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Refactor where results of compilation are stored (#2086)

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* Refactor where results of compilation are stored

This commit refactors the internals of compilation in Wasmtime to change
where results of individual function compilation are stored. Previously
compilation resulted in many maps being returned, and compilation
results generally held all these maps together. This commit instead
switches this to have all metadata stored in a `CompiledFunction`
instead of having a separate map for each item that can be stored.

The motivation for this is primarily to help out with future
module-linking-related PRs. What exactly "module level" is depends on
how we interpret modules and how many modules are in play, so it's a bit
easier for operations in wasmtime to work at the function level where
possible. This means that we don't have to pass around multiple
different maps and a function index, but instead just one map or just
one entry representing a compiled function.

Additionally this change updates where the parallelism of compilation
happens, pushing it into `wasmtime-jit` instead of `wasmtime-environ`.
This is another goal where `wasmtime-jit` will have more knowledge about
module-level pieces with module linking in play. User-facing-wise this
should be the same in terms of parallel compilation, though.

The ultimate goal of this refactoring is to make it easier for the
results of compilation to actually be a set of wasm modules. This means
we won't be able to have a map-per-metadata where the primary key is the
function index, because there will be many modules within one "object
file".

* Don't clear out fields, just don't store them

Persist a smaller set of fields in `CompilationArtifacts` instead of
trying to clear fields out and dynamically not accessing them.
This commit is contained in:
Alex Crichton
2020-08-03 12:20:51 -05:00
committed by GitHub
parent 026fb8d388
commit 65eaca35dd
31 changed files with 466 additions and 757 deletions
Download Patch File Download Diff File Expand all files Collapse all files

