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Reapply: Mark drop calls in landing pads cold instead of noinline

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Co-authored-by: Max Fan <git@max.fan>
Co-authored-by: Nikita Popov <npopov@redhat.com>
This commit is contained in:
Erik Desjardins 2022-03-10 17:10:36 -05:00 • committed by Nikita Popov
parent 15783292e5
commit 31ee8b1818
7 changed files with 85 additions and 12 deletions
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40
tests/codegen/unwind-landingpad-inline.rs Normal file
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// min-llvm-version: 15.0.0
// compile-flags: -Copt-level=3
// ignore-debug: the debug assertions get in the way
#![crate_type = "lib"]
// This test checks that we can inline drop_in_place in
// unwind landing pads.
// Without inlining, the box pointers escape via the call to drop_in_place,
// and LLVM will not optimize out the pointer comparison.
// With inlining, everything should be optimized out.
// See https://github.com/rust-lang/rust/issues/46515
// CHECK-LABEL: @check_no_escape_in_landingpad
// CHECK: start:
// CHECK-NEXT: __rust_no_alloc_shim_is_unstable
// CHECK-NEXT: __rust_no_alloc_shim_is_unstable
// 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();
}
}
// Without inlining, the compiler can't tell that
// dropping an empty string (in a landing pad) does nothing.
// With inlining, the landing pad should be optimized out.
// See https://github.com/rust-lang/rust/issues/87055
// CHECK-LABEL: @check_eliminate_noop_drop
// CHECK: start:
// CHECK-NEXT: call void %g()
// CHECK-NEXT: ret void
#[no_mangle]
pub fn check_eliminate_noop_drop(g: fn()) {
let _var = String::new();
g();
}