Infer nounwind and use it in MIR opts

Author: saethlin

compiler/rustc_interface/src/passes.rs

@@ -931,7 +931,7 @@ fn run_required_analyses(tcx: TyCtxt<'_>) {
     });
     sess.time("MIR_effect_checking", || {
         tcx.par_hir_body_owners(|def_id| {
-            tcx.ensure_ok().has_ffi_unwind_calls(def_id);
+            tcx.ensure_ok().mir_flags(def_id);
 
             // If we need to codegen, ensure that we emit all errors from
             // `mir_drops_elaborated_and_const_checked` now, to avoid discovering

compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs

@@ -347,6 +347,7 @@ provide! { tcx, def_id, other, cdata,
     is_mir_available => { cdata.is_item_mir_available(def_id.index) }
     is_ctfe_mir_available => { cdata.is_ctfe_mir_available(def_id.index) }
     cross_crate_inlinable => { table_direct }
+    mir_flags => { table_direct }
 
     dylib_dependency_formats => { cdata.get_dylib_dependency_formats(tcx) }
     is_private_dep => { cdata.private_dep }

compiler/rustc_metadata/src/rmeta/mod.rs

@@ -26,6 +26,7 @@ use rustc_middle::middle::debugger_visualizer::DebuggerVisualizerFile;
 use rustc_middle::middle::exported_symbols::{ExportedSymbol, SymbolExportInfo};
 use rustc_middle::middle::lib_features::FeatureStability;
 use rustc_middle::middle::resolve_bound_vars::ObjectLifetimeDefault;
+use rustc_middle::mir::MirFlags;
 use rustc_middle::ty::fast_reject::SimplifiedType;
 use rustc_middle::ty::{
     self, DeducedParamAttrs, ParameterizedOverTcx, Ty, TyCtxt, UnusedGenericParams,
@@ -402,6 +403,7 @@ define_tables! {
     // individually instead of `DefId`s.
     module_children_reexports: Table<DefIndex, LazyArray<ModChild>>,
     cross_crate_inlinable: Table<DefIndex, bool>,
+    mir_flags: Table<DefIndex, MirFlags>,
 
 - optional:
     attributes: Table<DefIndex, LazyArray<hir::Attribute>>,

compiler/rustc_metadata/src/rmeta/table.rs

@@ -53,6 +53,12 @@ impl IsDefault for UnusedGenericParams {
     }
 }
 
+impl IsDefault for MirFlags {
+    fn is_default(&self) -> bool {
+        *self == Self::default()
+    }
+}
+
 /// Helper trait, for encoding to, and decoding from, a fixed number of bytes.
 /// Used mainly for Lazy positions and lengths.
 /// Unchecked invariant: `Self::default()` should encode as `[0; BYTE_LEN]`,
@@ -291,6 +297,21 @@ impl FixedSizeEncoding for AttrFlags {
     }
 }
 
+impl FixedSizeEncoding for MirFlags {
+    type ByteArray = [u8; 1];
+
+    #[inline]
+    fn from_bytes(b: &[u8; 1]) -> Self {
+        MirFlags::from_bits_truncate(b[0])
+    }
+
+    #[inline]
+    fn write_to_bytes(self, b: &mut [u8; 1]) {
+        debug_assert!(!self.is_default());
+        b[0] = self.bits();
+    }
+}
+
 impl FixedSizeEncoding for bool {
     type ByteArray = [u8; 1];
 

compiler/rustc_middle/src/mir/mod.rs

@@ -1743,6 +1743,16 @@ pub fn find_self_call<'tcx>(
     None
 }
 
+#[derive(Copy, Clone, Debug, Default, PartialEq, Eq, TyEncodable, TyDecodable, HashStable)]
+pub struct MirFlags(u8);
+
+bitflags::bitflags! {
+    impl MirFlags: u8 {
+        const IS_NOUNWIND = 1 << 0;
+        const HAS_FFI_UNWIND_CALLS = 1 << 1;
+    }
+}
+
 // Some nodes are used a lot. Make sure they don't unintentionally get bigger.
 #[cfg(target_pointer_width = "64")]
 mod size_asserts {

compiler/rustc_middle/src/query/erase.rs

@@ -287,6 +287,7 @@ trivial! {
     rustc_middle::middle::resolve_bound_vars::ResolvedArg,
     rustc_middle::middle::stability::DeprecationEntry,
     rustc_middle::mir::ConstQualifs,
+    rustc_middle::mir::MirFlags,
     rustc_middle::mir::interpret::AllocId,
     rustc_middle::mir::interpret::CtfeProvenance,
     rustc_middle::mir::interpret::ErrorHandled,

