Auto merge of #74091 - richkadel:llvm-coverage-map-gen-4, r=tmandry

Generating the coverage map

@tmandry @wesleywiser

rustc now generates the coverage map and can support (limited)
coverage report generation, at the function level.

Example commands to generate a coverage report:
```shell
$ BUILD=$HOME/rust/build/x86_64-unknown-linux-gnu
$ $BUILD/stage1/bin/rustc -Zinstrument-coverage \
$HOME/rust/src/test/run-make-fulldeps/instrument-coverage/main.rs
$ LLVM_PROFILE_FILE="main.profraw" ./main
called
$ $BUILD/llvm/bin/llvm-profdata merge -sparse main.profraw -o main.profdata
$ $BUILD/llvm/bin/llvm-cov show --instr-profile=main.profdata main
```
![rust coverage report only 20200706](https://user-images.githubusercontent.com/3827298/86697299-1cbe8f80-bfc3-11ea-8955-451b48626991.png)

r? @wesleywiser

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

Author: bors

Cargo.lock

@@ -2821,6 +2821,13 @@ dependencies = [
  "rls-span",
 ]
 
+[[package]]
+name = "rust-demangler"
+version = "0.0.0"
+dependencies = [
+ "rustc-demangle",
+]
+
 [[package]]
 name = "rustbook"
 version = "0.1.0"

Cargo.toml

@@ -17,6 +17,7 @@ members = [
   "src/tools/remote-test-client",
   "src/tools/remote-test-server",
   "src/tools/rust-installer",
+  "src/tools/rust-demangler",
   "src/tools/cargo",
   "src/tools/rustdoc",
   "src/tools/rls",

src/bootstrap/builder.rs

@@ -370,6 +370,7 @@ impl<'a> Builder<'a> {
                 tool::Cargo,
                 tool::Rls,
                 tool::RustAnalyzer,
+                tool::RustDemangler,
                 tool::Rustdoc,
                 tool::Clippy,
                 tool::CargoClippy,

src/bootstrap/test.rs

@@ -1022,6 +1022,10 @@ impl Step for Compiletest {
             cmd.arg("--rustdoc-path").arg(builder.rustdoc(compiler));
         }
 
+        if mode == "run-make" && suite.ends_with("fulldeps") {
+            cmd.arg("--rust-demangler-path").arg(builder.tool_exe(Tool::RustDemangler));
+        }
+
         cmd.arg("--src-base").arg(builder.src.join("src/test").join(suite));
         cmd.arg("--build-base").arg(testdir(builder, compiler.host).join(suite));
         cmd.arg("--stage-id").arg(format!("stage{}-{}", compiler.stage, target));

src/bootstrap/tool.rs

@@ -361,6 +361,7 @@ bootstrap_tool!(
     Compiletest, "src/tools/compiletest", "compiletest", is_unstable_tool = true;
     BuildManifest, "src/tools/build-manifest", "build-manifest";
     RemoteTestClient, "src/tools/remote-test-client", "remote-test-client";
+    RustDemangler, "src/tools/rust-demangler", "rust-demangler";
     RustInstaller, "src/tools/rust-installer", "fabricate", is_external_tool = true;
     RustdocTheme, "src/tools/rustdoc-themes", "rustdoc-themes";
     ExpandYamlAnchors, "src/tools/expand-yaml-anchors", "expand-yaml-anchors";

src/libcore/intrinsics.rs

@@ -1958,15 +1958,23 @@ extern "rust-intrinsic" {
     /// Internal placeholder for injecting code coverage counters when the "instrument-coverage"
     /// option is enabled. The placeholder is replaced with `llvm.instrprof.increment` during code
     /// generation.
+    #[cfg(not(bootstrap))]
     #[lang = "count_code_region"]
-    pub fn count_code_region(index: u32, start_byte_pos: u32, end_byte_pos: u32);
+    pub fn count_code_region(
+        function_source_hash: u64,
+        index: u32,
+        start_byte_pos: u32,
+        end_byte_pos: u32,
+    );
 
