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Document some safety constraints and use more safe wrappers #135549

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Feb 12, 2025
Merged

Document some safety constraints and use more safe wrappers #135549

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b2cd1b8
Remove an unsafe closure invariant by inlining the closure wrapper in…
oli-obk Jan 14, 2025
4b83038
Add a safe wrapper for `WriteBitcodeToFile`
oli-obk Jan 14, 2025
dcf1e4d
Document some safety constraints and use more safe wrappers
oli-obk Jan 14, 2025
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4 changes: 2 additions & 2 deletions compiler/rustc_codegen_llvm/src/allocator.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -81,13 +81,13 @@ pub(crate) unsafe fn codegen(
llvm::set_visibility(ll_g, llvm::Visibility::from_generic(tcx.sess.default_visibility()));
let val = tcx.sess.opts.unstable_opts.oom.should_panic();
let llval = llvm::LLVMConstInt(i8, val as u64, False);
llvm::LLVMSetInitializer(ll_g, llval);
llvm::set_initializer(ll_g, llval);

let name = NO_ALLOC_SHIM_IS_UNSTABLE;
let ll_g = llvm::LLVMRustGetOrInsertGlobal(llmod, name.as_c_char_ptr(), name.len(), i8);
llvm::set_visibility(ll_g, llvm::Visibility::from_generic(tcx.sess.default_visibility()));
let llval = llvm::LLVMConstInt(i8, 0, False);
llvm::LLVMSetInitializer(ll_g, llval);
llvm::set_initializer(ll_g, llval);
}

if tcx.sess.opts.debuginfo != DebugInfo::None {
Expand Down
11 changes: 4 additions & 7 deletions compiler/rustc_codegen_llvm/src/back/archive.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -11,7 +11,7 @@ use rustc_codegen_ssa::back::archive::{
use rustc_session::Session;

use crate::llvm::archive_ro::{ArchiveRO, Child};
use crate::llvm::{self, ArchiveKind};
use crate::llvm::{self, ArchiveKind, last_error};

/// Helper for adding many files to an archive.
#[must_use = "must call build() to finish building the archive"]
Expand Down Expand Up @@ -169,6 +169,8 @@ impl<'a> LlvmArchiveBuilder<'a> {
.unwrap_or_else(|kind| self.sess.dcx().emit_fatal(UnknownArchiveKind { kind }));

let mut additions = mem::take(&mut self.additions);
// Values in the `members` list below will contain pointers to the strings allocated here.
// So they need to get dropped after all elements of `members` get freed.
let mut strings = Vec::new();
let mut members = Vec::new();

Expand Down Expand Up @@ -229,12 +231,7 @@ impl<'a> LlvmArchiveBuilder<'a> {
self.sess.target.arch == "arm64ec",
);
let ret = if r.into_result().is_err() {
let err = llvm::LLVMRustGetLastError();
let msg = if err.is_null() {
"failed to write archive".into()
} else {
String::from_utf8_lossy(CStr::from_ptr(err).to_bytes())
};
let msg = last_error().unwrap_or_else(|| "failed to write archive".into());
Err(io::Error::new(io::ErrorKind::Other, msg))
} else {
Ok(!members.is_empty())
Expand Down
212 changes: 88 additions & 124 deletions compiler/rustc_codegen_llvm/src/back/write.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -40,7 +40,7 @@ use crate::errors::{
WithLlvmError, WriteBytecode,
};
use crate::llvm::diagnostic::OptimizationDiagnosticKind::*;
use crate::llvm::{self, DiagnosticInfo, PassManager};
use crate::llvm::{self, DiagnosticInfo};
use crate::type_::Type;
use crate::{LlvmCodegenBackend, ModuleLlvm, base, common, llvm_util};

