Add -Zinstrument-mcount-opts

This facilitates support for inserting nop's and/or recording the
location of each mcount call in a special section named `__mcount_loc`.

Author: pmur

compiler/rustc_codegen_llvm/src/attributes.rs

@@ -229,6 +229,13 @@ fn instrument_function_attr<'ll>(
         if instrument_entry && sess.opts.unstable_opts.instrument_fentry {
             attrs.push(llvm::CreateAttrStringValue(cx.llcx, "fentry-call", "true"));
         }
+
+        if sess.opts.unstable_opts.instrument_mcount_opts.no_call {
+            attrs.push(llvm::CreateAttrString(cx.llcx, "mnop-mcount"));
+        }
+        if sess.opts.unstable_opts.instrument_mcount_opts.record {
+            attrs.push(llvm::CreateAttrString(cx.llcx, "mrecord-mcount"));
+        }
     }
     if let Some(options) = &sess.opts.unstable_opts.instrument_xray {
         // XRay instrumentation is similar to __cyg_profile_func_{enter,exit}.

compiler/rustc_session/src/config.rs

@@ -246,6 +246,15 @@ pub enum AnnotateMoves {
     Enabled(Option<u64>),
 }
 
+/// Settings for `-Z instrument-mcount-opts` flag.
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, Hash)]
+pub struct InstrumentMcountOpts {
+    // Insert a nop which could be replaced by an mcount call.
+    pub no_call: bool,
+    // Record the location of the call instrument in a special linker section.
+    pub record: bool,
+}
+
 /// Settings for `-Z instrument-xray` flag.
 #[derive(Clone, Copy, Debug, Default, PartialEq, Eq, Hash)]
 pub struct InstrumentXRay {
@@ -3050,10 +3059,11 @@ pub(crate) mod dep_tracking {
     use super::{
         AnnotateMoves, AutoDiff, BranchProtection, CFGuard, CFProtection, CoverageOptions,
         CrateType, DebugInfo, DebugInfoCompression, ErrorOutputType, FmtDebug, FunctionReturn,
-        InliningThreshold, InstrumentCoverage, InstrumentXRay, LinkerPluginLto, LocationDetail,
-        LtoCli, MirStripDebugInfo, NextSolverConfig, Offload, OptLevel, OutFileName, OutputType,
-        OutputTypes, PatchableFunctionEntry, Polonius, ResolveDocLinks, SourceFileHashAlgorithm,
-        SplitDwarfKind, SwitchWithOptPath, SymbolManglingVersion, WasiExecModel,
+        InliningThreshold, InstrumentCoverage, InstrumentMcountOpts, InstrumentXRay,
+        LinkerPluginLto, LocationDetail, LtoCli, MirStripDebugInfo, NextSolverConfig, Offload,
+        OptLevel, OutFileName, OutputType, OutputTypes, PatchableFunctionEntry, Polonius,
+        ResolveDocLinks, SourceFileHashAlgorithm, SplitDwarfKind, SwitchWithOptPath,
+        SymbolManglingVersion, WasiExecModel,
     };
     use crate::lint;
     use crate::utils::NativeLib;
@@ -3115,6 +3125,7 @@ pub(crate) mod dep_tracking {
         TlsModel,
         InstrumentCoverage,
         CoverageOptions,
+        InstrumentMcountOpts,
         InstrumentXRay,
         CrateType,
         MergeFunctions,

compiler/rustc_session/src/options.rs

@@ -783,6 +783,8 @@ mod desc {
     pub(crate) const parse_dump_mono_stats: &str = "`markdown` (default) or `json`";
     pub(crate) const parse_instrument_coverage: &str = parse_bool;
     pub(crate) const parse_coverage_options: &str = "`block` | `branch` | `condition`";
+    pub(crate) const parse_instrument_mcount_opts: &str =
+        "a comma separated list of options: `call`,`no-call`,`record`,`no-record`.";
     pub(crate) const parse_instrument_xray: &str = "either a boolean (`yes`, `no`, `on`, `off`, etc), or a comma separated list of settings: `always` or `never` (mutually exclusive), `ignore-loops`, `instruction-threshold=N`, `skip-entry`, `skip-exit`";
     pub(crate) const parse_unpretty: &str = "`string` or `string=string`";
     pub(crate) const parse_treat_err_as_bug: &str = "either no value or a non-negative number";
@@ -1538,6 +1540,32 @@ pub mod parse {
         true
     }
 
