wgpu/src/valid/function.rs

use super::{analyzer::FunctionInfo, ExpressionError, TypeFlags, ValidationFlags};
use crate::{
    arena::{Arena, Handle},
    proc::{ResolveContext, TypifyError},
};

#[derive(Clone, Debug, thiserror::Error)]
pub enum CallError {
    #[error("Bad function")]
    InvalidFunction,
    #[error("The callee is declared after the caller")]
    ForwardDeclaredFunction,
    #[error("Argument {index} expression is invalid")]
    Argument {
        index: usize,
        #[source]
        error: ExpressionError,
    },
    #[error("Result expression {0:?} has already been introduced earlier")]
    ResultAlreadyInScope(Handle<crate::Expression>),
    #[error("Result value is invalid")]
    ResultValue(#[source] ExpressionError),
    #[error("Requires {required} arguments, but {seen} are provided")]
    ArgumentCount { required: usize, seen: usize },
    #[error("Argument {index} value {seen_expression:?} doesn't match the type {required:?}")]
    ArgumentType {
        index: usize,
        required: Handle<crate::Type>,
        seen_expression: Handle<crate::Expression>,
    },
    #[error("Result value {seen_expression:?} does not match the type {required:?}")]
    ResultType {
        required: Option<Handle<crate::Type>>,
        seen_expression: Option<Handle<crate::Expression>>,
    },
}

#[derive(Clone, Debug, thiserror::Error)]
pub enum LocalVariableError {
    #[error("Initializer doesn't match the variable type")]
    InitializerType,
}

#[derive(Clone, Debug, thiserror::Error)]
pub enum FunctionError {
    #[error(transparent)]
    Resolve(#[from] TypifyError),
    #[error("Expression {handle:?} is invalid")]
    Expression {
        handle: Handle<crate::Expression>,
        #[source]
        error: ExpressionError,
    },
    #[error("Expression {0:?} can't be introduced - it's already in scope")]
    ExpressionAlreadyInScope(Handle<crate::Expression>),
    #[error("Local variable {handle:?} '{name}' is invalid")]
    LocalVariable {
        handle: Handle<crate::LocalVariable>,
        name: String,
        #[source]
        error: LocalVariableError,
    },
    #[error("Argument '{name}' at index {index} has a type that can't be passed into functions.")]
    InvalidArgumentType { index: usize, name: String },
    #[error("There are instructions after `return`/`break`/`continue`")]
    InstructionsAfterReturn,
    #[error("The `break`/`continue` is used outside of a loop context")]
    BreakContinueOutsideOfLoop,
    #[error("The `return` is called within a `continuing` block")]
    InvalidReturnSpot,
    #[error("The `return` value {0:?} does not match the function return value")]
    InvalidReturnType(Option<Handle<crate::Expression>>),
    #[error("The `if` condition {0:?} is not a boolean scalar")]
    InvalidIfType(Handle<crate::Expression>),
    #[error("The `switch` value {0:?} is not an integer scalar")]
    InvalidSwitchType(Handle<crate::Expression>),
    #[error("Multiple `switch` cases for {0} are present")]
    ConflictingSwitchCase(i32),
    #[error("The pointer {0:?} doesn't relate to a valid destination for a store")]
    InvalidStorePointer(Handle<crate::Expression>),
    #[error("The value {0:?} can not be stored")]
    InvalidStoreValue(Handle<crate::Expression>),
    #[error("Store of {value:?} into {pointer:?} doesn't have matching types")]
    InvalidStoreTypes {
        pointer: Handle<crate::Expression>,
        value: Handle<crate::Expression>,
    },
    #[error("The image array can't be indexed by {0:?}")]
    InvalidArrayIndex(Handle<crate::Expression>),
    #[error("The expression {0:?} is currupted")]
    InvalidExpression(Handle<crate::Expression>),
    #[error("The expression {0:?} is not an image")]
    InvalidImage(Handle<crate::Expression>),
    #[error("Call to {function:?} is invalid")]
    InvalidCall {
        function: Handle<crate::Function>,
        #[source]
        error: CallError,
    },
}

bitflags::bitflags! {
    #[repr(transparent)]
    struct Flags: u8 {
        /// The control can jump out of this block.
        const CAN_JUMP = 0x1;
        /// The control is in a loop, can break and continue.
        const IN_LOOP = 0x2;
    }
}

