Auto merge of #134177 - matthiaskrgr:rollup-hgp8q60, r=matthiaskrgr

Rollup of 6 pull requests

Successful merges:

 - #132975 (De-duplicate and improve definition of core::ffi::c_char)
 - #133598 (Change `GetManyMutError` to match T-libs-api decision)
 - #134148 (add comments in check_expr_field)
 - #134163 (coverage: Rearrange the code for embedding per-function coverage metadata)
 - #134165 (wasm(32|64): update alignment string)
 - #134170 (Subtree update of `rust-analyzer`)

r? `@ghost`
`@rustbot` modify labels: rollup

5 files changed, 268 insertions, 182 deletions

diff --git a/compiler/rustc_codegen_llvm/src/context.rs b/compiler/rustc_codegen_llvm/src/context.rs
index e0506c0c5fd..c602d99ff9d 100644
--- a/compiler/rustc_codegen_llvm/src/context.rs
+++ b/compiler/rustc_codegen_llvm/src/context.rs
@@ -164,6 +164,11 @@ pub(crate) unsafe fn create_module<'ll>(
             // See https://github.com/llvm/llvm-project/pull/118004
             target_data_layout = target_data_layout.replace("-i128:128", "");
         }
+        if sess.target.arch.starts_with("wasm32") || sess.target.arch.starts_with("wasm64") {
+            // LLVM 20 updates the wasm(32|64) layout to correctly align 128 bit integers to 128 bit.
+            // See https://github.com/llvm/llvm-project/pull/119204
+            target_data_layout = target_data_layout.replace("-i128:128", "");
+        }
     }
 
     // Ensure the data-layout values hardcoded remain the defaults.
diff --git a/compiler/rustc_codegen_llvm/src/coverageinfo/ffi.rs b/compiler/rustc_codegen_llvm/src/coverageinfo/ffi.rs
index a6e07ea2a60..1f133141c18 100644
--- a/compiler/rustc_codegen_llvm/src/coverageinfo/ffi.rs
+++ b/compiler/rustc_codegen_llvm/src/coverageinfo/ffi.rs
@@ -152,6 +152,34 @@ impl CoverageSpan {
     }
 }
 
+/// Holds tables of the various region types in one struct.
+///
+/// Don't pass this struct across FFI; pass the individual region tables as
+/// pointer/length pairs instead.
+///
+/// Each field name has a `_regions` suffix for improved readability after
+/// exhaustive destructing, which ensures that all region types are handled.
+#[derive(Clone, Debug, Default)]
+pub(crate) struct Regions {
+    pub(crate) code_regions: Vec<CodeRegion>,
+    pub(crate) branch_regions: Vec<BranchRegion>,
+    pub(crate) mcdc_branch_regions: Vec<MCDCBranchRegion>,
+    pub(crate) mcdc_decision_regions: Vec<MCDCDecisionRegion>,
+}
+
+impl Regions {
+    /// Returns true if none of this structure's tables contain any regions.
+    pub(crate) fn has_no_regions(&self) -> bool {
+        let Self { code_regions, branch_regions, mcdc_branch_regions, mcdc_decision_regions } =
+            self;
+
+        code_regions.is_empty()
+            && branch_regions.is_empty()
+            && mcdc_branch_regions.is_empty()
+            && mcdc_decision_regions.is_empty()
+    }
+}
+
 /// Must match the layout of `LLVMRustCoverageCodeRegion`.
 #[derive(Clone, Debug)]
 #[repr(C)]
diff --git a/compiler/rustc_codegen_llvm/src/coverageinfo/llvm_cov.rs b/compiler/rustc_codegen_llvm/src/coverageinfo/llvm_cov.rs
index 99c2d12b261..086cf1f44a0 100644
--- a/compiler/rustc_codegen_llvm/src/coverageinfo/llvm_cov.rs
+++ b/compiler/rustc_codegen_llvm/src/coverageinfo/llvm_cov.rs
@@ -62,11 +62,10 @@ pub(crate) fn write_filenames_to_buffer<'a>(
 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],
+    regions: &ffi::Regions,
 ) -> Vec<u8> {
+    let ffi::Regions { code_regions, branch_regions, mcdc_branch_regions, mcdc_decision_regions } =
+        regions;
     llvm::build_byte_buffer(|buffer| unsafe {
         llvm::LLVMRustCoverageWriteFunctionMappingsToBuffer(
             virtual_file_mapping.as_ptr(),
diff --git a/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs b/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs
index a6c3caf9e2b..a573a37beb3 100644
--- a/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs
+++ b/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs
@@ -1,4 +1,3 @@
-use std::ffi::CString;
 use std::iter;
 
