[Scalarizer][DirectX] support structs return types (#111569)

Based on this RFC:
https://discourse.llvm.org/t/rfc-allow-the-scalarizer-pass-to-scalarize-vectors-returned-in-structs/82306

LLVM intrinsics do not support out params. To get around this limitation
implementers will make intrinsics return structs to capture a return
type and an out param. This implementation detail should not impact
scalarization since these cases should be elementwise operations.

## Three changes are needed. 
- The CallInst visitor needs to be updated to handle Structs
- A new visitor is needed for `ExtractValue` instructions
- finsh needs to be update to handle structs so that insert elements are
properly propogated.

## Testing changes
- Add support for `llvm.frexp`
- Add support for `llvm.dx.splitdouble`

fixes llvm/llvm-project#111437

Author: farzonl

llvm/include/llvm/Analysis/VectorUtils.h

@@ -154,6 +154,11 @@ bool isVectorIntrinsicWithScalarOpAtArg(Intrinsic::ID ID,
 /// the operand at index \p OpdIdx, or on the return type if \p OpdIdx is -1.
 bool isVectorIntrinsicWithOverloadTypeAtArg(Intrinsic::ID ID, int OpdIdx);
 
+/// Identifies if the vector form of the intrinsic that returns a struct is
+/// overloaded at the struct element index \p RetIdx.
+bool isVectorIntrinsicWithStructReturnOverloadAtField(Intrinsic::ID ID,
+                                                      int RetIdx);
+
 /// Returns intrinsic ID for call.
 /// For the input call instruction it finds mapping intrinsic and returns
 /// its intrinsic ID, in case it does not found it return not_intrinsic.

llvm/include/llvm/IR/IntrinsicsDirectX.td

@@ -94,5 +94,7 @@ def int_dx_wave_is_first_lane : DefaultAttrsIntrinsic<[llvm_i1_ty], [], [IntrCon
 def int_dx_wave_readlane : DefaultAttrsIntrinsic<[llvm_any_ty], [LLVMMatchType<0>, llvm_i32_ty], [IntrConvergent, IntrNoMem]>;
 def int_dx_sign : DefaultAttrsIntrinsic<[LLVMScalarOrSameVectorWidth<0, llvm_i32_ty>], [llvm_any_ty], [IntrNoMem]>;
 def int_dx_step : DefaultAttrsIntrinsic<[LLVMMatchType<0>], [llvm_anyfloat_ty, LLVMMatchType<0>], [IntrNoMem]>;
+def int_dx_splitdouble : DefaultAttrsIntrinsic<[llvm_anyint_ty, LLVMMatchType<0>], 
+    [LLVMScalarOrSameVectorWidth<0, llvm_double_ty>], [IntrNoMem]>;
 def int_dx_radians : DefaultAttrsIntrinsic<[llvm_anyfloat_ty], [LLVMMatchType<0>], [IntrNoMem]>;
 }

llvm/lib/Analysis/VectorUtils.cpp

@@ -152,6 +152,16 @@ bool llvm::isVectorIntrinsicWithOverloadTypeAtArg(Intrinsic::ID ID,
   }
 }
 
+bool llvm::isVectorIntrinsicWithStructReturnOverloadAtField(Intrinsic::ID ID,
+                                                            int RetIdx) {
+  switch (ID) {
+  case Intrinsic::frexp:
+    return RetIdx == 0 || RetIdx == 1;
+  default:
+    return RetIdx == 0;
+  }
+}
+
 /// Returns intrinsic ID for call.
 /// For the input call instruction it finds mapping intrinsic and returns
 /// its ID, in case it does not found it return not_intrinsic.

