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Introduce EmitObj.

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Currently, there are three fields in `ModuleConfig` that dictate
how object files are emitted: `emit_obj`, `obj_is_bitcode`, and
`embed_bitcode`.

Some of the combinations of these fields are nonsensical, in particular
having both `obj_is_bitcode` and `embed_bitcode` true at the same time.

Also, currently:
- we needlessly emit and then delete a bytecode file if `obj_is_bitcode`
  is true but `emit_obj` is false;
- we needlessly embed bitcode in the LLVM module if `embed_bitcode` is
  true and `emit_obj` is false.

This commit combines the three fields into one, with a new type
`EmitObj` (and the auxiliary `BitcodeSection`) which can encode five
different possibilities.

In the old code, `set_flags` would set `obj_is_bitcode` and
`embed_bitcode` on all three of the configs (`modules`, `allocator`,
`metadata`) if the relevant other conditions were met, even if no object
code needed to be emitted for one or more of them. Whereas
`start_async_codegen` would set `emit_obj`, but only for those configs
that need it.

In the new code, `start_async_codegen` does all the work of setting
`emit_obj`, and it only does that for the configs that need it.
`set_flags` no longer sets anything related to object file emission.
This commit is contained in:
Nicholas Nethercote 2020-03-24 12:24:52 +11:00
parent e1d1db790f
commit 87ef16c9dc
2 changed files with 64 additions and 49 deletions
src
librustc_codegen_llvm/back
write.rs
librustc_codegen_ssa/back
write.rs

32
src/librustc_codegen_llvm/back/write.rs

@ -16,7 +16,9 @@ use crate::ModuleLlvm;
use log::debug;
use rustc::bug;
use rustc::ty::TyCtxt;
use rustc_codegen_ssa::back::write::{run_assembler, CodegenContext, EmbedBitcode, ModuleConfig};
use rustc_codegen_ssa::back::write::{
run_assembler, BitcodeSection, CodegenContext, EmitObj, ModuleConfig,
};
use rustc_codegen_ssa::traits::*;
use rustc_codegen_ssa::{CompiledModule, ModuleCodegen, RLIB_BYTECODE_EXTENSION};
use rustc_data_structures::small_c_str::SmallCStr;
@ -651,7 +653,7 @@ pub(crate) unsafe fn codegen(
let thin = ThinBuffer::new(llmod);
let data = thin.data();
if config.emit_bc || config.obj_is_bitcode {
if config.emit_bc || config.emit_obj == EmitObj::Bitcode {
let _timer = cgcx.prof.generic_activity_with_arg(
"LLVM_module_codegen_emit_bitcode",
&module.name[..],
@ -662,7 +664,7 @@ pub(crate) unsafe fn codegen(
}
}
if config.embed_bitcode == EmbedBitcode::Full {
if config.emit_obj == EmitObj::ObjectCode(BitcodeSection::Full) {
let _timer = cgcx.prof.generic_activity_with_arg(
"LLVM_module_codegen_embed_bitcode",
&module.name[..],
@ -682,7 +684,7 @@ pub(crate) unsafe fn codegen(
diag_handler.err(&msg);
}
}
} else if config.embed_bitcode == EmbedBitcode::Marker {
} else if config.emit_obj == EmitObj::ObjectCode(BitcodeSection::Marker) {
embed_bitcode(cgcx, llcx, llmod, None);
}
@ -732,9 +734,9 @@ pub(crate) unsafe fn codegen(
})?;
}
let config_emit_normal_obj = config.emit_obj && !config.obj_is_bitcode;
let config_emit_object_code = matches!(config.emit_obj, EmitObj::ObjectCode(_));
if config.emit_asm || (config_emit_normal_obj && config.no_integrated_as) {
if config.emit_asm || (config_emit_object_code && config.no_integrated_as) {
let _timer = cgcx
.prof
.generic_activity_with_arg("LLVM_module_codegen_emit_asm", &module.name[..]);
@ -743,13 +745,13 @@ pub(crate) unsafe fn codegen(
// We can't use the same module for asm and binary output, because that triggers
// various errors like invalid IR or broken binaries, so we might have to clone the
// module to produce the asm output
let llmod = if config.emit_obj { llvm::LLVMCloneModule(llmod) } else { llmod };
let llmod = if config_emit_object_code { llvm::LLVMCloneModule(llmod) } else { llmod };
with_codegen(tm, llmod, config.no_builtins, |cpm| {
write_output_file(diag_handler, tm, cpm, llmod, &path, llvm::FileType::AssemblyFile)
})?;
}
if config_emit_normal_obj {
if config_emit_object_code {
if !config.no_integrated_as {
let _timer = cgcx
.prof
@ -775,14 +777,10 @@ pub(crate) unsafe fn codegen(
drop(fs::remove_file(&assembly));
}
}
}
if config.obj_is_bitcode {
if config.emit_obj {
debug!("copying bitcode {:?} to obj {:?}", bc_out, obj_out);
if let Err(e) = link_or_copy(&bc_out, &obj_out) {
diag_handler.err(&format!("failed to copy bitcode to object file: {}", e));
}
} else if config.emit_obj == EmitObj::Bitcode {
debug!("copying bitcode {:?} to obj {:?}", bc_out, obj_out);
if let Err(e) = link_or_copy(&bc_out, &obj_out) {
diag_handler.err(&format!("failed to copy bitcode to object file: {}", e));
}
if !config.emit_bc {
@ -796,7 +794,7 @@ pub(crate) unsafe fn codegen(
drop(handlers);
}
Ok(module.into_compiled_module(
config.emit_obj,
config.emit_obj != EmitObj::None,
config.emit_bc,
config.emit_bc_compressed,
&cgcx.output_filenames,

