Prevent use of uninitialized scalar Parameters in JIT code (#7847, partial)

python_bindings/src/halide/halide_/PyParameter.cpp

@@ -30,11 +30,6 @@ void define_parameter(py::module &m) {
             .def(py::init<const Parameter &>(), py::arg("p"))
             .def(py::init<const Type &, bool, int>())
             .def(py::init<const Type &, bool, int, const std::string &>())
-            .def(py::init<const Type &, bool, int, const std::string &,
-                          const Buffer<void> &, int, const std::vector<BufferConstraint> &,
-                          MemoryType>())
-            .def(py::init<const Type &, bool, int, const std::string &,
-                          uint64_t, const Expr &, const Expr &, const Expr &, const Expr &>())
             .def("_to_argument", [](const Parameter &p) -> Argument {
                 return Argument(p.name(),
                                 p.is_buffer() ? Argument::InputBuffer : Argument::InputScalar,

src/Deserialization.cpp

@@ -1159,14 +1159,24 @@ Parameter Deserializer::deserialize_parameter(const Serialize::Parameter *parame
             deserialize_vector<Serialize::BufferConstraint, BufferConstraint>(parameter->buffer_constraints(),
                                                                               &Deserializer::deserialize_buffer_constraint);
         const auto memory_type = deserialize_memory_type(parameter->memory_type());
-        return Parameter(type, is_buffer, dimensions, name, Buffer<>(), host_alignment, buffer_constraints, memory_type);
+        return Parameter(type, dimensions, name, Buffer<>(), host_alignment, buffer_constraints, memory_type);
     } else {
-        const uint64_t data = parameter->data();
+        static_assert(FLATBUFFERS_USE_STD_OPTIONAL);
+        const auto make_optional_halide_scalar_value_t = [](const std::optional<uint64_t> &v) -> std::optional<halide_scalar_value_t> {
+            if (v.has_value()) {
+                halide_scalar_value_t scalar_data;
+                scalar_data.u.u64 = v.value();
+                return std::optional<halide_scalar_value_t>(scalar_data);
+            } else {
+                return std::nullopt;
+            }
+        };
+        const std::optional<halide_scalar_value_t> scalar_data = make_optional_halide_scalar_value_t(parameter->scalar_data());
         const auto scalar_default = deserialize_expr(parameter->scalar_default_type(), parameter->scalar_default());
         const auto scalar_min = deserialize_expr(parameter->scalar_min_type(), parameter->scalar_min());
         const auto scalar_max = deserialize_expr(parameter->scalar_max_type(), parameter->scalar_max());
         const auto scalar_estimate = deserialize_expr(parameter->scalar_estimate_type(), parameter->scalar_estimate());
-        return Parameter(type, is_buffer, dimensions, name, data, scalar_default, scalar_min, scalar_max, scalar_estimate);
+        return Parameter(type, dimensions, name, scalar_data, scalar_default, scalar_min, scalar_max, scalar_estimate);
     }
 }
 

src/Generator.h

@@ -2001,7 +2001,8 @@ class GeneratorInput_Scalar : public GeneratorInputImpl<T, Expr> {
 
     void set_def_min_max() override {
         for (Parameter &p : this->parameters_) {
-            p.set_scalar<TBase>(def_);
+            // No: we want to leave the Parameter unset here.
+            // p.set_scalar<TBase>(def_);
             p.set_default_value(def_expr_);
         }
     }

src/InferArguments.cpp

@@ -5,6 +5,7 @@
 
 #include "ExternFuncArgument.h"
 #include "Function.h"
+#include "IROperator.h"
 #include "IRVisitor.h"
 #include "InferArguments.h"
 
@@ -197,7 +198,9 @@ class InferArguments : public IRGraphVisitor {
 
         ArgumentEstimates argument_estimates = p.get_argument_estimates();
         if (!p.is_buffer()) {
-            argument_estimates.scalar_def = p.scalar_expr();
+            // We don't want to crater here if a scalar param isn't set;
+            // instead, default to a zero of the right type, like we used to.
+            argument_estimates.scalar_def = p.has_scalar_value() ? p.scalar_expr() : make_zero(p.type());
             argument_estimates.scalar_min = p.min_value();
             argument_estimates.scalar_max = p.max_value();
             argument_estimates.scalar_estimate = p.estimate();

src/Parameter.cpp

@@ -15,7 +15,7 @@ struct ParameterContents {
     const int dimensions;
     const std::string name;
     Buffer<> buffer;
-    uint64_t data = 0;
+    std::optional<halide_scalar_value_t> scalar_data;
     int host_alignment;
     std::vector<BufferConstraint> buffer_constraints;
     Expr scalar_default, scalar_min, scalar_max, scalar_estimate;
@@ -82,21 +82,21 @@ Parameter::Parameter(const Type &t, bool is_buffer, int d, const std::string &na
     internal_assert(is_buffer || d == 0) << "Scalar parameters should be zero-dimensional";
 }
 
