Start creating module_builder

compiler/gen_wasm/src/module_builder.rs

@@ -0,0 +1,286 @@
+use bumpalo::collections::vec::Vec;
+use bumpalo::Bump;
+use roc_module::symbol::{Interns, Symbol};
+
+use crate::code_builder::Align;
+use crate::serialize::{SerialBuffer, Serialize};
+
+#[repr(u8)]
+#[derive(PartialEq, Eq, Clone, Copy, Debug)]
+pub enum SectionId {
+    Custom = 0,
+    Type = 1,
+    Import = 2,
+    Function = 3,
+    Table = 4,
+    Memory = 5,
+    Global = 6,
+    Export = 7,
+    Start = 8,
+    Element = 9,
+    Code = 10,
+    Data = 11,
+    DataCount = 12,
+}
+
+/// Write a section header, returning the position of the encoded length
+fn _write_section_header<T: SerialBuffer>(buffer: &mut T, id: SectionId) -> usize {
+    buffer.append_byte(id as u8);
+    buffer.encode_padded_u32(u32::MAX)
+}
+
+/// Write a custom section header, returning the position of the encoded length
+fn write_custom_section_header<'s, T: SerialBuffer>(
+    buffer: &mut T,
+    id: SectionId,
+    name: &'s str,
+) -> usize {
+    buffer.append_byte(id as u8);
+    let size_position = buffer.encode_padded_u32(u32::MAX);
+    buffer.append_slice(name.as_bytes());
+    size_position
+}
+
+/*******************************************************************
+ *
+ * Relocation sections
+ *
+ * https://github.com/WebAssembly/tool-conventions/blob/main/Linking.md#relocation-sections
+ *
+ *******************************************************************/
+
+pub struct IndexRelocation {
+    offset: u32,       // offset 0 means the next byte after section id and size
+    symbol_index: u32, // index in symbol table
+}
+
+pub struct OffsetRelocation {
+    offset: u32,       // offset 0 means the next byte after section id and size
+    symbol_index: u32, // index in symbol table
+    addend: u32,
+}
+
+pub enum RelocationEntry {
+    FunctionIndexLeb(IndexRelocation),
+    TableIndexSleb(IndexRelocation),
+    TableIndexI32(IndexRelocation),
+    MemoryAddrLeb(OffsetRelocation),
+    MemoryAddrSleb(OffsetRelocation),
+    MemoryAddrI32(OffsetRelocation),
+    TypeIndexLeb(IndexRelocation),
+    GlobalIndexLeb(IndexRelocation),
+    FunctionOffsetI32(OffsetRelocation),
+    SectionOffsetI32(OffsetRelocation),
+    EventIndexLeb(IndexRelocation),
+    // ... gap ...
+    GlobalIndexI32(IndexRelocation),
+    MemoryAddrLeb64(OffsetRelocation),
+    MemoryAddrSleb64(OffsetRelocation),
+    MemoryAddrI64(OffsetRelocation),
+    // ... gap ...
+    TableIndexSleb64(IndexRelocation),
+    TableIndexI64(IndexRelocation),
+    TableNumberLeb(IndexRelocation),
+}
+
+impl Serialize for RelocationEntry {
+    fn serialize<T: SerialBuffer>(&self, buffer: &mut T) {
+        let type_id = match self {
+            Self::FunctionIndexLeb(_) => 0,
+            Self::TableIndexSleb(_) => 1,
+            Self::TableIndexI32(_) => 2,
+            Self::MemoryAddrLeb(_) => 3,
+            Self::MemoryAddrSleb(_) => 4,
+            Self::MemoryAddrI32(_) => 5,
+            Self::TypeIndexLeb(_) => 6,
+            Self::GlobalIndexLeb(_) => 7,
+            Self::FunctionOffsetI32(_) => 8,
+            Self::SectionOffsetI32(_) => 9,
+            Self::EventIndexLeb(_) => 10,
+            // ... gap ...
+            Self::GlobalIndexI32(_) => 13,
+            Self::MemoryAddrLeb64(_) => 14,
+            Self::MemoryAddrSleb64(_) => 15,
+            Self::MemoryAddrI64(_) => 16,
+            // ... gap ...
+            Self::TableIndexSleb64(_) => 18,
+            Self::TableIndexI64(_) => 19,
+            Self::TableNumberLeb(_) => 20,
+        };
+
+        buffer.append_byte(type_id);
+        buffer.encode_u32(self.offset);
+        buffer.encode_u32(self.symbol_index);
+        if let Some(addend) = self.addend {
+            buffer.encode_i32(addend);
+        }
+    }
+}
+
+pub struct RelocationSection<'s, 'bump> {
+    name: &'s str,
+    entries: Vec<'bump, RelocationEntry>,
+}
+
+impl<'s, 'bump> Serialize for RelocationSection<'s, 'bump> {
+    fn serialize<T: SerialBuffer>(&self, buffer: &mut T) {
+        let size_position = write_custom_section_header(buffer, SectionId::Custom, self.name);
+        for entry in self.entries.iter() {
+            entry.serialize(buffer);
+        }
+        let size = buffer.size() - size_position;
+        buffer.overwrite_padded_u32(size_position, size as u32);
+    }
+}
+
+/*******************************************************************
+ *
+ * Linking section
+ *
+ * https://github.com/WebAssembly/tool-conventions/blob/main/Linking.md#linking-metadata-section
+ *
+ *******************************************************************/
+
+/// Linking metadata for data segments
+pub struct LinkingSegment<'s> {
+    name: &'s str,
+    alignment: Align,
+    flags: u32,
+}
+
+/// Linking metadata for init (start) functions
+pub struct LinkingInitFunc {
+    priority: u32,
+    symbol_index: u32, // index in the symbol table, not the function index
+}
+
+/*****************
+ * Common data
+ *****************/
+
+#[repr(u8)]
+#[derive(PartialEq, Eq, Clone, Copy, Debug)]
+pub enum ComdatSymKind {
+    Data = 0,
+    Function = 1,
+    Global = 2,
+    Event = 3,
+    Table = 4,
+    Section = 5,
+}
+
+pub struct ComdatSym {
+    kind: ComdatSymKind,
+    index: u32,
+}
+
+/// Linking metadata for common data
+/// A COMDAT group may contain one or more functions, data segments, and/or custom sections.
