coverage: Pull region conversion out of map_data.rs

Author: Zalathar

compiler/rustc_codegen_llvm/src/coverageinfo/map_data.rs

@@ -1,6 +1,4 @@
-use rustc_middle::mir::coverage::{
-    CovTerm, CoverageIdsInfo, FunctionCoverageInfo, Mapping, MappingKind, SourceRegion,
-};
+use rustc_middle::mir::coverage::{CoverageIdsInfo, FunctionCoverageInfo};
 
 pub(crate) struct FunctionCoverage<'tcx> {
     pub(crate) function_coverage_info: &'tcx FunctionCoverageInfo,
@@ -30,25 +28,4 @@ impl<'tcx> FunctionCoverage<'tcx> {
     pub(crate) fn source_hash(&self) -> u64 {
         if self.is_used() { self.function_coverage_info.function_source_hash } else { 0 }
     }
-
-    /// Converts this function's coverage mappings into an intermediate form
-    /// that will be used by `mapgen` when preparing for FFI.
-    pub(crate) fn counter_regions(
-        &self,
-    ) -> impl Iterator<Item = (MappingKind, &SourceRegion)> + ExactSizeIterator {
-        self.function_coverage_info.mappings.iter().map(move |mapping| {
-            let Mapping { kind, source_region } = mapping;
-            let kind =
-                kind.map_terms(|term| if self.is_zero_term(term) { CovTerm::Zero } else { term });
-            (kind, source_region)
-        })
-    }
-
-    fn is_zero_term(&self, term: CovTerm) -> bool {
-        match self.ids_info {
-            Some(ids_info) => ids_info.is_zero_term(term),
-            // This function is unused, so all coverage counters/expressions are zero.
-            None => true,
-        }
-    }
 }

compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/covfun.rs

@@ -12,7 +12,7 @@ use rustc_codegen_ssa::traits::{
 };
 use rustc_middle::bug;
 use rustc_middle::mir::coverage::{
-    CoverageIdsInfo, Expression, FunctionCoverageInfo, MappingKind, Op,
+    CovTerm, CoverageIdsInfo, Expression, FunctionCoverageInfo, Mapping, MappingKind, Op,
 };
 use rustc_middle::ty::{Instance, TyCtxt};
 use rustc_target::spec::HasTargetSpec;
@@ -65,7 +65,7 @@ pub(crate) fn prepare_covfun_record<'tcx>(
         regions: ffi::Regions::default(),
     };
 
-    fill_region_tables(tcx, global_file_table, function_coverage, &mut covfun);
+    fill_region_tables(tcx, global_file_table, fn_cov_info, ids_info, &mut covfun);
 
     if covfun.regions.has_no_regions() {
         if covfun.is_used {
@@ -117,16 +117,12 @@ fn prepare_expressions(
 fn fill_region_tables<'tcx>(
     tcx: TyCtxt<'tcx>,
     global_file_table: &mut GlobalFileTable,
-    function_coverage: &FunctionCoverage<'tcx>,
+    fn_cov_info: &'tcx FunctionCoverageInfo,
+    ids_info: &'tcx CoverageIdsInfo,
     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);
+    let file_name = span_file_name(tcx, fn_cov_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);
@@ -140,10 +136,14 @@ fn fill_region_tables<'tcx>(
 
     // 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 {
+    let is_zero_term = |term| !covfun.is_used || ids_info.is_zero_term(term);
+    for Mapping { kind, ref source_region } in &fn_cov_info.mappings {
+        // If the mapping refers to counters/expressions that were removed by
+        // MIR opts, replace those occurrences with zero.
+        let kind = kind.map_terms(|term| if is_zero_term(term) { CovTerm::Zero } else { term });
+
+        let span = ffi::CoverageSpan::from_source_region(local_file_id, source_region);
+        match kind {
             MappingKind::Code(term) => {
                 code_regions.push(ffi::CodeRegion { span, counter: ffi::Counter::from_term(term) });
             }