Stabilize -Z symbol-mangling-version as -C symbol-mangling-version

This allows selecting `v0` symbol-mangling without an unstable option.
Selecting `legacy` still requires -Z unstable-options.

Continue supporting -Z symbol-mangling-version for compatibility for
now, but show a deprecation warning for it.

Author: joshtriplett

Diff for: compiler/rustc_interface/src/tests.rs

@@ -594,6 +594,7 @@ fn test_codegen_options_tracking_hash() {
     tracked!(relocation_model, Some(RelocModel::Pic));
     tracked!(soft_float, true);
     tracked!(split_debuginfo, Some(SplitDebuginfo::Packed));
+    tracked!(symbol_mangling_version, Some(SymbolManglingVersion::V0));
     tracked!(target_cpu, Some(String::from("abc")));
     tracked!(target_feature, String::from("all the features, all of them"));
 }

Diff for: compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -721,7 +721,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
             no_builtins: tcx.sess.contains_name(&attrs, sym::no_builtins),
             panic_runtime: tcx.sess.contains_name(&attrs, sym::panic_runtime),
             profiler_runtime: tcx.sess.contains_name(&attrs, sym::profiler_runtime),
-            symbol_mangling_version: tcx.sess.opts.debugging_opts.get_symbol_mangling_version(),
+            symbol_mangling_version: tcx.sess.opts.get_symbol_mangling_version(),
 
             crate_deps,
             dylib_dependency_formats,

Diff for: compiler/rustc_session/src/config.rs

@@ -781,6 +781,10 @@ impl Options {
             },
         }
     }
+
+    pub fn get_symbol_mangling_version(&self) -> SymbolManglingVersion {
+        self.cg.symbol_mangling_version.unwrap_or(SymbolManglingVersion::Legacy)
+    }
 }
 
 impl DebuggingOptions {
@@ -794,10 +798,6 @@ impl DebuggingOptions {
             deduplicate_diagnostics: self.deduplicate_diagnostics,
         }
     }
-
-    pub fn get_symbol_mangling_version(&self) -> SymbolManglingVersion {
-        self.symbol_mangling_version.unwrap_or(SymbolManglingVersion::Legacy)
-    }
 }
 
 // The type of entry function, so users can have their own entry functions
@@ -2116,6 +2116,34 @@ pub fn build_session_options(matches: &getopts::Matches) -> Options {
         );
     }
 
+    // Handle both `-Z symbol-mangling-version` and `-C symbol-mangling-version`; the latter takes
+    // precedence.
+    match (cg.symbol_mangling_version, debugging_opts.symbol_mangling_version) {
+        (Some(smv_c), Some(smv_z)) if smv_c != smv_z => {
+            early_error(
+                error_format,
+                "incompatible values passed for `-C symbol-mangling-version` \
+                and `-Z symbol-mangling-version`",
+            );
+        }
+        (Some(SymbolManglingVersion::V0), _) => {}
+        (Some(_), _) if !debugging_opts.unstable_options => {
+            early_error(
+                error_format,
+                "`-C symbol-mangling-version=legacy` requires `-Z unstable-options`",
+            );
+        }
+        (None, None) => {}
+        (None, smv) => {
+            early_warn(
+                error_format,
+                "`-Z symbol-mangling-version` is deprecated; use `-C symbol-mangling-version`",
+            );
+            cg.symbol_mangling_version = smv;
+        }
+        _ => {}
+    }
+
     if debugging_opts.instrument_coverage.is_some()
         && debugging_opts.instrument_coverage != Some(InstrumentCoverage::Off)
     {
@@ -2127,19 +2155,17 @@ pub fn build_session_options(matches: &getopts::Matches) -> Options {
             );
         }
 
-        // `-Z instrument-coverage` implies `-Z symbol-mangling-version=v0` - to ensure consistent
+        // `-Z instrument-coverage` implies `-C symbol-mangling-version=v0` - to ensure consistent
         // and reversible name mangling. Note, LLVM coverage tools can analyze coverage over
         // multiple runs, including some changes to source code; so mangled names must be consistent
         // across compilations.
-        match debugging_opts.symbol_mangling_version {
-            None => {
-                debugging_opts.symbol_mangling_version = Some(SymbolManglingVersion::V0);
-            }
+        match cg.symbol_mangling_version {
+            None => cg.symbol_mangling_version = Some(SymbolManglingVersion::V0),
             Some(SymbolManglingVersion::Legacy) => {
                 early_warn(
                     error_format,
                     "-Z instrument-coverage requires symbol mangling version `v0`, \
-                    but `-Z symbol-mangling-version=legacy` was specified",
+                    but `-C symbol-mangling-version=legacy` was specified",
                 );
             }
             Some(SymbolManglingVersion::V0) => {}

Diff for: compiler/rustc_session/src/options.rs

@@ -1083,6 +1083,9 @@ options! {
         "how to handle split-debuginfo, a platform-specific option"),
     strip: Strip = (Strip::None, parse_strip, [UNTRACKED],
         "tell the linker which information to strip (`none` (default), `debuginfo` or `symbols`)"),
+    symbol_mangling_version: Option<SymbolManglingVersion> = (None,
+        parse_symbol_mangling_version, [TRACKED],
+        "which mangling version to use for symbol names ('legacy' (default) or 'v0')"),
     target_cpu: Option<String> = (None, parse_opt_string, [TRACKED],
         "select target processor (`rustc --print target-cpus` for details)"),
     target_feature: String = (String::new(), parse_target_feature, [TRACKED],

Diff for: compiler/rustc_symbol_mangling/src/lib.rs

@@ -245,7 +245,7 @@ fn compute_symbol_name<'tcx>(
     // 2. we favor `instantiating_crate` where possible (i.e. when `Some`)
     let mangling_version_crate = instantiating_crate.unwrap_or(def_id.krate);
     let mangling_version = if mangling_version_crate == LOCAL_CRATE {
-        tcx.sess.opts.debugging_opts.get_symbol_mangling_version()
+        tcx.sess.opts.get_symbol_mangling_version()
     } else {
         tcx.symbol_mangling_version(mangling_version_crate)
     };