1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
use crate::llvm;

use crate::builder::Builder;
use crate::common::CodegenCx;
use crate::coverageinfo::ffi::{CounterExpression, CounterMappingRegion};
use crate::coverageinfo::map_data::FunctionCoverageCollector;

use libc::c_uint;
use rustc_codegen_ssa::traits::{
    BaseTypeMethods, BuilderMethods, ConstMethods, CoverageInfoBuilderMethods, MiscMethods,
    StaticMethods,
};
use rustc_data_structures::fx::{FxHashMap, FxIndexMap};
use rustc_llvm::RustString;
use rustc_middle::bug;
use rustc_middle::mir::coverage::CoverageKind;
use rustc_middle::ty::layout::HasTyCtxt;
use rustc_middle::ty::Instance;
use rustc_target::abi::Align;

use std::cell::RefCell;

pub(crate) mod ffi;
pub(crate) mod map_data;
pub mod mapgen;

/// A context object for maintaining all state needed by the coverageinfo module.
pub struct CrateCoverageContext<'ll, 'tcx> {
    /// Coverage data for each instrumented function identified by DefId.
    pub(crate) function_coverage_map:
        RefCell<FxIndexMap<Instance<'tcx>, FunctionCoverageCollector<'tcx>>>,
    pub(crate) pgo_func_name_var_map: RefCell<FxHashMap<Instance<'tcx>, &'ll llvm::Value>>,
}

impl<'ll, 'tcx> CrateCoverageContext<'ll, 'tcx> {
    pub fn new() -> Self {
        Self {
            function_coverage_map: Default::default(),
            pgo_func_name_var_map: Default::default(),
        }
    }

    pub fn take_function_coverage_map(
        &self,
    ) -> FxIndexMap<Instance<'tcx>, FunctionCoverageCollector<'tcx>> {
        self.function_coverage_map.replace(FxIndexMap::default())
    }
}

// These methods used to be part of trait `CoverageInfoMethods`, which no longer
// exists after most coverage code was moved out of SSA.
impl<'ll, 'tcx> CodegenCx<'ll, 'tcx> {
    pub(crate) fn coverageinfo_finalize(&self) {
        mapgen::finalize(self)
    }

    /// For LLVM codegen, returns a function-specific `Value` for a global
    /// string, to hold the function name passed to LLVM intrinsic
    /// `instrprof.increment()`. The `Value` is only created once per instance.
    /// Multiple invocations with the same instance return the same `Value`.
    fn get_pgo_func_name_var(&self, instance: Instance<'tcx>) -> &'ll llvm::Value {
        if let Some(coverage_context) = self.coverage_context() {
            debug!("getting pgo_func_name_var for instance={:?}", instance);
            let mut pgo_func_name_var_map = coverage_context.pgo_func_name_var_map.borrow_mut();
            pgo_func_name_var_map
                .entry(instance)
                .or_insert_with(|| create_pgo_func_name_var(self, instance))
        } else {
            bug!("Could not get the `coverage_context`");
        }
    }
}

impl<'tcx> CoverageInfoBuilderMethods<'tcx> for Builder<'_, '_, 'tcx> {
    #[instrument(level = "debug", skip(self))]
    fn add_coverage(&mut self, instance: Instance<'tcx>, kind: &CoverageKind) {
        // Our caller should have already taken care of inlining subtleties,
        // so we can assume that counter/expression IDs in this coverage
        // statement are meaningful for the given instance.
        //
        // (Either the statement was not inlined and directly belongs to this
        // instance, or it was inlined *from* this instance.)

        let bx = self;

        let Some(function_coverage_info) =
            bx.tcx.instance_mir(instance.def).function_coverage_info.as_deref()
        else {
            debug!("function has a coverage statement but no coverage info");
            return;
        };

        let Some(coverage_context) = bx.coverage_context() else { return };
        let mut coverage_map = coverage_context.function_coverage_map.borrow_mut();
        let func_coverage = coverage_map
            .entry(instance)
            .or_insert_with(|| FunctionCoverageCollector::new(instance, function_coverage_info));

        match *kind {
            CoverageKind::SpanMarker | CoverageKind::BlockMarker { .. } => unreachable!(
                "marker statement {kind:?} should have been removed by CleanupPostBorrowck"
            ),
            CoverageKind::CounterIncrement { id } => {
                func_coverage.mark_counter_id_seen(id);
                // We need to explicitly drop the `RefMut` before calling into `instrprof_increment`,
                // as that needs an exclusive borrow.
                drop(coverage_map);

