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Use the object crate for metadata reading

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This commit is contained in:
bjorn3 2021-03-29 11:39:13 +02:00
parent e5f83d24ae
commit 267d55d44a
8 changed files with 79 additions and 156 deletions
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2
compiler/rustc_codegen_llvm/src/lib.rs
View file

@ -250,7 +250,7 @@ impl CodegenBackend for LlvmCodegenBackend {
}
fn metadata_loader(&self) -> Box<MetadataLoaderDyn> {
Box::new(metadata::LlvmMetadataLoader)
Box::new(rustc_codegen_ssa::back::metadata::DefaultMetadataLoader)
}
fn provide(&self, providers: &mut ty::query::Providers) {

89
compiler/rustc_codegen_llvm/src/metadata.rs
View file

@ -1,94 +1,9 @@
use crate::llvm;
use crate::llvm::archive_ro::ArchiveRO;
use crate::llvm::{mk_section_iter, False, ObjectFile};
use rustc_middle::middle::cstore::MetadataLoader;
use rustc_target::spec::Target;
use rustc_codegen_ssa::METADATA_FILENAME;
use rustc_data_structures::owning_ref::OwningRef;
use rustc_data_structures::rustc_erase_owner;
use tracing::debug;
use rustc_fs_util::path_to_c_string;
use std::path::Path;
use std::slice;
pub use rustc_data_structures::sync::MetadataRef;
pub struct LlvmMetadataLoader;
impl MetadataLoader for LlvmMetadataLoader {
fn get_rlib_metadata(&self, _: &Target, filename: &Path) -> Result<MetadataRef, String> {
// Use ArchiveRO for speed here, it's backed by LLVM and uses mmap
// internally to read the file. We also avoid even using a memcpy by
// just keeping the archive along while the metadata is in use.
let archive =
ArchiveRO::open(filename).map(|ar| OwningRef::new(Box::new(ar))).map_err(|e| {
debug!("llvm didn't like `{}`: {}", filename.display(), e);
format!("failed to read rlib metadata in '{}': {}", filename.display(), e)
})?;
let buf: OwningRef<_, [u8]> = archive.try_map(|ar| {
ar.iter()
.filter_map(|s| s.ok())
.find(|sect| sect.name() == Some(METADATA_FILENAME))
.map(|s| s.data())
.ok_or_else(|| {
debug!("didn't find '{}' in the archive", METADATA_FILENAME);
format!("failed to read rlib metadata: '{}'", filename.display())
})
})?;
Ok(rustc_erase_owner!(buf))
}
fn get_dylib_metadata(&self, target: &Target, filename: &Path) -> Result<MetadataRef, String> {
unsafe {
let buf = path_to_c_string(filename);
let mb = llvm::LLVMRustCreateMemoryBufferWithContentsOfFile(buf.as_ptr())
.ok_or_else(|| format!("error reading library: '{}'", filename.display()))?;
let of =
ObjectFile::new(mb).map(|of| OwningRef::new(Box::new(of))).ok_or_else(|| {
format!("provided path not an object file: '{}'", filename.display())
})?;
let buf = of.try_map(|of| search_meta_section(of, target, filename))?;
Ok(rustc_erase_owner!(buf))
}
}
}
fn search_meta_section<'a>(
of: &'a ObjectFile,
target: &Target,
filename: &Path,
) -> Result<&'a [u8], String> {
unsafe {
let si = mk_section_iter(of.llof);
while llvm::LLVMIsSectionIteratorAtEnd(of.llof, si.llsi) == False {
let mut name_buf = None;
let name_len = llvm::LLVMRustGetSectionName(si.llsi, &mut name_buf);
let name = name_buf.map_or_else(
String::new, // We got a null ptr, ignore `name_len`.
|buf| {
String::from_utf8(
slice::from_raw_parts(buf.as_ptr() as *const u8, name_len as usize)
.to_vec(),
)
.unwrap()
},
);
debug!("get_metadata_section: name {}", name);
if read_metadata_section_name(target) == name {
let cbuf = llvm::LLVMGetSectionContents(si.llsi);
let csz = llvm::LLVMGetSectionSize(si.llsi) as usize;
// The buffer is valid while the object file is around
let buf: &'a [u8] = slice::from_raw_parts(cbuf as *const u8, csz);
return Ok(buf);
}
llvm::LLVMMoveToNextSection(si.llsi);
}
}
Err(format!("metadata not found: '{}'", filename.display()))
}
pub fn metadata_section_name(target: &Target) -> &'static str {
// Historical note:
//
@ -106,7 +21,3 @@ pub fn metadata_section_name(target: &Target) -> &'static str {
if target.is_like_osx { "__DATA,.rustc" } else { ".rustc" }
}
fn read_metadata_section_name(_target: &Target) -> &'static str {
".rustc"
}