[RISCV] Support __riscv_v_fixed_vlen for vbool types. (llvm#76551)

This adopts a similar behavior to AArch64 SVE, where bool vectors are
represented as a vector of chars with 1/8 the number of elements. This
ensures the vector always occupies a power of 2 number of bytes.

A consequence of this is that vbool64_t, vbool32_t, and vool16_t can
only be used with a vector length that guarantees at least 8 bits.

clang/docs/ReleaseNotes.rst

@@ -1227,6 +1227,8 @@ RISC-V Support
 - Default ABI with F but without D was changed to ilp32f for RV32 and to lp64f
   for RV64.
 
+- ``__attribute__((rvv_vector_bits(N))) is now supported for RVV vbool*_t types.
+
 CUDA/HIP Language Changes
 ^^^^^^^^^^^^^^^^^^^^^^^^^
 

clang/include/clang/AST/Type.h

@@ -3495,6 +3495,9 @@ enum class VectorKind {
 
   /// is RISC-V RVV fixed-length data vector
   RVVFixedLengthData,
+
+  /// is RISC-V RVV fixed-length mask vector
+  RVVFixedLengthMask,
 };
 
 /// Represents a GCC generic vector type. This type is created using

clang/include/clang/Basic/AttrDocs.td

@@ -2424,7 +2424,10 @@ only be a power of 2 between 64 and 65536.
 For types where LMUL!=1, ``__riscv_v_fixed_vlen`` needs to be scaled by the LMUL
 of the type before passing to the attribute.
 
-``vbool*_t`` types are not supported at this time.
+For ``vbool*_t`` types, ``__riscv_v_fixed_vlen`` needs to be divided by the
+number from the type name. For example, ``vbool8_t`` needs to use
+``__riscv_v_fixed_vlen`` / 8. If the resulting value is not a multiple of 8,
+the type is not supported for that value of ``__riscv_v_fixed_vlen``.
 }];
 }
 

clang/lib/AST/ASTContext.cpp

@@ -1945,7 +1945,8 @@ TypeInfo ASTContext::getTypeInfoImpl(const Type *T) const {
     else if (VT->getVectorKind() == VectorKind::SveFixedLengthPredicate)
       // Adjust the alignment for fixed-length SVE predicates.
       Align = 16;
-    else if (VT->getVectorKind() == VectorKind::RVVFixedLengthData)
+    else if (VT->getVectorKind() == VectorKind::RVVFixedLengthData ||
+             VT->getVectorKind() == VectorKind::RVVFixedLengthMask)
       // Adjust the alignment for fixed-length RVV vectors.
       Align = std::min<unsigned>(64, Width);
     break;
@@ -9416,7 +9417,9 @@ bool ASTContext::areCompatibleVectorTypes(QualType FirstVec,
       Second->getVectorKind() != VectorKind::SveFixedLengthData &&
       Second->getVectorKind() != VectorKind::SveFixedLengthPredicate &&
       First->getVectorKind() != VectorKind::RVVFixedLengthData &&
-      Second->getVectorKind() != VectorKind::RVVFixedLengthData)
+      Second->getVectorKind() != VectorKind::RVVFixedLengthData &&
+      First->getVectorKind() != VectorKind::RVVFixedLengthMask &&
+      Second->getVectorKind() != VectorKind::RVVFixedLengthMask)
     return true;
 
   return false;
@@ -9522,8 +9525,11 @@ static uint64_t getRVVTypeSize(ASTContext &Context, const BuiltinType *Ty) {
 
   ASTContext::BuiltinVectorTypeInfo Info = Context.getBuiltinVectorTypeInfo(Ty);
 
-  uint64_t EltSize = Context.getTypeSize(Info.ElementType);
-  uint64_t MinElts = Info.EC.getKnownMinValue();
+  unsigned EltSize = Context.getTypeSize(Info.ElementType);
+  if (Info.ElementType == Context.BoolTy)
+    EltSize = 1;
+
+  unsigned MinElts = Info.EC.getKnownMinValue();
   return VScale->first * MinElts * EltSize;
 }
 
