[Clang] Support generic bit counting builtins on fixed boolean vectors

clang/docs/LanguageExtensions.rst

@@ -4182,7 +4182,7 @@ builtin, the mangler emits their usual pattern without any special treatment.
 -----------------------
 
 ``__builtin_popcountg`` returns the number of 1 bits in the argument. The
-argument can be of any unsigned integer type.
+argument can be of any unsigned integer type or fixed boolean vector.
 
 **Syntax**:
 
@@ -4214,7 +4214,13 @@ such as ``unsigned __int128`` and C23 ``unsigned _BitInt(N)``.
 
 ``__builtin_clzg`` (respectively ``__builtin_ctzg``) returns the number of
 leading (respectively trailing) 0 bits in the first argument. The first argument
-can be of any unsigned integer type.
+can be of any unsigned integer type or fixed boolean vector.
+
+For boolean vectors, these builtins interpret the vector like a bit-field where
+the ith element of the vector is bit i of the bit-field, counting from the
+least significant end. ``__builtin_clzg`` returns the number of zero elements at
+the end of the vector, while ``__builtin_ctzg`` returns the number of zero
+elements at the start of the vector.
 
 If the first argument is 0 and an optional second argument of ``int`` type is
 provided, then the second argument is returned. If the first argument is 0, but

clang/docs/ReleaseNotes.rst

@@ -143,10 +143,12 @@ Non-comprehensive list of changes in this release
 - Added ``__builtin_masked_load`` and ``__builtin_masked_store`` for conditional
   memory loads from vectors. Binds to the LLVM intrinsic of the same name.
 
+- The ``__builtin_popcountg``, ``__builtin_ctzg``, and ``__builtin_clzg``
+  functions now accept fixed-size boolean vectors.
+
 - Use of ``__has_feature`` to detect the ``ptrauth_qualifier`` and ``ptrauth_intrinsics``
   features has been deprecated, and is restricted to the arm64e target only. The
   correct method to check for these features is to test for the ``__PTRAUTH__``
-  macro.
 
 - Added a new builtin, ``__builtin_dedup_pack``, to remove duplicate types from a parameter pack.
   This feature is particularly useful in template metaprogramming for normalizing type lists.

clang/lib/AST/ByteCode/InterpBuiltin.cpp

@@ -141,6 +141,22 @@ static void diagnoseNonConstexprBuiltin(InterpState &S, CodePtr OpPC,
     S.CCEDiag(Loc, diag::note_invalid_subexpr_in_const_expr);
 }
 
+static llvm::APSInt convertBoolVectorToInt(const Pointer &Val) {
+  assert(Val.getFieldDesc()->isPrimitiveArray() &&
+         Val.getFieldDesc()->getElemQualType()->isBooleanType() &&
+         "Not a boolean vector");
+  unsigned NumElts = Val.getNumElems();
+
+  // Each element is one bit, so create an integer with NumElts bits.
+  llvm::APSInt Result(NumElts, 0);
+  for (unsigned I = 0; I < NumElts; ++I) {
+    if (Val.elem<bool>(I))
+      Result.setBit(I);
+  }
+
+  return Result;
+}
+
 static bool interp__builtin_is_constant_evaluated(InterpState &S, CodePtr OpPC,
                                                   const InterpFrame *Frame,
                                                   const CallExpr *Call) {
@@ -638,8 +654,14 @@ static bool interp__builtin_abs(InterpState &S, CodePtr OpPC,
 static bool interp__builtin_popcount(InterpState &S, CodePtr OpPC,
                                      const InterpFrame *Frame,
                                      const CallExpr *Call) {
-  PrimType ArgT = *S.getContext().classify(Call->getArg(0)->getType());
-  APSInt Val = popToAPSInt(S.Stk, ArgT);
+  APSInt Val;
+  if (Call->getArg(0)->getType()->isExtVectorBoolType()) {
+    const Pointer &Arg = S.Stk.pop<Pointer>();
+    Val = convertBoolVectorToInt(Arg);
+  } else {
+    PrimType ArgT = *S.getContext().classify(Call->getArg(0)->getType());
+    Val = popToAPSInt(S.Stk, ArgT);
+  }
   pushInteger(S, Val.popcount(), Call->getType());
   return true;
 }
@@ -935,8 +957,14 @@ static bool interp__builtin_clz(InterpState &S, CodePtr OpPC,
     PrimType FallbackT = *S.getContext().classify(Call->getArg(1));
     Fallback = popToAPSInt(S.Stk, FallbackT);
   }
-  PrimType ValT = *S.getContext().classify(Call->getArg(0));
-  const APSInt &Val = popToAPSInt(S.Stk, ValT);
+  APSInt Val;
+  if (Call->getArg(0)->getType()->isExtVectorBoolType()) {
+    const Pointer &Arg = S.Stk.pop<Pointer>();
+    Val = convertBoolVectorToInt(Arg);
+  } else {
+    PrimType ValT = *S.getContext().classify(Call->getArg(0));
+    Val = popToAPSInt(S.Stk, ValT);
+  }
 
