[FFI][Runtime] Use TVMValue::v_int64 to represent boolean values

This is a follow-up to apache#16183, which
added handling of boolean values in the TVM FFI.  The initial
implementation added both a new type code (`kTVMArgBool`) and a new
`TVMValue::v_bool` variant.  This commit removes the
`TVMValue::v_bool` variant, since the `kTVMArgBool` type code is
sufficient to handle boolean arguments.

Removing the `TVMValue::v_bool` variant also makes all `TVMValue`
variants be 64-bit (assuming a 64-bit CPU).  This can simplify
debugging in some cases, since it prevents partial values from
inactive variants from being present in memory.

include/tvm/runtime/c_runtime_api.h

@@ -209,7 +209,6 @@ typedef DLTensor* TVMArrayHandle;
  */
 typedef union {
   int64_t v_int64;
-  bool v_bool;
   double v_float64;
   void* v_handle;
   const char* v_str;

include/tvm/runtime/packed_func.h

@@ -642,7 +642,7 @@ class TVMPODValue_ {
     // conversions.  This is publicly exposed, as it can be useful in
     // specializations of PackedFuncValueConverter.
     if (type_code_ == kTVMArgBool) {
-      return value_.v_bool;
+      return static_cast<bool>(value_.v_int64);
     } else {
       return std::nullopt;
     }
@@ -1014,7 +1014,7 @@ class TVMRetValue : public TVMPODValue_CRTP_<TVMRetValue> {
   TVMRetValue& operator=(const DataType& other) { return operator=(other.operator DLDataType()); }
   TVMRetValue& operator=(bool value) {
     this->SwitchToPOD(kTVMArgBool);
-    value_.v_bool = value;
+    value_.v_int64 = value;
     return *this;
   }
   TVMRetValue& operator=(std::string value) {
@@ -1804,7 +1804,7 @@ class TVMArgsSetter {
     type_codes_[i] = kDLInt;
   }
   TVM_ALWAYS_INLINE void operator()(size_t i, bool value) const {
-    values_[i].v_bool = value;
+    values_[i].v_int64 = value;
     type_codes_[i] = kTVMArgBool;
   }
   TVM_ALWAYS_INLINE void operator()(size_t i, uint64_t value) const {
@@ -2115,7 +2115,7 @@ inline void TVMArgsSetter::SetObject(size_t i, T&& value) const {
                 std::is_base_of_v<ContainerType, Bool::ContainerType>) {
     if (std::is_base_of_v<Bool::ContainerType, ContainerType> ||
         ptr->IsInstance<Bool::ContainerType>()) {
-      values_[i].v_bool = static_cast<Bool::ContainerType*>(ptr)->value;
+      values_[i].v_int64 = static_cast<Bool::ContainerType*>(ptr)->value;
       type_codes_[i] = kTVMArgBool;
       return;
     }
@@ -2300,7 +2300,7 @@ inline TObjectRef TVMPODValue_CRTP_<Derived>::AsObjectRef() const {
 
   if constexpr (std::is_base_of_v<TObjectRef, Bool>) {
     if (type_code_ == kTVMArgBool) {
-      return Bool(value_.v_bool);
+      return Bool(value_.v_int64);
     }
   }
 

rust/tvm-sys/src/packed_func.rs

@@ -96,7 +96,7 @@ macro_rules! TVMPODValue {
                         DLDataTypeCode_kDLInt => Int($value.v_int64),
                         DLDataTypeCode_kDLUInt => UInt($value.v_int64),
                         DLDataTypeCode_kDLFloat => Float($value.v_float64),
-                        TVMArgTypeCode_kTVMArgBool => Bool($value.v_bool),
+                        TVMArgTypeCode_kTVMArgBool => Bool($value.v_int64 != 0),
                         TVMArgTypeCode_kTVMNullptr => Null,
                         TVMArgTypeCode_kTVMDataType => DataType($value.v_type),
                         TVMArgTypeCode_kDLDevice => Device($value.v_device),
@@ -119,7 +119,7 @@ macro_rules! TVMPODValue {
                     Int(val) => (TVMValue { v_int64: *val }, DLDataTypeCode_kDLInt),
                     UInt(val) => (TVMValue { v_int64: *val as i64 }, DLDataTypeCode_kDLUInt),
                     Float(val) => (TVMValue { v_float64: *val }, DLDataTypeCode_kDLFloat),
-                    Bool(val) => (TVMValue { v_bool: *val }, TVMArgTypeCode_kTVMArgBool),
+                    Bool(val) => (TVMValue { v_int64: *val as i64 }, TVMArgTypeCode_kTVMArgBool),
                     Null => (TVMValue{ v_int64: 0 },TVMArgTypeCode_kTVMNullptr),
                     DataType(val) => (TVMValue { v_type: *val }, TVMArgTypeCode_kTVMDataType),
                     Device(val) => (TVMValue { v_device: val.clone() }, TVMArgTypeCode_kDLDevice),