@@ -9537,6 +9543,12 @@ bool ASTContext::areCompatibleRVVTypes(QualType FirstType,
   auto IsValidCast = [this](QualType FirstType, QualType SecondType) {
     if (const auto *BT = FirstType->getAs<BuiltinType>()) {
       if (const auto *VT = SecondType->getAs<VectorType>()) {
+        if (VT->getVectorKind() == VectorKind::RVVFixedLengthMask) {
+          BuiltinVectorTypeInfo Info = getBuiltinVectorTypeInfo(BT);
+          return FirstType->isRVVVLSBuiltinType() &&
+                 Info.ElementType == BoolTy &&
+                 getTypeSize(SecondType) == getRVVTypeSize(*this, BT);
+        }
         if (VT->getVectorKind() == VectorKind::RVVFixedLengthData ||
             VT->getVectorKind() == VectorKind::Generic)
           return FirstType->isRVVVLSBuiltinType() &&

clang/lib/AST/ItaniumMangle.cpp

@@ -3994,7 +3994,8 @@ void CXXNameMangler::mangleAArch64FixedSveVectorType(
 }
 
 void CXXNameMangler::mangleRISCVFixedRVVVectorType(const VectorType *T) {
-  assert(T->getVectorKind() == VectorKind::RVVFixedLengthData &&
+  assert((T->getVectorKind() == VectorKind::RVVFixedLengthData ||
+          T->getVectorKind() == VectorKind::RVVFixedLengthMask) &&
          "expected fixed-length RVV vector!");
 
   QualType EltType = T->getElementType();
@@ -4009,7 +4010,10 @@ void CXXNameMangler::mangleRISCVFixedRVVVectorType(const VectorType *T) {
     TypeNameOS << "int8";
     break;
   case BuiltinType::UChar:
-    TypeNameOS << "uint8";
+    if (T->getVectorKind() == VectorKind::RVVFixedLengthData)
+      TypeNameOS << "uint8";
+    else
+      TypeNameOS << "bool";
     break;
   case BuiltinType::Short:
     TypeNameOS << "int16";
@@ -4048,12 +4052,16 @@ void CXXNameMangler::mangleRISCVFixedRVVVectorType(const VectorType *T) {
   auto VScale = getASTContext().getTargetInfo().getVScaleRange(
       getASTContext().getLangOpts());
   unsigned VLen = VScale->first * llvm::RISCV::RVVBitsPerBlock;
-  TypeNameOS << 'm';
-  if (VecSizeInBits >= VLen)
-    TypeNameOS << (VecSizeInBits / VLen);
-  else
-    TypeNameOS << 'f' << (VLen / VecSizeInBits);
 
+  if (T->getVectorKind() == VectorKind::RVVFixedLengthData) {
+    TypeNameOS << 'm';
+    if (VecSizeInBits >= VLen)
+      TypeNameOS << (VecSizeInBits / VLen);
+    else
+      TypeNameOS << 'f' << (VLen / VecSizeInBits);
+  } else {
+    TypeNameOS << (VLen / VecSizeInBits);
+  }
   TypeNameOS << "_t";
 
   Out << "9__RVV_VLSI" << 'u' << TypeNameStr.size() << TypeNameStr << "Lj"
@@ -4093,7 +4101,8 @@ void CXXNameMangler::mangleType(const VectorType *T) {
              T->getVectorKind() == VectorKind::SveFixedLengthPredicate) {
     mangleAArch64FixedSveVectorType(T);
     return;
-  } else if (T->getVectorKind() == VectorKind::RVVFixedLengthData) {
+  } else if (T->getVectorKind() == VectorKind::RVVFixedLengthData ||
+             T->getVectorKind() == VectorKind::RVVFixedLengthMask) {
     mangleRISCVFixedRVVVectorType(T);
     return;
   }

clang/lib/AST/JSONNodeDumper.cpp

@@ -703,6 +703,9 @@ void JSONNodeDumper::VisitVectorType(const VectorType *VT) {
   case VectorKind::RVVFixedLengthData:
     JOS.attribute("vectorKind", "fixed-length rvv data vector");
     break;
+  case VectorKind::RVVFixedLengthMask:
+    JOS.attribute("vectorKind", "fixed-length rvv mask vector");
+    break;
   }
 }
 

