diff --git a/compiler/rustc_codegen_gcc/src/builder.rs b/compiler/rustc_codegen_gcc/src/builder.rs index 3def9a5c015cc..1b0a4e0b67959 100644 --- a/compiler/rustc_codegen_gcc/src/builder.rs +++ b/compiler/rustc_codegen_gcc/src/builder.rs @@ -1653,6 +1653,10 @@ impl<'a, 'gcc, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'gcc, 'tcx> { unimplemented!(); } + fn get_funclet_cleanuppad(&self, _funclet: &Funclet) -> RValue<'gcc> { + unimplemented!(); + } + // Atomic Operations fn atomic_cmpxchg( &mut self, diff --git a/compiler/rustc_codegen_llvm/src/builder.rs b/compiler/rustc_codegen_llvm/src/builder.rs index ca4805a93e017..c3e15eadfced1 100644 --- a/compiler/rustc_codegen_llvm/src/builder.rs +++ b/compiler/rustc_codegen_llvm/src/builder.rs @@ -1309,6 +1309,10 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> { ret } + fn get_funclet_cleanuppad(&self, funclet: &Funclet<'ll>) -> &'ll Value { + funclet.cleanuppad() + } + // Atomic Operations fn atomic_cmpxchg( &mut self, diff --git a/compiler/rustc_codegen_ssa/src/mir/block.rs b/compiler/rustc_codegen_ssa/src/mir/block.rs index 35de8b5e1486b..4859380daa662 100644 --- a/compiler/rustc_codegen_ssa/src/mir/block.rs +++ b/compiler/rustc_codegen_ssa/src/mir/block.rs @@ -215,19 +215,18 @@ impl<'a, 'tcx> TerminatorCodegenHelper<'tcx> { mir::UnwindAction::Continue => None, mir::UnwindAction::Unreachable => None, mir::UnwindAction::Terminate(reason) => { - if fx.mir[self.bb].is_cleanup && base::wants_new_eh_instructions(fx.cx.tcx().sess) { + if fx.mir[self.bb].is_cleanup && base::wants_wasm_eh(fx.cx.tcx().sess) { + // For wasm, we need to generate a nested `cleanuppad within %outer_pad` + // to catch exceptions during cleanup and call `panic_in_cleanup`. + Some(fx.terminate_block(reason, Some(self.bb))) + } else if fx.mir[self.bb].is_cleanup + && base::wants_new_eh_instructions(fx.cx.tcx().sess) + { // MSVC SEH will abort automatically if an exception tries to // propagate out from cleanup. - - // FIXME(@mirkootter): For wasm, we currently do not support terminate during - // cleanup, because this requires a few more changes: The current code - // caches the `terminate_block` for each function; funclet based code - however - - // requires a different terminate_block for each funclet - // Until this is implemented, we just do not unwind inside cleanup blocks - None } else { - Some(fx.terminate_block(reason)) + Some(fx.terminate_block(reason, None)) } } }; @@ -239,7 +238,7 @@ impl<'a, 'tcx> TerminatorCodegenHelper<'tcx> { if let Some(unwind_block) = unwind_block { let ret_llbb = if let Some((_, target)) = destination { - fx.llbb(target) + self.llbb_with_cleanup(fx, target) } else { fx.unreachable_block() }; @@ -310,7 +309,7 @@ impl<'a, 'tcx> TerminatorCodegenHelper<'tcx> { ) -> MergingSucc { let unwind_target = match unwind { mir::UnwindAction::Cleanup(cleanup) => Some(self.llbb_with_cleanup(fx, cleanup)), - mir::UnwindAction::Terminate(reason) => Some(fx.terminate_block(reason)), + mir::UnwindAction::Terminate(reason) => Some(fx.terminate_block(reason, None)), mir::UnwindAction::Continue => None, mir::UnwindAction::Unreachable => None, }; @@ -318,7 +317,7 @@ impl<'a, 'tcx> TerminatorCodegenHelper<'tcx> { if operands.iter().any(|x| matches!(x, InlineAsmOperandRef::Label { .. })) { assert!(unwind_target.is_none()); let ret_llbb = if let Some(target) = destination { - fx.llbb(target) + self.llbb_with_cleanup(fx, target) } else { fx.unreachable_block() }; @@ -335,7 +334,7 @@ impl<'a, 'tcx> TerminatorCodegenHelper<'tcx> { MergingSucc::False } else if let Some(cleanup) = unwind_target { let ret_llbb = if let Some(target) = destination { - fx.llbb(target) + self.llbb_with_cleanup(fx, target) } else { fx.unreachable_block() }; @@ -1830,8 +1829,39 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> { }) } - fn terminate_block(&mut self, reason: UnwindTerminateReason) -> Bx::BasicBlock { - if let Some((cached_bb, cached_reason)) = self.terminate_block + fn terminate_block( + &mut self, + reason: UnwindTerminateReason, + outer_catchpad_bb: Option, + ) -> Bx::BasicBlock { + // mb_funclet_bb should be present if and only if the target is wasm and + // we're terminating because of an unwind in a cleanup block. In that + // case we have nested funclets and the inner catch_switch needs to know + // what outer catch_pad it is contained in. + debug_assert!