-Parameter::Parameter(const Type &t, bool is_buffer, int dimensions, const std::string &name,
+Parameter::Parameter(const Type &t, int dimensions, const std::string &name,
                      const Buffer<void> &buffer, int host_alignment, const std::vector<BufferConstraint> &buffer_constraints,
                      MemoryType memory_type)
-    : contents(new Internal::ParameterContents(t, is_buffer, dimensions, name)) {
+    : contents(new Internal::ParameterContents(t, /*is_buffer*/ true, dimensions, name)) {
     contents->buffer = buffer;
     contents->host_alignment = host_alignment;
     contents->buffer_constraints = buffer_constraints;
     contents->memory_type = memory_type;
 }
 
-Parameter::Parameter(const Type &t, bool is_buffer, int dimensions, const std::string &name,
-                     uint64_t data, const Expr &scalar_default, const Expr &scalar_min,
+Parameter::Parameter(const Type &t, int dimensions, const std::string &name,
+                     const std::optional<halide_scalar_value_t> &scalar_data, const Expr &scalar_default, const Expr &scalar_min,
                      const Expr &scalar_max, const Expr &scalar_estimate)
-    : contents(new Internal::ParameterContents(t, is_buffer, dimensions, name)) {
-    contents->data = data;
+    : contents(new Internal::ParameterContents(t, /*is_buffer*/ false, dimensions, name)) {
+    contents->scalar_data = scalar_data;
     contents->scalar_default = scalar_default;
     contents->scalar_min = scalar_min;
     contents->scalar_max = scalar_max;
@@ -123,51 +123,55 @@ bool Parameter::is_buffer() const {
     return contents->is_buffer;
 }
 
+bool Parameter::has_scalar_value() const {
+    return defined() && !contents->is_buffer && contents->scalar_data.has_value();
+}
+
 Expr Parameter::scalar_expr() const {
-    check_is_scalar();
+    const auto sv = scalar_data_checked();
     const Type t = type();
     if (t.is_float()) {
         switch (t.bits()) {
         case 16:
             if (t.is_bfloat()) {
-                return Expr(scalar<bfloat16_t>());
+                return Expr(bfloat16_t::make_from_bits(sv.u.u16));
             } else {
-                return Expr(scalar<float16_t>());
+                return Expr(float16_t::make_from_bits(sv.u.u16));
             }
         case 32:
-            return Expr(scalar<float>());
+            return Expr(sv.u.f32);
         case 64:
-            return Expr(scalar<double>());
+            return Expr(sv.u.f64);
         }
     } else if (t.is_int()) {
         switch (t.bits()) {
         case 8:
-            return Expr(scalar<int8_t>());
+            return Expr(sv.u.i8);
         case 16:
-            return Expr(scalar<int16_t>());
+            return Expr(sv.u.i16);
         case 32:
-            return Expr(scalar<int32_t>());
+            return Expr(sv.u.i32);
         case 64:
-            return Expr(scalar<int64_t>());
+            return Expr(sv.u.i64);
         }
     } else if (t.is_uint()) {
         switch (t.bits()) {
         case 1:
-            return Internal::make_bool(scalar<bool>());
+            return Internal::make_bool(sv.u.b);
         case 8:
-            return Expr(scalar<uint8_t>());
+            return Expr(sv.u.u8);
         case 16:
-            return Expr(scalar<uint16_t>());
+            return Expr(sv.u.u16);
         case 32:
-            return Expr(scalar<uint32_t>());
+            return Expr(sv.u.u32);
         case 64:
-            return Expr(scalar<uint64_t>());
+            return Expr(sv.u.u64);
         }
     } else if (t.is_handle()) {
         // handles are always uint64 internally.
         switch (t.bits()) {
         case 64:
-            return Expr(scalar<uint64_t>());
+            return Expr(sv.u.u64);
         }
     }
     internal_error << "Unsupported type " << t << " in scalar_expr\n";
@@ -198,14 +202,48 @@ void Parameter::set_buffer(const Buffer<> &b) {
     contents->buffer = b;
 }
 
-void *Parameter::scalar_address() const {
+const void *Parameter::read_only_scalar_address() const {
     check_is_scalar();
-    return &contents->data;
+    // Use explicit if here (rather than user_assert) so that we don't
+    // have to disable bugprone-unchecked-optional-access in clang-tidy,
+    // which is a useful check.
+    const auto &sv = contents->scalar_data;
+    if (sv.has_value()) {
+        return std::addressof(sv.value());
+    } else {
+        user_error << "Parameter " << name() << " does not have a valid scalar value.\n";
+        return nullptr;
+    }
+}
+
+std::optional<halide_scalar_value_t> Parameter::scalar_data() const {
+    return defined() ? contents->scalar_data : std::nullopt;
 }
 
