jasonwyatt/KWasm

/*
 * Copyright 2020 Google LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific language governing permissions and
 * limitations under the License.
 */

package kwasm.validation.instruction.memory

import kwasm.ast.instruction.MemoryInstruction
import kwasm.ast.type.ValueType
import kwasm.util.Impossible
import kwasm.validation.FunctionBodyValidationVisitor
import kwasm.validation.ValidationContext
import kwasm.validation.validate

/**
 * Validator of [MemoryInstruction.StoreFloat] nodes.
 *
 * From
 * [the docs](https://webassembly.github.io/spec/core/valid/instructions.html#memory-instructions):
 *
 * ```
 *   t.store memarg
 * ```
 * * The memory `C.mems[0]` must be defined in the context.
 * * The alignment `2^memarg.align` must not be larger than the bit width of `t` divided by `8`.
 * * Then the instruction is valid with type `[i32 t] => []`.
 */
object StoreFloatValidator : FunctionBodyValidationVisitor<MemoryInstruction.StoreFloat> {
    override fun visit(
        node: MemoryInstruction.StoreFloat,
        context: ValidationContext.FunctionBody
    ): ValidationContext.FunctionBody {
        context.validateMemoryExists()
        validate(node.arg.isAlignmentValid(node.byteWidth), parseContext = null) {
            "Invalid alignment for N=${node.byteWidth} (alignment must not be larger than natural)"
        }
        val (topTwo, updatedContext) = context.popStack(2)
        val storeType = when (node.bitWidth) {
            32 -> ValueType.F32
            64 -> ValueType.F64
            else -> Impossible()
        }

        validate(
            topTwo.size == 2,
            parseContext = null,
            message = "Store expects at least two stack entries"
        )
        validate(topTwo[1] == storeType, parseContext = null) {
            "Store requires that the top of the stack has the same type as the instruction type"
        }
        validate(topTwo[0] == ValueType.I32, parseContext = null) {
            "Store requires an i32 at the second position in the stack, but ${topTwo[0]} is present"
        }

        return updatedContext
    }
}