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wasm: use __data_end to account for all constant data including zero (bss) data

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Brian Carroll 2022-03-08 08:56:34 +00:00
parent 4d14fbf562
commit 9ae26c5aac
3 changed files with 67 additions and 34 deletions
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12
compiler/gen_wasm/src/backend.rs
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@ -29,11 +29,6 @@ use crate::{
PTR_SIZE, PTR_TYPE, STACK_POINTER_GLOBAL_ID, STACK_POINTER_NAME, TARGET_INFO,
};
/// The memory address where the constants data will be loaded during module instantiation.
/// We avoid address zero and anywhere near it. They're valid addresses but maybe bug-prone.
/// Follow Emscripten's example by leaving 1kB unused (though 4 bytes would probably do!)
const CONST_SEGMENT_BASE_ADDR: u32 = 1024;
pub struct WasmBackend<'a> {
pub env: &'a Env<'a>,
interns: &'a mut Interns,
@ -57,7 +52,6 @@ pub struct WasmBackend<'a> {
}
impl<'a> WasmBackend<'a> {
#[allow(clippy::too_many_arguments)]
pub fn new(
env: &'a Env<'a>,
interns: &'a mut Interns,
@ -78,8 +72,10 @@ impl<'a> WasmBackend<'a> {
index: STACK_POINTER_GLOBAL_ID,
});
// TODO: Examine the actual address ranges of every preloaded data segment in case they are not simply sequential
let next_constant_addr = CONST_SEGMENT_BASE_ADDR + module.data.bytes.len() as u32;
// The preloaded binary has a global to tell us where its data section ends
// Note: We need this to account for zero data (.bss), which doesn't have an explicit DataSegment!
let data_end_idx = module.export.globals_lookup["__data_end".as_bytes()];
let next_constant_addr = module.global.parse_u32_at_index(data_end_idx);
WasmBackend {
env,