Provide option for specifying the profiler runtime

Currently, if `-Zinstrument-coverage` is enabled, the target is linked
against the `library/profiler_builtins` crate (which pulls in LLVM's
compiler-rt runtime).

This option enables backends to specify an alternative runtime crate for
handling injected instrumentation calls.

compiler/rustc_interface/src/tests.rs

@@ -713,7 +713,6 @@ fn test_debugging_options_tracking_hash() {
     tracked!(no_codegen, true);
     tracked!(no_generate_arange_section, true);
     tracked!(no_link, true);
-    tracked!(no_profiler_runtime, true);
     tracked!(osx_rpath_install_name, true);
     tracked!(panic_abort_tests, true);
     tracked!(plt, Some(true));
@@ -722,6 +721,7 @@ fn test_debugging_options_tracking_hash() {
     tracked!(print_fuel, Some("abc".to_string()));
     tracked!(profile, true);
     tracked!(profile_emit, Some(PathBuf::from("abc")));
+    tracked!(profiler_runtime, None);
     tracked!(relax_elf_relocations, Some(true));
     tracked!(relro_level, Some(RelroLevel::Full));
     tracked!(simulate_remapped_rust_src_base, Some(PathBuf::from("/rustc/abc")));

compiler/rustc_metadata/src/creader.rs

@@ -769,27 +769,31 @@ impl<'a> CrateLoader<'a> {
     }
 
     fn inject_profiler_runtime(&mut self, krate: &ast::Crate) {
-        if (self.sess.instrument_coverage()
+        if self.sess.instrument_coverage()
             || self.sess.opts.debugging_opts.profile
-            || self.sess.opts.cg.profile_generate.enabled())
-            && !self.sess.opts.debugging_opts.no_profiler_runtime
+            || self.sess.opts.cg.profile_generate.enabled()
         {
-            info!("loading profiler");
-
-            if self.sess.contains_name(&krate.attrs, sym::no_core) {
-                self.sess.err(
-                    "`profiler_builtins` crate (required by compiler options) \
-                               is not compatible with crate attribute `#![no_core]`",
-                );
-            }
+            if let Some(name) =
+                self.sess.opts.debugging_opts.profiler_runtime.as_deref().map(Symbol::intern)
+            {
+                info!("loading profiler");
+
+                if name == sym::profiler_builtins
+                    && self.sess.contains_name(&krate.attrs, sym::no_core)
+                {
+                    self.sess.err(
+                        "`profiler_builtins` crate (required by compiler options) \
+                                is not compatible with crate attribute `#![no_core]`",
+                    );
+                }
 
-            let name = sym::profiler_builtins;
-            let cnum = self.resolve_crate(name, DUMMY_SP, CrateDepKind::Implicit, None);
-            let data = self.cstore.get_crate_data(cnum);
+                let cnum = self.resolve_crate(name, DUMMY_SP, CrateDepKind::Implicit, None);
+                let data = self.cstore.get_crate_data(cnum);
 
-            // Sanity check the loaded crate to ensure it is indeed a profiler runtime
-            if !data.is_profiler_runtime() {
-                self.sess.err("the crate `profiler_builtins` is not a profiler runtime");
+                // Sanity check the loaded crate to ensure it is indeed a profiler runtime
+                if !data.is_profiler_runtime() {
+                    self.sess.err(&format!("the crate `{}` is not a profiler runtime", name));
+                }
             }
         }
     }

compiler/rustc_metadata/src/locator.rs

@@ -1100,7 +1100,9 @@ impl CrateError {
                         if sess.is_nightly_build() && std::env::var("CARGO").is_ok() {
                             err.help("consider building the standard library from source with `cargo build -Zbuild-std`");
                         }
-                    } else if crate_name == sym::profiler_builtins {
+                    } else if Some(crate_name)
+                        == sess.opts.debugging_opts.profiler_runtime.as_deref().map(Symbol::intern)
+                    {
                         err.note(&"the compiler may have been built without the profiler runtime");
                     }
                     err.span_label(span, "can't find crate");

compiler/rustc_session/src/options.rs

@@ -1148,8 +1148,6 @@ options! {
         "compile without linking"),
     no_parallel_llvm: bool = (false, parse_no_flag, [UNTRACKED],
         "run LLVM in non-parallel mode (while keeping codegen-units and ThinLTO)"),
-    no_profiler_runtime: bool = (false, parse_no_flag, [TRACKED],
-        "prevent automatic injection of the profiler_builtins crate"),
     normalize_docs: bool = (false, parse_bool, [TRACKED],
         "normalize associated items in rustdoc when generating documentation"),
     osx_rpath_install_name: bool = (false, parse_bool, [TRACKED],
@@ -1193,6 +1191,8 @@ options! {
     profile_emit: Option<PathBuf> = (None, parse_opt_pathbuf, [TRACKED],
         "file path to emit profiling data at runtime when using 'profile' \
         (default based on relative source path)"),
+    profiler_runtime: Option<String> = (Some(String::from("profiler_builtins")), parse_opt_string, [TRACKED],
+        "name of the profiler runtime crate to automatically inject, or None to disable"),
     query_dep_graph: bool = (false, parse_bool, [UNTRACKED],
         "enable queries of the dependency graph for regression testing (default: no)"),
     query_stats: bool = (false, parse_bool, [UNTRACKED],