+/// The linker will include all of these elements with a given group name from one object file,
+/// and will exclude any element with this group name from all other object files.
+pub struct LinkingComdat<'s, 'bump> {
+    name: &'s str,
+    flags: u32,
+    syms: Vec<'bump, ComdatSym>,
+}
+
+/*****************
+ * Symbol table
+*****************/
+
+/// Indicating that this is a weak symbol.  When
+/// linking multiple modules defining the same symbol, all weak definitions are
+/// discarded if any strong definitions exist; then if multiple weak definitions
+/// exist all but one (unspecified) are discarded; and finally it is an error if
+/// more than one definition remains.
+pub const WASM_SYM_BINDING_WEAK: u32 = 1;
+
+/// Indicating that this is a local symbol (this is exclusive with `WASM_SYM_BINDING_WEAK`).
+/// Local symbols are not to be exported, or linked to other modules/sections.
+/// The names of all non-local symbols must be unique, but the names of local symbols
+/// are not considered for uniqueness. A local function or global symbol cannot reference an import.
+pub const WASM_SYM_BINDING_LOCAL: u32 = 2;
+
+/// Indicating that this is a hidden symbol.
+/// Hidden symbols are not to be exported when performing the final link, but
+/// may be linked to other modules.
+pub const WASM_SYM_VISIBILITY_HIDDEN: u32 = 4;
+
+/// Indicating that this symbol is not defined.
+/// For non-data symbols, this must match whether the symbol is an import
+/// or is defined; for data symbols, determines whether a segment is specified.
+pub const WASM_SYM_UNDEFINED: u32 = 0x10; // required if the symbol refers to an import
+
+/// The symbol is intended to be exported from the
+/// wasm module to the host environment. This differs from the visibility flags
+/// in that it effects the static linker.
+pub const WASM_SYM_EXPORTED: u32 = 0x20;
+
+/// The symbol uses an explicit symbol name,
+/// rather than reusing the name from a wasm import. This allows it to remap
+/// imports from foreign WebAssembly modules into local symbols with different
+/// names.
+pub const WASM_SYM_EXPLICIT_NAME: u32 = 0x40; // use the name from the symbol table, not from the import
+
+/// The symbol is intended to be included in the
+/// linker output, regardless of whether it is used by the program.
+pub const WASM_SYM_NO_STRIP: u32 = 0x80;
+
+pub struct DefinedWasmObjectSymbol<'s> {
+    wasm_object_index: u32, // Wasm index of the function/global/event/table
+    name: &'s str,
+}
+
+pub enum WasmObjectSymbol<'s> {
+    Defined(DefinedWasmObjectSymbol<'s>),
+    Imported(u32),
+}
+
+pub struct DefinedDataSymbol<'s> {
+    name: &'s str,
+    index: u32,
+    offset: u32,
+    size: u32,
+}
+
+pub enum DataSymbol<'s> {
+    Defined(DefinedDataSymbol<'s>),
+    Imported(&'s str),
+}
+
+pub enum SymTableInfo<'s> {
+    Data(DataSymbol<'s>),
+    Function(WasmObjectSymbol<'s>),
+    Global(WasmObjectSymbol<'s>),
+    /// section index (not id)
+    Section(u32),
+    Event(WasmObjectSymbol<'s>),
+    Table(WasmObjectSymbol<'s>),
+}
+
+pub struct SymTableEntry<'s> {
+    flags: u32,
+    kind: SymTableInfo<'s>,
+}
+
+/**********************************
+ * Linking section & subsections
+ **********************************/
+
+pub enum LinkingSubSection<'s, 'bump> {
+    SegmentInfo(Vec<'bump, LinkingSegment<'s>>),
+    InitFuncs(Vec<'bump, LinkingInitFunc>),
+    ComdatInfo(Vec<'bump, LinkingComdat<'s, 'bump>>),
+    SymbolTable(Vec<'bump, SymTableEntry<'s>>),
+}
+
+#[repr(u8)]
+#[derive(PartialEq, Eq, Clone, Copy, Debug)]
+pub enum LinkingVersion {
+    V2 = 2,
+}
+
+pub struct LinkingSection<'s, 'bump> {
+    version: LinkingVersion,
+    subsections: Vec<'bump, LinkingSubSection<'s, 'bump>>,
+}