llvm/lib/Target/DirectX/DirectXTargetTransformInfo.cpp

@@ -1,38 +1,39 @@
-//===- DirectXTargetTransformInfo.cpp - DirectX TTI ---------------*- C++
-//-*-===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-///
-//===----------------------------------------------------------------------===//
-
-#include "DirectXTargetTransformInfo.h"
-#include "llvm/IR/Intrinsics.h"
-#include "llvm/IR/IntrinsicsDirectX.h"
-
-using namespace llvm;
-
-bool DirectXTTIImpl::isTargetIntrinsicWithScalarOpAtArg(Intrinsic::ID ID,
-                                                        unsigned ScalarOpdIdx) {
-  switch (ID) {
-  case Intrinsic::dx_wave_readlane:
-    return ScalarOpdIdx == 1;
-  default:
-    return false;
-  }
-}
-
-bool DirectXTTIImpl::isTargetIntrinsicTriviallyScalarizable(
-    Intrinsic::ID ID) const {
-  switch (ID) {
-  case Intrinsic::dx_frac:
-  case Intrinsic::dx_rsqrt:
-  case Intrinsic::dx_wave_readlane:
-    return true;
-  default:
-    return false;
-  }
-}
+//===- DirectXTargetTransformInfo.cpp - DirectX TTI ---------------*- C++
+//-*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+//===----------------------------------------------------------------------===//
+
+#include "DirectXTargetTransformInfo.h"
+#include "llvm/IR/Intrinsics.h"
+#include "llvm/IR/IntrinsicsDirectX.h"
+
+using namespace llvm;
+
+bool DirectXTTIImpl::isTargetIntrinsicWithScalarOpAtArg(Intrinsic::ID ID,
+                                                        unsigned ScalarOpdIdx) {
+  switch (ID) {
+  case Intrinsic::dx_wave_readlane:
+    return ScalarOpdIdx == 1;
+  default:
+    return false;
+  }
+}
+
+bool DirectXTTIImpl::isTargetIntrinsicTriviallyScalarizable(
+    Intrinsic::ID ID) const {
+  switch (ID) {
+  case Intrinsic::dx_frac:
+  case Intrinsic::dx_rsqrt:
+  case Intrinsic::dx_wave_readlane:
+  case Intrinsic::dx_splitdouble:
+    return true;
+  default:
+    return false;
+  }
+}

llvm/lib/Transforms/Scalar/Scalarizer.cpp

@@ -197,6 +197,24 @@ struct VectorLayout {
   uint64_t SplitSize = 0;
 };
 
+static bool isStructOfMatchingFixedVectors(Type *Ty) {
+  if (!isa<StructType>(Ty))
+    return false;
+  unsigned StructSize = Ty->getNumContainedTypes();
+  if (StructSize < 1)
+    return false;
+  FixedVectorType *VecTy = dyn_cast<FixedVectorType>(Ty->getContainedType(0));
+  if (!VecTy)
+    return false;
+  unsigned VecSize = VecTy->getNumElements();
+  for (unsigned I = 1; I < StructSize; I++) {
+    VecTy = dyn_cast<FixedVectorType>(Ty->getContainedType(I));
+    if (!VecTy || VecSize != VecTy->getNumElements())
+      return false;
+  }
+  return true;
+}
+
 /// Concatenate the given fragments to a single vector value of the type
 /// described in @p VS.
 static Value *concatenate(IRBuilder<> &Builder, ArrayRef<Value *> Fragments,
@@ -276,6 +294,7 @@ class ScalarizerVisitor : public InstVisitor<ScalarizerVisitor, bool> {
   bool visitBitCastInst(BitCastInst &BCI);
   bool visitInsertElementInst(InsertElementInst &IEI);
   bool visitExtractElementInst(ExtractElementInst &EEI);
+  bool visitExtractValueInst(ExtractValueInst &EVI);
   bool visitShuffleVectorInst(ShuffleVectorInst &SVI);
   bool visitPHINode(PHINode &PHI);
   bool visitLoadInst(LoadInst &LI);
@@ -667,14 +686,26 @@ bool ScalarizerVisitor::splitBinary(Instruction &I, const Splitter &Split) {
 bool ScalarizerVisitor::isTriviallyScalarizable(Intrinsic::ID ID) {
   if (isTriviallyVectorizable(ID))
     return true;
+  // TODO: Move frexp to isTriviallyVectorizable.
+  // https://github.com/llvm/llvm-project/issues/112408
+  switch (ID) {
+  case Intrinsic::frexp:
+    return true;
+  }
   return Intrinsic::isTargetIntrinsic(ID) &&
          TTI->isTargetIntrinsicTriviallyScalarizable(ID);
 }
 
 /// If a call to a vector typed intrinsic function, split into a scalar call per
 /// element if possible for the intrinsic.
 bool ScalarizerVisitor::splitCall(CallInst &CI) {
-  std::optional<VectorSplit> VS = getVectorSplit(CI.getType());
+  Type *CallType = CI.getType();
+  bool AreAllVectorsOfMatchingSize = isStructOfMatchingFixedVectors(CallType);
+  std::optional<VectorSplit> VS;
+  if (AreAllVectorsOfMatchingSize)
+    VS = getVectorSplit(CallType->getContainedType(0));
+  else
+    VS = getVectorSplit(CallType);
   if (!VS)
     return false;
 
@@ -699,6 +730,23 @@ bool ScalarizerVisitor::splitCall(CallInst &CI) {
   if (isVectorIntrinsicWithOverloadTypeAtArg(ID, -1))
     Tys.push_back(VS->SplitTy);
 