 use itertools::Itertools as _;
@@ -9,21 +8,22 @@ use rustc_codegen_ssa::traits::{
 use rustc_data_structures::fx::{FxHashSet, FxIndexMap, FxIndexSet};
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_index::IndexVec;
-use rustc_middle::mir::coverage::MappingKind;
 use rustc_middle::ty::{self, TyCtxt};
 use rustc_middle::{bug, mir};
 use rustc_session::RemapFileNameExt;
 use rustc_session::config::RemapPathScopeComponents;
 use rustc_span::def_id::DefIdSet;
 use rustc_span::{Span, Symbol};
-use rustc_target::spec::HasTargetSpec;
 use tracing::debug;
 
 use crate::common::CodegenCx;
+use crate::coverageinfo::llvm_cov;
 use crate::coverageinfo::map_data::FunctionCoverage;
-use crate::coverageinfo::{ffi, llvm_cov};
+use crate::coverageinfo::mapgen::covfun::prepare_covfun_record;
 use crate::llvm;
 
+mod covfun;
+
 /// Generates and exports the coverage map, which is embedded in special
 /// linker sections in the final binary.
 ///
@@ -80,47 +80,28 @@ pub(crate) fn finalize(cx: &CodegenCx<'_, '_>) {
     let filenames_val = cx.const_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.
-    generate_covmap_record(cx, covmap_version, filenames_size, filenames_val);
-
     let mut unused_function_names = Vec::new();
 
-    // Encode coverage mappings and generate function records
-    for (instance, function_coverage) in function_coverage_map {
-        debug!("Generate function coverage for {}, {:?}", cx.codegen_unit.name(), instance);
-
-        let mangled_function_name = tcx.symbol_name(instance).name;
-        let source_hash = function_coverage.source_hash();
-        let is_used = function_coverage.is_used();
-
-        let coverage_mapping_buffer =
-            encode_mappings_for_function(tcx, &global_file_table, &function_coverage);
-
-        if coverage_mapping_buffer.is_empty() {
-            if function_coverage.is_used() {
-                bug!(
-                    "A used function should have had coverage mapping data but did not: {}",
-                    mangled_function_name
-                );
-            } else {
-                debug!("unused function had no coverage mapping data: {}", mangled_function_name);
-                continue;
-            }
-        }
+    let covfun_records = function_coverage_map
+        .into_iter()
+        .filter_map(|(instance, function_coverage)| {
+            prepare_covfun_record(tcx, &global_file_table, instance, &function_coverage)
+        })
+        .collect::<Vec<_>>();
+
+    // If there are no covfun records for this CGU, don't generate a covmap record.
+    // Emitting a covmap record without any covfun records causes `llvm-cov` to
+    // fail when generating coverage reports, and if there are no covfun records
+    // then the covmap record isn't useful anyway.
+    // This should prevent a repeat of <https://github.com/rust-lang/rust/issues/133606>.
+    if covfun_records.is_empty() {
+        return;
+    }
 
-        if !is_used {
-            unused_function_names.push(mangled_function_name);
-        }
+    for covfun in &covfun_records {
+        unused_function_names.extend(covfun.mangled_function_name_if_unused());
 