( + outer_catchpad_bb.is_some() + == (base::wants_wasm_eh(self.cx.tcx().sess) + && reason == UnwindTerminateReason::InCleanup) + ); + + // When we aren't in a wasm InCleanup block, there's only one terminate + // block needed so we cache at START_BLOCK index. + let mut cache_bb = mir::START_BLOCK; + // In wasm eh InCleanup, use the outer funclet's cleanup BB as the cache + // key. + if let Some(outer_bb) = outer_catchpad_bb { + let cleanup_kinds = + self.cleanup_kinds.as_ref().expect("cleanup_kinds required for funclets"); + cache_bb = cleanup_kinds[outer_bb] + .funclet_bb(outer_bb) + .expect("funclet_bb should be in a funclet"); + + // Ensure the outer funclet is created first + if self.funclets[cache_bb].is_none() { + self.landing_pad_for(cache_bb); + } + } + if let Some((cached_bb, cached_reason)) = self.terminate_blocks[cache_bb] && reason == cached_reason { return cached_bb; @@ -1869,12 +1899,35 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> { // cp_terminate: // %cp = catchpad within %cs [null, i32 64, null] // ... + // + // By contrast, on WebAssembly targets, we specifically _do_ want to + // catch foreign exceptions. The situation with MSVC is a + // regrettable hack which we don't want to extend to other targets + // unless necessary. For WebAssembly, to generate catch(...) and + // catch only C++ exception instead of generating a catch_all, we + // need to call the intrinsics @llvm.wasm.get.exception and + // @llvm.wasm.get.ehselector in the catch pad. Since we don't do + // this, we generate a catch_all. We originally got this behavior + // by accident but it luckily matches our intention. llbb = Bx::append_block(self.cx, self.llfn, "cs_terminate"); - let cp_llbb = Bx::append_block(self.cx, self.llfn, "cp_terminate"); let mut cs_bx = Bx::build(self.cx, llbb); - let cs = cs_bx.catch_switch(None, None, &[cp_llbb]); + + // For wasm InCleanup blocks, our catch_switch is nested within the + // outer catchpad, so we need to provide it as the parent value to + // catch_switch. + let mut outer_cleanuppad = None; + if outer_catchpad_bb.is_some() { + // Get the outer funclet's catchpad + let outer_funclet = self.funclets[cache_bb] + .as_ref() + .expect("landing_pad_for didn't create funclet"); + outer_cleanuppad = Some(cs_bx.get_funclet_cleanuppad(outer_funclet)); + } + let cp_llbb = Bx::append_block(self.cx, self.llfn, "cp_terminate"); + let cs = cs_bx.catch_switch(outer_cleanuppad, None, &[cp_llbb]); + drop(cs_bx); bx = Bx::build(self.cx, cp_llbb); let null = @@ -1895,13 +1948,18 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> { } else { // Specifying more arguments than necessary usually doesn't // hurt, but the `WasmEHPrepare` LLVM pass does not recognize - // anything other than a single `null` as a `catch (...)` block, + // anything other than a single `null` as a `catch_all` block, // leading to problems down the line during instruction // selection. &[null] as &[_] }; funclet = Some(bx.catch_pad(cs, args)); + // On wasm, if we wanted to generate a catch(...) and only catch C++ + // exceptions, we'd call @llvm.wasm.get.exception and + // @llvm.wasm.get.ehselector selectors here. We want a catch_all so + // we leave them out. This is intentionally diverging from the MSVC + // behavior. } else { llbb = Bx::append_block(self.cx, self.llfn, "terminate"); bx = Bx::build(self.cx, llbb); @@ -1927,7 +1985,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> { bx.unreachable(); - self.terminate_block = Some((llbb, reason)); + self.terminate_blocks[cache_bb] = Some((llbb, reason)); llbb } diff --git a/compiler/rustc_codegen_ssa/src/mir/mod.rs b/compiler/rustc_codegen_ssa/src/mir/mod.rs index 819abb9ae644d..1a0f66d31cca4 100644 --- a/compiler/rustc_codegen_ssa/src/mir/mod.rs +++ b/compiler/rustc_codegen_ssa/src/mir/mod.rs @@ -90,8 +90,11 @@ pub struct FunctionCx<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> { /// Cached unreachable block unreachable_block: Option, - /// Cached terminate upon unwinding block and its reason - terminate_block: Option<(Bx::BasicBlock, UnwindTerminateReason)>, + /// Cached terminate upon unwinding block and its reason. For non-wasm + /// targets, there is at most one such block