From 2b662217e745d88d93dcc6f5f5169bf7a0d9720e Mon Sep 17 00:00:00 2001 From: Erik Desjardins Date: Wed, 29 Dec 2021 15:28:31 -0500 Subject: [PATCH] Mark drop calls in landing pads cold instead of noinline Now that deferred inlining has been disabled in LLVM, this shouldn't cause catastrophic size blowup. --- compiler/rustc_codegen_gcc/src/builder.rs | 2 +- compiler/rustc_codegen_llvm/src/builder.rs | 4 ++-- compiler/rustc_codegen_ssa/src/mir/block.rs | 7 ++---- .../rustc_codegen_ssa/src/traits/builder.rs | 2 +- src/test/codegen/unwind-landingpad-cold.rs | 14 ++++++++++++ src/test/codegen/unwind-landingpad-inline.rs | 22 +++++++++++++++++++ 6 files changed, 42 insertions(+), 9 deletions(-) create mode 100644 src/test/codegen/unwind-landingpad-cold.rs create mode 100644 src/test/codegen/unwind-landingpad-inline.rs diff --git a/compiler/rustc_codegen_gcc/src/builder.rs b/compiler/rustc_codegen_gcc/src/builder.rs index fff2aa6df7c7..997213d43e8c 100644 --- a/compiler/rustc_codegen_gcc/src/builder.rs +++ b/compiler/rustc_codegen_gcc/src/builder.rs @@ -1404,7 +1404,7 @@ impl<'a, 'gcc, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'gcc, 'tcx> { self.cx } - fn do_not_inline(&mut self, _llret: RValue<'gcc>) { + fn mark_callsite_cold(&mut self, _llret: RValue<'gcc>) { unimplemented!(); } diff --git a/compiler/rustc_codegen_llvm/src/builder.rs b/compiler/rustc_codegen_llvm/src/builder.rs index 8c3054b23ff4..107300ed304f 100644 --- a/compiler/rustc_codegen_llvm/src/builder.rs +++ b/compiler/rustc_codegen_llvm/src/builder.rs @@ -1201,8 +1201,8 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> { unsafe { llvm::LLVMBuildZExt(self.llbuilder, val, dest_ty, UNNAMED) } } - fn do_not_inline(&mut self, llret: &'ll Value) { - llvm::Attribute::NoInline.apply_callsite(llvm::AttributePlace::Function, llret); + fn mark_callsite_cold(&mut self, llret: &'ll Value) { + llvm::Attribute::Cold.apply_callsite(llvm::AttributePlace::Function, llret); } } diff --git a/compiler/rustc_codegen_ssa/src/mir/block.rs b/compiler/rustc_codegen_ssa/src/mir/block.rs index e914e4932693..8cefd415e28b 100644 --- a/compiler/rustc_codegen_ssa/src/mir/block.rs +++ b/compiler/rustc_codegen_ssa/src/mir/block.rs @@ -160,11 +160,8 @@ impl<'a, 'tcx> TerminatorCodegenHelper<'tcx> { let llret = bx.call(fn_ty, fn_ptr, &llargs, self.funclet(fx)); bx.apply_attrs_callsite(&fn_abi, llret); if fx.mir[self.bb].is_cleanup { - // Cleanup is always the cold path. Don't inline - // drop glue. Also, when there is a deeply-nested - // struct, there are "symmetry" issues that cause - // exponential inlining - see issue #41696. - bx.do_not_inline(llret); + // Cleanup is always the cold path. + bx.mark_callsite_cold(llret); } if let Some((ret_dest, target)) = destination { diff --git a/compiler/rustc_codegen_ssa/src/traits/builder.rs b/compiler/rustc_codegen_ssa/src/traits/builder.rs index 158e658301ee..c1cdff3addad 100644 --- a/compiler/rustc_codegen_ssa/src/traits/builder.rs +++ b/compiler/rustc_codegen_ssa/src/traits/builder.rs @@ -311,5 +311,5 @@ pub trait BuilderMethods<'a, 'tcx>: ) -> Self::Value; fn zext(&mut self, val: Self::Value, dest_ty: Self::Type) -> Self::Value; - fn do_not_inline(&mut self, llret: Self::Value); + fn mark_callsite_cold(&mut self, llret: Self::Value); } diff --git a/src/test/codegen/unwind-landingpad-cold.rs b/src/test/codegen/unwind-landingpad-cold.rs new file mode 100644 index 000000000000..0bf2941374a6 --- /dev/null +++ b/src/test/codegen/unwind-landingpad-cold.rs @@ -0,0 +1,14 @@ +// compile-flags: -Cno-prepopulate-passes +#![crate_type = "lib"] + +// This test checks that drop calls in unwind landing pads +// get the `cold` attribute. + +// CHECK-LABEL: @check_cold +// CHECK: call void {{.+}}drop_in_place{{.+}} [[ATTRIBUTES:#[0-9]+]] +// CHECK: attributes [[ATTRIBUTES]] = { cold } +#[no_mangle] +pub fn check_cold(f: fn(), x: Box) { + // this may unwind + f(); +} diff --git a/src/test/codegen/unwind-landingpad-inline.rs b/src/test/codegen/unwind-landingpad-inline.rs new file mode 100644 index 000000000000..d641c908ea99 --- /dev/null +++ b/src/test/codegen/unwind-landingpad-inline.rs @@ -0,0 +1,22 @@ +// no-system-llvm: needs patch for Rust alloc/dealloc functions +// compile-flags: -Copt-level=3 +#![crate_type = "lib"] + +// This test checks that we can inline drop_in_place in +// unwind landing pads. Without this, the box pointers escape, +// and LLVM will not optimize out the pointer comparison. +// See https://github.com/rust-lang/rust/issues/46515 + +// Everything should be optimized out. +// CHECK-LABEL: @check_no_escape_in_landingpad +// CHECK: start: +// CHECK-NEXT: ret void +#[no_mangle] +pub fn check_no_escape_in_landingpad(f: fn()) { + let x = &*Box::new(0); + let y = &*Box::new(0); + + if x as *const _ == y as *const _ { + f(); + } +}