-        generate_covfun_record(
-            cx,
-            mangled_function_name,
-            source_hash,
-            filenames_ref,
-            coverage_mapping_buffer,
-            is_used,
-        );
+        covfun::generate_covfun_record(cx, filenames_ref, covfun)
     }
 
     // For unused functions, we need to take their mangled names and store them
@@ -141,6 +122,11 @@ pub(crate) fn finalize(cx: &CodegenCx<'_, '_>) {
         llvm::set_linkage(array, llvm::Linkage::InternalLinkage);
         llvm::set_initializer(array, initializer);
     }
+
+    // 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 is skipped if we returned early due to having no covfun records.)
+    generate_covmap_record(cx, covmap_version, filenames_size, filenames_val);
 }
 
 /// Maps "global" (per-CGU) file ID numbers to their underlying filenames.
@@ -208,7 +194,7 @@ rustc_index::newtype_index! {
 
 /// Holds a mapping from "local" (per-function) file IDs to "global" (per-CGU)
 /// file IDs.
-#[derive(Default)]
+#[derive(Debug, Default)]
 struct VirtualFileMapping {
     local_to_global: IndexVec<LocalFileId, GlobalFileId>,
     global_to_local: FxIndexMap<GlobalFileId, LocalFileId>,
@@ -222,10 +208,10 @@ impl VirtualFileMapping {
             .or_insert_with(|| self.local_to_global.push(global_file_id))
     }
 
-    fn into_vec(self) -> Vec<u32> {
-        // This conversion should be optimized away to ~zero overhead.
-        // In any case, it's probably not hot enough to worry about.
-        self.local_to_global.into_iter().map(|global| global.as_u32()).collect()
+    fn to_vec(&self) -> Vec<u32> {
+        // This clone could be avoided by transmuting `&[GlobalFileId]` to `&[u32]`,
+        // but it isn't hot or expensive enough to justify the extra unsafety.
+        self.local_to_global.iter().map(|&global| GlobalFileId::as_u32(global)).collect()
     }
 }
 
@@ -236,83 +222,6 @@ fn span_file_name(tcx: TyCtxt<'_>, span: Span) -> Symbol {
     Symbol::intern(&name)
 }
 
-/// Using the expressions and counter regions collected for a single function,
-/// generate the variable-sized payload of its corresponding `__llvm_covfun`
-/// entry. The payload is returned as a vector of bytes.
-///
-/// Newly-encountered filenames will be added to the global file table.
-fn encode_mappings_for_function(
-    tcx: TyCtxt<'_>,
-    global_file_table: &GlobalFileTable,
-    function_coverage: &FunctionCoverage<'_>,
-) -> Vec<u8> {
-    let counter_regions = function_coverage.counter_regions();
-    if counter_regions.is_empty() {
-        return Vec::new();
-    }
-
-    let expressions = function_coverage.counter_expressions().collect::<Vec<_>>();
-
-    let mut virtual_file_mapping = VirtualFileMapping::default();
-    let mut code_regions = vec![];
-    let mut branch_regions = vec![];
-    let mut mcdc_branch_regions = vec![];
-    let mut mcdc_decision_regions = vec![];
-
-    // Currently a function's mappings must all be in the same file as its body span.
-    let file_name = span_file_name(tcx, function_coverage.function_coverage_info.body_span);
-
-    // Look up the global file ID for that filename.
-    let global_file_id = global_file_table.global_file_id_for_file_name(file_name);
-
-    // Associate that global file ID with a local file ID for this function.
-    let local_file_id = virtual_file_mapping.local_id_for_global(global_file_id);
-    debug!("  file id: {local_file_id:?} => {global_file_id:?} = '{file_name:?}'");
-
-    // For each counter/region pair in this function+file, convert it to a
-    // form suitable for FFI.
-    for (mapping_kind, region) in counter_regions {
-        debug!("Adding counter {mapping_kind:?} to map for {region:?}");
-        let span = ffi::CoverageSpan::from_source_region(local_file_id, region);
-        match mapping_kind {
-            MappingKind::Code(term) => {
-                code_regions.push(ffi::CodeRegion { span, counter: ffi::Counter::from_term(term) });
-            }
-            MappingKind::Branch { true_term, false_term } => {
-                branch_regions.push(ffi::BranchRegion {
-                    span,
-                    true_counter: ffi::Counter::from_term(true_term),
-                    false_counter: ffi::Counter::from_term(false_term),
-                });
-            }
-            MappingKind::MCDCBranch { true_term, false_term, mcdc_params } => {
-                mcdc_branch_regions.push(ffi::MCDCBranchRegion {
-                    span,
-                    true_counter: ffi::Counter::from_term(true_term),
-                    false_counter: ffi::Counter::from_term(false_term),
-                    mcdc_branch_params: ffi::mcdc::BranchParameters::from(mcdc_params),
-                });
-            }
-            MappingKind::MCDCDecision(mcdc_decision_params) => {
-                mcdc_decision_regions.push(ffi::MCDCDecisionRegion {
-                    span,
-                    mcdc_decision_params: ffi::mcdc::DecisionParameters::from(mcdc_decision_params),
-                });
-            }
-        }
-    }
-
-    // Encode the function's coverage mappings into a 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
 /// consists of a header and a list of filenames. The record is then stored
 /// as a global variable in the `__llvm_covmap` section.
@@ -350,61 +259,6 @@ fn generate_covmap_record<'ll>(
     cx.add_used_global(llglobal);
 }
 