struct BlockContext<'a> {
    flags: Flags,
    expressions: &'a Arena<crate::Expression>,
    types: &'a Arena<crate::Type>,
    functions: &'a Arena<crate::Function>,
    return_type: Option<Handle<crate::Type>>,
}

impl<'a> BlockContext<'a> {
    pub(super) fn new(fun: &'a crate::Function, module: &'a crate::Module) -> Self {
        Self {
            flags: Flags::CAN_JUMP,
            expressions: &fun.expressions,
            types: &module.types,
            functions: &module.functions,
            return_type: fun.result.as_ref().map(|fr| fr.ty),
        }
    }

    fn with_flags(&self, flags: Flags) -> Self {
        BlockContext {
            flags,
            expressions: self.expressions,
            types: self.types,
            functions: self.functions,
            return_type: self.return_type,
        }
    }

    fn get_expression(
        &self,
        handle: Handle<crate::Expression>,
    ) -> Result<&'a crate::Expression, FunctionError> {
        self.expressions
            .try_get(handle)
            .ok_or(FunctionError::InvalidExpression(handle))
    }
}

impl super::Validator {
    fn validate_call(
        &mut self,
        function: Handle<crate::Function>,
        arguments: &[Handle<crate::Expression>],
        result: Option<Handle<crate::Expression>>,
        context: &BlockContext,
    ) -> Result<(), CallError> {
        let fun = context
            .functions
            .try_get(function)
            .ok_or(CallError::InvalidFunction)?;
        if fun.arguments.len() != arguments.len() {
            return Err(CallError::ArgumentCount {
                required: fun.arguments.len(),
                seen: arguments.len(),
            });
        }
        for (index, (arg, &expr)) in fun.arguments.iter().zip(arguments).enumerate() {
            let ty = self
                .resolve_statement_type_impl(expr, context.types)
                .map_err(|error| CallError::Argument { index, error })?;
            if ty != &context.types[arg.ty].inner {
                return Err(CallError::ArgumentType {
                    index,
                    required: arg.ty,
                    seen_expression: expr,
                });
            }
        }

        if let Some(expr) = result {
            if self.valid_expression_set.insert(expr.index()) {
                self.valid_expression_list.push(expr);
            } else {
                return Err(CallError::ResultAlreadyInScope(expr));
            }
        }

        let result_ty = result
            .map(|expr| self.resolve_statement_type_impl(expr, context.types))
            .transpose()
            .map_err(CallError::ResultValue)?;
        let expected_ty = fun.result.as_ref().map(|fr| &context.types[fr.ty].inner);
        if result_ty != expected_ty {
            log::error!(
                "Called function returns {:?} where {:?} is expected",
                result_ty,
                expected_ty
            );
            return Err(CallError::ResultType {
                required: fun.result.as_ref().map(|fr| fr.ty),
                seen_expression: result,
            });
        }
        Ok(())
    }

    fn resolve_statement_type_impl<'a>(
        &'a self,
        handle: Handle<crate::Expression>,
        types: &'a Arena<crate::Type>,
    ) -> Result<&'a crate::TypeInner, ExpressionError> {
        if !self.valid_expression_set.contains(handle.index()) {
            return Err(ExpressionError::NotInScope);
        }
        self.typifier
            .try_get(handle, types)
            .ok_or(ExpressionError::DoesntExist)
    }

    fn resolve_statement_type<'a>(
        &'a self,
        handle: Handle<crate::Expression>,
        types: &'a Arena<crate::Type>,
    ) -> Result<&'a crate::TypeInner, FunctionError> {
        self.resolve_statement_type_impl(handle, types)
            .map_err(|error| FunctionError::Expression { handle, error })
    }

