Rollup merge of #73488 - richkadel:llvm-coverage-map-gen, r=tmandry

code coverage foundation for hash and num_counters

This PR is the next iteration after PR #73011 (which is still waiting on bors to merge).

@wesleywiser - PTAL
r? @tmandry

(FYI, I'm also working on injecting the coverage maps, in another branch, while waiting for these to merge.)

Thanks!

11 files changed, 240 insertions, 84 deletions

diff --git a/src/librustc_codegen_llvm/intrinsic.rs b/src/librustc_codegen_llvm/intrinsic.rs
index 0a8525f06fa..0a1cc31044a 100644
--- a/src/librustc_codegen_llvm/intrinsic.rs
+++ b/src/librustc_codegen_llvm/intrinsic.rs
@@ -23,7 +23,6 @@ use rustc_middle::ty::layout::{FnAbiExt, HasTyCtxt};
 use rustc_middle::ty::{self, Ty};
 use rustc_middle::{bug, span_bug};
 use rustc_span::Span;
-use rustc_span::Symbol;
 use rustc_target::abi::{self, HasDataLayout, LayoutOf, Primitive};
 use rustc_target::spec::PanicStrategy;
 
@@ -141,26 +140,20 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
                 self.call(llfn, &[], None)
             }
             "count_code_region" => {
-                if let ty::InstanceDef::Item(fn_def_id) = caller_instance.def {
-                    let caller_fn_path = tcx.def_path_str(fn_def_id);
-                    debug!(
-                        "count_code_region to llvm.instrprof.increment(fn_name={})",
-                        caller_fn_path
-                    );
-
-                    // FIXME(richkadel): (1) Replace raw function name with mangled function name;
-                    // (2) Replace hardcoded `1234` in `hash` with a computed hash (as discussed in)
-                    // the MCP (compiler-team/issues/278); and replace the hardcoded `1` for
-                    // `num_counters` with the actual number of counters per function (when the
-                    // changes are made to inject more than one counter per function).
-                    let (fn_name, _len_val) = self.const_str(Symbol::intern(&caller_fn_path));
-                    let index = args[0].immediate();
-                    let hash = self.const_u64(1234);
-                    let num_counters = self.const_u32(1);
-                    self.instrprof_increment(fn_name, hash, num_counters, index)
-                } else {
-                    bug!("intrinsic count_code_region: no src.instance");
-                }
+                // FIXME(richkadel): The current implementation assumes the MIR for the given
+                // caller_instance represents a single function. Validate and/or correct if inlining
+                // and/or monomorphization invalidates these assumptions.
+                let coverage_data = tcx.coverage_data(caller_instance.def_id());
+                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 num_counters = self.const_u32(coverage_data.num_counters);
+                let index = args[0].immediate();
+                debug!(
+                    "count_code_region to LLVM intrinsic instrprof.increment(fn_name={}, hash={:?}, num_counters={:?}, index={:?})",
+                    mangled_fn.name, hash, num_counters, index
+                );
+                self.instrprof_increment(mangled_fn_name, hash, num_counters, index)
             }
             "va_start" => self.va_start(args[0].immediate()),
             "va_end" => self.va_end(args[0].immediate()),
diff --git a/src/librustc_metadata/locator.rs b/src/librustc_metadata/locator.rs
index 5a4862d4521..1bdac1039b5 100644
--- a/src/librustc_metadata/locator.rs
+++ b/src/librustc_metadata/locator.rs
@@ -488,6 +488,8 @@ impl<'a> CrateLocator<'a> {
                 && self.triple != TargetTriple::from_triple(config::host_triple())
             {
                 err.note(&format!("the `{}` target may not be installed", self.triple));
+            } else if self.crate_name == sym::profiler_builtins {
+                err.note(&"the compiler may have been built without the profiler runtime");
             }
             err.span_label(self.span, "can't find crate");
             err
diff --git a/src/librustc_middle/hir/map/mod.rs b/src/librustc_middle/hir/map/mod.rs
index d1cfc4867a2..3a4fc581f5f 100644
--- a/src/librustc_middle/hir/map/mod.rs
+++ b/src/librustc_middle/hir/map/mod.rs
@@ -56,7 +56,7 @@ fn fn_sig<'hir>(node: Node<'hir>) -> Option<&'hir FnSig<'hir>> {
     }
 }
 