     /// Internal marker for code coverage expressions, injected into the MIR when the
     /// "instrument-coverage" option is enabled. This intrinsic is not converted into a
     /// backend intrinsic call, but its arguments are extracted during the production of a
     /// "coverage map", which is injected into the generated code, as additional data.
     /// This marker identifies a code region and two other counters or counter expressions
     /// whose sum is the number of times the code region was executed.
+    #[cfg(not(bootstrap))]
+    #[lang = "coverage_counter_add"]
     pub fn coverage_counter_add(
         index: u32,
         left_index: u32,
@@ -1978,6 +1986,8 @@ extern "rust-intrinsic" {
     /// This marker identifies a code region and two other counters or counter expressions
     /// whose difference is the number of times the code region was executed.
     /// (See `coverage_counter_add` for more information.)
+    #[cfg(not(bootstrap))]
+    #[lang = "coverage_counter_subtract"]
     pub fn coverage_counter_subtract(
         index: u32,
         left_index: u32,

src/librustc_codegen_llvm/attributes.rs

@@ -133,6 +133,9 @@ fn set_probestack(cx: &CodegenCx<'ll, '_>, llfn: &'ll Value) {
         return;
     }
 
+    // FIXME(richkadel): Make sure probestack plays nice with `-Z instrument-coverage`
+    // or disable it if not, similar to above early exits.
+
     // Flag our internal `__rust_probestack` function as the stack probe symbol.
     // This is defined in the `compiler-builtins` crate for each architecture.
     llvm::AddFunctionAttrStringValue(

src/librustc_codegen_llvm/base.rs

@@ -144,17 +144,18 @@ pub fn compile_codegen_unit(
                 }
             }
 
+            // Finalize code coverage by injecting the coverage map. Note, the coverage map will
+            // also be added to the `llvm.used` variable, created next.
+            if cx.sess().opts.debugging_opts.instrument_coverage {
+                cx.coverageinfo_finalize();
+            }
+
             // Create the llvm.used variable
             // This variable has type [N x i8*] and is stored in the llvm.metadata section
             if !cx.used_statics().borrow().is_empty() {
                 cx.create_used_variable()
             }
 
-            // Finalize code coverage by injecting the coverage map
-            if cx.sess().opts.debugging_opts.instrument_coverage {
-                cx.coverageinfo_finalize();
-            }
-
             // Finalize debuginfo
             if cx.sess().opts.debuginfo != DebugInfo::None {
                 cx.debuginfo_finalize();

src/librustc_codegen_llvm/builder.rs

@@ -1060,7 +1060,7 @@ impl BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
             fn_name, hash, num_counters, index
         );
 
-        let llfn = unsafe { llvm::LLVMRustGetInstrprofIncrementIntrinsic(self.cx().llmod) };
+        let llfn = unsafe { llvm::LLVMRustGetInstrProfIncrementIntrinsic(self.cx().llmod) };
         let args = &[fn_name, hash, num_counters, index];
         let args = self.check_call("call", llfn, args);
 

src/librustc_codegen_llvm/consts.rs

@@ -493,10 +493,14 @@ impl StaticMethods for CodegenCx<'ll, 'tcx> {
             }
 
             if attrs.flags.contains(CodegenFnAttrFlags::USED) {
-                // This static will be stored in the llvm.used variable which is an array of i8*
-                let cast = llvm::LLVMConstPointerCast(g, self.type_i8p());
-                self.used_statics.borrow_mut().push(cast);
+                self.add_used_global(g);
             }
         }
     }
+
+    /// Add a global value to a list to be stored in the `llvm.used` variable, an array of i8*.
+    fn add_used_global(&self, global: &'ll Value) {
+        let cast = unsafe { llvm::LLVMConstPointerCast(global, self.type_i8p()) };
+        self.used_statics.borrow_mut().push(cast);
+    }
 }