Infer nounwind and use it in MIR opts

Author: saethlin

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

@@ -352,6 +352,7 @@ 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 }
+    is_nounwind => { table_direct }
 
     dylib_dependency_formats => { cdata.get_dylib_dependency_formats(tcx) }
     is_private_dep => { cdata.private_dep }

compiler/rustc_metadata/src/rmeta/mod.rs

@@ -404,6 +404,7 @@ define_tables! {
     // individually instead of `DefId`s.
     module_children_reexports: Table<DefIndex, LazyArray<ModChild>>,
     cross_crate_inlinable: Table<DefIndex, bool>,
+    is_nounwind: Table<DefIndex, bool>,
 
 - optional:
     attributes: Table<DefIndex, LazyArray<ast::Attribute>>,

compiler/rustc_middle/src/query/mod.rs

@@ -1499,6 +1499,10 @@ rustc_queries! {
         desc { |tcx| "checking if `{}` contains FFI-unwind calls", tcx.def_path_str(key) }
         cache_on_disk_if { true }
     }
+    query is_nounwind(key: DefId) -> bool {
+        desc { |tcx| "checking if `{}` contains unwinds", tcx.def_path_str(key) }
+        separate_provide_extern
+    }
     query required_panic_strategy(_: CrateNum) -> Option<PanicStrategy> {
         fatal_cycle
         desc { "getting a crate's required panic strategy" }

compiler/rustc_mir_transform/src/instsimplify.rs

@@ -326,7 +326,9 @@ impl<'tcx> InstSimplifyContext<'_, 'tcx> {
             _ => bug!("unexpected body ty: {:?}", body_ty),
         };
 
-        if !layout::fn_can_unwind(self.tcx, Some(def_id), body_abi) {
+        if !layout::fn_can_unwind(self.tcx, Some(def_id), body_abi)
+            || (self.tcx.sess.opts.incremental.is_none() && self.tcx.is_nounwind(def_id))
+        {
             *unwind = UnwindAction::Unreachable;
         }
     }

compiler/rustc_mir_transform/src/lib.rs

@@ -134,6 +134,7 @@ pub fn provide(providers: &mut Providers) {
         promoted_mir,
         deduced_param_attrs: deduce_param_attrs::deduced_param_attrs,
         coroutine_by_move_body_def_id: coroutine::coroutine_by_move_body_def_id,
+        is_nounwind,
         ..providers.queries
     };
 }
@@ -338,6 +339,8 @@ fn mir_promoted(
         tcx.ensure_with_value().coroutine_by_move_body_def_id(def);
     }
 
+    tcx.ensure_with_value().is_nounwind(def);
+
     let mut body = tcx.mir_built(def).steal();
     if let Some(error_reported) = const_qualifs.tainted_by_errors {
         body.tainted_by_errors = Some(error_reported);
@@ -360,6 +363,24 @@ fn mir_promoted(
     (tcx.alloc_steal_mir(body), tcx.alloc_steal_promoted(promoted))
 }
 
+fn is_nounwind<'tcx>(tcx: TyCtxt<'tcx>, local_def_id: LocalDefId) -> bool {
+    if !tcx.is_mir_available(local_def_id) {
+        return false;
+    }
+
+    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();
+    if body.basic_blocks.iter().all(|block| block.terminator().unwind().is_none()) {
+        return true;
+    }
+    false
+}
+
 /// Compute the MIR that is used during CTFE (and thus has no optimizations run on it)
 fn mir_for_ctfe(tcx: TyCtxt<'_>, def_id: LocalDefId) -> &Body<'_> {
     tcx.arena.alloc(inner_mir_for_ctfe(tcx, def_id))

tests/codegen/drop.rs

@@ -23,7 +23,7 @@ pub fn droppy() {
     // FIXME(eddyb) the `void @` forces a match on the instruction, instead of the
     // comment, that's `; call core::ptr::drop_in_place::<drop::SomeUniqueName>`
     // for the `v0` mangling, should switch to matching on that once `legacy` is gone.
-    // CHECK-COUNT-6: {{(call|invoke) void @.*}}drop_in_place{{.*}}SomeUniqueName
+    // CHECK-COUNT-5: {{(call|invoke) void @.*}}drop_in_place{{.*}}SomeUniqueName
     // CHECK-NOT: {{(call|invoke) void @.*}}drop_in_place{{.*}}SomeUniqueName
     // The next line checks for the } that ends the function definition
     // CHECK-LABEL: {{^[}]}}