-fn associated_body<'hir>(node: Node<'hir>) -> Option<BodyId> {
+pub fn associated_body<'hir>(node: Node<'hir>) -> Option<BodyId> {
     match node {
         Node::Item(Item {
             kind: ItemKind::Const(_, body) | ItemKind::Static(.., body) | ItemKind::Fn(.., body),
diff --git a/src/librustc_middle/ich/hcx.rs b/src/librustc_middle/ich/hcx.rs
index 69b4adb3a0e..f5b0b73c49d 100644
--- a/src/librustc_middle/ich/hcx.rs
+++ b/src/librustc_middle/ich/hcx.rs
@@ -67,13 +67,15 @@ impl<'a> StableHashingContext<'a> {
     /// Don't use it for anything else or you'll run the risk of
     /// leaking data out of the tracking system.
     #[inline]
-    pub fn new(
+    fn new_with_or_without_spans(
         sess: &'a Session,
         krate: &'a hir::Crate<'a>,
         definitions: &'a Definitions,
         cstore: &'a dyn CrateStore,
+        always_ignore_spans: bool,
     ) -> Self {
-        let hash_spans_initial = !sess.opts.debugging_opts.incremental_ignore_spans;
+        let hash_spans_initial =
+            !always_ignore_spans && !sess.opts.debugging_opts.incremental_ignore_spans;
 
         StableHashingContext {
             sess,
@@ -89,6 +91,33 @@ impl<'a> StableHashingContext<'a> {
     }
 
     #[inline]
+    pub fn new(
+        sess: &'a Session,
+        krate: &'a hir::Crate<'a>,
+        definitions: &'a Definitions,
+        cstore: &'a dyn CrateStore,
+    ) -> Self {
+        Self::new_with_or_without_spans(
+            sess,
+            krate,
+            definitions,
+            cstore,
+            /*always_ignore_spans=*/ false,
+        )
+    }
+
+    #[inline]
+    pub fn ignore_spans(
+        sess: &'a Session,
+        krate: &'a hir::Crate<'a>,
+        definitions: &'a Definitions,
+        cstore: &'a dyn CrateStore,
+    ) -> Self {
+        let always_ignore_spans = true;
+        Self::new_with_or_without_spans(sess, krate, definitions, cstore, always_ignore_spans)
+    }
+
+    #[inline]
     pub fn sess(&self) -> &'a Session {
         self.sess
     }
diff --git a/src/librustc_middle/mir/mod.rs b/src/librustc_middle/mir/mod.rs
index 64976654799..d89c35d313c 100644
--- a/src/librustc_middle/mir/mod.rs
+++ b/src/librustc_middle/mir/mod.rs
@@ -164,8 +164,8 @@ pub struct Body<'tcx> {
     /// The user may be writing e.g. `&[(SOME_CELL, 42)][i].1` and this would get promoted, because
     /// we'd statically know that no thing with interior mutability will ever be available to the
     /// user without some serious unsafe code.  Now this means that our promoted is actually
-    /// `&[(SOME_CELL, 42)]` and the MIR using it will do the `&promoted[i].1` projection because the
-    /// index may be a runtime value. Such a promoted value is illegal because it has reachable
+    /// `&[(SOME_CELL, 42)]` and the MIR using it will do the `&promoted[i].1` projection because
+    /// the index may be a runtime value. Such a promoted value is illegal because it has reachable
     /// interior mutability. This flag just makes this situation very obvious where the previous
     /// implementation without the flag hid this situation silently.
     /// FIXME(oli-obk): rewrite the promoted during promotion to eliminate the cell components.
@@ -2921,3 +2921,18 @@ impl Location {
         }
     }
 }
+
+/// Coverage data associated with each function (MIR) instrumented with coverage counters, when
+/// compiled with `-Zinstrument_coverage`. The query `tcx.coverage_data(DefId)` computes these
+/// values on demand (during code generation). This query is only valid after executing the MIR pass
+/// `InstrumentCoverage`.
+#[derive(Clone, RustcEncodable, RustcDecodable, Debug, HashStable)]
+pub struct CoverageData {
+    /// A hash value that can be used by the consumer of the coverage profile data to detect
+    /// changes to the instrumented source of the associated MIR body (typically, for an
+    /// individual function).
+    pub hash: u64,
+
+    /// The total number of coverage region counters added to the MIR `Body`.
+    pub num_counters: u32,
+}
diff --git a/src/librustc_middle/query/mod.rs b/src/librustc_middle/query/mod.rs
index 9fd45ddf6e6..2f51b98085b 100644
--- a/src/librustc_middle/query/mod.rs
+++ b/src/librustc_middle/query/mod.rs
@@ -231,6 +231,12 @@ rustc_queries! {
             cache_on_disk_if { key.is_local() }
         }
 