+    pub(crate) fn parse_instrument_mcount_opts(
+        slot: &mut InstrumentMcountOpts,
+        v: Option<&str>,
+    ) -> bool {
+        for option in v.into_iter().flat_map(|v| v.split(',')) {
+            match option {
+                "no-call" => {
+                    slot.no_call = true;
+                }
+                "call" => {
+                    slot.no_call = false;
+                }
+                "no-record" => {
+                    slot.record = false;
+                }
+                "record" => {
+                    slot.record = true;
+                }
+                _ => {
+                    return false;
+                }
+            }
+        }
+        v.is_some()
+    }
+
     pub(crate) fn parse_instrument_xray(
         slot: &mut Option<InstrumentXRay>,
         v: Option<&str>,
@@ -2396,6 +2424,12 @@ options! {
         "insert function instrument code for fentry-based tracing (default: no)"),
     instrument_mcount: bool = (false, parse_bool, [TRACKED],
         "insert function instrument code for mcount-based tracing (default: no)"),
+    instrument_mcount_opts: InstrumentMcountOpts = (InstrumentMcountOpts::default(), parse_instrument_mcount_opts, [TRACKED],
+        "mcount instrumentation configuration options (default: `call,no-record`).
+         Optional extra settings:
+         `=call` or `=no-call`
+         `=no-record` or `=record`
+         Multiple options can be combined with commas."),
     instrument_xray: Option<InstrumentXRay> = (None, parse_instrument_xray, [TRACKED],
         "insert function instrument code for XRay-based tracing (default: no)
          Optional extra settings:

tests/codegen-llvm/instrument-mcount-opts.rs

@@ -0,0 +1,31 @@
+//@ revisions: dflt ncyr ycnr ncnr ycyr
+//@ add-minicore
+//@ needs-llvm-components: systemz
+//@ compile-flags: -Zinstrument-fentry=y -Copt-level=0 --target=s390x-unknown-linux-gnu
+//@[ncyr] compile-flags: -Zinstrument-mcount-opts=no-call,record
+//@[ncnr] compile-flags: -Zinstrument-mcount-opts=no-call,no-record
+//@[ycnr] compile-flags: -Zinstrument-mcount-opts=call,no-record
+//@[ycyr] compile-flags: -Zinstrument-mcount-opts=call,record
+#![feature(no_core)]
+#![crate_type = "rlib"]
+#![no_core]
+
+extern crate minicore;
+use minicore::*;
+
+// dflt: attributes #{{.*}} {{.*}} "fentry-call"="true"
+// dflt-NOT: attributes #{{.*}} {{.*}} "mnop-mcount"
+// dflt-NOT: attributes #{{.*}} {{.*}} "mrecord-mcount"
+//
+// ncyr: attributes #{{.*}} {{.*}} "fentry-call"="true" "mnop-mcount" "mrecord-mcount"
+//
+// ncnr: attributes #{{.*}} {{.*}} "fentry-call"="true" "mnop-mcount"
+// ncnr-NOT: attributes #{{.*}} {{.*}} "mrecord-mcount"
+//
+// ycnr: attributes #{{.*}} {{.*}} "fentry-call"="true"
+// ycnr-NOT: attributes #{{.*}} {{.*}} "mnop-mcount"
+// ycnr-NOT: attributes #{{.*}} {{.*}} "mrecord-mcount"
+//
+// ycyr: attributes #{{.*}} {{.*}} "fentry-call"="true" "mrecord-mcount"
+// ycyr-NOT: attributes #{{.*}} {{.*}} "mnop-mcount"
+pub fn foo() {}