coverage: Don't store a body span in FunctionCoverageInfo

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

@@ -105,9 +105,14 @@ fn fill_region_tables<'tcx>(
     ids_info: &'tcx CoverageIdsInfo,
     covfun: &mut CovfunRecord<'tcx>,
 ) {
-    // Currently a function's mappings must all be in the same file as its body span.
+    // Currently a function's mappings must all be in the same file, so use the
+    // first mapping's span to determine the file.
     let source_map = tcx.sess.source_map();
-    let source_file = source_map.lookup_source_file(fn_cov_info.body_span.lo());
+    let Some(first_span) = (try { fn_cov_info.mappings.first()?.span }) else {
+        debug_assert!(false, "function has no mappings: {:?}", covfun.mangled_function_name);
+        return;
+    };
+    let source_file = source_map.lookup_source_file(first_span.lo());
 
     // Look up the global file ID for that file.
     let global_file_id = global_file_table.global_file_id_for_file(&source_file);
@@ -118,9 +123,8 @@ fn fill_region_tables<'tcx>(
     let ffi::Regions { code_regions, branch_regions, mcdc_branch_regions, mcdc_decision_regions } =
         &mut covfun.regions;
 
-    let make_cov_span = |span: Span| {
-        spans::make_coverage_span(local_file_id, source_map, fn_cov_info, &source_file, span)
-    };
+    let make_cov_span =
+        |span: Span| spans::make_coverage_span(local_file_id, source_map, &source_file, span);
     let discard_all = tcx.sess.coverage_discard_all_spans_in_codegen();
 
     // For each counter/region pair in this function+file, convert it to a

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

@@ -1,4 +1,3 @@
-use rustc_middle::mir::coverage::FunctionCoverageInfo;
 use rustc_span::source_map::SourceMap;
 use rustc_span::{BytePos, Pos, SourceFile, Span};
 use tracing::debug;
@@ -19,11 +18,10 @@ use crate::coverageinfo::mapgen::LocalFileId;
 pub(crate) fn make_coverage_span(
     file_id: LocalFileId,
     source_map: &SourceMap,
-    fn_cov_info: &FunctionCoverageInfo,
     file: &SourceFile,
     span: Span,
 ) -> Option<ffi::CoverageSpan> {
-    let span = ensure_non_empty_span(source_map, fn_cov_info, span)?;
+    let span = ensure_non_empty_span(source_map, span)?;
 
     let lo = span.lo();
     let hi = span.hi();
@@ -55,36 +53,22 @@ pub(crate) fn make_coverage_span(
     })
 }
 
-fn ensure_non_empty_span(
-    source_map: &SourceMap,
-    fn_cov_info: &FunctionCoverageInfo,
-    span: Span,
-) -> Option<Span> {
+fn ensure_non_empty_span(source_map: &SourceMap, span: Span) -> Option<Span> {
     if !span.is_empty() {
         return Some(span);
     }
 
-    let lo = span.lo();
-    let hi = span.hi();
-
-    // The span is empty, so try to expand it to cover an adjacent '{' or '}',
-    // but only within the bounds of the body span.
-    let try_next = hi < fn_cov_info.body_span.hi();
-    let try_prev = fn_cov_info.body_span.lo() < lo;
-    if !(try_next || try_prev) {
-        return None;
-    }
-
+    // The span is empty, so try to enlarge it to cover an adjacent '{' or '}'.
     source_map
         .span_to_source(span, |src, start, end| try {
             // Adjusting span endpoints by `BytePos(1)` is normally a bug,
             // but in this case we have specifically checked that the character
             // we're skipping over is one of two specific ASCII characters, so
             // adjusting by exactly 1 byte is correct.
-            if try_next && src.as_bytes()[end] == b'{' {
-                Some(span.with_hi(hi + BytePos(1)))
-            } else if try_prev && src.as_bytes()[start - 1] == b'}' {
-                Some(span.with_lo(lo - BytePos(1)))
+            if src.as_bytes().get(end).copied() == Some(b'{') {
+                Some(span.with_hi(span.hi() + BytePos(1)))
+            } else if start > 0 && src.as_bytes()[start - 1] == b'}' {
+                Some(span.with_lo(span.lo() - BytePos(1)))
             } else {
                 None
             }

compiler/rustc_middle/src/mir/coverage.rs

@@ -194,7 +194,6 @@ pub struct Mapping {
 #[derive(TyEncodable, TyDecodable, Hash, HashStable)]
 pub struct FunctionCoverageInfo {
     pub function_source_hash: u64,
-    pub body_span: Span,
 
     /// Used in conjunction with `priority_list` to create physical counters
     /// and counter expressions, after MIR optimizations.

compiler/rustc_middle/src/mir/pretty.rs

@@ -620,9 +620,8 @@ fn write_function_coverage_info(
     function_coverage_info: &coverage::FunctionCoverageInfo,
     w: &mut dyn io::Write,
 ) -> io::Result<()> {
-    let coverage::FunctionCoverageInfo { body_span, mappings, .. } = function_coverage_info;
+    let coverage::FunctionCoverageInfo { mappings, .. } = function_coverage_info;
 
