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coverage: Collect HIR info during MIR building
The coverage instrumentor pass operates on MIR, but it needs access to some source-related information that is normally not present in MIR. Historically, that information was obtained by looking back at HIR during MIR transformation. This patch arranges for the necessary information to be collected ahead of time during MIR building instead.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,117 @@ | ||
| use rustc_middle::hir; | ||
| use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags; | ||
| use rustc_middle::mir; | ||
| use rustc_middle::ty::TyCtxt; | ||
| use rustc_span::def_id::LocalDefId; | ||
| use rustc_span::{ExpnKind, Span}; | ||
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| /// If the given item is eligible for coverage instrumentation, collect relevant | ||
| /// HIR information that will be needed by the instrumentor pass. | ||
| pub(crate) fn make_coverage_hir_info_if_eligible( | ||
| tcx: TyCtxt<'_>, | ||
| def_id: LocalDefId, | ||
| ) -> Option<Box<mir::coverage::HirInfo>> { | ||
| assert!(tcx.sess.instrument_coverage()); | ||
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| is_eligible_for_coverage(tcx, def_id).then(|| Box::new(make_coverage_hir_info(tcx, def_id))) | ||
| } | ||
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| fn is_eligible_for_coverage(tcx: TyCtxt<'_>, def_id: LocalDefId) -> bool { | ||
| let is_fn_like = tcx.hir().get_by_def_id(def_id).fn_kind().is_some(); | ||
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| // Only instrument functions, methods, and closures (not constants since they are evaluated | ||
| // at compile time by Miri). | ||
| // FIXME(#73156): Handle source code coverage in const eval, but note, if and when const | ||
| // expressions get coverage spans, we will probably have to "carve out" space for const | ||
| // expressions from coverage spans in enclosing MIR's, like we do for closures. (That might | ||
| // be tricky if const expressions have no corresponding statements in the enclosing MIR. | ||
| // Closures are carved out by their initial `Assign` statement.) | ||
| if !is_fn_like { | ||
| return false; | ||
| } | ||
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|
||
| let codegen_fn_attrs = tcx.codegen_fn_attrs(def_id); | ||
| if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::NO_COVERAGE) { | ||
| return false; | ||
| } | ||
|
|
||
| true | ||
| } | ||
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| fn make_coverage_hir_info(tcx: TyCtxt<'_>, def_id: LocalDefId) -> mir::coverage::HirInfo { | ||
| let (maybe_fn_sig, hir_body) = fn_sig_and_body(tcx, def_id); | ||
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| let function_source_hash = hash_mir_source(tcx, hir_body); | ||
| let body_span = get_body_span(tcx, hir_body, def_id); | ||
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||
| let spans_are_compatible = { | ||
| let source_map = tcx.sess.source_map(); | ||
| |a: Span, b: Span| { | ||
| a.eq_ctxt(b) | ||
| && source_map.lookup_source_file_idx(a.lo()) | ||
| == source_map.lookup_source_file_idx(b.lo()) | ||
| } | ||
| }; | ||
|
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| let fn_sig_span = if let Some(fn_sig) = maybe_fn_sig | ||
| && spans_are_compatible(fn_sig.span, body_span) | ||
| && fn_sig.span.lo() <= body_span.lo() | ||
| { | ||
| fn_sig.span.with_hi(body_span.lo()) | ||
| } else { | ||
| body_span.shrink_to_lo() | ||
| }; | ||
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| mir::coverage::HirInfo { function_source_hash, fn_sig_span, body_span } | ||
| } | ||
|
|
||
| fn fn_sig_and_body( | ||
| tcx: TyCtxt<'_>, | ||
| def_id: LocalDefId, | ||
| ) -> (Option<&rustc_hir::FnSig<'_>>, &rustc_hir::Body<'_>) { | ||
| // FIXME(#79625): Consider improving MIR to provide the information needed, to avoid going back | ||
| // to HIR for it. | ||
| let hir_node = tcx.hir().get_by_def_id(def_id); | ||
| let (_, fn_body_id) = | ||
| hir::map::associated_body(hir_node).expect("HIR node is a function with body"); | ||
| (hir_node.fn_sig(), tcx.hir().body(fn_body_id)) | ||
| } | ||
|
|
||
| fn get_body_span<'tcx>( | ||
| tcx: TyCtxt<'tcx>, | ||
| hir_body: &rustc_hir::Body<'tcx>, | ||
| def_id: LocalDefId, | ||
| ) -> Span { | ||
| let mut body_span = hir_body.value.span; | ||
|
|
||
| if tcx.is_closure(def_id.to_def_id()) { | ||
| // If the MIR function is a closure, and if the closure body span | ||
| // starts from a macro, but it's content is not in that macro, try | ||
| // to find a non-macro callsite, and instrument the spans there | ||
| // instead. | ||
| loop { | ||
| let expn_data = body_span.ctxt().outer_expn_data(); | ||
| if expn_data.is_root() { | ||
| break; | ||
| } | ||
| if let ExpnKind::Macro { .. } = expn_data.kind { | ||
| body_span = expn_data.call_site; | ||
| } else { | ||
| break; | ||
| } | ||
| } | ||
| } | ||
|
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||
| body_span | ||
| } | ||
|
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| fn hash_mir_source<'tcx>(tcx: TyCtxt<'tcx>, hir_body: &'tcx rustc_hir::Body<'tcx>) -> u64 { | ||
| // FIXME(cjgillot) Stop hashing HIR manually here. | ||
| let owner = hir_body.id().hir_id.owner; | ||
| tcx.hir_owner_nodes(owner) | ||
| .unwrap() | ||
| .opt_hash_including_bodies | ||
| .unwrap() | ||
| .to_smaller_hash() | ||
| .as_u64() | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
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@@ -281,6 +281,7 @@ fn new_body<'tcx>( | |
| None, | ||
| // FIXME(compiler-errors): is this correct? | ||
| None, | ||
| None, | ||
| ) | ||
| } | ||
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