256 lines
4.2 KiB
Rust
256 lines
4.2 KiB
Rust
//! An instruction set used by wasmi.
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//!
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//! The instruction set is mostly derived from Wasm. However,
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//! there is a substantial difference.
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//!
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//! # Structured Stack Machine vs Traditional One
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//!
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//! Wasm is a structured stack machine. Wasm encodes control flow in structures
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//! similar to that commonly found in a programming languages
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//! such as if, while. That contrasts to a traditional stack machine which
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//! encodes all control flow with goto-like instructions.
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//!
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//! Structured stack machine code aligns well with goals of Wasm,
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//! namely providing fast validation of Wasm code and compilation to native code.
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//!
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//! Unfortunately, the downside of structured stack machine code is
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//! that it is less convenient to interpret. For example, let's look at
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//! the following example in hypothetical structured stack machine:
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//!
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//! ```plain
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//! loop
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//! ...
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//! if_true_jump_to_end
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//! ...
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//! end
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//! ```
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//!
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//! To execute `if_true_jump_to_end` , the interpreter needs to skip all instructions
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//! until it reaches the *matching* `end`. That's quite inefficient compared
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//! to a plain goto to the specific position.
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//!
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//! # Differences from Wasm
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//!
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//! - There is no `nop` instruction.
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//! - All control flow strucutres are flattened to plain gotos.
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//! - Implicit returns via reaching function scope `End` are replaced with an explicit `return` instruction.
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//! - Locals live on the value stack now.
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//! - Load/store instructions doesn't take `align` parameter.
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//! - *.const store value in straight encoding.
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//! - Reserved immediates are ignored for `call_indirect`, `current_memory`, `grow_memory`.
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//!
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#[derive(Debug, Clone, PartialEq, Eq)]
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pub struct Target {
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pub dst_pc: u32,
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pub drop: u32,
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pub keep: u8,
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}
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#[allow(unused)] // TODO: Remove
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#[derive(Debug, Clone, PartialEq)]
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pub enum Instruction {
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/// Push a local variable or an argument from the specified depth.
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GetLocal(u32),
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/// Pop a value and put it in at the specified depth.
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SetLocal(u32),
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/// Copy a value to the specified depth.
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TeeLocal(u32),
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/// Similar to the Wasm ones, but instead of a label depth
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/// they specify direct PC.
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Br(Target),
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BrIfEqz(Target),
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BrIfNez(Target),
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/// Last one is the default.
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///
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/// Can be less than zero.
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BrTable(Box<[Target]>),
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Unreachable,
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Return {
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drop: u32,
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keep: u8,
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},
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Call(u32),
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CallIndirect(u32),
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Drop,
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Select,
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GetGlobal(u32),
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SetGlobal(u32),
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I32Load(u32),
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I64Load(u32),
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F32Load(u32),
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F64Load(u32),
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I32Load8S(u32),
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I32Load8U(u32),
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I32Load16S(u32),
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I32Load16U(u32),
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I64Load8S(u32),
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I64Load8U(u32),
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I64Load16S(u32),
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I64Load16U(u32),
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I64Load32S(u32),
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I64Load32U(u32),
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I32Store(u32),
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I64Store(u32),
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F32Store(u32),
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F64Store(u32),
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I32Store8(u32),
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I32Store16(u32),
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I64Store8(u32),
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I64Store16(u32),
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I64Store32(u32),
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CurrentMemory,
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GrowMemory,
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I32Const(i32),
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I64Const(i64),
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F32Const(u32),
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F64Const(u64),
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I32Eqz,
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I32Eq,
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I32Ne,
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I32LtS,
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I32LtU,
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I32GtS,
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I32GtU,
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I32LeS,
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I32LeU,
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I32GeS,
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I32GeU,
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I64Eqz,
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I64Eq,
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I64Ne,
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I64LtS,
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I64LtU,
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I64GtS,
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I64GtU,
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I64LeS,
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I64LeU,
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I64GeS,
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I64GeU,
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F32Eq,
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F32Ne,
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F32Lt,
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F32Gt,
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F32Le,
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F32Ge,
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F64Eq,
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F64Ne,
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F64Lt,
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F64Gt,
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F64Le,
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F64Ge,
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I32Clz,
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I32Ctz,
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I32Popcnt,
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I32Add,
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I32Sub,
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I32Mul,
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I32DivS,
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I32DivU,
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I32RemS,
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I32RemU,
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I32And,
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I32Or,
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I32Xor,
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I32Shl,
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I32ShrS,
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I32ShrU,
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I32Rotl,
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I32Rotr,
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I64Clz,
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I64Ctz,
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I64Popcnt,
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I64Add,
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I64Sub,
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I64Mul,
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I64DivS,
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I64DivU,
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I64RemS,
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I64RemU,
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I64And,
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I64Or,
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I64Xor,
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I64Shl,
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I64ShrS,
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I64ShrU,
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I64Rotl,
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I64Rotr,
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F32Abs,
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F32Neg,
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F32Ceil,
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F32Floor,
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F32Trunc,
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F32Nearest,
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F32Sqrt,
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F32Add,
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F32Sub,
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F32Mul,
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F32Div,
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F32Min,
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F32Max,
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F32Copysign,
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F64Abs,
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F64Neg,
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F64Ceil,
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F64Floor,
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F64Trunc,
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F64Nearest,
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F64Sqrt,
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F64Add,
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F64Sub,
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F64Mul,
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F64Div,
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F64Min,
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F64Max,
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F64Copysign,
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I32WrapI64,
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I32TruncSF32,
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I32TruncUF32,
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I32TruncSF64,
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I32TruncUF64,
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I64ExtendSI32,
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I64ExtendUI32,
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I64TruncSF32,
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I64TruncUF32,
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I64TruncSF64,
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I64TruncUF64,
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F32ConvertSI32,
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F32ConvertUI32,
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F32ConvertSI64,
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F32ConvertUI64,
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F32DemoteF64,
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F64ConvertSI32,
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F64ConvertUI32,
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F64ConvertSI64,
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F64ConvertUI64,
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F64PromoteF32,
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I32ReinterpretF32,
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I64ReinterpretF64,
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F32ReinterpretI32,
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F64ReinterpretI64,
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}
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#[derive(Debug, Clone)]
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pub struct Instructions {
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pub code: Vec<Instruction>,
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}
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