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Add support for leaf fn frame pointer elimination

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This PR adds ability for the target specifications to specify frame
pointer emission type that's not just “always” or “whatever cg decides”.

In particular there's a new mode that allows omission of the frame
pointer for leaf functions (those that don't call any other functions).

We then set this new mode for Aarch64-based Apple targets.

Fixes #86196
This commit is contained in:
Simonas Kazlauskas 2021-06-26 23:53:35 +03:00
parent 3ddb78a346
commit 9b67cba4f6
24 changed files with 149 additions and 60 deletions
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55
compiler/rustc_target/src/spec/mod.rs
View file

@ -671,6 +671,42 @@ impl ToJson for SanitizerSet {
}
}
#[derive(Clone, Copy, PartialEq, Hash, Debug)]
pub enum FramePointer {
/// Forces the machine code generator to always preserve the frame pointers.
Always,
/// Forces the machine code generator to preserve the frame pointers except for the leaf
/// functions (i.e. those that don't call other functions).
NonLeaf,
/// Allows the machine code generator to omit the frame pointers.
///
/// This option does not guarantee that the frame pointers will be omitted.
MayOmit,
}
impl FromStr for FramePointer {
type Err = ();
fn from_str(s: &str) -> Result<Self, ()> {
Ok(match s {
"always" => Self::Always,
"non-leaf" => Self::NonLeaf,
"may-omit" => Self::MayOmit,
_ => return Err(()),
})
}
}
impl ToJson for FramePointer {
fn to_json(&self) -> Json {
match *self {
Self::Always => "always",
Self::NonLeaf => "non-leaf",
Self::MayOmit => "may-omit",
}
.to_json()
}
}
macro_rules! supported_targets {
( $(($( $triple:literal, )+ $module:ident ),)+ ) => {
$(mod $module;)+
@ -1068,8 +1104,8 @@ pub struct TargetOptions {
pub tls_model: TlsModel,
/// Do not emit code that uses the "red zone", if the ABI has one. Defaults to false.
pub disable_redzone: bool,
/// Eliminate frame pointers from stack frames if possible. Defaults to true.
pub eliminate_frame_pointer: bool,
/// Frame pointer mode for this target. Defaults to `MayOmit`.
pub frame_pointer: FramePointer,
/// Emit each function in its own section. Defaults to true.
pub function_sections: bool,
/// String to prepend to the name of every dynamic library. Defaults to "lib".
@ -1330,7 +1366,7 @@ impl Default for TargetOptions {
code_model: None,
tls_model: TlsModel::GeneralDynamic,
disable_redzone: false,
eliminate_frame_pointer: true,
frame_pointer: FramePointer::MayOmit,
function_sections: true,
dll_prefix: "lib".to_string(),
dll_suffix: ".so".to_string(),
@ -1833,6 +1869,16 @@ impl Target {
}
}
if let Some(fp) = obj.remove_key("frame-pointer") {
if let Some(s) = Json::as_string(&fp) {
base.frame_pointer = s
.parse()
.map_err(|()| format!("'{}' is not a valid value for frame-pointer", s))?;
} else {
incorrect_type.push("frame-pointer".to_string())
}
}
key!(is_builtin, bool);
key!(c_int_width = "target-c-int-width");
key!(os);
@ -1864,7 +1910,6 @@ impl Target {
key!(code_model, CodeModel)?;
key!(tls_model, TlsModel)?;
key!(disable_redzone, bool);
key!(eliminate_frame_pointer, bool);
key!(function_sections, bool);
key!(dll_prefix);
key!(dll_suffix);
@ -2128,7 +2173,7 @@ impl ToJson for Target {
target_option_val!(code_model);
target_option_val!(tls_model);
target_option_val!(disable_redzone);
target_option_val!(eliminate_frame_pointer);
target_option_val!(frame_pointer);
target_option_val!(function_sections);
target_option_val!(dll_prefix);
target_option_val!(dll_suffix);