Expand All @@ -54,7 +54,7 @@ pub(crate) fn llvm_err<'a>(dcx: DiagCtxtHandle<'_>, err: LlvmError<'a>) -> Fatal
fn write_output_file<'ll>(
dcx: DiagCtxtHandle<'_>,
target: &'ll llvm::TargetMachine,
pm: &llvm::PassManager<'ll>,
no_builtins: bool,
m: &'ll llvm::Module,
output: &Path,
dwo_output: Option<&Path>,
Expand All @@ -63,39 +63,42 @@ fn write_output_file<'ll>(
verify_llvm_ir: bool,
) -> Result<(), FatalError> {
debug!("write_output_file output={:?} dwo_output={:?}", output, dwo_output);
unsafe {
let output_c = path_to_c_string(output);
let dwo_output_c;
let dwo_output_ptr = if let Some(dwo_output) = dwo_output {
dwo_output_c = path_to_c_string(dwo_output);
dwo_output_c.as_ptr()
} else {
std::ptr::null()
};
let result = llvm::LLVMRustWriteOutputFile(
let output_c = path_to_c_string(output);
let dwo_output_c;
let dwo_output_ptr = if let Some(dwo_output) = dwo_output {
dwo_output_c = path_to_c_string(dwo_output);
dwo_output_c.as_ptr()
} else {
std::ptr::null()
};
let result = unsafe {
let pm = llvm::LLVMCreatePassManager();
llvm::LLVMAddAnalysisPasses(target, pm);
llvm::LLVMRustAddLibraryInfo(pm, m, no_builtins);
llvm::LLVMRustWriteOutputFile(
target,
pm,
m,
output_c.as_ptr(),
dwo_output_ptr,
file_type,
verify_llvm_ir,
);
)
};

// Record artifact sizes for self-profiling
if result == llvm::LLVMRustResult::Success {
let artifact_kind = match file_type {
llvm::FileType::ObjectFile => "object_file",
llvm::FileType::AssemblyFile => "assembly_file",
};
record_artifact_size(self_profiler_ref, artifact_kind, output);
if let Some(dwo_file) = dwo_output {
record_artifact_size(self_profiler_ref, "dwo_file", dwo_file);
}
// Record artifact sizes for self-profiling
if result == llvm::LLVMRustResult::Success {
let artifact_kind = match file_type {
llvm::FileType::ObjectFile => "object_file",
llvm::FileType::AssemblyFile => "assembly_file",
};
record_artifact_size(self_profiler_ref, artifact_kind, output);
if let Some(dwo_file) = dwo_output {
record_artifact_size(self_profiler_ref, "dwo_file", dwo_file);
}

result.into_result().map_err(|()| llvm_err(dcx, LlvmError::WriteOutput { path: output }))
}

result.into_result().map_err(|()| llvm_err(dcx, LlvmError::WriteOutput { path: output }))
}

pub(crate) fn create_informational_target_machine(
Expand Down Expand Up @@ -325,13 +328,17 @@ pub(crate) fn save_temp_bitcode(
if !cgcx.save_temps {
return;
}
let ext = format!("{name}.bc");
let cgu = Some(&module.name[..]);
let path = cgcx.output_filenames.temp_path_ext(&ext, cgu);
write_bitcode_to_file(module, &path)
}

fn write_bitcode_to_file(module: &ModuleCodegen<ModuleLlvm>, path: &Path) {
unsafe {
let ext = format!("{name}.bc");
let cgu = Some(&module.name[..]);
let path = cgcx.output_filenames.temp_path_ext(&ext, cgu);
let cstr = path_to_c_string(&path);
let path = path_to_c_string(&path);
let llmod = module.module_llvm.llmod();
llvm::LLVMWriteBitcodeToFile(llmod, cstr.as_ptr());
llvm::LLVMWriteBitcodeToFile(llmod, path.as_ptr());
}
}

Expand Down Expand Up @@ -676,7 +683,6 @@ pub(crate) unsafe fn optimize(
) -> Result<(), FatalError> {
let _timer = cgcx.prof.generic_activity_with_arg("LLVM_module_optimize", &*module.name);

let llmod = module.module_llvm.llmod();
let llcx = &*module.module_llvm.llcx;
let _handlers = DiagnosticHandlers::new(cgcx, dcx, llcx, module, CodegenDiagnosticsStage::Opt);

Expand All @@ -685,8 +691,7 @@ pub(crate) unsafe fn optimize(

if config.emit_no_opt_bc {
let out = cgcx.output_filenames.temp_path_ext("no-opt.bc", module_name);
let out = path_to_c_string(&out);
unsafe { llvm::LLVMWriteBitcodeToFile(llmod, out.as_ptr()) };
write_bitcode_to_file(module, &out)
}