81
src/librustc_codegen_ssa/back/write.rs

@ -51,11 +51,31 @@ use std::thread;
const PRE_LTO_BC_EXT: &str = "pre-lto.bc";
/// The kind of bitcode to embed in object files.
#[derive(PartialEq)]
pub enum EmbedBitcode {
/// What kind of object file to emit.
#[derive(Clone, Copy, PartialEq)]
pub enum EmitObj {
// No object file.
None,
// Just uncompressed llvm bitcode. Provides easy compatibility with
// emscripten's ecc compiler, when used as the linker.
Bitcode,
// Object code, possibly augmented with a bitcode section.
ObjectCode(BitcodeSection),
}
/// What kind of llvm bitcode section to embed in an object file.
#[derive(Clone, Copy, PartialEq)]
pub enum BitcodeSection {
// No bitcode section.
None,
// An empty bitcode section (to placate tools such as the iOS linker that
// require this section even if they don't use it).
Marker,
// A full, uncompressed bitcode section.
Full,
}
@ -84,7 +104,7 @@ pub struct ModuleConfig {
pub emit_bc_compressed: bool,
pub emit_ir: bool,
pub emit_asm: bool,
pub emit_obj: bool,
pub emit_obj: EmitObj,
// Miscellaneous flags. These are mostly copied from command-line
// options.
pub verify_llvm_ir: bool,
@ -96,12 +116,7 @@ pub struct ModuleConfig {
pub merge_functions: bool,
pub inline_threshold: Option<usize>,
pub new_llvm_pass_manager: Option<bool>,
// Instead of creating an object file by doing LLVM codegen, just
// make the object file bitcode. Provides easy compatibility with
// emscripten's ecc compiler, when used as the linker.
pub obj_is_bitcode: bool,
pub no_integrated_as: bool,
pub embed_bitcode: EmbedBitcode,
}
impl ModuleConfig {
@ -124,9 +139,7 @@ impl ModuleConfig {
emit_bc_compressed: false,
emit_ir: false,
emit_asm: false,
emit_obj: false,
obj_is_bitcode: false,
embed_bitcode: EmbedBitcode::None,
emit_obj: EmitObj::None,
no_integrated_as: false,
verify_llvm_ir: false,
@ -147,16 +160,6 @@ impl ModuleConfig {
self.no_builtins = no_builtins || sess.target.target.options.no_builtins;
self.inline_threshold = sess.opts.cg.inline_threshold;
self.new_llvm_pass_manager = sess.opts.debugging_opts.new_llvm_pass_manager;
self.obj_is_bitcode =
sess.target.target.options.obj_is_bitcode || sess.opts.cg.linker_plugin_lto.enabled();
self.embed_bitcode = if sess.opts.debugging_opts.embed_bitcode {
match sess.opts.optimize {
config::OptLevel::No | config::OptLevel::Less => EmbedBitcode::Marker,
_ => EmbedBitcode::Full,
}
} else {
EmbedBitcode::None
};
// Copy what clang does by turning on loop vectorization at O2 and
// slp vectorization at O3. Otherwise configure other optimization aspects
@ -193,9 +196,9 @@ impl ModuleConfig {
pub fn bitcode_needed(&self) -> bool {
self.emit_bc
|| self.obj_is_bitcode
|| self.emit_bc_compressed
|| self.embed_bitcode == EmbedBitcode::Full
|| self.emit_obj == EmitObj::Bitcode
|| self.emit_obj == EmitObj::ObjectCode(BitcodeSection::Full)
}
}
@ -396,6 +399,20 @@ pub fn start_async_codegen<B: ExtraBackendMethods>(
allocator_config.emit_bc_compressed = true;
}
let emit_obj =
if sess.target.target.options.obj_is_bitcode || sess.opts.cg.linker_plugin_lto.enabled() {
EmitObj::Bitcode
} else if sess.opts.debugging_opts.embed_bitcode {
match sess.opts.optimize {
config::OptLevel::No | config::OptLevel::Less => {
EmitObj::ObjectCode(BitcodeSection::Marker)
}
_ => EmitObj::ObjectCode(BitcodeSection::Full),
}
} else {
EmitObj::ObjectCode(BitcodeSection::None)
};
modules_config.emit_pre_lto_bc = need_pre_lto_bitcode_for_incr_comp(sess);
modules_config.no_integrated_as =
@ -415,20 +432,20 @@ pub fn start_async_codegen<B: ExtraBackendMethods>(
// could be invoked specially with output_type_assembly, so
// in this case we still want the metadata object file.
if !sess.opts.output_types.contains_key(&OutputType::Assembly) {
metadata_config.emit_obj = true;
allocator_config.emit_obj = true;
metadata_config.emit_obj = emit_obj;
allocator_config.emit_obj = emit_obj;
}
}
OutputType::Object => {
modules_config.emit_obj = true;
modules_config.emit_obj = emit_obj;
}
OutputType::Metadata => {
metadata_config.emit_obj = true;
metadata_config.emit_obj = emit_obj;
}
OutputType::Exe => {
modules_config.emit_obj = true;
metadata_config.emit_obj = true;
allocator_config.emit_obj = true;
modules_config.emit_obj = emit_obj;
metadata_config.emit_obj = emit_obj;
allocator_config.emit_obj = emit_obj;
}
OutputType::Mir => {}
OutputType::DepInfo => {}
@ -879,7 +896,7 @@ fn execute_copy_from_cache_work_item<B: ExtraBackendMethods>(
}
}
assert_eq!(object.is_some(), module_config.emit_obj);
assert_eq!(object.is_some(), module_config.emit_obj != EmitObj::None);
assert_eq!(bytecode.is_some(), module_config.emit_bc);
assert_eq!(bytecode_compressed.is_some(), module_config.emit_bc_compressed);