   // When the argument is 0, the result of GCC builtins is undefined, whereas
   // for Microsoft intrinsics, the result is the bit-width of the argument.
@@ -966,8 +994,14 @@ static bool interp__builtin_ctz(InterpState &S, CodePtr OpPC,
     PrimType FallbackT = *S.getContext().classify(Call->getArg(1));
     Fallback = popToAPSInt(S.Stk, FallbackT);
   }
-  PrimType ValT = *S.getContext().classify(Call->getArg(0));
-  const APSInt &Val = popToAPSInt(S.Stk, ValT);
+  APSInt Val;
+  if (Call->getArg(0)->getType()->isExtVectorBoolType()) {
+    const Pointer &Arg = S.Stk.pop<Pointer>();
+    Val = convertBoolVectorToInt(Arg);
+  } else {
+    PrimType ValT = *S.getContext().classify(Call->getArg(0));
+    Val = popToAPSInt(S.Stk, ValT);
+  }
 
   if (Val == 0) {
     if (Fallback) {

clang/lib/AST/ExprConstant.cpp

@@ -11314,6 +11314,24 @@ static bool EvaluateVector(const Expr* E, APValue& Result, EvalInfo &Info) {
   return VectorExprEvaluator(Info, Result).Visit(E);
 }
 
+static llvm::APInt ConvertBoolVectorToInt(const APValue &Val) {
+  assert(Val.isVector() && "expected vector APValue");
+  unsigned NumElts = Val.getVectorLength();
+
+  // Each element is one bit, so create an integer with NumElts bits.
+  llvm::APInt Result(NumElts, 0);
+
+  for (unsigned I = 0; I < NumElts; ++I) {
+    const APValue &Elt = Val.getVectorElt(I);
+    assert(Elt.isInt() && "expected integer element in bool vector");
+
+    if (Elt.getInt().getBoolValue())
+      Result.setBit(I);
+  }
+
+  return Result;
+}
+
 bool VectorExprEvaluator::VisitCastExpr(const CastExpr *E) {
   const VectorType *VTy = E->getType()->castAs<VectorType>();
   unsigned NElts = VTy->getNumElements();
@@ -13456,8 +13474,14 @@ bool IntExprEvaluator::VisitBuiltinCallExpr(const CallExpr *E,
   case Builtin::BI__lzcnt:
   case Builtin::BI__lzcnt64: {
     APSInt Val;
-    if (!EvaluateInteger(E->getArg(0), Val, Info))
+    if (E->getArg(0)->getType()->isExtVectorBoolType()) {
+      APValue Vec;
+      if (!EvaluateVector(E->getArg(0), Vec, Info))
+        return false;
+      Val = ConvertBoolVectorToInt(Vec);
+    } else if (!EvaluateInteger(E->getArg(0), Val, Info)) {
       return false;
+    }
 