// FIXME(ZuseZ4): support SanitizeHWAddress and prevent illegal/unsupported opts
Expand Down Expand Up @@ -755,31 +760,6 @@ pub(crate) unsafe fn codegen(
create_msvc_imps(cgcx, llcx, llmod);
}

// A codegen-specific pass manager is used to generate object
// files for an LLVM module.
//
// Apparently each of these pass managers is a one-shot kind of
// thing, so we create a new one for each type of output. The
// pass manager passed to the closure should be ensured to not
// escape the closure itself, and the manager should only be
// used once.
unsafe fn with_codegen<'ll, F, R>(
tm: &'ll llvm::TargetMachine,
llmod: &'ll llvm::Module,
no_builtins: bool,
f: F,
) -> R
where
F: FnOnce(&'ll mut PassManager<'ll>) -> R,
{
unsafe {
let cpm = llvm::LLVMCreatePassManager();
llvm::LLVMAddAnalysisPasses(tm, cpm);
llvm::LLVMRustAddLibraryInfo(cpm, llmod, no_builtins);
f(cpm)
}
}

// Note that if object files are just LLVM bitcode we write bitcode,
// copy it to the .o file, and delete the bitcode if it wasn't
// otherwise requested.
Expand Down Expand Up @@ -898,21 +878,17 @@ pub(crate) unsafe fn codegen(
} else {
llmod
};
unsafe {
with_codegen(tm, llmod, config.no_builtins, |cpm| {
write_output_file(
dcx,
tm,
cpm,
llmod,
&path,
None,
llvm::FileType::AssemblyFile,
&cgcx.prof,
config.verify_llvm_ir,
)
})?;
}
write_output_file(
dcx,
tm,
config.no_builtins,
llmod,
&path,
None,
llvm::FileType::AssemblyFile,
&cgcx.prof,
config.verify_llvm_ir,
)?;
}

match config.emit_obj {
Expand All @@ -936,21 +912,17 @@ pub(crate) unsafe fn codegen(
(_, SplitDwarfKind::Split) => Some(dwo_out.as_path()),
};

unsafe {
with_codegen(tm, llmod, config.no_builtins, |cpm| {
write_output_file(
dcx,
tm,
cpm,
llmod,
&obj_out,
dwo_out,
llvm::FileType::ObjectFile,
&cgcx.prof,
config.verify_llvm_ir,
)
})?;
}
write_output_file(
dcx,
tm,
config.no_builtins,
llmod,
&obj_out,
dwo_out,
llvm::FileType::ObjectFile,
&cgcx.prof,
config.verify_llvm_ir,
)?;
}

EmitObj::Bitcode => {
Expand Down Expand Up @@ -1077,24 +1049,18 @@ unsafe fn embed_bitcode(
{
// We don't need custom section flags, create LLVM globals.
let llconst = common::bytes_in_context(llcx, bitcode);
let llglobal = llvm::LLVMAddGlobal(
llmod,
common::val_ty(llconst),
c"rustc.embedded.module".as_ptr(),
);
llvm::LLVMSetInitializer(llglobal, llconst);
let llglobal =
llvm::add_global(llmod, common::val_ty(llconst), c"rustc.embedded.module");
llvm::set_initializer(llglobal, llconst);

llvm::set_section(llglobal, bitcode_section_name(cgcx));
llvm::set_linkage(llglobal, llvm::Linkage::PrivateLinkage);
llvm::LLVMSetGlobalConstant(llglobal, llvm::True);

let llconst = common::bytes_in_context(llcx, cmdline.as_bytes());
let llglobal = llvm::LLVMAddGlobal(
llmod,
common::val_ty(llconst),
c"rustc.embedded.cmdline".as_ptr(),
);
llvm::LLVMSetInitializer(llglobal, llconst);
let llglobal =
llvm::add_global(llmod, common::val_ty(llconst), c"rustc.embedded.cmdline");
llvm::set_initializer(llglobal, llconst);
let section = if cgcx.target_is_like_osx {
c"__LLVM,__cmdline"
} else if cgcx.target_is_like_aix {
Expand Down Expand Up @@ -1134,31 +1100,29 @@ fn create_msvc_imps(
// underscores added in front).
let prefix = if cgcx.target_arch == "x86" { "\x01__imp__" } else { "\x01__imp_" };

