy, OldLoad->getPointerOperand()));
-      NewLoad->copyMetadata(I);
-
-      // Replace all users.
-      auto OldShuffles = SmallVector<ShuffleVectorInst *, 4u>{};
-      for (auto &Use : I.uses()) {
-        auto *Shuffle = cast<ShuffleVectorInst>(Use.getUser());
-
-        Builder.SetInsertPoint(Shuffle);
-        Builder.SetCurrentDebugLocation(Shuffle->getDebugLoc());
-        auto *NewShuffle = Builder.CreateShuffleVector(
-            NewLoad, PoisonValue::get(NewVecTy), Shuffle->getShuffleMask());
-
-        Shuffle->replaceAllUsesWith(NewShuffle);
-        OldShuffles.push_back(Shuffle);
-      }
-
-      // Erase old users.
-      for (auto *Shuffle : OldShuffles)
-        Shuffle->eraseFromParent();
-
-      I.eraseFromParent();
-      return true;
-    }
-  }
-  return false;
-}
-
 namespace {
 class StrNCmpInliner {
 public:
@@ -1413,7 +1325,6 @@ static bool foldUnusualPatterns(Function &F, DominatorTree &DT,
       MadeChange |= foldConsecutiveLoads(I, DL, TTI, AA, DT);
       MadeChange |= foldPatternedLoads(I, DL);
       MadeChange |= foldICmpOrChain(I, DL, TTI, AA, DT);
-      MadeChange |= shrinkLoadsForBroadcast(I);
       // NOTE: This function introduces erasing of the instruction `I`, so it
       // needs to be called at the end of this sequence, otherwise we may make
       // bugs.
diff --git a/llvm/lib/Transforms/Vectorize/VectorCombine.cpp b/llvm/lib/Transforms/Vectorize/VectorCombine.cpp
@@ -137,6 +137,7 @@ class VectorCombine {
   bool foldSelectShuffle(Instruction &I, bool FromReduction = false);
   bool foldInterleaveIntrinsics(Instruction &I);
   bool shrinkType(Instruction &I);
+  bool shrinkLoadForShuffles(Instruction &I);
 
   void replaceValue(Value &Old, Value &New) {
     LLVM_DEBUG(dbgs() << "VC: Replacing: " << Old << '\n');
@@ -3691,6 +3692,101 @@ bool VectorCombine::foldInterleaveIntrinsics(Instruction &I) {
   return true;
 }
 
+// If `I` is a load instruction, used only by shufflevector instructions with
+// poison values, attempt to shrink the load to only the lanes being used.
+bool VectorCombine::shrinkLoadForShuffles(Instruction &I) {
+  auto *OldLoad = dyn_cast<LoadInst>(&I);
+  if (!OldLoad || !OldLoad->isSimple())
+    return false;
+
+  auto *VecTy = dyn_cast<FixedVectorType>(I.getType());
+  if (!VecTy)
+    return false;
+
+  auto IsPoisonOrUndef = [](Value *V) -> bool {
+    if (auto *C = dyn_cast<Constant>(V)) {
+      return isa<PoisonValue>(C) || isa<UndefValue>(C);
+    }
+    return false;
+  };
+
+  using IndexRange = std::pair<int, int>;
+  auto GetIndexRangeInShuffles = [&]() -> std::optional<IndexRange> {
+    auto OutputRange = IndexRange(VecTy->getNumElements(), -1);
+    for (auto &Use : I.uses()) {
+      // All uses must be ShuffleVector instructions.
+      auto *Shuffle = dyn_cast<ShuffleVectorInst>(Use.getUser());
+      if (!Shuffle)
+        return {};
+
+      // Get index range for value.
+      auto *Op0 = Shuffle->getOperand(0u);
+      auto *Op1 = Shuffle->getOperand(1u);
+      if (!IsPoisonOrUndef(Op1))
+        return {};
+
+      // Find the min and max indices used by the ShuffleVector instruction.
+      auto Mask = Shuffle->getShuffleMask();
+      auto *Op0Ty = cast<FixedVectorType>(Op0->getType());
+      auto NumElems = int(Op0Ty->getNumElements());
+
+      for (auto Index : Mask) {
+        if (Index >= 0 && Index < NumElems) {
+          OutputRange.first = std::min(Index, OutputRange.first);
+          OutputRange.second = std::max(Index, OutputRange.second);
+        }
+      }
+
+      if (OutputRange.second < OutputRange.first)
+        return {};
+    }
+    return OutputRange;
+  };
+
+  if (auto Indices = GetIndexRangeInShuffles()) {
+    auto OldSize = VecTy->getNumElements();
+    auto NewSize = Indices->second + 1u;
+
+    if (NewSize < OldSize) {
+      auto Builder = IRBuilder(&I);
+      Builder.SetCurrentDebugLocation(I.getDebugLoc());
+
+      // Create new load of smaller vector.
+      auto *ElemTy = VecTy->getElementType();
+      auto *NewVecTy = FixedVectorType::get(ElemTy, NewSize);
+      auto *NewLoad = cast<LoadInst>(
+          Builder.CreateLoad(NewVecTy, OldLoad->getPointerOperand()));
+      NewLoad->copyMetadata(I);
+
+      // Compare cost of old and new loads.
+      auto OldCost = TTI.getMemoryOpCost(
+          Instruction::Load, OldLoad->getType(), OldLoad->getAlign(),
+          OldLoad->getPointerAddressSpace(), CostKind);
+      auto NewCost = TTI.getMemoryOpCost(
+          Instruction::Load, NewLoad->getType(), NewLoad->getAlign(),
+          NewLoad->getPointerAddressSpace(), CostKind);
+
+      if (OldCost < NewCost || !NewCost.isValid())
+        return false;
+
+      // Replace all users.
+      for (auto &Use : I.uses()) {
+        auto *Shuffle = cast<ShuffleVectorInst>(Use.getUser());
+
+        Builder.SetInsertPoint(Shuffle);
+        Builder.SetCurrentDebugLocation(Shuffle->getDebugLoc());
+        auto *NewShuffle = Builder.CreateShuffleVector(
+            NewLoad, PoisonValue::get(NewVecTy), Shuffle->getShuffleMask());
+
+        replaceValue(*Shuffle, *NewShuffle);
+      }
+
+      return true;
+    }
+  }
+  return false;
+}
+
 /// This is the entry point for all transforms. Pass manager differences are
 /// handled in the callers of this function.
 bool VectorCombine::run() {
@@ -3775,6 +3871,9 @@ bool VectorCombine::run() {
       case Instruction::Xor:
         MadeChange |= foldBitOpOfBitcasts(I);
         break;
+      case Instruction::Load:
+        MadeChange |= shrinkLoadForShuffles(I);
+        break;
       default:
         MadeChange |= shrinkType(I);
         break;
diff --git a/llvm/test/Transforms/PhaseOrdering/X86/vec-load-combine.ll b/llvm/test/Transforms/PhaseOrdering/X86/vec-load-combine.ll
@@ -11,13 +11,13 @@ $getAt = comdat any
 