-    writeln!(w, "{INDENT}coverage body span: {body_span:?}")?;
     for coverage::Mapping { kind, span } in mappings {
         writeln!(w, "{INDENT}coverage {kind:?} => {span:?};")?;
     }

compiler/rustc_mir_transform/src/coverage/mod.rs

@@ -107,7 +107,6 @@ fn instrument_function_for_coverage<'tcx>(tcx: TyCtxt<'tcx>, mir_body: &mut mir:
 
     mir_body.function_coverage_info = Some(Box::new(FunctionCoverageInfo {
         function_source_hash: hir_info.function_source_hash,
-        body_span: hir_info.body_span,
 
         node_flow_data,
         priority_list,

tests/mir-opt/coverage/branch_match_arms.main.InstrumentCoverage.diff

@@ -26,7 +26,6 @@
           debug a => _9;
       }
 
-+     coverage body span: $DIR/branch_match_arms.rs:14:11: 21:2 (#0)
 +     coverage Code { bcb: bcb0 } => $DIR/branch_match_arms.rs:14:1: 15:21 (#0);
 +     coverage Code { bcb: bcb1 } => $DIR/branch_match_arms.rs:16:17: 16:33 (#0);
 +     coverage Code { bcb: bcb3 } => $DIR/branch_match_arms.rs:17:17: 17:33 (#0);

tests/mir-opt/coverage/instrument_coverage.bar.InstrumentCoverage.diff

@@ -4,8 +4,7 @@
   fn bar() -> bool {
       let mut _0: bool;
 
-+     coverage body span: $DIR/instrument_coverage.rs:29:18: 31:2 (#0)
-+     coverage Code { bcb: bcb0 } => $DIR/instrument_coverage.rs:29:1: 31:2 (#0);
++     coverage Code { bcb: bcb0 } => $DIR/instrument_coverage.rs:27:1: 29:2 (#0);
 + 
       bb0: {
 +         Coverage::VirtualCounter(bcb0);

tests/mir-opt/coverage/instrument_coverage.main.InstrumentCoverage.diff

@@ -7,12 +7,11 @@
       let mut _2: bool;
       let mut _3: !;
 
-+     coverage body span: $DIR/instrument_coverage.rs:14:11: 20:2 (#0)
-+     coverage Code { bcb: bcb0 } => $DIR/instrument_coverage.rs:14:1: 14:11 (#0);
-+     coverage Code { bcb: bcb1 } => $DIR/instrument_coverage.rs:16:12: 16:17 (#0);
-+     coverage Code { bcb: bcb2 } => $DIR/instrument_coverage.rs:17:13: 17:18 (#0);
-+     coverage Code { bcb: bcb3 } => $DIR/instrument_coverage.rs:18:10: 18:10 (#0);
-+     coverage Code { bcb: bcb2 } => $DIR/instrument_coverage.rs:20:2: 20:2 (#0);
++     coverage Code { bcb: bcb0 } => $DIR/instrument_coverage.rs:13:1: 13:11 (#0);
++     coverage Code { bcb: bcb1 } => $DIR/instrument_coverage.rs:15:12: 15:17 (#0);
++     coverage Code { bcb: bcb2 } => $DIR/instrument_coverage.rs:16:13: 16:18 (#0);
++     coverage Code { bcb: bcb3 } => $DIR/instrument_coverage.rs:17:10: 17:10 (#0);
++     coverage Code { bcb: bcb2 } => $DIR/instrument_coverage.rs:19:2: 19:2 (#0);
 + 
       bb0: {
 +         Coverage::VirtualCounter(bcb0);

tests/mir-opt/coverage/instrument_coverage.rs

@@ -7,7 +7,6 @@
 
 // EMIT_MIR instrument_coverage.main.InstrumentCoverage.diff
 // CHECK-LABEL: fn main()
-// CHECK: coverage body span:
 // CHECK: coverage Code { bcb: bcb{{[0-9]+}} } =>
 // CHECK: bb0:
 // CHECK: Coverage::VirtualCounter
@@ -21,7 +20,6 @@ fn main() {
 
 // EMIT_MIR instrument_coverage.bar.InstrumentCoverage.diff
 // CHECK-LABEL: fn bar()
-// CHECK: coverage body span:
 // CHECK: coverage Code { bcb: bcb{{[0-9]+}} } =>
 // CHECK: bb0:
 // CHECK: Coverage::VirtualCounter

tests/mir-opt/coverage/instrument_coverage_cleanup.main.CleanupPostBorrowck.diff

@@ -7,7 +7,6 @@
 
       coverage branch { true: BlockMarkerId(0), false: BlockMarkerId(1) } => $DIR/instrument_coverage_cleanup.rs:14:8: 14:36 (#0)
 
-      coverage body span: $DIR/instrument_coverage_cleanup.rs:13:11: 15:2 (#0)
       coverage Code { bcb: bcb0 } => $DIR/instrument_coverage_cleanup.rs:13:1: 14:36 (#0);
       coverage Code { bcb: bcb3 } => $DIR/instrument_coverage_cleanup.rs:14:37: 14:39 (#0);
       coverage Code { bcb: bcb1 } => $DIR/instrument_coverage_cleanup.rs:14:39: 14:39 (#0);

tests/mir-opt/coverage/instrument_coverage_cleanup.main.InstrumentCoverage.diff

@@ -7,7 +7,6 @@
 
       coverage branch { true: BlockMarkerId(0), false: BlockMarkerId(1) } => $DIR/instrument_coverage_cleanup.rs:14:8: 14:36 (#0)
 
-+     coverage body span: $DIR/instrument_coverage_cleanup.rs:13:11: 15:2 (#0)
 +     coverage Code { bcb: bcb0 } => $DIR/instrument_coverage_cleanup.rs:13:1: 14:36 (#0);
 +     coverage Code { bcb: bcb3 } => $DIR/instrument_coverage_cleanup.rs:14:37: 14:39 (#0);
 +     coverage Code { bcb: bcb1 } => $DIR/instrument_coverage_cleanup.rs:14:39: 14:39 (#0);