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coverage: Extract safe FFI wrapper functions to llvm_cov

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This commit is contained in:
Zalathar 2024-11-01 20:32:20 +11:00
parent fbab78289d
commit b790e4473c
3 changed files with 132 additions and 126 deletions
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102
compiler/rustc_codegen_llvm/src/coverageinfo/llvm_cov.rs Normal file
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@ -0,0 +1,102 @@
//! Safe wrappers for coverage-specific FFI functions.
use std::ffi::CString;
use libc::c_uint;
use crate::common::AsCCharPtr;
use crate::coverageinfo::ffi;
use crate::llvm;
pub(crate) fn covmap_var_name() -> CString {
CString::new(llvm::build_byte_buffer(|s| unsafe {
llvm::LLVMRustCoverageWriteMappingVarNameToString(s);
}))
.expect("covmap variable name should not contain NUL")
}
pub(crate) fn covmap_section_name(llmod: &llvm::Module) -> CString {
CString::new(llvm::build_byte_buffer(|s| unsafe {
llvm::LLVMRustCoverageWriteMapSectionNameToString(llmod, s);
}))
.expect("covmap section name should not contain NUL")
}
pub(crate) fn covfun_section_name(llmod: &llvm::Module) -> CString {
CString::new(llvm::build_byte_buffer(|s| unsafe {
llvm::LLVMRustCoverageWriteFuncSectionNameToString(llmod, s);
}))
.expect("covfun section name should not contain NUL")
}
pub(crate) fn create_pgo_func_name_var<'ll>(
llfn: &'ll llvm::Value,
mangled_fn_name: &str,
) -> &'ll llvm::Value {
unsafe {
llvm::LLVMRustCoverageCreatePGOFuncNameVar(
llfn,
mangled_fn_name.as_c_char_ptr(),
mangled_fn_name.len(),
)
}
}
pub(crate) fn write_filenames_to_buffer<'a>(
filenames: impl IntoIterator<Item = &'a str>,
) -> Vec<u8> {
let (pointers, lengths) = filenames
.into_iter()
.map(|s: &str| (s.as_c_char_ptr(), s.len()))
.unzip::<_, _, Vec<_>, Vec<_>>();
llvm::build_byte_buffer(|buffer| unsafe {
llvm::LLVMRustCoverageWriteFilenamesSectionToBuffer(
pointers.as_ptr(),
pointers.len(),
lengths.as_ptr(),
lengths.len(),
buffer,
);
})
}
pub(crate) fn write_function_mappings_to_buffer(
virtual_file_mapping: &[u32],
expressions: &[ffi::CounterExpression],
code_regions: &[ffi::CodeRegion],
branch_regions: &[ffi::BranchRegion],
mcdc_branch_regions: &[ffi::MCDCBranchRegion],
mcdc_decision_regions: &[ffi::MCDCDecisionRegion],
) -> Vec<u8> {
llvm::build_byte_buffer(|buffer| unsafe {
llvm::LLVMRustCoverageWriteMappingToBuffer(
virtual_file_mapping.as_ptr(),
virtual_file_mapping.len() as c_uint,
expressions.as_ptr(),
expressions.len() as c_uint,
code_regions.as_ptr(),
code_regions.len() as c_uint,
branch_regions.as_ptr(),
branch_regions.len() as c_uint,
mcdc_branch_regions.as_ptr(),
mcdc_branch_regions.len() as c_uint,
mcdc_decision_regions.as_ptr(),
mcdc_decision_regions.len() as c_uint,
buffer,
)
})
}
/// Hashes some bytes into a 64-bit hash, via LLVM's `IndexedInstrProf::ComputeHash`,
/// as required for parts of the LLVM coverage mapping format.
pub(crate) fn hash_bytes(bytes: &[u8]) -> u64 {
unsafe { llvm::LLVMRustCoverageHashByteArray(bytes.as_c_char_ptr(), bytes.len()) }
}
/// Returns LLVM's `coverage::CovMapVersion::CurrentVersion` (CoverageMapping.h)
/// as a raw numeric value. For historical reasons, the numeric value is 1 less
/// than the number in the version's name, so `Version7` is actually `6u32`.
pub(crate) fn mapping_version() -> u32 {
unsafe { llvm::LLVMRustCoverageMappingVersion() }
}

57
compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs
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@ -1,4 +1,5 @@
use std::ffi::CString;
use std::iter;
use itertools::Itertools as _;
use rustc_abi::Align;
@ -17,9 +18,9 @@
use tracing::debug;
use crate::common::CodegenCx;
use crate::coverageinfo::ffi;
use crate::coverageinfo::map_data::{FunctionCoverage, FunctionCoverageCollector};
use crate::{coverageinfo, llvm};
use crate::coverageinfo::{ffi, llvm_cov};
use crate::llvm;
/// Generates and exports the coverage map, which is embedded in special
/// linker sections in the final binary.