 define dso_local noundef <4 x float> @ConvertVectors_ByRef(ptr noundef nonnull align 16 dereferenceable(16) %0) #0 {
 ; SSE-LABEL: @ConvertVectors_ByRef(
-; SSE-NEXT:    [[TMP2:%.*]] = load <4 x float>, ptr [[TMP0:%.*]], align 16
-; SSE-NEXT:    [[TMP3:%.*]] = shufflevector <4 x float> [[TMP2]], <4 x float> poison, <4 x i32> <i32 0, i32 1, i32 2, i32 2>
+; SSE-NEXT:    [[TMP2:%.*]] = load <3 x float>, ptr [[TMP0:%.*]], align 16
+; SSE-NEXT:    [[TMP3:%.*]] = shufflevector <3 x float> [[TMP2]], <3 x float> poison, <4 x i32> <i32 0, i32 1, i32 2, i32 2>
 ; SSE-NEXT:    ret <4 x float> [[TMP3]]
 ;
 ; AVX-LABEL: @ConvertVectors_ByRef(
-; AVX-NEXT:    [[TMP2:%.*]] = load <4 x float>, ptr [[TMP0:%.*]], align 16
-; AVX-NEXT:    [[TMP3:%.*]] = shufflevector <4 x float> [[TMP2]], <4 x float> poison, <4 x i32> <i32 0, i32 1, i32 2, i32 2>
+; AVX-NEXT:    [[TMP2:%.*]] = load <3 x float>, ptr [[TMP0:%.*]], align 16
+; AVX-NEXT:    [[TMP3:%.*]] = shufflevector <3 x float> [[TMP2]], <3 x float> poison, <4 x i32> <i32 0, i32 1, i32 2, i32 2>
 ; AVX-NEXT:    ret <4 x float> [[TMP3]]
 ;
   %2 = alloca ptr, align 8
diff --git a/llvm/test/Transforms/VectorCombine/X86/load-widening.ll b/llvm/test/Transforms/VectorCombine/X86/load-widening.ll
@@ -336,7 +336,7 @@ define <8 x float> @load_v2f32_v8f32(ptr dereferenceable(32) %p) {
 
 define <4 x i32> @load_v2i32_v4i32(ptr dereferenceable(16) %p) {
 ; CHECK-LABEL: @load_v2i32_v4i32(
-; CHECK-NEXT:    [[S:%.*]] = load <4 x i32>, ptr [[P:%.*]], align 1
+; CHECK-NEXT:    [[S:%.*]] = load <4 x i32>, ptr [[P:%.*]], align 4
 ; CHECK-NEXT:    ret <4 x i32> [[S]]
 ;
   %l = load <2 x i32>, ptr %p, align 1
@@ -443,8 +443,8 @@ define <8 x float> @load_v2f32_v8f32_hwasan(ptr dereferenceable(32) %p) sanitize
 
