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Rollup merge of #134208 - Zalathar:covmap-covfun, r=compiler-errors

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coverage: Tidy up creation of covmap and covfun records

This is a small follow-up to #134163 that mostly just inlines and renames some variables, and adds a few comments.

It also slightly defers the creation of the LLVM value that holds the filename table, to just before the value is needed.

---

try-job: x86_64-mingw-2
try-job: dist-x86_64-linux
This commit is contained in:
Matthias Krüger 2024-12-14 05:01:07 +01:00 • committed by GitHub
commit 704102c0f0
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2 changed files with 59 additions and 63 deletions
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65
compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs
View file

@ -75,10 +75,10 @@ pub(crate) fn finalize(cx: &CodegenCx<'_, '_>) {
// Encode all filenames referenced by coverage mappings in this CGU. // Encode all filenames referenced by coverage mappings in this CGU.
let filenames_buffer = global_file_table.make_filenames_buffer(tcx); let filenames_buffer = global_file_table.make_filenames_buffer(tcx);
// The `llvm-cov` tool uses this hash to associate each covfun record with
let filenames_size = filenames_buffer.len(); // its corresponding filenames table, since the final binary will typically
let filenames_val = cx.const_bytes(&filenames_buffer); // contain multiple covmap records from different compilation units.
let filenames_ref = llvm_cov::hash_bytes(&filenames_buffer); let filenames_hash = llvm_cov::hash_bytes(&filenames_buffer);
let mut unused_function_names = Vec::new(); let mut unused_function_names = Vec::new();
@ -101,7 +101,7 @@ pub(crate) fn finalize(cx: &CodegenCx<'_, '_>) {
for covfun in &covfun_records { for covfun in &covfun_records {
unused_function_names.extend(covfun.mangled_function_name_if_unused()); unused_function_names.extend(covfun.mangled_function_name_if_unused());
covfun::generate_covfun_record(cx, filenames_ref, covfun) covfun::generate_covfun_record(cx, filenames_hash, covfun)
} }
// For unused functions, we need to take their mangled names and store them // For unused functions, we need to take their mangled names and store them
@ -126,7 +126,7 @@ pub(crate) fn finalize(cx: &CodegenCx<'_, '_>) {
// Generate the coverage map header, which contains the filenames used by // Generate the coverage map header, which contains the filenames used by
// this CGU's coverage mappings, and store it in a well-known global. // this CGU's coverage mappings, and store it in a well-known global.
// (This is skipped if we returned early due to having no covfun records.) // (This is skipped if we returned early due to having no covfun records.)
generate_covmap_record(cx, covmap_version, filenames_size, filenames_val); generate_covmap_record(cx, covmap_version, &filenames_buffer);
} }
/// Maps "global" (per-CGU) file ID numbers to their underlying filenames. /// Maps "global" (per-CGU) file ID numbers to their underlying filenames.
@ -225,38 +225,35 @@ fn span_file_name(tcx: TyCtxt<'_>, span: Span) -> Symbol {
/// Generates the contents of the covmap record for this CGU, which mostly /// Generates the contents of the covmap record for this CGU, which mostly
/// consists of a header and a list of filenames. The record is then stored /// consists of a header and a list of filenames. The record is then stored
/// as a global variable in the `__llvm_covmap` section. /// as a global variable in the `__llvm_covmap` section.
fn generate_covmap_record<'ll>( fn generate_covmap_record<'ll>(cx: &CodegenCx<'ll, '_>, version: u32, filenames_buffer: &[u8]) {
cx: &CodegenCx<'ll, '_>, // A covmap record consists of four target-endian u32 values, followed by
version: u32, // the encoded filenames table. Two of the header fields are unused in
filenames_size: usize, // modern versions of the LLVM coverage mapping format, and are always 0.
filenames_val: &'ll llvm::Value, // <https://llvm.org/docs/CoverageMappingFormat.html#llvm-ir-representation>
) { // See also `src/llvm-project/clang/lib/CodeGen/CoverageMappingGen.cpp`.
debug!("cov map: filenames_size = {}, 0-based version = {}", filenames_size, version); let covmap_header = cx.const_struct(
&[
// Create the coverage data header (Note, fields 0 and 2 are now always zero, cx.const_u32(0), // (unused)
// as of `llvm::coverage::CovMapVersion::Version4`.) cx.const_u32(filenames_buffer.len() as u32),
let zero_was_n_records_val = cx.const_u32(0); cx.const_u32(0), // (unused)
let filenames_size_val = cx.const_u32(filenames_size as u32); cx.const_u32(version),
let zero_was_coverage_size_val = cx.const_u32(0); ],
let version_val = cx.const_u32(version); /* packed */ false,
let cov_data_header_val = cx.const_struct(
&[zero_was_n_records_val, filenames_size_val, zero_was_coverage_size_val, version_val],
/*packed=*/ false,
); );
let covmap_record = cx
.const_struct(&[covmap_header, cx.const_bytes(filenames_buffer)], /* packed */ false);
// Create the complete LLVM coverage data value to add to the LLVM IR let covmap_global =
let covmap_data = llvm::add_global(cx.llmod, cx.val_ty(covmap_record), &llvm_cov::covmap_var_name());
cx.const_struct(&[cov_data_header_val, filenames_val], /*packed=*/ false); llvm::set_initializer(covmap_global, covmap_record);
llvm::set_global_constant(covmap_global, true);
let llglobal = llvm::add_global(cx.llmod, cx.val_ty(covmap_data), &llvm_cov::covmap_var_name()); llvm::set_linkage(covmap_global, llvm::Linkage::PrivateLinkage);
llvm::set_initializer(llglobal, covmap_data); llvm::set_section(covmap_global, &llvm_cov::covmap_section_name(cx.llmod));
llvm::set_global_constant(llglobal, true);
llvm::set_linkage(llglobal, llvm::Linkage::PrivateLinkage);
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. // LLVM's coverage mapping format specifies 8-byte alignment for items in this section.
// <https://llvm.org/docs/CoverageMappingFormat.html> // <https://llvm.org/docs/CoverageMappingFormat.html>
llvm::set_alignment(llglobal, Align::EIGHT); llvm::set_alignment(covmap_global, Align::EIGHT);
cx.add_used_global(llglobal);
cx.add_used_global(covmap_global);
} }
/// Each CGU will normally only emit coverage metadata for the functions that it actually generates. /// Each CGU will normally only emit coverage metadata for the functions that it actually generates.