@ -33,7 +34,7 @@ pub(crate) fn finalize(cx: &CodegenCx<'_, '_>) {
// agrees with our Rust-side code. Expected versions (encoded as n-1) are:
// - `CovMapVersion::Version7` (6) used by LLVM 18-19
let covmap_version = {
let llvm_covmap_version = coverageinfo::mapping_version();
let llvm_covmap_version = llvm_cov::mapping_version();
let expected_versions = 6..=6;
assert!(
expected_versions.contains(&llvm_covmap_version),
@ -78,7 +79,7 @@ pub(crate) fn finalize(cx: &CodegenCx<'_, '_>) {
let filenames_size = filenames_buffer.len();
let filenames_val = cx.const_bytes(&filenames_buffer);
let filenames_ref = coverageinfo::hash_bytes(&filenames_buffer);
let filenames_ref = llvm_cov::hash_bytes(&filenames_buffer);
// Generate the coverage map header, which contains the filenames used by
// this CGU's coverage mappings, and store it in a well-known global.
@ -187,13 +188,10 @@ fn make_filenames_buffer(&self, tcx: TyCtxt<'_>) -> Vec<u8> {
.for_scope(tcx.sess, RemapPathScopeComponents::MACRO)
.to_string_lossy();
llvm::build_byte_buffer(|buffer| {
coverageinfo::write_filenames_section_to_buffer(
// Insert the working dir at index 0, before the other filenames.
std::iter::once(working_dir).chain(self.raw_file_table.iter().map(Symbol::as_str)),
buffer,
);
})
// Insert the working dir at index 0, before the other filenames.
let filenames =
iter::once(working_dir).chain(self.raw_file_table.iter().map(Symbol::as_str));
llvm_cov::write_filenames_to_buffer(filenames)
}
}
@ -296,17 +294,14 @@ fn encode_mappings_for_function(
}
// Encode the function's coverage mappings into a buffer.
llvm::build_byte_buffer(|buffer| {
coverageinfo::write_mapping_to_buffer(
virtual_file_mapping.into_vec(),
expressions,
&code_regions,
&branch_regions,
&mcdc_branch_regions,
&mcdc_decision_regions,
buffer,
);
})
llvm_cov::write_function_mappings_to_buffer(
&virtual_file_mapping.into_vec(),
&expressions,
&code_regions,
&branch_regions,
&mcdc_branch_regions,
&mcdc_decision_regions,
)
}
/// Generates the contents of the covmap record for this CGU, which mostly
@ -335,23 +330,11 @@ fn generate_covmap_record<'ll>(
let covmap_data =
cx.const_struct(&[cov_data_header_val, filenames_val], /*packed=*/ false);
let covmap_var_name = CString::new(llvm::build_byte_buffer(|s| unsafe {
llvm::LLVMRustCoverageWriteMappingVarNameToString(s);
}))
.unwrap();
debug!("covmap var name: {:?}", covmap_var_name);
let covmap_section_name = CString::new(llvm::build_byte_buffer(|s| unsafe {
llvm::LLVMRustCoverageWriteMapSectionNameToString(cx.llmod, s);
}))
.expect("covmap section name should not contain NUL");
debug!("covmap section name: {:?}", covmap_section_name);
let llglobal = llvm::add_global(cx.llmod, cx.val_ty(covmap_data), &covmap_var_name);
let llglobal = llvm::add_global(cx.llmod, cx.val_ty(covmap_data), &llvm_cov::covmap_var_name());
llvm::set_initializer(llglobal, covmap_data);
llvm::set_global_constant(llglobal, true);
llvm::set_linkage(llglobal, llvm::Linkage::PrivateLinkage);
llvm::set_section(llglobal, &covmap_section_name);
llvm::set_section(llglobal, &llvm_cov::covmap_section_name(cx.llmod));
// LLVM's coverage mapping format specifies 8-byte alignment for items in this section.