tests/codegen/personality_lifetimes.rs

@@ -13,7 +13,9 @@ impl Drop for S {
 }
 
 #[inline(never)]
-fn might_unwind() {}
+fn might_unwind() {
+    panic!()
+}
 
 // CHECK-LABEL: @test
 #[no_mangle]

tests/mir-opt/inline/caller_with_trivial_bound.foo.Inline.panic-unwind.diff

@@ -10,7 +10,7 @@
 
       bb0: {
           StorageLive(_1);
-          _1 = bar::<T>() -> [return: bb1, unwind continue];
+          _1 = bar::<T>() -> [return: bb1, unwind unreachable];
       }
 
       bb1: {

tests/mir-opt/inline/inline_coroutine.main.Inline.panic-unwind.diff

@@ -31,7 +31,7 @@
           StorageLive(_2);
           StorageLive(_3);
           StorageLive(_4);
--         _4 = g() -> [return: bb1, unwind continue];
+-         _4 = g() -> [return: bb1, unwind unreachable];
 +         _4 = {coroutine@$DIR/inline_coroutine.rs:20:5: 20:8 (#0)};
 +         _3 = &mut _4;
 +         _2 = Pin::<&mut {coroutine@$DIR/inline_coroutine.rs:20:5: 20:8}> { __pointer: copy _3 };

tests/mir-opt/inline/inline_options.main.Inline.after.panic-unwind.mir

@@ -21,7 +21,7 @@ fn main() -> () {
         StorageLive(_3);
         StorageLive(_4);
         StorageLive(_5);
-        _3 = g() -> [return: bb3, unwind continue];
+        _3 = g() -> [return: bb3, unwind unreachable];
     }
 
     bb2: {
@@ -34,10 +34,10 @@ fn main() -> () {
     }
 
     bb3: {
-        _4 = g() -> [return: bb4, unwind continue];
+        _4 = g() -> [return: bb4, unwind unreachable];
     }
 
     bb4: {
-        _5 = g() -> [return: bb2, unwind continue];
+        _5 = g() -> [return: bb2, unwind unreachable];
     }
 }

tests/mir-opt/inline/inline_trait_method.test.Inline.after.panic-unwind.mir

@@ -8,7 +8,7 @@ fn test(_1: &dyn X) -> u32 {
     bb0: {
         StorageLive(_2);
         _2 = copy _1;
-        _0 = <dyn X as X>::y(move _2) -> [return: bb1, unwind continue];
+        _0 = <dyn X as X>::y(move _2) -> [return: bb1, unwind unreachable];
     }
 
     bb1: {

tests/mir-opt/inline/inline_trait_method_2.test2.Inline.after.panic-unwind.mir

@@ -15,7 +15,7 @@ fn test2(_1: &dyn X) -> bool {
         _3 = copy _1;
         _2 = move _3;
         StorageDead(_3);
-        _0 = <dyn X as X>::y(move _2) -> [return: bb1, unwind continue];
+        _0 = <dyn X as X>::y(move _2) -> [return: bb1, unwind unreachable];
     }
 
     bb1: {

tests/mir-opt/inline/issue_78442.bar.Inline.panic-unwind.diff

@@ -15,7 +15,7 @@
           StorageLive(_2);
           StorageLive(_3);
           StorageLive(_4);
--         _4 = hide_foo() -> [return: bb1, unwind: bb4];
+-         _4 = hide_foo() -> [return: bb1, unwind unreachable];
 -     }
 - 
 -     bb1: {

tests/mir-opt/inline/rustc_no_mir_inline.caller.Inline.panic-unwind.diff

@@ -7,7 +7,7 @@
 
       bb0: {
           StorageLive(_1);
-          _1 = callee() -> [return: bb1, unwind continue];
+          _1 = callee() -> [return: bb1, unwind unreachable];
       }
 
       bb1: {

tests/mir-opt/inline/rustc_no_mir_inline.caller.PreCodegen.after.panic-unwind.mir