    fn validate_block_impl(
        &mut self,
        statements: &[crate::Statement],
        context: &BlockContext,
    ) -> Result<(), FunctionError> {
        use crate::{Statement as S, TypeInner as Ti};
        let mut finished = false;
        for statement in statements {
            if finished {
                return Err(FunctionError::InstructionsAfterReturn);
            }
            match *statement {
                S::Emit(ref range) => {
                    for handle in range.clone() {
                        if self.valid_expression_set.insert(handle.index()) {
                            self.valid_expression_list.push(handle);
                        } else {
                            return Err(FunctionError::ExpressionAlreadyInScope(handle));
                        }
                    }
                }
                S::Block(ref block) => self.validate_block(block, context)?,
                S::If {
                    condition,
                    ref accept,
                    ref reject,
                } => {
                    match *self.resolve_statement_type(condition, context.types)? {
                        Ti::Scalar {
                            kind: crate::ScalarKind::Bool,
                            width: _,
                        } => {}
                        _ => return Err(FunctionError::InvalidIfType(condition)),
                    }
                    self.validate_block(accept, context)?;
                    self.validate_block(reject, context)?;
                }
                S::Switch {
                    selector,
                    ref cases,
                    ref default,
                } => {
                    match *self.resolve_statement_type(selector, context.types)? {
                        Ti::Scalar {
                            kind: crate::ScalarKind::Sint,
                            width: _,
                        } => {}
                        _ => return Err(FunctionError::InvalidSwitchType(selector)),
                    }
                    self.select_cases.clear();
                    for case in cases {
                        if !self.select_cases.insert(case.value) {
                            return Err(FunctionError::ConflictingSwitchCase(case.value));
                        }
                    }
                    for case in cases {
                        self.validate_block(&case.body, context)?;
                    }
                    self.validate_block(default, context)?;
                }
                S::Loop {
                    ref body,
                    ref continuing,
                } => {
                    // special handling for block scoping is needed here,
                    // because the continuing{} block inherits the scope
                    let base_expression_count = self.valid_expression_list.len();
                    self.validate_block_impl(
                        body,
                        &context.with_flags(Flags::CAN_JUMP | Flags::IN_LOOP),
                    )?;
                    self.validate_block_impl(continuing, &context.with_flags(Flags::empty()))?;
                    for handle in self.valid_expression_list.drain(base_expression_count..) {
                        self.valid_expression_set.remove(handle.index());
                    }
                }
                S::Break | S::Continue => {
                    if !context.flags.contains(Flags::IN_LOOP) {
                        return Err(FunctionError::BreakContinueOutsideOfLoop);
                    }
                    finished = true;
                }
                S::Return { value } => {
                    if !context.flags.contains(Flags::CAN_JUMP) {
                        return Err(FunctionError::InvalidReturnSpot);
                    }
                    let value_ty = value
                        .map(|expr| self.resolve_statement_type(expr, context.types))
                        .transpose()?;
                    let expected_ty = context.return_type.map(|ty| &context.types[ty].inner);
                    if value_ty != expected_ty {
                        log::error!(
                            "Returning {:?} where {:?} is expected",
                            value_ty,
                            expected_ty
                        );
                        return Err(FunctionError::InvalidReturnType(value));
                    }
                    finished = true;
                }
                S::Kill => {
                    finished = true;
                }
                S::Store { pointer, value } => {
                    let mut current = pointer;
                    loop {
                        self.typifier.try_get(current, context.types).ok_or(
                            FunctionError::Expression {
                                handle: current,
                                error: ExpressionError::DoesntExist,
                            },
                        )?;
                        match context.expressions[current] {
                            crate::Expression::Access { base, .. }
                            | crate::Expression::AccessIndex { base, .. } => current = base,
                            crate::Expression::LocalVariable(_)
                            | crate::Expression::GlobalVariable(_)
                            | crate::Expression::FunctionArgument(_) => break,
                            _ => return Err(FunctionError::InvalidStorePointer(current)),
                        }
                    }