-uint64_t Parameter::scalar_raw_value() const {
+halide_scalar_value_t Parameter::scalar_data_checked() const {
     check_is_scalar();
-    return contents->data;
+    // Use explicit if here (rather than user_assert) so that we don't
+    // have to disable bugprone-unchecked-optional-access in clang-tidy,
+    // which is a useful check.
+    halide_scalar_value_t result;
+    const auto &sv = contents->scalar_data;
+    if (sv.has_value()) {
+        result = sv.value();
+    } else {
+        user_error << "Parameter " << name() << " does not have a valid scalar value.\n";
+        result.u.u64 = 0;  // silence "possibly uninitialized" compiler warning
+    }
+    return result;
+}
+
+halide_scalar_value_t Parameter::scalar_data_checked(const Type &val_type) const {
+    check_type(val_type);
+    return scalar_data_checked();
+}
+
+void Parameter::set_scalar(const Type &val_type, halide_scalar_value_t val) {
+    check_type(val_type);
+    contents->scalar_data = std::optional<halide_scalar_value_t>(val);
 }
 
 /** Tests if this handle is the same as another handle */

src/Parameter.h

@@ -4,6 +4,7 @@
 /** \file
  * Defines the internal representation of parameters to halide piplines
  */
+#include <optional>
 #include <string>
 
 #include "Buffer.h"
@@ -25,7 +26,9 @@ struct BufferConstraint {
 };
 
 namespace Internal {
+
 #ifdef WITH_SERIALIZATION
+class Deserializer;
 class Serializer;
 #endif
 struct ParameterContents;
@@ -45,21 +48,41 @@ class Parameter {
     Internal::IntrusivePtr<Internal::ParameterContents> contents;
 
 #ifdef WITH_SERIALIZATION
-    friend class Internal::Serializer;  //< for scalar_raw_value()
+    friend class Internal::Deserializer;  //< for scalar_data()
+    friend class Internal::Serializer;    //< for scalar_data()
 #endif
-    friend class Pipeline;  //< for scalar_address()
+    friend class Pipeline;  //< for read_only_scalar_address()
 
     /** Get the raw currently-bound buffer. null if unbound */
     const halide_buffer_t *raw_buffer() const;
 
     /** Get the pointer to the current value of the scalar
      * parameter. For a given parameter, this address will never
-     * change. Only relevant when jitting. */
-    void *scalar_address() const;
+     * change. Note that this can only be used to *read* from -- it must
+     * not be written to, so don't cast away the constness. Only relevant when jitting. */
+    const void *read_only_scalar_address() const;
+
+    /** If the Parameter is a scalar, and the scalar data is valid, return
+     * the scalar data. Otherwise, return nullopt. */
+    std::optional<halide_scalar_value_t> scalar_data() const;
+
+    /** If the Parameter is a scalar and has a valid scalar value, return it.
+     * Otherwise, assert-fail. */
+    halide_scalar_value_t scalar_data_checked() const;
+
+    /** If the Parameter is a scalar *of the given type* and has a valid scalar value, return it.
+     * Otherwise, assert-fail. */
+    halide_scalar_value_t scalar_data_checked(const Type &val_type) const;
 
-    /** Get the raw data of the current value of the scalar
-     * parameter. Only relevant when serializing. */
-    uint64_t scalar_raw_value() const;
+    /** Construct a new buffer parameter via deserialization. */
+    Parameter(const Type &t, int dimensions, const std::string &name,
+              const Buffer<void> &buffer, int host_alignment, const std::vector<BufferConstraint> &buffer_constraints,
+              MemoryType memory_type);
+
+    /** Construct a new scalar parameter via deserialization. */
+    Parameter(const Type &t, int dimensions, const std::string &name,
+              const std::optional<halide_scalar_value_t> &scalar_data, const Expr &scalar_default, const Expr &scalar_min,
+              const Expr &scalar_max, const Expr &scalar_estimate);
 
 public:
     /** Construct a new undefined handle */
@@ -81,15 +104,6 @@ class Parameter {
      * explicitly specified (as opposed to autogenerated). */
     Parameter(const Type &t, bool is_buffer, int dimensions, const std::string &name);
 