@@ -5,7 +5,7 @@ fn caller() -> () {
     let _1: ();
 
     bb0: {
-        _1 = callee() -> [return: bb1, unwind continue];
+        _1 = callee() -> [return: bb1, unwind unreachable];
     }
 
     bb1: {

tests/mir-opt/inline/unsized_argument.caller.Inline.diff

@@ -13,7 +13,7 @@
           StorageLive(_3);
           _3 = move _1;
           _4 = copy (((_3.0: std::ptr::Unique<[i32]>).0: std::ptr::NonNull<[i32]>).0: *const [i32]);
-          _2 = callee(move (*_4)) -> [return: bb1, unwind: bb3];
+          _2 = callee(move (*_4)) -> [return: bb1, unwind unreachable];
       }
 
       bb1: {

tests/mir-opt/simplify_if.main.SimplifyConstCondition-after-const-prop.panic-unwind.diff

@@ -11,7 +11,7 @@
       }
 
       bb1: {
-          _1 = noop() -> [return: bb2, unwind continue];
+          _1 = noop() -> [return: bb2, unwind unreachable];
       }
 
       bb2: {

tests/mir-opt/simplify_match.main.GVN.panic-unwind.diff

@@ -23,7 +23,7 @@
       }
 
       bb1: {
-          _0 = noop() -> [return: bb2, unwind continue];
+          _0 = noop() -> [return: bb2, unwind unreachable];
       }
 
       bb2: {

tests/ui/lint/unused/lint-unused-variables.stderr

@@ -1,8 +1,8 @@
 error: unused variable: `a`
-  --> $DIR/lint-unused-variables.rs:8:5
+  --> $DIR/lint-unused-variables.rs:68:9
    |
-LL |     a: i32,
-   |     ^ help: if this is intentional, prefix it with an underscore: `_a`
+LL |         a: i32,
+   |         ^ help: if this is intentional, prefix it with an underscore: `_a`
    |
 note: the lint level is defined here
   --> $DIR/lint-unused-variables.rs:5:9
@@ -11,13 +11,13 @@ LL | #![deny(unused_variables)]
    |         ^^^^^^^^^^^^^^^^
 
 error: unused variable: `a`
-  --> $DIR/lint-unused-variables.rs:22:9
+  --> $DIR/lint-unused-variables.rs:8:5
    |
-LL |         a: i32,
-   |         ^ help: if this is intentional, prefix it with an underscore: `_a`
+LL |     a: i32,
+   |     ^ help: if this is intentional, prefix it with an underscore: `_a`
 
 error: unused variable: `a`
-  --> $DIR/lint-unused-variables.rs:68:9
+  --> $DIR/lint-unused-variables.rs:22:9
    |
 LL |         a: i32,
    |         ^ help: if this is intentional, prefix it with an underscore: `_a`

tests/ui/rfcs/rfc-2565-param-attrs/param-attrs-cfg.stderr

@@ -1,8 +1,8 @@
 error: unused variable: `a`
-  --> $DIR/param-attrs-cfg.rs:24:23
+  --> $DIR/param-attrs-cfg.rs:107:27
    |
-LL |     #[cfg(something)] a: i32,
-   |                       ^ help: if this is intentional, prefix it with an underscore: `_a`
+LL |         #[cfg(something)] a: i32,
+   |                           ^ help: if this is intentional, prefix it with an underscore: `_a`
    |
 note: the lint level is defined here
   --> $DIR/param-attrs-cfg.rs:5:9
@@ -11,13 +11,13 @@ LL | #![deny(unused_variables)]
    |         ^^^^^^^^^^^^^^^^
 
 error: unused variable: `a`
-  --> $DIR/param-attrs-cfg.rs:41:27
+  --> $DIR/param-attrs-cfg.rs:24:23
    |
-LL |         #[cfg(something)] a: i32,
-   |                           ^ help: if this is intentional, prefix it with an underscore: `_a`
+LL |     #[cfg(something)] a: i32,
+   |                       ^ help: if this is intentional, prefix it with an underscore: `_a`
 
 error: unused variable: `a`
-  --> $DIR/param-attrs-cfg.rs:107:27
+  --> $DIR/param-attrs-cfg.rs:41:27
    |
 LL |         #[cfg(something)] a: i32,
    |                           ^ help: if this is intentional, prefix it with an underscore: `_a`