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Wasm: Implement SkipBytes for OpCode

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This commit is contained in:
Brian Carroll 2022-01-11 08:54:42 +00:00
parent 2ade357ea9
commit 48f14f9a83
1 changed files with 62 additions and 1 deletions
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63
compiler/gen_wasm/src/wasm_module/opcodes.rs
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@ -1,5 +1,7 @@
use roc_reporting::internal_error;
use super::serialize::{parse_u32_or_panic, SkipBytes};
#[repr(u8)]
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum OpCode {
@ -196,8 +198,8 @@ enum OpImmediates {
impl From<OpCode> for OpImmediates {
fn from(op: OpCode) -> Self {
use OpImmediates::*;
use OpCode::*;
use OpImmediates::*;
match op {
UNREACHABLE => NoImmediate,
@ -252,3 +254,62 @@ impl From<OpCode> for OpImmediates {
}
}
}
impl SkipBytes for OpCode {
fn skip_bytes(bytes: &[u8], cursor: &mut usize) {
use OpImmediates::*;
let opcode_byte: u8 = bytes[*cursor];
let opcode: OpCode = unsafe { std::mem::transmute(opcode_byte) };
let immediates = OpImmediates::from(opcode); // will panic if transmute was invalid
match immediates {
NoImmediate => {
*cursor += 1;
}
Byte1 => {
*cursor += 1 + 1;
}
Bytes4 => {
*cursor += 1 + 4;
}
Bytes8 => {
*cursor += 1 + 8;
}
Leb32x1 => {
let i = *cursor + 1;
*cursor = skip_leb(bytes, i, 5);
}
Leb64x1 => {
let i = *cursor + 1;
*cursor = skip_leb(bytes, i, 10);
}
Leb32x2 => {
let mut i = *cursor + 1;
i = skip_leb(bytes, i, 5);
i = skip_leb(bytes, i, 5);
*cursor = i;
}
BrTable => {
*cursor += 1;
let n_labels = 1 + parse_u32_or_panic(bytes, cursor);
let mut i = *cursor;
for _ in 0..n_labels {
i = skip_leb(bytes, i, 5);
}
*cursor = i;
}
}
}
}
#[inline(always)]
fn skip_leb(bytes: &[u8], mut i: usize, max_len: usize) -> usize {
let imax = i + max_len;
while (bytes[i] & 0x80 != 0) && (i < imax) {
i += 1;
}
debug_assert!(i < imax);
i + 1
}