unsafe {
let ptr_ty = Type::ptr_llcx(llcx);
let globals = base::iter_globals(llmod)
.filter(|&val| {
llvm::get_linkage(val) == llvm::Linkage::ExternalLinkage
&& llvm::LLVMIsDeclaration(val) == 0
})
.filter_map(|val| {
// Exclude some symbols that we know are not Rust symbols.
let name = llvm::get_value_name(val);
if ignored(name) { None } else { Some((val, name)) }
})
.map(move |(val, name)| {
let mut imp_name = prefix.as_bytes().to_vec();
imp_name.extend(name);
let imp_name = CString::new(imp_name).unwrap();
(imp_name, val)
})
.collect::<Vec<_>>();
let ptr_ty = Type::ptr_llcx(llcx);
let globals = base::iter_globals(llmod)
.filter(|&val| {
llvm::get_linkage(val) == llvm::Linkage::ExternalLinkage && !llvm::is_declaration(val)
})
.filter_map(|val| {
// Exclude some symbols that we know are not Rust symbols.
let name = llvm::get_value_name(val);
if ignored(name) { None } else { Some((val, name)) }
})
.map(move |(val, name)| {
let mut imp_name = prefix.as_bytes().to_vec();
imp_name.extend(name);
let imp_name = CString::new(imp_name).unwrap();
(imp_name, val)
})
.collect::<Vec<_>>();

for (imp_name, val) in globals {
let imp = llvm::LLVMAddGlobal(llmod, ptr_ty, imp_name.as_ptr());
llvm::LLVMSetInitializer(imp, val);
llvm::set_linkage(imp, llvm::Linkage::ExternalLinkage);
}
for (imp_name, val) in globals {
let imp = llvm::add_global(llmod, ptr_ty, &imp_name);

llvm::set_initializer(imp, val);
llvm::set_linkage(imp, llvm::Linkage::ExternalLinkage);
}

// Use this function to exclude certain symbols from `__imp` generation.
Expand Down
2 changes: 1 addition & 1 deletion compiler/rustc_codegen_llvm/src/common.rs
View file
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Original file line number Diff line number Diff line change
Expand Up @@ -219,8 +219,8 @@ impl<'ll, 'tcx> ConstCodegenMethods<'tcx> for CodegenCx<'ll, 'tcx> {
let g = self.define_global(&sym, self.val_ty(sc)).unwrap_or_else(|| {
bug!("symbol `{}` is already defined", sym);
});
llvm::set_initializer(g, sc);
unsafe {
llvm::LLVMSetInitializer(g, sc);
llvm::LLVMSetGlobalConstant(g, True);
llvm::LLVMSetUnnamedAddress(g, llvm::UnnamedAddr::Global);
}
Expand Down
6 changes: 3 additions & 3 deletions compiler/rustc_codegen_llvm/src/consts.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -191,7 +191,7 @@ fn check_and_apply_linkage<'ll, 'tcx>(
})
});
llvm::set_linkage(g2, llvm::Linkage::InternalLinkage);
unsafe { llvm::LLVMSetInitializer(g2, g1) };
llvm::set_initializer(g2, g1);
g2
} else if cx.tcx.sess.target.arch == "x86"
&& common::is_mingw_gnu_toolchain(&cx.tcx.sess.target)
Expand Down Expand Up @@ -235,7 +235,7 @@ impl<'ll> CodegenCx<'ll, '_> {
}
_ => self.define_private_global(self.val_ty(cv)),
};
unsafe { llvm::LLVMSetInitializer(gv, cv) };
llvm::set_initializer(gv, cv);
set_global_alignment(self, gv, align);
llvm::SetUnnamedAddress(gv, llvm::UnnamedAddr::Global);
gv
Expand Down Expand Up @@ -458,7 +458,7 @@ impl<'ll> CodegenCx<'ll, '_> {
new_g
};
set_global_alignment(self, g, alloc.align);
llvm::LLVMSetInitializer(g, v);
llvm::set_initializer(g, v);

if self.should_assume_dso_local(g, true) {
llvm::LLVMRustSetDSOLocal(g, true);
Expand Down
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