clang/lib/AST/TextNodeDumper.cpp

@@ -1623,6 +1623,9 @@ void TextNodeDumper::VisitVectorType(const VectorType *T) {
   case VectorKind::RVVFixedLengthData:
     OS << " fixed-length rvv data vector";
     break;
+  case VectorKind::RVVFixedLengthMask:
+    OS << " fixed-length rvv mask vector";
+    break;
   }
   OS << " " << T->getNumElements();
 }

clang/lib/AST/Type.cpp

@@ -2479,6 +2479,9 @@ bool Type::isRVVVLSBuiltinType() const {
                         IsFP, IsBF)                                            \
   case BuiltinType::Id:                                                        \
     return NF == 1;
+#define RVV_PREDICATE_TYPE(Name, Id, SingletonId, NumEls)                      \
+  case BuiltinType::Id:                                                        \
+    return true;
 #include "clang/Basic/RISCVVTypes.def"
     default:
       return false;
@@ -2491,7 +2494,17 @@ QualType Type::getRVVEltType(const ASTContext &Ctx) const {
   assert(isRVVVLSBuiltinType() && "unsupported type!");
 
   const BuiltinType *BTy = castAs<BuiltinType>();
-  return Ctx.getBuiltinVectorTypeInfo(BTy).ElementType;
+
+  switch (BTy->getKind()) {
+#define RVV_PREDICATE_TYPE(Name, Id, SingletonId, NumEls)                      \
+  case BuiltinType::Id:                                                        \
+    return Ctx.UnsignedCharTy;
+  default:
+    return Ctx.getBuiltinVectorTypeInfo(BTy).ElementType;
+#include "clang/Basic/RISCVVTypes.def"
+  }
+
+  llvm_unreachable("Unhandled type");
 }
 
 bool QualType::isPODType(const ASTContext &Context) const {

clang/lib/AST/TypePrinter.cpp

@@ -694,6 +694,7 @@ void TypePrinter::printVectorBefore(const VectorType *T, raw_ostream &OS) {
     printBefore(T->getElementType(), OS);
     break;
   case VectorKind::RVVFixedLengthData:
+  case VectorKind::RVVFixedLengthMask:
     // FIXME: We prefer to print the size directly here, but have no way
     // to get the size of the type.
     OS << "__attribute__((__riscv_rvv_vector_bits__(";
@@ -773,6 +774,7 @@ void TypePrinter::printDependentVectorBefore(
     printBefore(T->getElementType(), OS);
     break;
   case VectorKind::RVVFixedLengthData:
+  case VectorKind::RVVFixedLengthMask:
     // FIXME: We prefer to print the size directly here, but have no way
     // to get the size of the type.
     OS << "__attribute__((__riscv_rvv_vector_bits__(";

clang/lib/CodeGen/Targets/RISCV.cpp

@@ -321,20 +321,28 @@ ABIArgInfo RISCVABIInfo::coerceVLSVector(QualType Ty) const {
   assert(Ty->isVectorType() && "expected vector type!");
 
   const auto *VT = Ty->castAs<VectorType>();
-  assert(VT->getVectorKind() == VectorKind::RVVFixedLengthData &&
-         "Unexpected vector kind");
-
   assert(VT->getElementType()->isBuiltinType() && "expected builtin type!");
 
   auto VScale =
       getContext().getTargetInfo().getVScaleRange(getContext().getLangOpts());
+
+  unsigned NumElts = VT->getNumElements();
+  llvm::Type *EltType;
+  if (VT->getVectorKind() == VectorKind::RVVFixedLengthMask) {
+    NumElts *= 8;
+    EltType = llvm::Type::getInt1Ty(getVMContext());
+  } else {
+    assert(VT->getVectorKind() == VectorKind::RVVFixedLengthData &&
+           "Unexpected vector kind");
+    EltType = CGT.ConvertType(VT->getElementType());
+  }
+
   // The MinNumElts is simplified from equation:
   // NumElts / VScale =
   //  (EltSize * NumElts / (VScale * RVVBitsPerBlock))
   //    * (RVVBitsPerBlock / EltSize)
   llvm::ScalableVectorType *ResType =
-      llvm::ScalableVectorType::get(CGT.ConvertType(VT->getElementType()),
-                                    VT->getNumElements() / VScale->first);
+      llvm::ScalableVectorType::get(EltType, NumElts / VScale->first);
   return ABIArgInfo::getDirect(ResType);
 }
 