+  if (AreAllVectorsOfMatchingSize) {
+    for (unsigned I = 1; I < CallType->getNumContainedTypes(); I++) {
+      std::optional<VectorSplit> CurrVS =
+          getVectorSplit(cast<FixedVectorType>(CallType->getContainedType(I)));
+      // This case does not seem to happen, but it is possible for
+      // VectorSplit.NumPacked >= NumElems. If that happens a VectorSplit
+      // is not returned and we will bailout of handling this call.
+      // The secondary bailout case is if NumPacked does not match.
+      // This can happen if ScalarizeMinBits is not set to the default.
+      // This means with certain ScalarizeMinBits intrinsics like frexp
+      // will only scalarize when the struct elements have the same bitness.
+      if (!CurrVS || CurrVS->NumPacked != VS->NumPacked)
+        return false;
+      if (isVectorIntrinsicWithStructReturnOverloadAtField(ID, I))
+        Tys.push_back(CurrVS->SplitTy);
+    }
+  }
   // Assumes that any vector type has the same number of elements as the return
   // vector type, which is true for all current intrinsics.
   for (unsigned I = 0; I != NumArgs; ++I) {
@@ -1030,6 +1078,31 @@ bool ScalarizerVisitor::visitInsertElementInst(InsertElementInst &IEI) {
   return true;
 }
 
+bool ScalarizerVisitor::visitExtractValueInst(ExtractValueInst &EVI) {
+  Value *Op = EVI.getOperand(0);
+  Type *OpTy = Op->getType();
+  ValueVector Res;
+  if (!isStructOfMatchingFixedVectors(OpTy))
+    return false;
+  Type *VecType = cast<FixedVectorType>(OpTy->getContainedType(0));
+  std::optional<VectorSplit> VS = getVectorSplit(VecType);
+  if (!VS)
+    return false;
+  IRBuilder<> Builder(&EVI);
+  Scatterer Op0 = scatter(&EVI, Op, *VS);
+  assert(!EVI.getIndices().empty() && "Make sure an index exists");
+  // Note for our use case we only care about the top level index.
+  unsigned Index = EVI.getIndices()[0];
+  for (unsigned OpIdx = 0; OpIdx < Op0.size(); ++OpIdx) {
+    Value *ResElem = Builder.CreateExtractValue(
+        Op0[OpIdx], Index, EVI.getName() + ".elem" + Twine(Index));
+    Res.push_back(ResElem);
+  }
+
+  gather(&EVI, Res, *VS);
+  return true;
+}
+
 bool ScalarizerVisitor::visitExtractElementInst(ExtractElementInst &EEI) {
   std::optional<VectorSplit> VS = getVectorSplit(EEI.getOperand(0)->getType());
   if (!VS)
@@ -1209,6 +1282,35 @@ bool ScalarizerVisitor::finish() {
         Res = concatenate(Builder, CV, VS, Op->getName());
 
         Res->takeName(Op);
+      } else if (auto *Ty = dyn_cast<StructType>(Op->getType())) {
+        BasicBlock *BB = Op->getParent();
+        IRBuilder<> Builder(Op);
+        if (isa<PHINode>(Op))
+          Builder.SetInsertPoint(BB, BB->getFirstInsertionPt());
+
+        // Iterate over each element in the struct
+        unsigned NumOfStructElements = Ty->getNumElements();
+        SmallVector<ValueVector, 4> ElemCV(NumOfStructElements);
+        for (unsigned I = 0; I < NumOfStructElements; ++I) {
+          for (auto *CVelem : CV) {
+            Value *Elem = Builder.CreateExtractValue(
+                CVelem, I, Op->getName() + ".elem" + Twine(I));
+            ElemCV[I].push_back(Elem);
+          }
+        }
+        Res = PoisonValue::get(Ty);
+        for (unsigned I = 0; I < NumOfStructElements; ++I) {
+          Type *ElemTy = Ty->getElementType(I);
+          assert(isa<FixedVectorType>(ElemTy) &&
+                 "Only Structs of all FixedVectorType supported");
+          VectorSplit VS = *getVectorSplit(ElemTy);
+          assert(VS.NumFragments == CV.size());
+
+          Value *ConcatenatedVector =
+              concatenate(Builder, ElemCV[I], VS, Op->getName());
+          Res = Builder.CreateInsertValue(Res, ConcatenatedVector, I,
+                                          Op->getName() + ".insert");
+        }
       } else {
         assert(CV.size() == 1 && Op->getType() == CV[0]->getType());
         Res = CV[0];

