Rollup merge of rust-lang#138659 - Zalathar:no-body-span, r=oli-obk

coverage: Don't store a body span in `FunctionCoverageInfo`

We aren't using this body span for anything truly essential, and having it around will be awkward when we eventually start to support expansion regions, since they aren't necessarily within the main body.

Author: matthiaskrgr

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);