     std::optional<APSInt> Fallback;
     if ((BuiltinOp == Builtin::BI__builtin_clzg ||
@@ -13542,8 +13566,14 @@ bool IntExprEvaluator::VisitBuiltinCallExpr(const CallExpr *E,
   case Builtin::BI__builtin_ctzg:
   case Builtin::BI__builtin_elementwise_cttz: {
     APSInt Val;
-    if (!EvaluateInteger(E->getArg(0), Val, Info))
+    if (E->getArg(0)->getType()->isExtVectorBoolType()) {
+      APValue Vec;
+      if (!EvaluateVector(E->getArg(0), Vec, Info))
+        return false;
+      Val = ConvertBoolVectorToInt(Vec);
+    } else if (!EvaluateInteger(E->getArg(0), Val, Info)) {
       return false;
+    }
 
     std::optional<APSInt> Fallback;
     if ((BuiltinOp == Builtin::BI__builtin_ctzg ||
@@ -13758,8 +13788,14 @@ bool IntExprEvaluator::VisitBuiltinCallExpr(const CallExpr *E,
   case Builtin::BI__popcnt:
   case Builtin::BI__popcnt64: {
     APSInt Val;
-    if (!EvaluateInteger(E->getArg(0), Val, Info))
+    if (E->getArg(0)->getType()->isExtVectorBoolType()) {
+      APValue Vec;
+      if (!EvaluateVector(E->getArg(0), Vec, Info))
+        return false;
+      Val = ConvertBoolVectorToInt(Vec);
+    } else if (!EvaluateInteger(E->getArg(0), Val, Info)) {
       return false;
+    }
 
     return Success(Val.popcount(), E);
   }

clang/lib/CodeGen/CGBuiltin.cpp

@@ -1693,6 +1693,23 @@ getBitTestAtomicOrdering(BitTest::InterlockingKind I) {
   llvm_unreachable("invalid interlocking");
 }
 
+static llvm::Value *EmitBitCountExpr(CodeGenFunction &CGF, const Expr *E) {
+  llvm::Value *ArgValue = CGF.EmitScalarExpr(E);
+  llvm::Type *ArgType = ArgValue->getType();
+
+  // Boolean vectors can be casted directly to its bitfield representation. We
+  // intentionally do not round up to the next power of two size and let LLVM
+  // handle the trailing bits.
+  if (auto *VT = dyn_cast<llvm::FixedVectorType>(ArgType);
+      VT && VT->getElementType()->isIntegerTy(1)) {
+    llvm::Type *StorageType =
+        llvm::Type::getIntNTy(CGF.getLLVMContext(), VT->getNumElements());
+    ArgValue = CGF.Builder.CreateBitCast(ArgValue, StorageType);
+  }
+
+  return ArgValue;
+}
+
 /// Emit a _bittest* intrinsic. These intrinsics take a pointer to an array of
 /// bits and a bit position and read and optionally modify the bit at that
 /// position. The position index can be arbitrarily large, i.e. it can be larger
@@ -2020,7 +2037,7 @@ Value *CodeGenFunction::EmitCheckedArgForBuiltin(const Expr *E,
   assert((Kind == BCK_CLZPassedZero || Kind == BCK_CTZPassedZero) &&
          "Unsupported builtin check kind");
 
-  Value *ArgValue = EmitScalarExpr(E);
+  Value *ArgValue = EmitBitCountExpr(*this, E);
   if (!SanOpts.has(SanitizerKind::Builtin))
     return ArgValue;
 
@@ -3334,7 +3351,7 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
         E->getNumArgs() > 1;
 
     Value *ArgValue =
-        HasFallback ? EmitScalarExpr(E->getArg(0))
+        HasFallback ? EmitBitCountExpr(*this, E->getArg(0))
                     : EmitCheckedArgForBuiltin(E->getArg(0), BCK_CTZPassedZero);
 
     llvm::Type *ArgType = ArgValue->getType();
@@ -3371,7 +3388,7 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
         E->getNumArgs() > 1;
 
