Rollup merge of #73011 - richkadel:llvm-count-from-mir-pass, r=tmandry

first stage of implementing LLVM code coverage

This PR replaces #70680 (WIP toward LLVM Code Coverage for Rust) since I am re-implementing the Rust LLVM code coverage feature in a different part of the compiler (in MIR pass(es) vs AST).

This PR updates rustc with `-Zinstrument-coverage` option that injects the llvm intrinsic `instrprof.increment()` for code generation.

This initial version only injects counters at the top of each function, and does not yet implement the required coverage map.

Upcoming PRs will add the coverage map, and add more counters and/or counter expressions for each conditional code branch.

Rust compiler MCP https://github.com/rust-lang/compiler-team/issues/278
Relevant issue: #34701 - Implement support for LLVMs code coverage instrumentation

***[I put together some development notes here, under a separate branch.](https://github.com/richkadel/rust/blob/cfa0b21d34ee64e4ebee226101bd2ef0c6757865/src/test/codegen/coverage-experiments/README-THIS-IS-TEMPORARY.md)***

4 files changed, 16 insertions, 0 deletions

diff --git a/src/librustc_codegen_ssa/back/write.rs b/src/librustc_codegen_ssa/back/write.rs
index c118e5ebdb7..49054765b9d 100644
--- a/src/librustc_codegen_ssa/back/write.rs
+++ b/src/librustc_codegen_ssa/back/write.rs
@@ -175,6 +175,12 @@ impl ModuleConfig {
                     if sess.opts.debugging_opts.profile && !is_compiler_builtins {
                         passes.push("insert-gcov-profiling".to_owned());
                     }
+
+                    // The rustc option `-Zinstrument_coverage` injects intrinsic calls to
+                    // `llvm.instrprof.increment()`, which requires the LLVM `instrprof` pass.
+                    if sess.opts.debugging_opts.instrument_coverage {
+                        passes.push("instrprof".to_owned());
+                    }
                     passes
                 },
                 vec![]
diff --git a/src/librustc_codegen_ssa/mir/block.rs b/src/librustc_codegen_ssa/mir/block.rs
index c486d5c64ba..d56c816811b 100644
--- a/src/librustc_codegen_ssa/mir/block.rs
+++ b/src/librustc_codegen_ssa/mir/block.rs
@@ -693,6 +693,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 &args,
                 dest,
                 terminator.source_info.span,
+                self.instance,
             );
 
             if let ReturnDest::IndirectOperand(dst, _) = ret_dest {
diff --git a/src/librustc_codegen_ssa/traits/builder.rs b/src/librustc_codegen_ssa/traits/builder.rs
index caba7ebef59..7ffc9f15bff 100644
--- a/src/librustc_codegen_ssa/traits/builder.rs
+++ b/src/librustc_codegen_ssa/traits/builder.rs
@@ -260,6 +260,14 @@ pub trait BuilderMethods<'a, 'tcx>:
     /// Called for `StorageDead`
     fn lifetime_end(&mut self, ptr: Self::Value, size: Size);
 
+    fn instrprof_increment(
+        &mut self,
+        fn_name: Self::Value,
+        hash: Self::Value,
+        num_counters: Self::Value,
+        index: Self::Value,
+    ) -> Self::Value;
+
     fn call(
         &mut self,
         llfn: Self::Value,
diff --git a/src/librustc_codegen_ssa/traits/intrinsic.rs b/src/librustc_codegen_ssa/traits/intrinsic.rs
index 9d48e233de6..f6201949851 100644
--- a/src/librustc_codegen_ssa/traits/intrinsic.rs
+++ b/src/librustc_codegen_ssa/traits/intrinsic.rs
@@ -15,6 +15,7 @@ pub trait IntrinsicCallMethods<'tcx>: BackendTypes {
         args: &[OperandRef<'tcx, Self::Value>],
         llresult: Self::Value,
         span: Span,
+        caller_instance: ty::Instance<'tcx>,
     );
 
     fn abort(&mut self);