-/// Generates the contents of the covfun record for this function, which
-/// contains the function's coverage mapping data. The record is then stored
-/// as a global variable in the `__llvm_covfun` section.
-fn generate_covfun_record(
-    cx: &CodegenCx<'_, '_>,
-    mangled_function_name: &str,
-    source_hash: u64,
-    filenames_ref: u64,
-    coverage_mapping_buffer: Vec<u8>,
-    is_used: bool,
-) {
-    // Concatenate the encoded coverage mappings
-    let coverage_mapping_size = coverage_mapping_buffer.len();
-    let coverage_mapping_val = cx.const_bytes(&coverage_mapping_buffer);
-
-    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);
-    let filenames_ref_val = cx.const_u64(filenames_ref);
-    let func_record_val = cx.const_struct(
-        &[
-            func_name_hash_val,
-            coverage_mapping_size_val,
-            source_hash_val,
-            filenames_ref_val,
-            coverage_mapping_val,
-        ],
-        /*packed=*/ true,
-    );
-
-    // Choose a variable name to hold this function's covfun data.
-    // 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
-    // linker sees both it won't discard the used copy's data.
-    let func_record_var_name =
-        CString::new(format!("__covrec_{:X}{}", func_name_hash, if is_used { "u" } else { "" }))
-            .unwrap();
-    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);
-    llvm::set_initializer(llglobal, func_record_val);
-    llvm::set_global_constant(llglobal, true);
-    llvm::set_linkage(llglobal, llvm::Linkage::LinkOnceODRLinkage);
-    llvm::set_visibility(llglobal, llvm::Visibility::Hidden);
-    llvm::set_section(llglobal, cx.covfun_section_name());
-    // 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);
-    if cx.target_spec().supports_comdat() {
-        llvm::set_comdat(cx.llmod, llglobal, &func_record_var_name);
-    }
-    cx.add_used_global(llglobal);
-}
-
 /// Each CGU will normally only emit coverage metadata for the functions that it actually generates.
 /// But since we don't want unused functions to disappear from coverage reports, we also scan for
 /// functions that were instrumented but are not participating in codegen.
diff --git a/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/covfun.rs b/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/covfun.rs
new file mode 100644
index 00000000000..530e6827f55
--- /dev/null
+++ b/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/covfun.rs
@@ -0,0 +1,200 @@
+//! For each function that was instrumented for coverage, we need to embed its
+//! corresponding coverage mapping metadata inside the `__llvm_covfun`[^win]
+//! linker section of the final binary.
+//!
+//! [^win]: On Windows the section name is `.lcovfun`.
+
+use std::ffi::CString;
+
+use rustc_abi::Align;
+use rustc_codegen_ssa::traits::{
+    BaseTypeCodegenMethods, ConstCodegenMethods, StaticCodegenMethods,
+};
+use rustc_middle::bug;
+use rustc_middle::mir::coverage::MappingKind;
+use rustc_middle::ty::{Instance, TyCtxt};
+use rustc_target::spec::HasTargetSpec;
+use tracing::debug;
+
+use crate::common::CodegenCx;
+use crate::coverageinfo::map_data::FunctionCoverage;
+use crate::coverageinfo::mapgen::{GlobalFileTable, VirtualFileMapping, span_file_name};
+use crate::coverageinfo::{ffi, llvm_cov};
+use crate::llvm;
+
+/// Intermediate coverage metadata for a single function, used to help build