+        query coverage_data(key: DefId) -> mir::CoverageData {
+            desc { |tcx| "retrieving coverage data 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>)
diff --git a/src/librustc_middle/ty/context.rs b/src/librustc_middle/ty/context.rs
index fb9565e4b98..df08e083d2c 100644
--- a/src/librustc_middle/ty/context.rs
+++ b/src/librustc_middle/ty/context.rs
@@ -1307,6 +1307,13 @@ impl<'tcx> TyCtxt<'tcx> {
         StableHashingContext::new(self.sess, krate, self.definitions, &*self.cstore)
     }
 
+    #[inline(always)]
+    pub fn create_no_span_stable_hashing_context(self) -> StableHashingContext<'tcx> {
+        let krate = self.gcx.untracked_crate;
+
+        StableHashingContext::ignore_spans(self.sess, krate, self.definitions, &*self.cstore)
+    }
+
     // This method makes sure that we have a DepNode and a Fingerprint for
     // every upstream crate. It needs to be called once right after the tcx is
     // created.
diff --git a/src/librustc_mir/transform/instrument_coverage.rs b/src/librustc_mir/transform/instrument_coverage.rs
index c36614938e1..06b648ab5a9 100644
--- a/src/librustc_mir/transform/instrument_coverage.rs
+++ b/src/librustc_mir/transform/instrument_coverage.rs
@@ -1,10 +1,19 @@
 use crate::transform::{MirPass, MirSource};
 use crate::util::patch::MirPatch;
+use rustc_data_structures::fingerprint::Fingerprint;
+use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_hir::lang_items;
-use rustc_middle::mir::interpret::Scalar;
-use rustc_middle::mir::*;
+use rustc_middle::hir;
+use rustc_middle::ich::StableHashingContext;
+use rustc_middle::mir::interpret::{ConstValue, Scalar};
+use rustc_middle::mir::{
+    self, traversal, BasicBlock, BasicBlockData, CoverageData, Operand, Place, SourceInfo,
+    StatementKind, Terminator, TerminatorKind, START_BLOCK,
+};
 use rustc_middle::ty;
+use rustc_middle::ty::query::Providers;
 use rustc_middle::ty::TyCtxt;
+use rustc_middle::ty::{ConstKind, FnDef};
 use rustc_span::def_id::DefId;
 use rustc_span::Span;
 
@@ -12,64 +21,139 @@ use rustc_span::Span;
 /// the intrinsic llvm.instrprof.increment.
 pub struct InstrumentCoverage;
 
+/// The `query` provider for `CoverageData`, requested by `codegen_intrinsic_call()` when
+/// constructing the arguments for `llvm.instrprof.increment`.
+pub(crate) fn provide(providers: &mut Providers<'_>) {
+    providers.coverage_data = |tcx, def_id| {
+        let mir_body = tcx.optimized_mir(def_id);
+        // FIXME(richkadel): The current implementation assumes the MIR for the given DefId
+        // represents a single function. Validate and/or correct if inlining and/or monomorphization
+        // invalidates these assumptions.
+        let count_code_region_fn =
+            tcx.require_lang_item(lang_items::CountCodeRegionFnLangItem, None);
+        let mut num_counters: u32 = 0;
+        // The `num_counters` argument to `llvm.instrprof.increment` is the number of injected
+        // counters, with each counter having an index from `0..num_counters-1`. MIR optimization
+        // may split and duplicate some BasicBlock sequences. Simply counting the calls may not
+        // not work; but computing the num_counters by adding `1` to the highest index (for a given
+        // instrumented function) is valid.
+        for (_, data) in traversal::preorder(mir_body) {
+            if let Some(terminator) = &data.terminator {
+                if let TerminatorKind::Call { func: Operand::Constant(func), args, .. } =
+                    &terminator.kind
+                {
+                    if let FnDef(called_fn_def_id, _) = func.literal.ty.kind {
+                        if called_fn_def_id == count_code_region_fn {
+                            if let Operand::Constant(constant) =
+                                args.get(0).expect("count_code_region has at least one arg")
+                            {
+                                if let ConstKind::Value(ConstValue::Scalar(value)) =
+                                    constant.literal.val
+                                {
+                                    let index = value
+                                        .to_u32()
+                                        .expect("count_code_region index at arg0 is u32");
+                                    num_counters = std::cmp::max(num_counters, index + 1);
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+        let hash = if num_counters > 0 { hash_mir_source(tcx, def_id) } else { 0 };
+        CoverageData { num_counters, hash }
+    };
+}
+
+struct Instrumentor<'tcx> {
+    tcx: TyCtxt<'tcx>,
+    num_counters: u32,
+}
+
 impl<'tcx> MirPass<'tcx> for InstrumentCoverage {
-    fn run_pass(&self, tcx: TyCtxt<'tcx>, src: MirSource<'tcx>, body: &mut Body<'tcx>) {
+    fn run_pass(&self, tcx: TyCtxt<'tcx>, src: MirSource<'tcx>, mir_body: &mut mir::Body<'tcx>) {
         if tcx.sess.opts.debugging_opts.instrument_coverage {
-            debug!("instrumenting {:?}", src.def_id());
-            instrument_coverage(tcx, body);
+            // If the InstrumentCoverage pass is called on promoted MIRs, skip them.
+            // See: https://github.com/rust-lang/rust/pull/73011#discussion_r438317601
+            if src.promoted.is_none() {
+                debug!(
+                    "instrumenting {:?}, span: {}",
+                    src.def_id(),
+                    tcx.sess.source_map().span_to_string(mir_body.span)
+                );
+                Instrumentor::new(tcx).inject_counters(mir_body);
+            }
         }
     }
 }
 
