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target: default to the medium code model on LoongArch targets
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
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@ -1,4 +1,4 @@
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use crate::spec::{base, Target, TargetOptions};
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use crate::spec::{base, CodeModel, Target, TargetOptions};
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pub fn target() -> Target {
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Target {
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@ -7,6 +7,7 @@ pub fn target() -> Target {
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data_layout: "e-m:e-p:64:64-i64:64-i128:128-n64-S128".into(),
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arch: "loongarch64".into(),
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options: TargetOptions {
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code_model: Some(CodeModel::Medium),
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cpu: "generic".into(),
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features: "+f,+d".into(),
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llvm_abiname: "lp64d".into(),
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@ -16,7 +16,7 @@ pub fn target() -> Target {
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max_atomic_width: Some(64),
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relocation_model: RelocModel::Static,
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panic_strategy: PanicStrategy::Abort,
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code_model: Some(CodeModel::Small),
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code_model: Some(CodeModel::Medium),
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..Default::default()
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},
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}
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@ -17,7 +17,7 @@ pub fn target() -> Target {
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max_atomic_width: Some(64),
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relocation_model: RelocModel::Static,
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panic_strategy: PanicStrategy::Abort,
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code_model: Some(CodeModel::Small),
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code_model: Some(CodeModel::Medium),
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..Default::default()
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},
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}
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