implemented query for coverage data

This commit adds a query that allows the CoverageData to be pulled from
a call on tcx, avoiding the need to change the
`codegen_intrinsic_call()` signature (no need to pass in the FunctionCx
or any additional arguments.

The commit does not change where/when the CoverageData is computed. It's
still done in the `pass`, and saved in the MIR `Body`.

See discussion (in progress) here:
rust-lang#73488 (comment)

Author: richkadel

src/librustc_codegen_llvm/intrinsic.rs

@@ -16,7 +16,6 @@ use rustc_codegen_ssa::common::TypeKind;
 use rustc_codegen_ssa::glue;
 use rustc_codegen_ssa::mir::operand::{OperandRef, OperandValue};
 use rustc_codegen_ssa::mir::place::PlaceRef;
-use rustc_codegen_ssa::mir::FunctionCx;
 use rustc_codegen_ssa::traits::*;
 use rustc_codegen_ssa::MemFlags;
 use rustc_hir as hir;
@@ -82,14 +81,14 @@ fn get_simple_intrinsic(cx: &CodegenCx<'ll, '_>, name: &str) -> Option<&'ll Valu
 }
 
 impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
-    fn codegen_intrinsic_call<'b, Bx: BuilderMethods<'b, 'tcx>>(
+    fn codegen_intrinsic_call(
         &mut self,
-        fx: &FunctionCx<'b, 'tcx, Bx>,
         instance: ty::Instance<'tcx>,
         fn_abi: &FnAbi<'tcx, Ty<'tcx>>,
         args: &[OperandRef<'tcx, &'ll Value>],
         llresult: &'ll Value,
         span: Span,
+        caller_instance: ty::Instance<'tcx>,
     ) {
         let tcx = self.tcx;
         let callee_ty = instance.monomorphic_ty(tcx);
@@ -141,8 +140,11 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
                 self.call(llfn, &[], None)
             }
             "count_code_region" => {
-                let coverage_data = fx.mir.coverage_data.as_ref().unwrap();
-                let mangled_fn = tcx.symbol_name(fx.instance);
+                let coverage_data = tcx
+                    .coverage_data(caller_instance.def_id())
+                    .as_ref()
+                    .expect("LLVM intrinsic count_code_region call has associated coverage_data");
+                let mangled_fn = tcx.symbol_name(caller_instance);
                 let (mangled_fn_name, _len_val) = self.const_str(mangled_fn.name);
                 let hash = self.const_u64(coverage_data.hash);
                 let index = args[0].immediate();

src/librustc_codegen_ssa/mir/block.rs

@@ -688,12 +688,12 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 .collect();
 
             bx.codegen_intrinsic_call(
-                self,
                 *instance.as_ref().unwrap(),
                 &fn_abi,
                 &args,
                 dest,
                 terminator.source_info.span,
+                self.instance,
             );
 
             if let ReturnDest::IndirectOperand(dst, _) = ret_dest {

src/librustc_codegen_ssa/mir/mod.rs

@@ -21,9 +21,9 @@ use self::operand::{OperandRef, OperandValue};
 
 /// Master context for codegenning from MIR.
 pub struct FunctionCx<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> {
-    pub instance: Instance<'tcx>,
+    instance: Instance<'tcx>,
 
-    pub mir: &'tcx mir::Body<'tcx>,
+    mir: &'tcx mir::Body<'tcx>,
 
     debug_context: Option<FunctionDebugContext<Bx::DIScope>>,
 

src/librustc_codegen_ssa/traits/intrinsic.rs

@@ -1,7 +1,5 @@
 use super::BackendTypes;
 use crate::mir::operand::OperandRef;
-use crate::mir::FunctionCx;
-use crate::traits::BuilderMethods;
 use rustc_middle::ty::{self, Ty};
 use rustc_span::Span;
 use rustc_target::abi::call::FnAbi;
@@ -10,14 +8,14 @@ pub trait IntrinsicCallMethods<'tcx>: BackendTypes {
     /// Remember to add all intrinsics here, in librustc_typeck/check/mod.rs,
     /// and in libcore/intrinsics.rs; if you need access to any llvm intrinsics,
     /// add them to librustc_codegen_llvm/context.rs
-    fn codegen_intrinsic_call<'a, Bx: BuilderMethods<'a, 'tcx>>(
+    fn codegen_intrinsic_call(
         &mut self,
-        fx: &FunctionCx<'a, 'tcx, Bx>,
         instance: ty::Instance<'tcx>,
         fn_abi: &FnAbi<'tcx, Ty<'tcx>>,
         args: &[OperandRef<'tcx, Self::Value>],
         llresult: Self::Value,
         span: Span,
+        caller_instance: ty::Instance<'tcx>,
     );
 
     fn abort(&mut self);

src/librustc_middle/query/mod.rs

@@ -214,6 +214,12 @@ rustc_queries! {
             cache_on_disk_if { key.is_local() }
         }
 
+        query coverage_data(key: DefId) -> Option<mir::CoverageData> {
+            desc { |tcx| "retrieving coverage data, if computed from MIR for `{}`", tcx.def_path_str(key) }
+            storage(ArenaCacheSelector<'tcx>)
+            cache_on_disk_if { key.is_local() }
+        }
+
         query promoted_mir(key: DefId) -> IndexVec<mir::Promoted, mir::Body<'tcx>> {
             desc { |tcx| "optimizing promoted MIR for `{}`", tcx.def_path_str(key) }
             storage(ArenaCacheSelector<'tcx>)

src/librustc_mir/transform/mod.rs

@@ -6,7 +6,7 @@ use rustc_hir::def_id::{CrateNum, DefId, LocalDefId, LOCAL_CRATE};
 use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
 use rustc_index::vec::IndexVec;
 use rustc_middle::mir::visit::Visitor as _;
-use rustc_middle::mir::{traversal, Body, ConstQualifs, MirPhase, Promoted};
+use rustc_middle::mir::{traversal, Body, ConstQualifs, CoverageData, MirPhase, Promoted};
 use rustc_middle::ty::query::Providers;
 use rustc_middle::ty::steal::Steal;
 use rustc_middle::ty::{InstanceDef, TyCtxt, TypeFoldable};
@@ -53,6 +53,7 @@ pub(crate) fn provide(providers: &mut Providers<'_>) {
         mir_drops_elaborated_and_const_checked,
         optimized_mir,
         is_mir_available,
+        coverage_data,
         promoted_mir,
         ..*providers
     };
@@ -422,6 +423,11 @@ fn run_optimization_passes<'tcx>(
     );
 }
 
+fn coverage_data(tcx: TyCtxt<'_>, def_id: DefId) -> Option<CoverageData> {
+    let body = tcx.optimized_mir(def_id);
+    body.coverage_data.clone()
+}
+
 fn optimized_mir(tcx: TyCtxt<'_>, def_id: DefId) -> Body<'_> {
     if tcx.is_constructor(def_id) {
         // There's no reason to run all of the MIR passes on constructors when