-// The first counter (start of the function) is index zero.
-const INIT_FUNCTION_COUNTER: u32 = 0;
-
-/// Injects calls to placeholder function `count_code_region()`.
-// FIXME(richkadel): As a first step, counters are only injected at the top of each function.
-// The complete solution will inject counters at each conditional code branch.
-pub fn instrument_coverage<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
-    let span = body.span.shrink_to_lo();
-
-    let count_code_region_fn = function_handle(
-        tcx,
-        tcx.require_lang_item(lang_items::CountCodeRegionFnLangItem, None),
-        span,
-    );
-    let counter_index = Operand::const_from_scalar(
-        tcx,
-        tcx.types.u32,
-        Scalar::from_u32(INIT_FUNCTION_COUNTER),
-        span,
-    );
-
-    let mut patch = MirPatch::new(body);
-
-    let new_block = patch.new_block(placeholder_block(SourceInfo::outermost(body.span)));
-    let next_block = START_BLOCK;
-
-    let temp = patch.new_temp(tcx.mk_unit(), body.span);
-    patch.patch_terminator(
-        new_block,
-        TerminatorKind::Call {
-            func: count_code_region_fn,
-            args: vec![counter_index],
-            // new_block will swapped with the next_block, after applying patch
-            destination: Some((Place::from(temp), new_block)),
-            cleanup: None,
-            from_hir_call: false,
-            fn_span: span,
-        },
-    );
-
-    patch.add_statement(new_block.start_location(), StatementKind::StorageLive(temp));
-    patch.add_statement(next_block.start_location(), StatementKind::StorageDead(temp));
-
-    patch.apply(body);
-
-    // To insert the `new_block` in front of the first block in the counted branch (for example,
-    // the START_BLOCK, at the top of the function), just swap the indexes, leaving the rest of the
-    // graph unchanged.
-    body.basic_blocks_mut().swap(next_block, new_block);
+impl<'tcx> Instrumentor<'tcx> {
+    fn new(tcx: TyCtxt<'tcx>) -> Self {
+        Self { tcx, num_counters: 0 }
+    }
+
+    fn next_counter(&mut self) -> u32 {
+        let next = self.num_counters;
+        self.num_counters += 1;
+        next
+    }
+
+    fn inject_counters(&mut self, mir_body: &mut mir::Body<'tcx>) {
+        // FIXME(richkadel): As a first step, counters are only injected at the top of each
+        // function. The complete solution will inject counters at each conditional code branch.
+        let top_of_function = START_BLOCK;
+        let entire_function = mir_body.span;
+
+        self.inject_counter(mir_body, top_of_function, entire_function);
+    }
+
+    fn inject_counter(
+        &mut self,
+        mir_body: &mut mir::Body<'tcx>,
+        next_block: BasicBlock,
+        code_region: Span,
+    ) {
+        let injection_point = code_region.shrink_to_lo();
+
+        let count_code_region_fn = function_handle(
+            self.tcx,
+            self.tcx.require_lang_item(lang_items::CountCodeRegionFnLangItem, None),
+            injection_point,
+        );
+        let counter_index = Operand::const_from_scalar(
+            self.tcx,
+            self.tcx.types.u32,
+            Scalar::from_u32(self.next_counter()),
+            injection_point,
+        );
+
+        let mut patch = MirPatch::new(mir_body);
+
+        let temp = patch.new_temp(self.tcx.mk_unit(), code_region);
+        let new_block = patch.new_block(placeholder_block(code_region));
+        patch.patch_terminator(
+            new_block,
+            TerminatorKind::Call {
+                func: count_code_region_fn,
+                args: vec![counter_index],
+                // new_block will swapped with the next_block, after applying patch
+                destination: Some((Place::from(temp), new_block)),
+                cleanup: None,
+                from_hir_call: false,
+                fn_span: injection_point,
+            },
+        );
+
+        patch.add_statement(new_block.start_location(), StatementKind::StorageLive(temp));
+        patch.add_statement(next_block.start_location(), StatementKind::StorageDead(temp));
+
+        patch.apply(mir_body);
+
+        // To insert the `new_block` in front of the first block in the counted branch (the
+        // `next_block`), just swap the indexes, leaving the rest of the graph unchanged.
+        mir_body.basic_blocks_mut().swap(next_block, new_block);
+    }
 }
 
