/// Tunable parameters for WebAssembly compilation.
#[derive(Clone)]
pub struct Tunables {
/// For static heaps, the size in wasm pages of the heap protected by bounds checking.
pub static_memory_bound: u32,
/// The size in bytes of the offset guard for static heaps.
pub static_memory_offset_guard_size: u64,
/// The size in bytes of the offset guard for dynamic heaps.
pub dynamic_memory_offset_guard_size: u64,
}
impl Default for Tunables {
fn default() -> Self {
Self {
#[cfg(target_pointer_width = "32")]
/// Size in wasm pages of the bound for static memories.
static_memory_bound: 0x4000,
#[cfg(target_pointer_width = "64")]
/// Size in wasm pages of the bound for static memories.
///
/// When we allocate 4 GiB of address space, we can avoid the
/// need for explicit bounds checks.
static_memory_bound: 0x1_0000,
#[cfg(target_pointer_width = "32")]
/// Size in bytes of the offset guard for static memories.
static_memory_offset_guard_size: 0x1_0000,
#[cfg(target_pointer_width = "64")]
/// Size in bytes of the offset guard for static memories.
///
/// Allocating 2 GiB of address space lets us translate wasm
/// offsets into x86 offsets as aggressively as we can.
static_memory_offset_guard_size: 0x8000_0000,
/// Size in bytes of the offset guard for dynamic memories.
///
/// Allocate a small guard to optimize common cases but without
/// wasting too much memor.
dynamic_memory_offset_guard_size: 0x1_0000,
}
}
}