                // The number of counters passed to `llvm.instrprof.increment` might
                // be smaller than the number originally inserted by the instrumentor,
                // if some high-numbered counters were removed by MIR optimizations.
                // If so, LLVM's profiler runtime will use fewer physical counters.
                let num_counters =
                    bx.tcx().coverage_ids_info(instance.def).max_counter_id.as_u32() + 1;
                assert!(
                    num_counters as usize <= function_coverage_info.num_counters,
                    "num_counters disagreement: query says {num_counters} but function info only has {}",
                    function_coverage_info.num_counters
                );

                let fn_name = bx.get_pgo_func_name_var(instance);
                let hash = bx.const_u64(function_coverage_info.function_source_hash);
                let num_counters = bx.const_u32(num_counters);
                let index = bx.const_u32(id.as_u32());
                debug!(
                    "codegen intrinsic instrprof.increment(fn_name={:?}, hash={:?}, num_counters={:?}, index={:?})",
                    fn_name, hash, num_counters, index,
                );
                bx.instrprof_increment(fn_name, hash, num_counters, index);
            }
            CoverageKind::ExpressionUsed { id } => {
                func_coverage.mark_expression_id_seen(id);
            }
        }
    }
}

/// 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_ptr().cast(),
            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_ptr().cast(), 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<CounterExpression>,
    mapping_regions: Vec<CounterMappingRegion>,
    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,
            mapping_regions.as_ptr(),
            mapping_regions.len() as c_uint,
            buffer,
        );
    }
}

pub(crate) fn hash_bytes(bytes: &[u8]) -> u64 {
    unsafe { llvm::LLVMRustCoverageHashByteArray(bytes.as_ptr().cast(), bytes.len()) }
}

pub(crate) fn mapping_version() -> u32 {
    unsafe { llvm::LLVMRustCoverageMappingVersion() }
}

pub(crate) fn save_cov_data_to_mod<'ll, 'tcx>(
    cx: &CodegenCx<'ll, 'tcx>,
    cov_data_val: &'ll llvm::Value,
) {
    let covmap_var_name = llvm::build_string(|s| unsafe {
        llvm::LLVMRustCoverageWriteMappingVarNameToString(s);
    })
    .expect("Rust Coverage Mapping var name failed UTF-8 conversion");
    debug!("covmap var name: {:?}", covmap_var_name);

    let covmap_section_name = llvm::build_string(|s| unsafe {
        llvm::LLVMRustCoverageWriteMapSectionNameToString(cx.llmod, s);
    })
    .expect("Rust Coverage section name failed UTF-8 conversion");
    debug!("covmap section name: {:?}", covmap_section_name);

    let llglobal = llvm::add_global(cx.llmod, cx.val_ty(cov_data_val), &covmap_var_name);
    llvm::set_initializer(llglobal, cov_data_val);
    llvm::set_global_constant(llglobal, true);
    llvm::set_linkage(llglobal, llvm::Linkage::PrivateLinkage);
    llvm::set_section(llglobal, &covmap_section_name);
    // LLVM's coverage mapping format specifies 8-byte alignment for items in this section.
    llvm::set_alignment(llglobal, Align::EIGHT);
    cx.add_used_global(llglobal);
}

pub(crate) fn save_func_record_to_mod<'ll, 'tcx>(
    cx: &CodegenCx<'ll, 'tcx>,
    covfun_section_name: &str,
    func_name_hash: u64,
    func_record_val: &'ll llvm::Value,
    is_used: bool,
) {
    // Assign a name to the function record. This is used to merge duplicates.
    //
    // In LLVM, a "translation unit" (effectively, a `Crate` in Rust) can describe functions that
    // are included-but-not-used. If (or when) Rust generates functions that are
    // included-but-not-used, note that a dummy description for a function included-but-not-used
    // in a Crate can be replaced by full description provided by a different Crate. The two kinds
    // of descriptions play distinct roles in LLVM IR; therefore, assign them different names (by
    // appending "u" to the end of the function record var name, to prevent `linkonce_odr` merging.
    let func_record_var_name =
        format!("__covrec_{:X}{}", func_name_hash, if is_used { "u" } else { "" });
    debug!("function record var name: {:?}", func_record_var_name);
    debug!("function record section name: {:?}", covfun_section_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, covfun_section_name);
    // LLVM's coverage mapping format specifies 8-byte alignment for items in this section.
    llvm::set_alignment(llglobal, Align::EIGHT);
    llvm::set_comdat(cx.llmod, llglobal, &func_record_var_name);
    cx.add_used_global(llglobal);
}

/// Returns the section name string to pass through to the linker when embedding
/// per-function coverage information in the object file, according to the target
/// platform's object file format.
///
/// LLVM's coverage tools read coverage mapping details from this section when
/// producing coverage reports.
///
/// Typical values are:
/// - `__llvm_covfun` on Linux
/// - `__LLVM_COV,__llvm_covfun` on macOS (includes `__LLVM_COV,` segment prefix)
/// - `.lcovfun$M` on Windows (includes `$M` sorting suffix)
pub(crate) fn covfun_section_name(cx: &CodegenCx<'_, '_>) -> String {
    llvm::build_string(|s| unsafe {
        llvm::LLVMRustCoverageWriteFuncSectionNameToString(cx.llmod, s);
    })
    .expect("Rust Coverage function record section name failed UTF-8 conversion")
}