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https://github.com/rust-lang/rust/pull/120661
From: WANG Xuerui <xen0n@gentoo.org>
Date: Mon, 5 Feb 2024 13:18:32 +0800
Subject: [PATCH] target: default to the medium code model on LoongArch targets
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
The Rust LoongArch targets have been using the default LLVM code model
so far, which is "small" in LLVM-speak and "normal" in LoongArch-speak.
As described in the "Code Model" section of LoongArch ELF psABI spec
v20231219 [1], one can only make function calls as far as ±128MiB with
the "normal" code model; this is insufficient for very large software
containing Rust components that needs to be linked into the big text
section, such as Chromium.
Because:
* we do not want to ask users to recompile std if they are to build
such software,
* objects compiled with larger code models can be linked with those
with smaller code models without problems, and
* the "medium" code model is comparable to the "small"/"normal" one
performance-wise (same data access pattern; each function call
becomes 2-insn long and indirect, but this may be relaxed back into
the direct 1-insn form in a future LLVM version), but is able to
perform function calls within ±128GiB,
it is better to just switch the targets to the "medium" code model,
which is also "medium" in LLVM-speak.
[1]: https://github.com/loongson/la-abi-specs/blob/v2.30/laelf.adoc#code-models
--- a/compiler/rustc_target/src/spec/targets/loongarch64_unknown_linux_gnu.rs
+++ b/compiler/rustc_target/src/spec/targets/loongarch64_unknown_linux_gnu.rs
@@ -1,4 +1,4 @@
-use crate::spec::{base, Target, TargetOptions};
+use crate::spec::{base, CodeModel, Target, TargetOptions};
pub fn target() -> Target {
Target {
@@ -7,6 +7,7 @@ pub fn target() -> Target {
data_layout: "e-m:e-p:64:64-i64:64-i128:128-n64-S128".into(),
arch: "loongarch64".into(),
options: TargetOptions {
+ code_model: Some(CodeModel::Medium),
cpu: "generic".into(),
features: "+f,+d".into(),
llvm_abiname: "lp64d".into(),
--- a/compiler/rustc_target/src/spec/targets/loongarch64_unknown_none.rs
+++ b/compiler/rustc_target/src/spec/targets/loongarch64_unknown_none.rs
@@ -16,7 +16,7 @@ pub fn target() -> Target {
max_atomic_width: Some(64),
relocation_model: RelocModel::Static,
panic_strategy: PanicStrategy::Abort,
- code_model: Some(CodeModel::Small),
+ code_model: Some(CodeModel::Medium),
..Default::default()
},
}
--- a/compiler/rustc_target/src/spec/targets/loongarch64_unknown_none_softfloat.rs
+++ b/compiler/rustc_target/src/spec/targets/loongarch64_unknown_none_softfloat.rs
@@ -17,7 +17,7 @@ pub fn target() -> Target {
max_atomic_width: Some(64),
relocation_model: RelocModel::Static,
panic_strategy: PanicStrategy::Abort,
- code_model: Some(CodeModel::Small),
+ code_model: Some(CodeModel::Medium),
..Default::default()
},
}
--
2.43.0
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