+/// the final record that will be embedded in the `__llvm_covfun` section.
+#[derive(Debug)]
+pub(crate) struct CovfunRecord<'tcx> {
+    mangled_function_name: &'tcx str,
+    source_hash: u64,
+    is_used: bool,
+
+    virtual_file_mapping: VirtualFileMapping,
+    expressions: Vec<ffi::CounterExpression>,
+    regions: ffi::Regions,
+}
+
+impl<'tcx> CovfunRecord<'tcx> {
+    /// FIXME(Zalathar): Make this the responsibility of the code that determines
+    /// which functions are unused.
+    pub(crate) fn mangled_function_name_if_unused(&self) -> Option<&'tcx str> {
+        (!self.is_used).then_some(self.mangled_function_name)
+    }
+}
+
+pub(crate) fn prepare_covfun_record<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    global_file_table: &GlobalFileTable,
+    instance: Instance<'tcx>,
+    function_coverage: &FunctionCoverage<'tcx>,
+) -> Option<CovfunRecord<'tcx>> {
+    let mut covfun = CovfunRecord {
+        mangled_function_name: tcx.symbol_name(instance).name,
+        source_hash: function_coverage.source_hash(),
+        is_used: function_coverage.is_used(),
+        virtual_file_mapping: VirtualFileMapping::default(),
+        expressions: function_coverage.counter_expressions().collect::<Vec<_>>(),
+        regions: ffi::Regions::default(),
+    };
+
+    fill_region_tables(tcx, global_file_table, function_coverage, &mut covfun);
+
+    if covfun.regions.has_no_regions() {
+        if covfun.is_used {
+            bug!("a used function should have had coverage mapping data but did not: {covfun:?}");
+        } else {
+            debug!(?covfun, "unused function had no coverage mapping data");
+            return None;
+        }
+    }
+
+    Some(covfun)
+}
+
+/// Populates the mapping region tables in the current function's covfun record.
+fn fill_region_tables<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    global_file_table: &GlobalFileTable,
+    function_coverage: &FunctionCoverage<'tcx>,
+    covfun: &mut CovfunRecord<'tcx>,
+) {
+    let counter_regions = function_coverage.counter_regions();
+    if counter_regions.is_empty() {
+        return;
+    }
+
+    // Currently a function's mappings must all be in the same file as its body span.
+    let file_name = span_file_name(tcx, function_coverage.function_coverage_info.body_span);
+
+    // Look up the global file ID for that filename.
+    let global_file_id = global_file_table.global_file_id_for_file_name(file_name);
+
+    // Associate that global file ID with a local file ID for this function.
+    let local_file_id = covfun.virtual_file_mapping.local_id_for_global(global_file_id);
+    debug!("  file id: {local_file_id:?} => {global_file_id:?} = '{file_name:?}'");
+
+    let ffi::Regions { code_regions, branch_regions, mcdc_branch_regions, mcdc_decision_regions } =
+        &mut covfun.regions;
+
+    // For each counter/region pair in this function+file, convert it to a
+    // form suitable for FFI.
+    for (mapping_kind, region) in counter_regions {
+        debug!("Adding counter {mapping_kind:?} to map for {region:?}");
+        let span = ffi::CoverageSpan::from_source_region(local_file_id, region);
+        match mapping_kind {
+            MappingKind::Code(term) => {
+                code_regions.push(ffi::CodeRegion { span, counter: ffi::Counter::from_term(term) });
+            }