src/runtime/crt/common/crt_runtime_api.c

@@ -362,10 +362,8 @@ int ModuleGetFunction(TVMValue* args, int* type_codes, int num_args, TVMValue* r
     return kTvmErrorFunctionCallWrongArgType;
   }
 
-  if (type_codes[2] == kDLInt) {
+  if (type_codes[2] == kDLInt || type_codes[2] == kTVMArgBool) {
     query_imports = args[2].v_int64 != 0;
-  } else if (type_codes[2] == kTVMArgBool) {
-    query_imports = args[2].v_bool;
   } else {
     TVMAPISetLastError("ModuleGetFunction expects third argument to be an integer");
     return kTvmErrorFunctionCallWrongArgType;

src/runtime/minrpc/rpc_reference.h

@@ -326,7 +326,7 @@ struct RPCReference {
           break;
         }
         case kTVMArgBool: {
-          channel->template Write<bool>(value.v_bool);
+          channel->template Write<int64_t>(value.v_int64);
           break;
         }
         case kTVMDataType: {
@@ -437,7 +437,7 @@ struct RPCReference {
           break;
         }
         case kTVMArgBool: {
-          channel->template Read<bool>(&(value.v_bool));
+          channel->template Read<int64_t>(&(value.v_int64));
           break;
         }
         case kTVMDataType: {

src/target/llvm/codegen_cpu.cc

@@ -1379,7 +1379,7 @@ llvm::Value* CodeGenCPU::CreateIntrinsic(const CallNode* op) {
     llvm::Value* struct_value = builder_->CreateLoad(ref.type, ref.addr);
 
     if (op->dtype == DataType::Bool()) {
-      struct_value = CreateCast(DataType::Int(8), op->dtype, struct_value);
+      struct_value = CreateCast(DataType::Int(64), op->dtype, struct_value);
     }
 
     return struct_value;

src/tir/transforms/ir_utils.h

@@ -155,8 +155,7 @@ inline DataType APIType(DataType t) {
   ICHECK(!t.is_void()) << "Cannot pass void type through packed API.";
   if (t.is_handle()) return t;
   ICHECK_EQ(t.lanes(), 1) << "Cannot pass vector type through packed API.";
-  if (t.is_bool()) return DataType::Bool();
-  if (t.is_uint() || t.is_int()) return DataType::Int(64);
+  if (t.is_bool() || t.is_uint() || t.is_int()) return DataType::Int(64);
   ICHECK(t.is_float());
   return DataType::Float(64);
 }

src/tir/transforms/make_packed_api.cc

@@ -81,7 +81,11 @@ class ReturnRewriter : public StmtMutator {
 
     // convert val's data type to FFI data type, return type code
     DataType dtype = val.dtype();
-    if (dtype.is_int() || dtype.is_uint()) {
+    if (dtype.is_bool()) {
+      info.tcode = kTVMArgBool;
+      info.expr = Cast(DataType::Int(64), val);
+
+    } else if (dtype.is_int() || dtype.is_uint()) {
       info.tcode = kTVMArgInt;
       info.expr = Cast(DataType::Int(64), val);
     } else if (dtype.is_float()) {

tests/python/codegen/test_target_codegen_llvm.py

@@ -1179,5 +1179,21 @@ def func(arg: T.bool) -> T.int32:
     assert output == 20
 
 
+def test_bool_return_value():
+    """Booleans may be returned from a PrimFunc"""
+
+    @T.prim_func
+    def func(value: T.int32) -> T.bool:
+        T.func_attr({"target": T.target("llvm")})
+        return value < 10
+
+    built = tvm.build(func)
+    assert isinstance(built(0), bool)
+    assert built(0)
+
+    assert isinstance(built(15), bool)
+    assert not built(15)
+
+
 if __name__ == "__main__":
     tvm.testing.main()