Auto merge of #124675 - matthiaskrgr:rollup-x6n79ua, r=matthiaskrgr

Rollup of 7 pull requests

Successful merges:

 - #122492 (Implement ptr_as_ref_unchecked)
 - #123815 (Fix cannot usage in time.rs)
 - #124059 (default_alloc_error_hook: explain difference to default __rdl_oom in alloc)
 - #124510 (Add raw identifier in a typo suggestion)
 - #124555 (coverage: Clean up creation of MC/DC condition bitmaps)
 - #124593 (Describe and use CStr literals in CStr and CString docs)
 - #124630 (CI: remove `env-x86_64-apple-tests` YAML anchor)

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

2 files changed, 9 insertions, 0 deletions

diff --git a/compiler/rustc_codegen_ssa/src/mir/mod.rs b/compiler/rustc_codegen_ssa/src/mir/mod.rs
index 0064c16f5d9..cf6e2e8d14c 100644
--- a/compiler/rustc_codegen_ssa/src/mir/mod.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/mod.rs
@@ -259,6 +259,10 @@ pub fn codegen_mir<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
     // Apply debuginfo to the newly allocated locals.
     fx.debug_introduce_locals(&mut start_bx);
 
+    // If the backend supports coverage, and coverage is enabled for this function,
+    // do any necessary start-of-function codegen (e.g. locals for MC/DC bitmaps).
+    start_bx.init_coverage(instance);
+
     // The builders will be created separately for each basic block at `codegen_block`.
     // So drop the builder of `start_llbb` to avoid having two at the same time.
     drop(start_bx);
diff --git a/compiler/rustc_codegen_ssa/src/traits/coverageinfo.rs b/compiler/rustc_codegen_ssa/src/traits/coverageinfo.rs
index d1d813bd389..906d8b87d3b 100644
--- a/compiler/rustc_codegen_ssa/src/traits/coverageinfo.rs
+++ b/compiler/rustc_codegen_ssa/src/traits/coverageinfo.rs
@@ -3,6 +3,11 @@ use rustc_middle::mir::coverage::CoverageKind;
 use rustc_middle::ty::Instance;
 
 pub trait CoverageInfoBuilderMethods<'tcx>: BackendTypes {
+    /// Performs any start-of-function codegen needed for coverage instrumentation.
+    ///
+    /// Can be a no-op in backends that don't support coverage instrumentation.
+    fn init_coverage(&mut self, _instance: Instance<'tcx>) {}
+
     /// Handle the MIR coverage info in a backend-specific way.
     ///
     /// This can potentially be a no-op in backends that don't support