 fn function_handle<'tcx>(tcx: TyCtxt<'tcx>, fn_def_id: DefId, span: Span) -> Operand<'tcx> {
@@ -79,14 +163,31 @@ fn function_handle<'tcx>(tcx: TyCtxt<'tcx>, fn_def_id: DefId, span: Span) -> Ope
     Operand::function_handle(tcx, fn_def_id, substs, span)
 }
 
-fn placeholder_block<'tcx>(source_info: SourceInfo) -> BasicBlockData<'tcx> {
+fn placeholder_block(span: Span) -> BasicBlockData<'tcx> {
     BasicBlockData {
         statements: vec![],
         terminator: Some(Terminator {
-            source_info,
+            source_info: SourceInfo::outermost(span),
             // this gets overwritten by the counter Call
             kind: TerminatorKind::Unreachable,
         }),
         is_cleanup: false,
     }
 }
+
+fn hash_mir_source<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> u64 {
+    let hir_node = tcx.hir().get_if_local(def_id).expect("DefId is local");
+    let fn_body_id = hir::map::associated_body(hir_node).expect("HIR node is a function with body");
+    let hir_body = tcx.hir().body(fn_body_id);
+    let mut hcx = tcx.create_no_span_stable_hashing_context();
+    hash(&mut hcx, &hir_body.value).to_smaller_hash()
+}
+
+fn hash(
+    hcx: &mut StableHashingContext<'tcx>,
+    node: &impl HashStable<StableHashingContext<'tcx>>,
+) -> Fingerprint {
+    let mut stable_hasher = StableHasher::new();
+    node.hash_stable(hcx, &mut stable_hasher);
+    stable_hasher.finish()
+}
diff --git a/src/librustc_mir/transform/mod.rs b/src/librustc_mir/transform/mod.rs
index 846ed1f86d8..8ca240d2c7d 100644
--- a/src/librustc_mir/transform/mod.rs
+++ b/src/librustc_mir/transform/mod.rs
@@ -56,6 +56,7 @@ pub(crate) fn provide(providers: &mut Providers<'_>) {
         promoted_mir,
         ..*providers
     };
+    instrument_coverage::provide(providers);
 }
 
 fn is_mir_available(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
diff --git a/src/librustc_session/options.rs b/src/librustc_session/options.rs
index 6c6f27502b6..973891eb84e 100644
--- a/src/librustc_session/options.rs
+++ b/src/librustc_session/options.rs
@@ -880,8 +880,9 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
         (such as entering an empty infinite loop) by inserting llvm.sideeffect \
         (default: no)"),
     instrument_coverage: bool = (false, parse_bool, [TRACKED],
-        "instrument the generated code with LLVM code region counters to \
-        (in the future) generate coverage reports (experimental; default: no)"),
+        "instrument the generated code with LLVM code region counters to (in the \
+        future) generate coverage reports (default: no; note, the compiler build \
+        config must include `profiler = true`)"),
     instrument_mcount: bool = (false, parse_bool, [TRACKED],
         "insert function instrument code for mcount-based tracing (default: no)"),
     keep_hygiene_data: bool = (false, parse_bool, [UNTRACKED],
diff --git a/src/librustc_span/symbol.rs b/src/librustc_span/symbol.rs
index 06d1f36622b..5b1bafe3955 100644
--- a/src/librustc_span/symbol.rs
+++ b/src/librustc_span/symbol.rs
@@ -587,6 +587,7 @@ symbols! {
         proc_macro_mod,
         proc_macro_non_items,
         proc_macro_path_invoc,
+        profiler_builtins,
         profiler_runtime,
         ptr_guaranteed_eq,
         ptr_guaranteed_ne,