Rollup merge of #113355 - Zalathar:ssa, r=oli-obk

Move most coverage code out of `rustc_codegen_ssa`

*This is one step in my larger coverage refactoring ambitions described at <https://github.com/rust-lang/compiler-team/issues/645>.*

The backend implementation of coverage instrumentation was originally split between SSA and LLVM, perhaps in the hopes that it could be used by other backends.

In practice, this split mostly just makes the coverage implementation harder to navigate and harder to modify. It seems unlikely that any backend will actually implement coverage instrumentation in the foreseeable future, especially since many parts of the existing implementation (outside the LLVM backend) are heavily tied to the specific details of LLVM's coverage instrumentation features.

The current shared implementation of `codegen_coverage` is heavily tied to the details of `StatementKind::Coverage`, which makes those details difficult to change. I have reason to want to change those details as part of future fixes/improvements, so this will reduce the amount of interface churn caused by those later changes.

---

This is intended to be a pure refactoring change, with no changes to actual behaviour. All of the “added” code has really just been moved from other files.

1 files changed, 70 insertions, 7 deletions

diff --git a/compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs b/compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs
index cd261293e9b..839a7f333ba 100644
--- a/compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs
+++ b/compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs
@@ -3,13 +3,13 @@ use crate::llvm;
 use crate::abi::Abi;
 use crate::builder::Builder;
 use crate::common::CodegenCx;
+use crate::coverageinfo::map_data::{CounterExpression, FunctionCoverage};
 
 use libc::c_uint;
 use llvm::coverageinfo::CounterMappingRegion;
-use rustc_codegen_ssa::coverageinfo::map::{CounterExpression, FunctionCoverage};
 use rustc_codegen_ssa::traits::{
-    BaseTypeMethods, BuilderMethods, ConstMethods, CoverageInfoBuilderMethods, CoverageInfoMethods,
-    MiscMethods, StaticMethods,
+    BaseTypeMethods, BuilderMethods, ConstMethods, CoverageInfoBuilderMethods, MiscMethods,
+    StaticMethods,
 };
 use rustc_data_structures::fx::FxHashMap;
 use rustc_hir as hir;
@@ -17,16 +17,19 @@ use rustc_hir::def_id::DefId;
 use rustc_llvm::RustString;
 use rustc_middle::bug;
 use rustc_middle::mir::coverage::{
-    CodeRegion, CounterValueReference, ExpressionOperandId, InjectedExpressionId, Op,
+    CodeRegion, CounterValueReference, CoverageKind, ExpressionOperandId, InjectedExpressionId, Op,
 };
+use rustc_middle::mir::Coverage;
 use rustc_middle::ty;
-use rustc_middle::ty::layout::FnAbiOf;
+use rustc_middle::ty::layout::{FnAbiOf, HasTyCtxt};
 use rustc_middle::ty::subst::InternalSubsts;
 use rustc_middle::ty::Instance;
 
 use std::cell::RefCell;
 use std::ffi::CString;
 
+mod ffi;
+pub(crate) mod map_data;
 pub mod mapgen;
 
 const UNUSED_FUNCTION_COUNTER_ID: CounterValueReference = CounterValueReference::START;
@@ -53,11 +56,17 @@ impl<'ll, 'tcx> CrateCoverageContext<'ll, 'tcx> {
     }
 }
 
-impl<'ll, 'tcx> CoverageInfoMethods<'tcx> for CodegenCx<'ll, 'tcx> {
-    fn coverageinfo_finalize(&self) {
+// These methods used to be part of trait `CoverageInfoMethods`, which no longer
+// exists after most coverage code was moved out of SSA.
+impl<'ll, 'tcx> CodegenCx<'ll, 'tcx> {
+    pub(crate) fn coverageinfo_finalize(&self) {
         mapgen::finalize(self)
     }
 