     Value *ArgValue =
-        HasFallback ? EmitScalarExpr(E->getArg(0))
+        HasFallback ? EmitBitCountExpr(*this, E->getArg(0))
                     : EmitCheckedArgForBuiltin(E->getArg(0), BCK_CLZPassedZero);
 
     llvm::Type *ArgType = ArgValue->getType();
@@ -3456,7 +3473,7 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
   case Builtin::BI__builtin_popcountl:
   case Builtin::BI__builtin_popcountll:
   case Builtin::BI__builtin_popcountg: {
-    Value *ArgValue = EmitScalarExpr(E->getArg(0));
+    Value *ArgValue = EmitBitCountExpr(*this, E->getArg(0));
 
     llvm::Type *ArgType = ArgValue->getType();
     Function *F = CGM.getIntrinsic(Intrinsic::ctpop, ArgType);

clang/lib/Sema/SemaChecking.cpp

@@ -2214,7 +2214,7 @@ static bool BuiltinPopcountg(Sema &S, CallExpr *TheCall) {
 
   QualType ArgTy = Arg->getType();
 
-  if (!ArgTy->isUnsignedIntegerType()) {
+  if (!ArgTy->isUnsignedIntegerType() && !ArgTy->isExtVectorBoolType()) {
     S.Diag(Arg->getBeginLoc(), diag::err_builtin_invalid_arg_type)
         << 1 << /* scalar */ 1 << /* unsigned integer ty */ 3 << /* no fp */ 0
         << ArgTy;
@@ -2239,7 +2239,7 @@ static bool BuiltinCountZeroBitsGeneric(Sema &S, CallExpr *TheCall) {
 
   QualType Arg0Ty = Arg0->getType();
 
-  if (!Arg0Ty->isUnsignedIntegerType()) {
+  if (!Arg0Ty->isUnsignedIntegerType() && !Arg0Ty->isExtVectorBoolType()) {
     S.Diag(Arg0->getBeginLoc(), diag::err_builtin_invalid_arg_type)
         << 1 << /* scalar */ 1 << /* unsigned integer ty */ 3 << /* no fp */ 0
         << Arg0Ty;

clang/test/AST/ByteCode/builtin-functions.cpp

@@ -454,6 +454,7 @@ namespace SourceLocation {
 }
 
 #define BITSIZE(x) (sizeof(x) * 8)
+constexpr bool __attribute__((ext_vector_type(4))) v4b{};
 namespace popcount {
   static_assert(__builtin_popcount(~0u) == __CHAR_BIT__ * sizeof(unsigned int), "");
   static_assert(__builtin_popcount(0) == 0, "");
@@ -471,6 +472,7 @@ namespace popcount {
   static_assert(__builtin_popcountg(0ul) == 0, "");
   static_assert(__builtin_popcountg(~0ull) == __CHAR_BIT__ * sizeof(unsigned long long), "");
   static_assert(__builtin_popcountg(0ull) == 0, "");
+  static_assert(__builtin_popcountg(v4b) == 0, "");
 #ifdef __SIZEOF_INT128__
   static_assert(__builtin_popcountg(~(unsigned __int128)0) == __CHAR_BIT__ * sizeof(unsigned __int128), "");
   static_assert(__builtin_popcountg((unsigned __int128)0) == 0, "");
@@ -743,6 +745,7 @@ namespace clz {
   char clz62[__builtin_clzg((unsigned _BitInt(128))0xf) == BITSIZE(_BitInt(128)) - 4 ? 1 : -1];
   char clz63[__builtin_clzg((unsigned _BitInt(128))0xf, 42) == BITSIZE(_BitInt(128)) - 4 ? 1 : -1];
 #endif
+  char clz64[__builtin_clzg(v4b, 0) == 0 ? 1 : -1];
 }
 
 namespace ctz {
@@ -813,6 +816,7 @@ namespace ctz {
   char ctz62[__builtin_ctzg((unsigned _BitInt(128))1 << (BITSIZE(_BitInt(128)) - 1)) == BITSIZE(_BitInt(128)) - 1 ? 1 : -1];
   char ctz63[__builtin_ctzg((unsigned _BitInt(128))1 << (BITSIZE(_BitInt(128)) - 1), 42) == BITSIZE(_BitInt(128)) - 1 ? 1 : -1];
 #endif
+  char clz64[__builtin_ctzg(v4b, 0) == 0 ? 1 : -1];
 }
 
 namespace bswap {