-    /** Construct a new parameter via deserialization. */
-    Parameter(const Type &t, bool is_buffer, int dimensions, const std::string &name,
-              const Buffer<void> &buffer, int host_alignment, const std::vector<BufferConstraint> &buffer_constraints,
-              MemoryType memory_type);
-
-    Parameter(const Type &t, bool is_buffer, int dimensions, const std::string &name,
-              uint64_t data, const Expr &scalar_default, const Expr &scalar_min,
-              const Expr &scalar_max, const Expr &scalar_estimate);
-
     Parameter(const Parameter &) = default;
     Parameter &operator=(const Parameter &) = default;
     Parameter(Parameter &&) = default;
@@ -111,28 +125,33 @@ class Parameter {
      * bound value. Only relevant when jitting */
     template<typename T>
     HALIDE_NO_USER_CODE_INLINE T scalar() const {
-        check_type(type_of<T>());
-        return *((const T *)(scalar_address()));
+        static_assert(sizeof(T) <= sizeof(halide_scalar_value_t));
+        const auto sv = scalar_data_checked(type_of<T>());
+        T t;
+        memcpy(&t, &sv.u.u64, sizeof(t));
+        return t;
     }
 
-    /** This returns the current value of scalar<type()>()
-     * as an Expr. */
+    /** This returns the current value of scalar<type()>() as an Expr.
+     * If the Parameter is not scalar, or its scalar data is not valid, this will assert-fail. */
     Expr scalar_expr() const;
 
+    /** This returns true if scalar_expr() would return a valid Expr,
+     * false if not. */
+    bool has_scalar_value() const;
+
     /** If the parameter is a scalar parameter, set its current
      * value. Only relevant when jitting */
     template<typename T>
     HALIDE_NO_USER_CODE_INLINE void set_scalar(T val) {
-        check_type(type_of<T>());
-        *((T *)(scalar_address())) = val;
+        halide_scalar_value_t sv;
+        memcpy(&sv.u.u64, &val, sizeof(val));
+        set_scalar(type_of<T>(), sv);
     }
 
     /** If the parameter is a scalar parameter, set its current
      * value. Only relevant when jitting */
-    HALIDE_NO_USER_CODE_INLINE void set_scalar(const Type &val_type, halide_scalar_value_t val) {
-        check_type(val_type);
-        memcpy(scalar_address(), &val, val_type.bytes());
-    }
+    void set_scalar(const Type &val_type, halide_scalar_value_t val);
 
     /** If the parameter is a buffer parameter, get its currently
      * bound buffer. Only relevant when jitting */

src/Pipeline.cpp

@@ -843,7 +843,7 @@ void Pipeline::prepare_jit_call_arguments(RealizationArg &outputs, const Target
                     }
                     debug(2) << "JIT input ImageParam argument ";
                 } else {
-                    args_result.store[arg_index++] = p.scalar_address();
+                    args_result.store[arg_index++] = p.read_only_scalar_address();
                     debug(2) << "JIT input scalar argument ";
                 }
             }

src/Serialization.cpp

@@ -1298,13 +1298,19 @@ Offset<Serialize::Parameter> Serializer::serialize_parameter(FlatBufferBuilder &
         return Serialize::CreateParameter(builder, defined, is_buffer, type_serialized, dimensions, name_serialized, host_alignment,
                                           builder.CreateVector(buffer_constraints_serialized), memory_type_serialized);
     } else {
-        const uint64_t data = parameter.scalar_raw_value();
+        static_assert(FLATBUFFERS_USE_STD_OPTIONAL);
+        const auto make_optional_u64 = [](const std::optional<halide_scalar_value_t> &v) -> std::optional<uint64_t> {
+            return v.has_value() ?
+                       std::optional<uint64_t>(v.value().u.u64) :
+                       std::nullopt;
+        };
+        const auto scalar_data = make_optional_u64(parameter.scalar_data());
         const auto scalar_default_serialized = serialize_expr(builder, parameter.default_value());
         const auto scalar_min_serialized = serialize_expr(builder, parameter.min_value());
         const auto scalar_max_serialized = serialize_expr(builder, parameter.max_value());
         const auto scalar_estimate_serialized = serialize_expr(builder, parameter.estimate());
         return Serialize::CreateParameter(builder, defined, is_buffer, type_serialized,
-                                          dimensions, name_serialized, 0, 0, Serialize::MemoryType_Auto, data,
+                                          dimensions, name_serialized, 0, 0, Serialize::MemoryType_Auto, scalar_data,
                                           scalar_default_serialized.first, scalar_default_serialized.second,
                                           scalar_min_serialized.first, scalar_min_serialized.second,
                                           scalar_max_serialized.first, scalar_max_serialized.second,

src/halide_ir.fbs

@@ -618,7 +618,7 @@ table Parameter {
     host_alignment: int32;
     buffer_constraints: [BufferConstraint];
     memory_type: MemoryType;
-    data: uint64;
+    scalar_data: uint64 = null;  // Note: it is valid for this to be omitted, even if is_buffer = false.
     scalar_default: Expr;
     scalar_min: Expr;
     scalar_max: Expr;