T0b1/wasmtime
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Optimize table.init instruction and instantiation (#2847)

Browse Source 
* Optimize `table.init` instruction and instantiation

This commit optimizes table initialization as part of instance
instantiation and also applies the same optimization to the `table.init`
instruction. One part of this commit is to remove some preexisting
duplication between instance instantiation and the `table.init`
instruction itself, after this the actual implementation of `table.init`
is optimized to effectively have fewer bounds checks in fewer places and
have a much tighter loop for instantiation.

A big fallout from this change is that memory/table initializer offsets
are now stored as `u32` instead of `usize` to remove a few casts in a
few places. This ended up requiring moving some overflow checks that
happened in parsing to later in code itself because otherwise the wrong
spec test errors are emitted during testing. I've tried to trace where
these can possibly overflow but I think that I managed to get
everything.

In a local synthetic test where an empty module with a single 80,000
element initializer this improves total instantiation time by 4x (562us
=> 141us)

* Review comments
This commit is contained in:
Alex Crichton
2021-04-19 18:44:48 -05:00
committed by GitHub
parent 2864bb4a0f
commit 193551a8d6
8 changed files with 137 additions and 126 deletions
Download Patch File Download Diff File Expand all files Collapse all files

16
cranelift/wasm/src/sections_translator.rs
View File

@@ -377,7 +377,7 @@ pub fn parse_element_section<'data>(
} => {
let mut init_expr_reader = init_expr.get_binary_reader();
let (base, offset) = match init_expr_reader.read_operator()? {
Operator::I32Const { value } => (None, value as u32 as usize),
Operator::I32Const { value } => (None, value as u32),
Operator::GlobalGet { global_index } => {
(Some(GlobalIndex::from_u32(global_index)), 0)
}
@@ -388,12 +388,6 @@ pub fn parse_element_section<'data>(
));
}
};
// Check for offset + len overflow
if offset.checked_add(segments.len()).is_none() {
return Err(wasm_unsupported!(
"element segment offset and length overflows"
));
}
environ.declare_table_elements(
TableIndex::from_u32(table_index),
base,
@@ -429,7 +423,7 @@ pub fn parse_data_section<'data>(
} => {
let mut init_expr_reader = init_expr.get_binary_reader();
let (base, offset) = match init_expr_reader.read_operator()? {
Operator::I32Const { value } => (None, value as u32 as usize),
Operator::I32Const { value } => (None, value as u32),
Operator::GlobalGet { global_index } => {
(Some(GlobalIndex::from_u32(global_index)), 0)
}
@@ -440,12 +434,6 @@ pub fn parse_data_section<'data>(
))
}
};
// Check for offset + len overflow
if offset.checked_add(data.len()).is_none() {
return Err(wasm_unsupported!(
"data segment offset and length overflows"
));
}
environ.declare_data_initialization(
MemoryIndex::from_u32(memory_index),
base,