@@ -437,7 +445,8 @@ ABIArgInfo RISCVABIInfo::classifyArgumentType(QualType Ty, bool IsFixed,
   }
 
   if (const VectorType *VT = Ty->getAs<VectorType>())
-    if (VT->getVectorKind() == VectorKind::RVVFixedLengthData)
+    if (VT->getVectorKind() == VectorKind::RVVFixedLengthData ||
+        VT->getVectorKind() == VectorKind::RVVFixedLengthMask)
       return coerceVLSVector(Ty);
 
   // Aggregates which are <= 2*XLen will be passed in registers if possible,

clang/lib/Sema/SemaExpr.cpp

@@ -11142,7 +11142,8 @@ QualType Sema::CheckVectorOperands(ExprResult &LHS, ExprResult &RHS,
       if (VecType->getVectorKind() == VectorKind::SveFixedLengthData ||
           VecType->getVectorKind() == VectorKind::SveFixedLengthPredicate)
         return true;
-      if (VecType->getVectorKind() == VectorKind::RVVFixedLengthData) {
+      if (VecType->getVectorKind() == VectorKind::RVVFixedLengthData ||
+          VecType->getVectorKind() == VectorKind::RVVFixedLengthMask) {
         SVEorRVV = 1;
         return true;
       }
@@ -11173,7 +11174,8 @@ QualType Sema::CheckVectorOperands(ExprResult &LHS, ExprResult &RHS,
             SecondVecType->getVectorKind() ==
                 VectorKind::SveFixedLengthPredicate)
           return true;
-        if (SecondVecType->getVectorKind() == VectorKind::RVVFixedLengthData) {
+        if (SecondVecType->getVectorKind() == VectorKind::RVVFixedLengthData ||
+            SecondVecType->getVectorKind() == VectorKind::RVVFixedLengthMask) {
           SVEorRVV = 1;
           return true;
         }

clang/lib/Sema/SemaType.cpp

@@ -8646,21 +8646,30 @@ static void HandleRISCVRVVVectorBitsTypeAttr(QualType &CurType,
 
   ASTContext::BuiltinVectorTypeInfo Info =
       S.Context.getBuiltinVectorTypeInfo(CurType->castAs<BuiltinType>());
-  unsigned EltSize = S.Context.getTypeSize(Info.ElementType);
   unsigned MinElts = Info.EC.getKnownMinValue();
 
+  VectorKind VecKind = VectorKind::RVVFixedLengthData;
+  unsigned ExpectedSize = VScale->first * MinElts;
+  QualType EltType = CurType->getRVVEltType(S.Context);
+  unsigned EltSize = S.Context.getTypeSize(EltType);
+  unsigned NumElts;
+  if (Info.ElementType == S.Context.BoolTy) {
+    NumElts = VecSize / S.Context.getCharWidth();
+    VecKind = VectorKind::RVVFixedLengthMask;
+  } else {
+    ExpectedSize *= EltSize;
+    NumElts = VecSize / EltSize;
+  }
+
   // The attribute vector size must match -mrvv-vector-bits.
-  unsigned ExpectedSize = VScale->first * MinElts * EltSize;
-  if (VecSize != ExpectedSize) {
+  if (ExpectedSize % 8 != 0 || VecSize != ExpectedSize) {
     S.Diag(Attr.getLoc(), diag::err_attribute_bad_rvv_vector_size)
         << VecSize << ExpectedSize;
     Attr.setInvalid();
     return;
   }
 
-  VectorKind VecKind = VectorKind::RVVFixedLengthData;
-  VecSize /= EltSize;
-  CurType = S.Context.getVectorType(Info.ElementType, VecSize, VecKind);
+  CurType = S.Context.getVectorType(EltType, NumElts, VecKind);
 }
 
 /// Handle OpenCL Access Qualifier Attribute.