                    let value_ty = self.resolve_statement_type(value, context.types)?;
                    match *value_ty {
                        Ti::Image { .. } | Ti::Sampler { .. } => {
                            return Err(FunctionError::InvalidStoreValue(value));
                        }
                        _ => {}
                    }
                    let good = match self.typifier.try_get(pointer, context.types) {
                        Some(&Ti::Pointer { base, class: _ }) => {
                            *value_ty == context.types[base].inner
                        }
                        Some(&Ti::ValuePointer {
                            size: Some(size),
                            kind,
                            width,
                            class: _,
                        }) => *value_ty == Ti::Vector { size, kind, width },
                        Some(&Ti::ValuePointer {
                            size: None,
                            kind,
                            width,
                            class: _,
                        }) => *value_ty == Ti::Scalar { kind, width },
                        _ => false,
                    };
                    if !good {
                        return Err(FunctionError::InvalidStoreTypes { pointer, value });
                    }
                }
                S::ImageStore {
                    image,
                    coordinate: _,
                    array_index,
                    value,
                } => {
                    let _expected_coordinate_ty = match *context.get_expression(image)? {
                        crate::Expression::GlobalVariable(_var_handle) => (), //TODO
                        _ => return Err(FunctionError::InvalidImage(image)),
                    };
                    let value_ty = self.typifier.get(value, context.types);
                    match *value_ty {
                        Ti::Scalar { .. } | Ti::Vector { .. } => {}
                        _ => {
                            return Err(FunctionError::InvalidStoreValue(value));
                        }
                    }
                    if let Some(expr) = array_index {
                        match *self.typifier.get(expr, context.types) {
                            Ti::Scalar {
                                kind: crate::ScalarKind::Sint,
                                width: _,
                            } => (),
                            _ => return Err(FunctionError::InvalidArrayIndex(expr)),
                        }
                    }
                }
                S::Call {
                    function,
                    ref arguments,
                    result,
                } => {
                    if let Err(error) = self.validate_call(function, arguments, result, context) {
                        return Err(FunctionError::InvalidCall { function, error });
                    }
                }
            }
        }
        Ok(())
    }

    fn validate_block(
        &mut self,
        statements: &[crate::Statement],
        context: &BlockContext,
    ) -> Result<(), FunctionError> {
        let base_expression_count = self.valid_expression_list.len();
        self.validate_block_impl(statements, context)?;
        for handle in self.valid_expression_list.drain(base_expression_count..) {
            self.valid_expression_set.remove(handle.index());
        }
        Ok(())
    }

    fn validate_local_var(
        &self,
        var: &crate::LocalVariable,
        types: &Arena<crate::Type>,
        constants: &Arena<crate::Constant>,
    ) -> Result<(), LocalVariableError> {
        log::debug!("var {:?}", var);
        if let Some(const_handle) = var.init {
            match constants[const_handle].inner {
                crate::ConstantInner::Scalar { width, ref value } => {
                    let ty_inner = crate::TypeInner::Scalar {
                        width,
                        kind: value.scalar_kind(),
                    };
                    if types[var.ty].inner != ty_inner {
                        return Err(LocalVariableError::InitializerType);
                    }
                }
                crate::ConstantInner::Composite { ty, components: _ } => {
                    if ty != var.ty {
                        return Err(LocalVariableError::InitializerType);
                    }
                }
            }
        }
        Ok(())
    }

    pub(super) fn validate_function(
        &mut self,
        fun: &crate::Function,
        _info: &FunctionInfo,
        module: &crate::Module,
    ) -> Result<(), FunctionError> {
        let resolve_ctx = ResolveContext {
            constants: &module.constants,
            global_vars: &module.global_variables,
            local_vars: &fun.local_variables,
            functions: &module.functions,
            arguments: &fun.arguments,
        };
        self.typifier
            .resolve_all(&fun.expressions, &module.types, &resolve_ctx)?;

        for (var_handle, var) in fun.local_variables.iter() {
            self.validate_local_var(var, &module.types, &module.constants)
                .map_err(|error| FunctionError::LocalVariable {
                    handle: var_handle,
                    name: var.name.clone().unwrap_or_default(),
                    error,
                })?;
        }

        for (index, argument) in fun.arguments.iter().enumerate() {
            if !self.type_flags[argument.ty.index()].contains(TypeFlags::DATA) {
                return Err(FunctionError::InvalidArgumentType {
                    index,
                    name: argument.name.clone().unwrap_or_default(),
                });
            }
        }

        self.valid_expression_set.clear();
        for (handle, expr) in fun.expressions.iter() {
            if expr.needs_pre_emit() {
                self.valid_expression_set.insert(handle.index());
            }
            if !self.flags.contains(ValidationFlags::EXPRESSIONS) {
                if let Err(error) = self.validate_expression(handle, expr, fun, module) {
                    return Err(FunctionError::Expression { handle, error });
                }
            }
        }

        if self.flags.contains(ValidationFlags::BLOCKS) {
            self.validate_block(&fun.body, &BlockContext::new(fun, module))
        } else {
            Ok(())
        }
    }
}