 define <4 x i32> @load_v2i32_v4i32_asan(ptr dereferenceable(16) %p) sanitize_address {
 ; CHECK-LABEL: @load_v2i32_v4i32_asan(
-; CHECK-NEXT:    [[L:%.*]] = load <2 x i32>, ptr [[P:%.*]], align 1
-; CHECK-NEXT:    [[S:%.*]] = shufflevector <2 x i32> [[L]], <2 x i32> poison, <4 x i32> <i32 0, i32 poison, i32 poison, i32 poison>
+; CHECK-NEXT:    [[TMP1:%.*]] = load <1 x i32>, ptr [[P:%.*]], align 4
+; CHECK-NEXT:    [[S:%.*]] = shufflevector <1 x i32> [[TMP1]], <1 x i32> poison, <4 x i32> <i32 0, i32 poison, i32 poison, i32 poison>
 ; CHECK-NEXT:    ret <4 x i32> [[S]]
 ;
   %l = load <2 x i32>, ptr %p, align 1
diff --git a/llvm/test/Transforms/VectorCombine/X86/shuffle-of-shuffles.ll b/llvm/test/Transforms/VectorCombine/X86/shuffle-of-shuffles.ll
@@ -47,21 +47,12 @@ define <8 x i32> @concat_extract_subvectors_poison(<8 x i32> %x) {
 ; broadcast loads are free on AVX (and blends are much cheap than general 2-operand shuffles)
 
 define  <4 x double> @blend_broadcasts_v4f64(ptr %p0, ptr %p1)  {
-; SSE-LABEL: define <4 x double> @blend_broadcasts_v4f64(
-; SSE-SAME: ptr [[P0:%.*]], ptr [[P1:%.*]]) #[[ATTR0]] {
-; SSE-NEXT:    [[LD0:%.*]] = load <4 x double>, ptr [[P0]], align 32
-; SSE-NEXT:    [[LD1:%.*]] = load <4 x double>, ptr [[P1]], align 32
-; SSE-NEXT:    [[BLEND:%.*]] = shufflevector <4 x double> [[LD0]], <4 x double> [[LD1]], <4 x i32> <i32 0, i32 4, i32 4, i32 0>
-; SSE-NEXT:    ret <4 x double> [[BLEND]]
-;
-; AVX-LABEL: define <4 x double> @blend_broadcasts_v4f64(
-; AVX-SAME: ptr [[P0:%.*]], ptr [[P1:%.*]]) #[[ATTR0]] {
-; AVX-NEXT:    [[LD0:%.*]] = load <4 x double>, ptr [[P0]], align 32
-; AVX-NEXT:    [[LD1:%.*]] = load <4 x double>, ptr [[P1]], align 32
-; AVX-NEXT:    [[BCST0:%.*]] = shufflevector <4 x double> [[LD0]], <4 x double> undef, <4 x i32> zeroinitializer
-; AVX-NEXT:    [[BCST1:%.*]] = shufflevector <4 x double> [[LD1]], <4 x double> undef, <4 x i32> zeroinitializer
-; AVX-NEXT:    [[BLEND:%.*]] = shufflevector <4 x double> [[BCST0]], <4 x double> [[BCST1]], <4 x i32> <i32 0, i32 5, i32 6, i32 3>
-; AVX-NEXT:    ret <4 x double> [[BLEND]]
+; CHECK-LABEL: define <4 x double> @blend_broadcasts_v4f64(
+; CHECK-SAME: ptr [[P0:%.*]], ptr [[P1:%.*]]) #[[ATTR0]] {
+; CHECK-NEXT:    [[TMP1:%.*]] = load <1 x double>, ptr [[P0]], align 8
+; CHECK-NEXT:    [[TMP2:%.*]] = load <1 x double>, ptr [[P1]], align 8
+; CHECK-NEXT:    [[BLEND:%.*]] = shufflevector <1 x double> [[TMP1]], <1 x double> [[TMP2]], <4 x i32> <i32 0, i32 1, i32 1, i32 0>
+; CHECK-NEXT:    ret <4 x double> [[BLEND]]
 ;
   %ld0 = load <4 x double>, ptr %p0, align 32
   %ld1 = load <4 x double>, ptr %p1, align 32
@@ -81,3 +72,6 @@ define <2 x float> @PR86068(<2 x float> %a0, <2 x float> %a1) {
   %s2 = shufflevector <2 x float> %s1, <2 x float> %a0, <2 x i32> <i32 0, i32 3>
   ret <2 x float> %s2
 }
+;; NOTE: These prefixes are unused and the list is autogenerated. Do not add tests below this line:
+; AVX: {{.*}}
+; SSE: {{.*}}
diff --git a/llvm/test/Transforms/VectorCombine/load-shufflevector.ll b/llvm/test/Transforms/VectorCombine/load-shufflevector.ll
@@ -1,5 +1,5 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
-; RUN: opt -passes=aggressive-instcombine -S < %s | FileCheck %s
+; RUN: opt -passes=vector-combine -S < %s | FileCheck %s
 
 define <8 x half> @shuffle_v4_v8f16_r0_1_volatile(ptr addrspace(1) nocapture readonly %arg0) local_unnamed_addr {
 ; CHECK-LABEL: define <8 x half> @shuffle_v4_v8f16_r0_1_volatile(