per function, stored at index + /// `START_BLOCK`. For wasm targets, each funclet needs its own terminate + /// block, indexed by the cleanup block that is the funclet's head. + terminate_blocks: IndexVec>, /// A bool flag for each basic block indicating whether it is a cold block. /// A cold block is a block that is unlikely to be executed at runtime. @@ -227,7 +230,7 @@ pub fn codegen_mir<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>( personality_slot: None, cached_llbbs, unreachable_block: None, - terminate_block: None, + terminate_blocks: IndexVec::from_elem(None, &mir.basic_blocks), cleanup_kinds, landing_pads: IndexVec::from_elem(None, &mir.basic_blocks), funclets: IndexVec::from_fn_n(|_| None, mir.basic_blocks.len()), diff --git a/compiler/rustc_codegen_ssa/src/traits/builder.rs b/compiler/rustc_codegen_ssa/src/traits/builder.rs index 3486bd140eceb..edabd8188a3b6 100644 --- a/compiler/rustc_codegen_ssa/src/traits/builder.rs +++ b/compiler/rustc_codegen_ssa/src/traits/builder.rs @@ -552,12 +552,12 @@ pub trait BuilderMethods<'a, 'tcx>: fn set_personality_fn(&mut self, personality: Self::Function); - // These are used by everyone except msvc + // These are used by everyone except msvc and wasm EH fn cleanup_landing_pad(&mut self, pers_fn: Self::Function) -> (Self::Value, Self::Value); fn filter_landing_pad(&mut self, pers_fn: Self::Function); fn resume(&mut self, exn0: Self::Value, exn1: Self::Value); - // These are used only by msvc + // These are used by msvc and wasm EH fn cleanup_pad(&mut self, parent: Option, args: &[Self::Value]) -> Self::Funclet; fn cleanup_ret(&mut self, funclet: &Self::Funclet, unwind: Option); fn catch_pad(&mut self, parent: Self::Value, args: &[Self::Value]) -> Self::Funclet; @@ -567,6 +567,7 @@ pub trait BuilderMethods<'a, 'tcx>: unwind: Option, handlers: &[Self::BasicBlock], ) -> Self::Value; + fn get_funclet_cleanuppad(&self, funclet: &Self::Funclet) -> Self::Value; fn atomic_cmpxchg( &mut self, diff --git a/tests/codegen-llvm/double_panic_wasm.rs b/tests/codegen-llvm/double_panic_wasm.rs new file mode 100644 index 0000000000000..1eafe60503809 --- /dev/null +++ b/tests/codegen-llvm/double_panic_wasm.rs @@ -0,0 +1,34 @@ +//@ compile-flags: -C panic=unwind -Copt-level=0 +//@ needs-unwind +//@ only-wasm32 + +#![crate_type = "lib"] + +// Test that `panic_in_cleanup` is called on webassembly targets when a panic +// occurs in a destructor during unwinding. + +extern "Rust" { + fn may_panic(); +} + +struct PanicOnDrop; + +impl Drop for PanicOnDrop { + fn drop(&mut self) { + unsafe { may_panic() } + } +} + +// CHECK-LABEL: @double_panic +// CHECK: invoke void @may_panic() +// CHECK: invoke void @{{.+}}drop_in_place{{.+}} +// CHECK: unwind label %[[TERMINATE:.*]] +// +// CHECK: [[TERMINATE]]: +// CHECK: call void @{{.*panic_in_cleanup}} +// CHECK: unreachable +#[no_mangle] +pub fn double_panic() { + let _guard = PanicOnDrop; + unsafe { may_panic() } +} diff --git a/tests/codegen-llvm/terminating-catchpad.rs b/tests/codegen-llvm/terminating-catchpad.rs index a2ec19871d1fc..7c98ea94fdc13 100644 --- a/tests/codegen-llvm/terminating-catchpad.rs +++ b/tests/codegen-llvm/terminating-catchpad.rs @@ -9,6 +9,10 @@ // Ensure a catch-all generates: // - `catchpad ... [ptr null]` on Wasm (otherwise LLVM gets confused) // - `catchpad ... [ptr null, i32 64, ptr null]` on Windows (otherwise we catch SEH exceptions) +// +// Unlike on windows, on Wasm, we specifically do want to catch foreign +// exceptions. To catch only C++ exceptions we'd need to call +// @llvm.wasm.get.exception and @llvm.wasm.get.ehselector in the catchpad. #![feature(no_core, lang_items, rustc_attrs)] #![crate_type = "lib"] @@ -36,8 +40,14 @@ fn panic_cannot_unwind() -> ! { #[no_mangle] #[rustc_nounwind] pub fn doesnt_unwind() { + // CHECK: catchswitch within none [label %{{.*}}] unwind to caller // emscripten: %catchpad = catchpad within %catchswitch [ptr null] // wasi: %catchpad = catchpad within %catchswitch [ptr null] // seh: %catchpad = catchpad within %catchswitch [ptr null, i32 64, ptr null] + // + // We don't call these intrinsics on wasm targets so we generate a catch_all + // instruction which also picks up foreign exceptions + // NOT: @llvm.wasm.get.exception + // NOT: @llvm.wasm.get.ehselector unwinds(); }