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Diffstat (limited to 'tests/codegen/frame-pointer-cli-control.rs')
| -rw-r--r-- | tests/codegen/frame-pointer-cli-control.rs | 61 |
1 files changed, 61 insertions, 0 deletions
diff --git a/tests/codegen/frame-pointer-cli-control.rs b/tests/codegen/frame-pointer-cli-control.rs new file mode 100644 index 00000000000..a65dd132763 --- /dev/null +++ b/tests/codegen/frame-pointer-cli-control.rs @@ -0,0 +1,61 @@ +//@ add-core-stubs +//@ compile-flags: --crate-type=rlib -Copt-level=0 +//@ revisions: force-on aarch64-apple aarch64-apple-on aarch64-apple-off +//@ [force-on] compile-flags: -Cforce-frame-pointers=on +//@ [aarch64-apple] needs-llvm-components: aarch64 +//@ [aarch64-apple] compile-flags: --target=aarch64-apple-darwin +//@ [aarch64-apple-on] needs-llvm-components: aarch64 +//@ [aarch64-apple-on] compile-flags: --target=aarch64-apple-darwin -Cforce-frame-pointers=on +//@ [aarch64-apple-off] needs-llvm-components: aarch64 +//@ [aarch64-apple-off] compile-flags: --target=aarch64-apple-darwin -Cforce-frame-pointers=off +/*! + +Tests the extent to which frame pointers can be controlled by the CLI. +The behavior of our frame pointer options, at present, is an irreversible ratchet, where +a "weaker" option that allows omitting frame pointers may be overridden by the target demanding +that all code (or all non-leaf code, more often) must be compiled with frame pointers. +This was discussed on 2025-05-22 in the T-compiler meeting and accepted as an intentional change, +ratifying the prior decisions by compiler contributors and reviewers as correct, +though it was also acknowledged that the flag allows somewhat confusing inputs. + +We find aarch64-apple-darwin useful because of its icy-clear policy regarding frame pointers, +e.g. <https://developer.apple.com/documentation/xcode/writing-arm64-code-for-apple-platforms> says: + +* The frame pointer register (x29) must always address a valid frame record. Some functions — + such as leaf functions or tail calls — may opt not to create an entry in this list. + As a result, stack traces are always meaningful, even without debug information. + +Many Rust fn, if externally visible, may be expected to follow target ABI by tools or asm code! +This can make it a problem to generate ABI-incorrect code, which may mean "with frame pointers". +For this and other reasons, `-Cforce-frame-pointers=off` cannot override the target definition. +This can cause some confusion because it is "reverse polarity" relative to C compilers, which have +commands like `-fomit-frame-pointer`, `-fomit-leaf-frame-pointer`, or `-fno-omit-frame-pointer`! + +Specific cases where platforms or tools rely on frame pointers for sound or correct unwinding: +- illumos: <https://smartos.org/bugview/OS-7515> +- aarch64-windows: <https://github.com/rust-lang/rust/issues/123686> +- aarch64-linux: <https://github.com/rust-lang/rust/issues/123733> +- dtrace (freebsd and openbsd): <https://github.com/rust-lang/rust/issues/97723> +- openbsd: <https://github.com/rust-lang/rust/issues/43575> +- i686-msvc <https://github.com/rust-lang/backtrace-rs/pull/584#issuecomment-1966177530> +- i686-mingw: <https://github.com/rust-lang/rust/commit/3f1d3948d6d434b34dd47f132c126a6cb6b8a4ab> +*/ +#![feature(no_core, lang_items)] +#![no_core] + +extern crate minicore; + +// CHECK: i32 @peach{{.*}}[[PEACH_ATTRS:\#[0-9]+]] { +#[no_mangle] +pub fn peach(x: u32) -> u32 { + x +} + +// CHECK: attributes [[PEACH_ATTRS]] = { +// force-on-SAME: {{.*}}"frame-pointer"="all" +// aarch64-apple-SAME: {{.*}}"frame-pointer"="non-leaf" +// aarch64-apple-on-SAME: {{.*}}"frame-pointer"="all" +// +// yes, we are testing this doesn't do anything: +// aarch64-apple-off-SAME: {{.*}}"frame-pointer"="non-leaf" +// CHECK-SAME: } |