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Make VMOffset calculation more readable (#3793)

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* Fix typo

* Move vmoffset field size and field name together

The previous code was quite confusing about what applied to which field.
The new code also makes it easier to move fields around and insert and
delete fields.

* Move builtin_functions before all variable sized fields

This allows the offset to be calculated at compile time

* Add cadd and cmul convenience functions

* Remove comment

* Change fields! syntax as per review

* Add implicit u32::from to fields!
This commit is contained in:
bjorn3
2022-02-22 16:48:53 +01:00
committed by GitHub
parent 084452acab
commit bbd52772de
2 changed files with 65 additions and 100 deletions
Download Patch File Download Diff File Expand all files Collapse all files

157
crates/environ/src/vmoffsets.rs
View File

@@ -7,6 +7,7 @@
// interrupts: *const VMInterrupts,
// externref_activations_table: *mut VMExternRefActivationsTable,
// store: *mut dyn Store,
// builtins: *mut VMBuiltinFunctionsArray,
// signature_ids: *const VMSharedSignatureIndex,
// imported_functions: [VMFunctionImport; module.num_imported_functions],
// imported_tables: [VMTableImport; module.num_imported_tables],
@@ -16,7 +17,6 @@
// memories: [VMMemoryDefinition; module.num_defined_memories],
// globals: [VMGlobalDefinition; module.num_defined_globals],
// anyfuncs: [VMCallerCheckedAnyfunc; module.num_imported_functions + module.num_defined_functions],
// builtins: *mut VMBuiltinFunctionsArray,
// }
use crate::{
@@ -74,6 +74,7 @@ pub struct VMOffsets<P> {
epoch_ptr: u32,
externref_activations_table: u32,
store: u32,
builtin_functions: u32,
signature_ids: u32,
imported_functions: u32,
imported_tables: u32,
@@ -83,7 +84,6 @@ pub struct VMOffsets<P> {
defined_memories: u32,
defined_globals: u32,
defined_anyfuncs: u32,
builtin_functions: u32,
size: u32,
}
@@ -172,6 +172,7 @@ impl<P: PtrSize> From<VMOffsetsFields<P>> for VMOffsets<P> {
epoch_ptr: 0,
externref_activations_table: 0,
store: 0,
builtin_functions: 0,
signature_ids: 0,
imported_functions: 0,
imported_tables: 0,
@@ -181,103 +182,67 @@ impl<P: PtrSize> From<VMOffsetsFields<P>> for VMOffsets<P> {
defined_memories: 0,
defined_globals: 0,
defined_anyfuncs: 0,
builtin_functions: 0,
size: 0,
};
ret.interrupts = 0;
ret.epoch_ptr = ret
.interrupts
.checked_add(u32::from(ret.ptr.size()))
.unwrap();
ret.externref_activations_table = ret
.epoch_ptr
.checked_add(u32::from(ret.ptr.size()))
.unwrap();
ret.store = ret
.externref_activations_table
.checked_add(u32::from(ret.ptr.size()))
.unwrap();
ret.signature_ids = ret
.store
.checked_add(u32::from(ret.ptr.size() * 2))
.unwrap();
ret.imported_functions = ret
.signature_ids
.checked_add(u32::from(ret.ptr.size()))
.unwrap();
ret.imported_tables = ret
.imported_functions
.checked_add(
ret.num_imported_functions
.checked_mul(u32::from(ret.size_of_vmfunction_import()))
.unwrap(),
)
.unwrap();
ret.imported_memories = ret
.imported_tables
.checked_add(
ret.num_imported_tables
.checked_mul(u32::from(ret.size_of_vmtable_import()))
.unwrap(),
)
.unwrap();
ret.imported_globals = ret
.imported_memories
.checked_add(
ret.num_imported_memories
.checked_mul(u32::from(ret.size_of_vmmemory_import()))
.unwrap(),
)
.unwrap();
ret.defined_tables = ret
.imported_globals
.checked_add(
ret.num_imported_globals
.checked_mul(u32::from(ret.size_of_vmglobal_import()))
.unwrap(),
)
.unwrap();
ret.defined_memories = ret
.defined_tables
.checked_add(
ret.num_defined_tables
.checked_mul(u32::from(ret.size_of_vmtable_definition()))
.unwrap(),
)
.unwrap();
ret.defined_globals = align(
ret.defined_memories
.checked_add(
ret.num_defined_memories
.checked_mul(u32::from(ret.size_of_vmmemory_definition()))
.unwrap(),
)
.unwrap(),
16,
);
ret.defined_anyfuncs = ret
.defined_globals
.checked_add(
ret.num_defined_globals
.checked_mul(u32::from(ret.size_of_vmglobal_definition()))
.unwrap(),
)
.unwrap();
ret.builtin_functions = ret
.defined_anyfuncs
.checked_add(
ret.num_imported_functions
.checked_add(ret.num_defined_functions)
.unwrap()
.checked_mul(u32::from(ret.size_of_vmcaller_checked_anyfunc()))
.unwrap(),
)
.unwrap();
ret.size = ret
.builtin_functions
.checked_add(u32::from(ret.pointer_size()))
.unwrap();
// Convenience functions for checked addition and multiplication.
// As side effect this reduces binary size by using only a single
// `#[track_caller]` location for each function instead of one for
// each individual invocation.
#[inline]
fn cadd(count: u32, size: u32) -> u32 {
count.checked_add(size).unwrap()
}
#[inline]
fn cmul(count: u32, size: u8) -> u32 {
count.checked_mul(u32::from(size)).unwrap()
}
let mut next_field_offset = 0;
macro_rules! fields {
(size($field:ident) = $size:expr, $($rest:tt)*) => {
ret.$field = next_field_offset;
next_field_offset = cadd(next_field_offset, u32::from($size));
fields!($($rest)*);
};
(align($align:literal), $($rest:tt)*) => {
next_field_offset = align(next_field_offset, $align);
fields!($($rest)*);
};
() => {};
}
fields! {
size(interrupts) = ret.ptr.size(),
size(epoch_ptr) = ret.ptr.size(),
size(externref_activations_table) = ret.ptr.size(),
size(store) = ret.ptr.size() * 2,
size(builtin_functions) = ret.pointer_size(),
size(signature_ids) = ret.ptr.size(),
size(imported_functions)
= cmul(ret.num_imported_functions, ret.size_of_vmfunction_import()),
size(imported_tables)
= cmul(ret.num_imported_tables, ret.size_of_vmtable_import()),
size(imported_memories)
= cmul(ret.num_imported_memories, ret.size_of_vmmemory_import()),
size(imported_globals)
= cmul(ret.num_imported_globals, ret.size_of_vmglobal_import()),
size(defined_tables)
= cmul(ret.num_defined_tables, ret.size_of_vmtable_definition()),
size(defined_memories)
= cmul(ret.num_defined_memories, ret.size_of_vmmemory_definition()),
align(16),
size(defined_globals)
= cmul(ret.num_defined_globals, ret.size_of_vmglobal_definition()),
size(defined_anyfuncs) = cmul(
cadd(ret.num_imported_functions, ret.num_defined_functions),
ret.size_of_vmcaller_checked_anyfunc(),
),
}
ret.size = next_field_offset;
return ret;
}