108
crates/obj/src/builder.rs
View File

@@ -28,12 +28,10 @@ use std::collections::HashMap;
use target_lexicon::Triple;
use wasmtime_debug::{DwarfSection, DwarfSectionRelocTarget};
use wasmtime_environ::entity::{EntityRef, PrimaryMap};
use wasmtime_environ::ir::{JumpTableOffsets, LibCall, Reloc};
use wasmtime_environ::ir::{LibCall, Reloc};
use wasmtime_environ::isa::unwind::UnwindInfo;
use wasmtime_environ::wasm::{DefinedFuncIndex, FuncIndex, SignatureIndex};
use wasmtime_environ::{
Compilation, CompiledFunction, Module, Relocation, RelocationTarget, Relocations,
};
use wasmtime_environ::{CompiledFunction, CompiledFunctions, Module, Relocation, RelocationTarget};
fn to_object_relocations<'a>(
it: impl Iterator<Item = &'a Relocation> + 'a,
@@ -41,7 +39,7 @@ fn to_object_relocations<'a>(
module: &'a Module,
funcs: &'a PrimaryMap<FuncIndex, SymbolId>,
libcalls: &'a HashMap<LibCall, SymbolId>,
jt_offsets: &'a PrimaryMap<DefinedFuncIndex, JumpTableOffsets>,
compiled_funcs: &'a CompiledFunctions,
) -> impl Iterator<Item = ObjectRelocation> + 'a {
it.filter_map(move |r| {
let (symbol, symbol_offset) = match r.reloc_target {
@@ -49,9 +47,9 @@ fn to_object_relocations<'a>(
RelocationTarget::LibCall(call) => (libcalls[&call], 0),
RelocationTarget::JumpTable(f, jt) => {
let df = module.local.defined_func_index(f).unwrap();
let offset = *jt_offsets
let offset = *compiled_funcs
.get(df)
.and_then(|ofs| ofs.get(jt))
.and_then(|f| f.jt_offsets.get(jt))
.expect("func jump table");
(funcs[f], offset)
}
@@ -258,20 +256,24 @@ pub struct ObjectBuilder<'a> {
target: ObjectBuilderTarget,
module: &'a Module,
code_alignment: u64,
compilation: Option<(Compilation, Relocations)>,
trampolines: PrimaryMap<SignatureIndex, (CompiledFunction, Vec<Relocation>)>,
compilation: &'a CompiledFunctions,
trampolines: PrimaryMap<SignatureIndex, CompiledFunction>,
dwarf_sections: Vec<DwarfSection>,
}
impl<'a> ObjectBuilder<'a> {
pub fn new(target: ObjectBuilderTarget, module: &'a Module) -> Self {
pub fn new(
target: ObjectBuilderTarget,
module: &'a Module,
compilation: &'a CompiledFunctions,
) -> Self {
Self {
target,
module,
code_alignment: 1,
compilation: None,
trampolines: PrimaryMap::new(),
dwarf_sections: vec![],
compilation,
}
}
@@ -280,18 +282,9 @@ impl<'a> ObjectBuilder<'a> {
self
}
pub fn set_compilation(
&mut self,
compilation: Compilation,
relocations: Relocations,
) -> &mut Self {
self.compilation = Some((compilation, relocations));
self
}
pub fn set_trampolines(
&mut self,
trampolines: PrimaryMap<SignatureIndex, (CompiledFunction, Vec<Relocation>)>,
trampolines: PrimaryMap<SignatureIndex, CompiledFunction>,
) -> &mut Self {
self.trampolines = trampolines;
self
@@ -319,17 +312,8 @@ impl<'a> ObjectBuilder<'a> {
SectionKind::Text,
);
let (compilation, jt_offsets, relocations) = self.compilation.map_or_else(
|| (None, PrimaryMap::new(), PrimaryMap::new()),
|(c, relocations)| {
let jt_offsets = c.get_jt_offsets();
(Some(c), jt_offsets, relocations)
},
);
// Create symbols for imports -- needed during linking.
let mut func_symbols =
PrimaryMap::with_capacity(compilation.as_ref().map_or_else(|| 0, |c| c.len()));
let mut func_symbols = PrimaryMap::with_capacity(self.compilation.len());
for index in 0..module.local.num_imported_funcs {
let symbol_id = obj.add_symbol(Symbol {
name: utils::func_symbol_name(FuncIndex::new(index))
@@ -346,38 +330,10 @@ impl<'a> ObjectBuilder<'a> {
func_symbols.push(symbol_id);
}
if let Some(compilation) = compilation {
// Create symbols and section data for the compiled functions.
for (index, func) in compilation.into_iter().enumerate() {
let off = obj.append_section_data(section_id, &func.body, 1);
let symbol_id = obj.add_symbol(Symbol {
name: utils::func_symbol_name(
module.local.func_index(DefinedFuncIndex::new(index)),
)
.as_bytes()
.to_vec(),
value: off,
size: func.body.len() as u64,
kind: SymbolKind::Text,
scope: SymbolScope::Compilation,
weak: false,
section: SymbolSection::Section(section_id),
flags: SymbolFlags::None,
});
func_symbols.push(symbol_id);
// Preserve function unwind info.
if let Some(info) = &func.unwind_info {
process_unwind_info(info, &mut obj, section_id);
}
}
}
// Create trampoline symbols for every signature.
let mut trampoline_relocs = HashMap::new();
for (i, (func, relocs)) in self.trampolines.into_iter() {
let mut append_func = |name: Vec<u8>, func: &CompiledFunction| {
let off = obj.append_section_data(section_id, &func.body, 1);
let symbol_id = obj.add_symbol(Symbol {
name: utils::trampoline_symbol_name(i).as_bytes().to_vec(),
name,
value: off,
size: func.body.len() as u64,
kind: SymbolKind::Text,
@@ -386,11 +342,25 @@ impl<'a> ObjectBuilder<'a> {
section: SymbolSection::Section(section_id),
flags: SymbolFlags::None,
});
trampoline_relocs.insert(symbol_id, relocs);
// Preserve trampoline function unwind info.
// Preserve function unwind info.
if let Some(info) = &func.unwind_info {
process_unwind_info(info, &mut obj, section_id);
}
symbol_id
};
// Create symbols and section data for the compiled functions.
for (index, func) in self.compilation.iter() {
let name = utils::func_symbol_name(module.local.func_index(index))
.as_bytes()
.to_vec();
let symbol_id = append_func(name, func);
func_symbols.push(symbol_id);
}
let mut trampolines = Vec::new();
for (i, func) in self.trampolines.iter() {
let name = utils::trampoline_symbol_name(i).as_bytes().to_vec();
trampolines.push(append_func(name, func));
}
obj.append_section_data(section_id, &[], self.code_alignment);
@@ -412,32 +382,32 @@ impl<'a> ObjectBuilder<'a> {
let libcalls = write_libcall_symbols(&mut obj);
// Write all functions relocations.
for (index, relocs) in relocations.into_iter() {
for (index, func) in self.compilation.into_iter() {
let func_index = module.local.func_index(index);
let (_, off) = obj
.symbol_section_and_offset(func_symbols[func_index])
.unwrap();
for r in to_object_relocations(
relocs.iter(),
func.relocations.iter(),
off,
module,
&func_symbols,
&libcalls,
&jt_offsets,
&self.compilation,
) {
obj.add_relocation(section_id, r)?;
}
}
for (symbol, relocs) in trampoline_relocs {
for (func, symbol) in self.trampolines.values().zip(trampolines) {
let (_, off) = obj.symbol_section_and_offset(symbol).unwrap();
for r in to_object_relocations(
relocs.iter(),
func.relocations.iter(),
off,
module,
&func_symbols,
&libcalls,
&jt_offsets,
&self.compilation,
) {
obj.add_relocation(section_id, r)?;
}

8
crates/obj/src/module.rs
View File

@@ -7,7 +7,7 @@ use object::write::{Object, Relocation, StandardSection, Symbol, SymbolSection};
use object::{RelocationEncoding, RelocationKind, SymbolFlags, SymbolKind, SymbolScope};
use wasmtime_debug::DwarfSection;
use wasmtime_environ::isa::TargetFrontendConfig;
use wasmtime_environ::{Compilation, DataInitializer, Module, Relocations};
use wasmtime_environ::{CompiledFunctions, DataInitializer, Module};
fn emit_vmcontext_init(
obj: &mut Object,
@@ -52,13 +52,11 @@ pub fn emit_module(
target: ObjectBuilderTarget,
module: &Module,
target_config: &TargetFrontendConfig,
compilation: Compilation,
relocations: Relocations,
compilation: CompiledFunctions,
dwarf_sections: Vec<DwarfSection>,
data_initializers: &[DataInitializer],
) -> Result<Object> {
let mut builder = ObjectBuilder::new(target, module);
builder.set_compilation(compilation, relocations);
let mut builder = ObjectBuilder::new(target, module, &compilation);
builder.set_dwarf_sections(dwarf_sections);
let mut obj = builder.build()?;