// <https://llvm.org/docs/CoverageMappingFormat.html>
llvm::set_alignment(llglobal, Align::EIGHT);
@ -373,7 +356,7 @@ fn generate_covfun_record(
let coverage_mapping_size = coverage_mapping_buffer.len();
let coverage_mapping_val = cx.const_bytes(&coverage_mapping_buffer);
let func_name_hash = coverageinfo::hash_bytes(mangled_function_name.as_bytes());
let func_name_hash = llvm_cov::hash_bytes(mangled_function_name.as_bytes());
let func_name_hash_val = cx.const_u64(func_name_hash);
let coverage_mapping_size_val = cx.const_u32(coverage_mapping_size as u32);
let source_hash_val = cx.const_u64(source_hash);

99
compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs
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@ -1,24 +1,23 @@
use std::cell::{OnceCell, RefCell};
use std::ffi::{CStr, CString};
use libc::c_uint;
use rustc_abi::Size;
use rustc_codegen_ssa::traits::{
BuilderMethods, ConstCodegenMethods, CoverageInfoBuilderMethods, MiscCodegenMethods,
};
use rustc_data_structures::fx::{FxHashMap, FxIndexMap};
use rustc_llvm::RustString;
use rustc_middle::mir::coverage::CoverageKind;
use rustc_middle::ty::Instance;
use rustc_middle::ty::layout::HasTyCtxt;
use tracing::{debug, instrument};
use crate::builder::Builder;
use crate::common::{AsCCharPtr, CodegenCx};
use crate::common::CodegenCx;
use crate::coverageinfo::map_data::FunctionCoverageCollector;
use crate::llvm;
pub(crate) mod ffi;
mod llvm_cov;
pub(crate) mod map_data;
mod mapgen;
@ -80,12 +79,9 @@ pub(crate) fn coverageinfo_finalize(&self) {
/// - `__LLVM_COV,__llvm_covfun` on macOS (includes `__LLVM_COV,` segment prefix)
/// - `.lcovfun$M` on Windows (includes `$M` sorting suffix)
fn covfun_section_name(&self) -> &CStr {
self.coverage_cx().covfun_section_name.get_or_init(|| {
CString::new(llvm::build_byte_buffer(|s| unsafe {
llvm::LLVMRustCoverageWriteFuncSectionNameToString(self.llmod, s);
}))
.expect("covfun section name should not contain NUL")
})
self.coverage_cx()
.covfun_section_name
.get_or_init(|| llvm_cov::covfun_section_name(self.llmod))
}
/// For LLVM codegen, returns a function-specific `Value` for a global
@ -95,9 +91,11 @@ fn covfun_section_name(&self) -> &CStr {
fn get_pgo_func_name_var(&self, instance: Instance<'tcx>) -> &'ll llvm::Value {
debug!("getting pgo_func_name_var for instance={:?}", instance);
let mut pgo_func_name_var_map = self.coverage_cx().pgo_func_name_var_map.borrow_mut();
pgo_func_name_var_map
.entry(instance)
.or_insert_with(|| create_pgo_func_name_var(self, instance))
pgo_func_name_var_map.entry(instance).or_insert_with(|| {
let llfn = self.get_fn(instance);
let mangled_fn_name: &str = self.tcx.symbol_name(instance).name;
llvm_cov::create_pgo_func_name_var(llfn, mangled_fn_name)
})
}
}
@ -225,80 +223,3 @@ fn add_coverage(&mut self, instance: Instance<'tcx>, kind: &CoverageKind) {
}
}
}
/// Calls llvm::createPGOFuncNameVar() with the given function instance's
/// mangled function name. The LLVM API returns an llvm::GlobalVariable
/// containing the function name, with the specific variable name and linkage
/// required by LLVM InstrProf source-based coverage instrumentation. Use
/// `bx.get_pgo_func_name_var()` to ensure the variable is only created once per
/// `Instance`.
fn create_pgo_func_name_var<'ll, 'tcx>(
cx: &CodegenCx<'ll, 'tcx>,
instance: Instance<'tcx>,
) -> &'ll llvm::Value {
let mangled_fn_name: &str = cx.tcx.symbol_name(instance).name;
let llfn = cx.get_fn(instance);
unsafe {
llvm::LLVMRustCoverageCreatePGOFuncNameVar(
llfn,
mangled_fn_name.as_c_char_ptr(),
mangled_fn_name.len(),
)
}
}
pub(crate) fn write_filenames_section_to_buffer<'a>(
filenames: impl IntoIterator<Item = &'a str>,
buffer: &RustString,
) {
let (pointers, lengths) = filenames
.into_iter()
.map(|s: &str| (s.as_c_char_ptr(), s.len()))
.unzip::<_, _, Vec<_>, Vec<_>>();
unsafe {
llvm::LLVMRustCoverageWriteFilenamesSectionToBuffer(
pointers.as_ptr(),
pointers.len(),
lengths.as_ptr(),
lengths.len(),
buffer,
);
}
}
pub(crate) fn write_mapping_to_buffer(
virtual_file_mapping: Vec<u32>,
expressions: Vec<ffi::CounterExpression>,
code_regions: &[ffi::CodeRegion],
branch_regions: &[ffi::BranchRegion],
mcdc_branch_regions: &[ffi::MCDCBranchRegion],
mcdc_decision_regions: &[ffi::MCDCDecisionRegion],
buffer: &RustString,
) {
unsafe {
llvm::LLVMRustCoverageWriteMappingToBuffer(
virtual_file_mapping.as_ptr(),
virtual_file_mapping.len() as c_uint,
expressions.as_ptr(),
expressions.len() as c_uint,
code_regions.as_ptr(),
code_regions.len() as c_uint,
branch_regions.as_ptr(),
branch_regions.len() as c_uint,
mcdc_branch_regions.as_ptr(),
mcdc_branch_regions.len() as c_uint,
mcdc_decision_regions.as_ptr(),
mcdc_decision_regions.len() as c_uint,
buffer,
);
}
}
pub(crate) fn hash_bytes(bytes: &[u8]) -> u64 {
unsafe { llvm::LLVMRustCoverageHashByteArray(bytes.as_c_char_ptr(), bytes.len()) }
}
pub(crate) fn mapping_version() -> u32 {
unsafe { llvm::LLVMRustCoverageMappingVersion() }
}