+            MappingKind::Branch { true_term, false_term } => {
+                branch_regions.push(ffi::BranchRegion {
+                    span,
+                    true_counter: ffi::Counter::from_term(true_term),
+                    false_counter: ffi::Counter::from_term(false_term),
+                });
+            }
+            MappingKind::MCDCBranch { true_term, false_term, mcdc_params } => {
+                mcdc_branch_regions.push(ffi::MCDCBranchRegion {
+                    span,
+                    true_counter: ffi::Counter::from_term(true_term),
+                    false_counter: ffi::Counter::from_term(false_term),
+                    mcdc_branch_params: ffi::mcdc::BranchParameters::from(mcdc_params),
+                });
+            }
+            MappingKind::MCDCDecision(mcdc_decision_params) => {
+                mcdc_decision_regions.push(ffi::MCDCDecisionRegion {
+                    span,
+                    mcdc_decision_params: ffi::mcdc::DecisionParameters::from(mcdc_decision_params),
+                });
+            }
+        }
+    }
+}
+
+/// Generates the contents of the covfun record for this function, which
+/// contains the function's coverage mapping data. The record is then stored
+/// as a global variable in the `__llvm_covfun` section.
+pub(crate) fn generate_covfun_record<'tcx>(
+    cx: &CodegenCx<'_, 'tcx>,
+    filenames_ref: u64,
+    covfun: &CovfunRecord<'tcx>,
+) {
+    let &CovfunRecord {
+        mangled_function_name,
+        source_hash,
+        is_used,
+        ref virtual_file_mapping,
+        ref expressions,
+        ref regions,
+    } = covfun;
+
+    // Encode the function's coverage mappings into a buffer.
+    let coverage_mapping_buffer = llvm_cov::write_function_mappings_to_buffer(
+        &virtual_file_mapping.to_vec(),
+        expressions,
+        regions,
+    );
+
+    // Concatenate the encoded coverage mappings
+    let coverage_mapping_size = coverage_mapping_buffer.len();
+    let coverage_mapping_val = cx.const_bytes(&coverage_mapping_buffer);
+
+    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);
+    let filenames_ref_val = cx.const_u64(filenames_ref);
+    let func_record_val = cx.const_struct(
+        &[
+            func_name_hash_val,
+            coverage_mapping_size_val,
+            source_hash_val,
+            filenames_ref_val,
+            coverage_mapping_val,
+        ],
+        /*packed=*/ true,
+    );
+
+    // Choose a variable name to hold this function's covfun data.
+    // 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
+    // linker sees both it won't discard the used copy's data.
+    let func_record_var_name =
+        CString::new(format!("__covrec_{:X}{}", func_name_hash, if is_used { "u" } else { "" }))
+            .unwrap();
+    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);
+    llvm::set_initializer(llglobal, func_record_val);
+    llvm::set_global_constant(llglobal, true);
+    llvm::set_linkage(llglobal, llvm::Linkage::LinkOnceODRLinkage);
+    llvm::set_visibility(llglobal, llvm::Visibility::Hidden);
+    llvm::set_section(llglobal, cx.covfun_section_name());
+    // 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);
+    if cx.target_spec().supports_comdat() {
+        llvm::set_comdat(cx.llmod, llglobal, &func_record_var_name);
+    }
+    cx.add_used_global(llglobal);
+}