+    /// For LLVM codegen, returns a function-specific `Value` for a global
+    /// string, to hold the function name passed to LLVM intrinsic
+    /// `instrprof.increment()`. The `Value` is only created once per instance.
+    /// Multiple invocations with the same instance return the same `Value`.
     fn get_pgo_func_name_var(&self, instance: Instance<'tcx>) -> &'ll llvm::Value {
         if let Some(coverage_context) = self.coverage_context() {
             debug!("getting pgo_func_name_var for instance={:?}", instance);
@@ -94,6 +103,54 @@ impl<'ll, 'tcx> CoverageInfoMethods<'tcx> for CodegenCx<'ll, 'tcx> {
 }
 
 impl<'tcx> CoverageInfoBuilderMethods<'tcx> for Builder<'_, '_, 'tcx> {
+    fn add_coverage(&mut self, instance: Instance<'tcx>, coverage: &Coverage) {
+        let bx = self;
+
+        let Coverage { kind, code_region } = coverage.clone();
+        match kind {
+            CoverageKind::Counter { function_source_hash, id } => {
+                if bx.set_function_source_hash(instance, function_source_hash) {
+                    // If `set_function_source_hash()` returned true, the coverage map is enabled,
+                    // so continue adding the counter.
+                    if let Some(code_region) = code_region {
+                        // Note: Some counters do not have code regions, but may still be referenced
+                        // from expressions. In that case, don't add the counter to the coverage map,
+                        // but do inject the counter intrinsic.
+                        bx.add_coverage_counter(instance, id, code_region);
+                    }
+
+                    let coverageinfo = bx.tcx().coverageinfo(instance.def);
+
+                    let fn_name = bx.get_pgo_func_name_var(instance);
+                    let hash = bx.const_u64(function_source_hash);
+                    let num_counters = bx.const_u32(coverageinfo.num_counters);
+                    let index = bx.const_u32(id.zero_based_index());
+                    debug!(
+                        "codegen intrinsic instrprof.increment(fn_name={:?}, hash={:?}, num_counters={:?}, index={:?})",
+                        fn_name, hash, num_counters, index,
+                    );
+                    bx.instrprof_increment(fn_name, hash, num_counters, index);
+                }
+            }
+            CoverageKind::Expression { id, lhs, op, rhs } => {
+                bx.add_coverage_counter_expression(instance, id, lhs, op, rhs, code_region);
+            }
+            CoverageKind::Unreachable => {
+                bx.add_coverage_unreachable(
+                    instance,
+                    code_region.expect("unreachable regions always have code regions"),
+                );
+            }
+        }
+    }
+}
+
+// These methods used to be part of trait `CoverageInfoBuilderMethods`, but
+// after moving most coverage code out of SSA they are now just ordinary methods.
+impl<'tcx> Builder<'_, '_, 'tcx> {
+    /// Returns true if the function source hash was added to the coverage map (even if it had
+    /// already been added, for this instance). Returns false *only* if `-C instrument-coverage` is
+    /// not enabled (a coverage map is not being generated).
     fn set_function_source_hash(
         &mut self,
         instance: Instance<'tcx>,
@@ -115,6 +172,8 @@ impl<'tcx> CoverageInfoBuilderMethods<'tcx> for Builder<'_, '_, 'tcx> {
         }
     }
 
+    /// Returns true if the counter was added to the coverage map; false if `-C instrument-coverage`
+    /// is not enabled (a coverage map is not being generated).
     fn add_coverage_counter(
         &mut self,
         instance: Instance<'tcx>,
@@ -137,6 +196,8 @@ impl<'tcx> CoverageInfoBuilderMethods<'tcx> for Builder<'_, '_, 'tcx> {
         }
     }
 
+    /// Returns true if the expression was added to the coverage map; false if
+    /// `-C instrument-coverage` is not enabled (a coverage map is not being generated).
     fn add_coverage_counter_expression(
         &mut self,
         instance: Instance<'tcx>,
@@ -163,6 +224,8 @@ impl<'tcx> CoverageInfoBuilderMethods<'tcx> for Builder<'_, '_, 'tcx> {
         }
     }
 
+    /// Returns true if the region was added to the coverage map; false if `-C instrument-coverage`
+    /// is not enabled (a coverage map is not being generated).
     fn add_coverage_unreachable(&mut self, instance: Instance<'tcx>, region: CodeRegion) -> bool {
         if let Some(coverage_context) = self.coverage_context() {
             debug!(