compiler/rustc_middle/src/query/mod.rs

@@ -53,6 +53,7 @@ use crate::middle::lib_features::LibFeatures;
 use crate::middle::privacy::EffectiveVisibilities;
 use crate::middle::resolve_bound_vars::{ObjectLifetimeDefault, ResolveBoundVars, ResolvedArg};
 use crate::middle::stability::{self, DeprecationEntry};
+use crate::mir::MirFlags;
 use crate::mir::interpret::{
     EvalStaticInitializerRawResult, EvalToAllocationRawResult, EvalToConstValueResult,
     EvalToValTreeResult, GlobalId, LitToConstInput,
@@ -1681,9 +1682,10 @@ rustc_queries! {
         desc { "checking if a crate is `#![profiler_runtime]`" }
         separate_provide_extern
     }
-    query has_ffi_unwind_calls(key: LocalDefId) -> bool {
-        desc { |tcx| "checking if `{}` contains FFI-unwind calls", tcx.def_path_str(key) }
-        cache_on_disk_if { true }
+    query mir_flags(key: DefId) -> MirFlags {
+        desc { |tcx| "stashing some local properties of `{}` before the body is stolen", tcx.def_path_str(key) }
+        cache_on_disk_if { key.is_local() }
+        separate_provide_extern
     }
     query required_panic_strategy(_: CrateNum) -> Option<PanicStrategy> {
         fatal_cycle

compiler/rustc_middle/src/ty/context.rs

@@ -65,7 +65,7 @@ use crate::metadata::ModChild;
 use crate::middle::codegen_fn_attrs::{CodegenFnAttrs, TargetFeature};
 use crate::middle::{resolve_bound_vars, stability};
 use crate::mir::interpret::{self, Allocation, ConstAllocation};
-use crate::mir::{Body, Local, Place, PlaceElem, ProjectionKind, Promoted};
+use crate::mir::{Body, Local, MirFlags, Place, PlaceElem, ProjectionKind, Promoted};
 use crate::query::plumbing::QuerySystem;
 use crate::query::{IntoQueryParam, LocalCrate, Providers, TyCtxtAt};
 use crate::thir::Thir;
@@ -3283,6 +3283,14 @@ impl<'tcx> TyCtxt<'tcx> {
         }
     }
 
+    pub fn is_nounwind(self, def_id: DefId) -> bool {
+        self.mir_flags(def_id).contains(MirFlags::IS_NOUNWIND)
+    }
+
+    pub fn has_ffi_unwind_calls(self, def_id: DefId) -> bool {
+        self.mir_flags(def_id).contains(MirFlags::HAS_FFI_UNWIND_CALLS)
+    }
+
     /// Whether this is a trait implementation that has `#[diagnostic::do_not_recommend]`
     pub fn do_not_recommend_impl(self, def_id: DefId) -> bool {
         self.get_diagnostic_attr(def_id, sym::do_not_recommend).is_some()

compiler/rustc_middle/src/ty/parameterized.rs

@@ -100,6 +100,7 @@ trivially_parameterized_over_tcx! {
     rustc_hir::PreciseCapturingArgKind<Symbol, Symbol>,
     rustc_index::bit_set::DenseBitSet<u32>,
     rustc_index::bit_set::FiniteBitSet<u32>,
+    rustc_middle::mir::MirFlags,
     rustc_session::cstore::ForeignModule,
     rustc_session::cstore::LinkagePreference,
     rustc_session::cstore::NativeLib,

compiler/rustc_mir_transform/src/ffi_unwind_calls.rs

@@ -1,5 +1,5 @@
 use rustc_abi::ExternAbi;
-use rustc_hir::def_id::{LOCAL_CRATE, LocalDefId};
+use rustc_hir::def_id::LOCAL_CRATE;
 use rustc_middle::mir::*;
 use rustc_middle::query::{LocalCrate, Providers};
 use rustc_middle::ty::{self, TyCtxt, layout};
@@ -11,17 +11,10 @@ use tracing::debug;
 use crate::errors;
 
 // Check if the body of this def_id can possibly leak a foreign unwind into Rust code.
-fn has_ffi_unwind_calls(tcx: TyCtxt<'_>, local_def_id: LocalDefId) -> bool {
-    debug!("has_ffi_unwind_calls({local_def_id:?})");
+pub(crate) fn has_ffi_unwind_calls<'tcx>(tcx: TyCtxt<'tcx>, body: &Body<'tcx>) -> bool {
+    let def_id = body.source.def_id();
 
-    // Only perform check on functions because constants cannot call FFI functions.
-    let def_id = local_def_id.to_def_id();
-    let kind = tcx.def_kind(def_id);
-    if !kind.is_fn_like() {
-        return false;
-    }
-
-    let body = &*tcx.mir_built(local_def_id).borrow();
+    debug!("has_ffi_unwind_calls({def_id:?})");
 
     let body_ty = tcx.type_of(def_id).skip_binder();
     let body_abi = match body_ty.kind() {
@@ -110,7 +103,7 @@ fn required_panic_strategy(tcx: TyCtxt<'_>, _: LocalCrate) -> Option<PanicStrate
     }
 
     for def_id in tcx.hir_body_owners() {
-        if tcx.has_ffi_unwind_calls(def_id) {
+        if tcx.has_ffi_unwind_calls(def_id.into()) {
             // Given that this crate is compiled in `-C panic=unwind`, the `AbortUnwindingCalls`
             // MIR pass will not be run on FFI-unwind call sites, therefore a foreign exception
             // can enter Rust through these sites.
@@ -141,5 +134,5 @@ fn required_panic_strategy(tcx: TyCtxt<'_>, _: LocalCrate) -> Option<PanicStrate
 }
 
 pub(crate) fn provide(providers: &mut Providers) {
-    *providers = Providers { has_ffi_unwind_calls, required_panic_strategy, ..*providers };
+    *providers = Providers { required_panic_strategy, ..*providers };
 }