57
compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/covfun.rs
View file

@ -136,7 +136,7 @@ fn fill_region_tables<'tcx>(
/// as a global variable in the `__llvm_covfun` section. /// as a global variable in the `__llvm_covfun` section.
pub(crate) fn generate_covfun_record<'tcx>( pub(crate) fn generate_covfun_record<'tcx>(
cx: &CodegenCx<'_, 'tcx>, cx: &CodegenCx<'_, 'tcx>,
filenames_ref: u64, filenames_hash: u64,
covfun: &CovfunRecord<'tcx>, covfun: &CovfunRecord<'tcx>,
) { ) {
let &CovfunRecord { let &CovfunRecord {
@ -155,46 +155,45 @@ pub(crate) fn generate_covfun_record<'tcx>(
regions, regions,
); );
// Concatenate the encoded coverage mappings // A covfun record consists of four target-endian integers, followed by the
let coverage_mapping_size = coverage_mapping_buffer.len(); // encoded mapping data in bytes. Note that the length field is 32 bits.
let coverage_mapping_val = cx.const_bytes(&coverage_mapping_buffer); // <https://llvm.org/docs/CoverageMappingFormat.html#llvm-ir-representation>
// See also `src/llvm-project/clang/lib/CodeGen/CoverageMappingGen.cpp` and
// `COVMAP_V3` in `src/llvm-project/llvm/include/llvm/ProfileData/InstrProfData.inc`.
let func_name_hash = llvm_cov::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 covfun_record = cx.const_struct(
let coverage_mapping_size_val = cx.const_u32(coverage_mapping_size as u32);
let source_hash_val = cx.const_u64(source_hash);
let filenames_ref_val = cx.const_u64(filenames_ref);
let func_record_val = cx.const_struct(
&[ &[
func_name_hash_val, cx.const_u64(func_name_hash),
coverage_mapping_size_val, cx.const_u32(coverage_mapping_buffer.len() as u32),
source_hash_val, cx.const_u64(source_hash),
filenames_ref_val, cx.const_u64(filenames_hash),
coverage_mapping_val, cx.const_bytes(&coverage_mapping_buffer),
], ],
/*packed=*/ true, // This struct needs to be packed, so that the 32-bit length field
// doesn't have unexpected padding.
true,
); );
// Choose a variable name to hold this function's covfun data. // Choose a variable name to hold this function's covfun data.
// Functions that are used have a suffix ("u") to distinguish them from // Functions that are used have a suffix ("u") to distinguish them from
// unused copies of the same function (from different CGUs), so that if a // unused copies of the same function (from different CGUs), so that if a
// linker sees both it won't discard the used copy's data. // linker sees both it won't discard the used copy's data.
let func_record_var_name = let u = if is_used { "u" } else { "" };
CString::new(format!("__covrec_{:X}{}", func_name_hash, if is_used { "u" } else { "" })) let covfun_var_name = CString::new(format!("__covrec_{func_name_hash:X}{u}")).unwrap();
.unwrap(); debug!("function record var name: {covfun_var_name:?}");
debug!("function record var name: {:?}", func_record_var_name);
let llglobal = llvm::add_global(cx.llmod, cx.val_ty(func_record_val), &func_record_var_name); let covfun_global = llvm::add_global(cx.llmod, cx.val_ty(covfun_record), &covfun_var_name);
llvm::set_initializer(llglobal, func_record_val); llvm::set_initializer(covfun_global, covfun_record);
llvm::set_global_constant(llglobal, true); llvm::set_global_constant(covfun_global, true);
llvm::set_linkage(llglobal, llvm::Linkage::LinkOnceODRLinkage); llvm::set_linkage(covfun_global, llvm::Linkage::LinkOnceODRLinkage);
llvm::set_visibility(llglobal, llvm::Visibility::Hidden); llvm::set_visibility(covfun_global, llvm::Visibility::Hidden);
llvm::set_section(llglobal, cx.covfun_section_name()); llvm::set_section(covfun_global, cx.covfun_section_name());
// LLVM's coverage mapping format specifies 8-byte alignment for items in this section. // LLVM's coverage mapping format specifies 8-byte alignment for items in this section.
// <https://llvm.org/docs/CoverageMappingFormat.html> // <https://llvm.org/docs/CoverageMappingFormat.html>
llvm::set_alignment(llglobal, Align::EIGHT); llvm::set_alignment(covfun_global, Align::EIGHT);
if cx.target_spec().supports_comdat() { if cx.target_spec().supports_comdat() {
llvm::set_comdat(cx.llmod, llglobal, &func_record_var_name); llvm::set_comdat(cx.llmod, covfun_global, &covfun_var_name);
} }
cx.add_used_global(llglobal);
cx.add_used_global(covfun_global);
} }