llvm/test/CodeGen/DirectX/split-double.ll

@@ -0,0 +1,45 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -passes='function(scalarizer)' -S -mtriple=dxil-pc-shadermodel6.3-library %s | FileCheck %s
+
+define void @test_vector_double_split_void(<2 x double> noundef %d) {
+; CHECK-LABEL: define void @test_vector_double_split_void(
+; CHECK-SAME: <2 x double> noundef [[D:%.*]]) {
+; CHECK-NEXT:    [[D_I0:%.*]] = extractelement <2 x double> [[D]], i64 0
+; CHECK-NEXT:    [[HLSL_ASUINT_I0:%.*]] = call { i32, i32 } @llvm.dx.splitdouble.i32(double [[D_I0]])
+; CHECK-NEXT:    [[D_I1:%.*]] = extractelement <2 x double> [[D]], i64 1
+; CHECK-NEXT:    [[HLSL_ASUINT_I1:%.*]] = call { i32, i32 } @llvm.dx.splitdouble.i32(double [[D_I1]])
+; CHECK-NEXT:    ret void
+;
+  %hlsl.asuint = call { <2 x i32>, <2 x i32> }  @llvm.dx.splitdouble.v2i32(<2 x double> %d)
+  ret void
+}
+
+define noundef <3 x i32> @test_vector_double_split(<3 x double> noundef %d) {
+; CHECK-LABEL: define noundef <3 x i32> @test_vector_double_split(
+; CHECK-SAME: <3 x double> noundef [[D:%.*]]) {
+; CHECK-NEXT:    [[D_I0:%.*]] = extractelement <3 x double> [[D]], i64 0
+; CHECK-NEXT:    [[HLSL_ASUINT_I0:%.*]] = call { i32, i32 } @llvm.dx.splitdouble.i32(double [[D_I0]])
+; CHECK-NEXT:    [[D_I1:%.*]] = extractelement <3 x double> [[D]], i64 1
+; CHECK-NEXT:    [[HLSL_ASUINT_I1:%.*]] = call { i32, i32 } @llvm.dx.splitdouble.i32(double [[D_I1]])
+; CHECK-NEXT:    [[D_I2:%.*]] = extractelement <3 x double> [[D]], i64 2
+; CHECK-NEXT:    [[HLSL_ASUINT_I2:%.*]] = call { i32, i32 } @llvm.dx.splitdouble.i32(double [[D_I2]])
+; CHECK-NEXT:    [[DOTELEM0:%.*]] = extractvalue { i32, i32 } [[HLSL_ASUINT_I0]], 0
+; CHECK-NEXT:    [[DOTELEM01:%.*]] = extractvalue { i32, i32 } [[HLSL_ASUINT_I1]], 0
+; CHECK-NEXT:    [[DOTELEM02:%.*]] = extractvalue { i32, i32 } [[HLSL_ASUINT_I2]], 0
+; CHECK-NEXT:    [[DOTELEM1:%.*]] = extractvalue { i32, i32 } [[HLSL_ASUINT_I0]], 1
+; CHECK-NEXT:    [[DOTELEM13:%.*]] = extractvalue { i32, i32 } [[HLSL_ASUINT_I1]], 1
+; CHECK-NEXT:    [[DOTELEM14:%.*]] = extractvalue { i32, i32 } [[HLSL_ASUINT_I2]], 1
+; CHECK-NEXT:    [[DOTI0:%.*]] = add i32 [[DOTELEM0]], [[DOTELEM1]]
+; CHECK-NEXT:    [[DOTI1:%.*]] = add i32 [[DOTELEM01]], [[DOTELEM13]]
+; CHECK-NEXT:    [[DOTI2:%.*]] = add i32 [[DOTELEM02]], [[DOTELEM14]]
+; CHECK-NEXT:    [[DOTUPTO015:%.*]] = insertelement <3 x i32> poison, i32 [[DOTI0]], i64 0
+; CHECK-NEXT:    [[DOTUPTO116:%.*]] = insertelement <3 x i32> [[DOTUPTO015]], i32 [[DOTI1]], i64 1
+; CHECK-NEXT:    [[TMP1:%.*]] = insertelement <3 x i32> [[DOTUPTO116]], i32 [[DOTI2]], i64 2
+; CHECK-NEXT:    ret <3 x i32> [[TMP1]]
+;
+  %hlsl.asuint = call { <3 x i32>, <3 x i32> }  @llvm.dx.splitdouble.v3i32(<3 x double> %d)
+  %1 = extractvalue { <3 x i32>, <3 x i32> } %hlsl.asuint, 0
+  %2 = extractvalue { <3 x i32>, <3 x i32> } %hlsl.asuint, 1
+  %3 = add <3 x i32> %1, %2
+  ret <3 x i32> %3
+}