Rollup merge of rust-lang#130266 - heiher:loong-medium-cmodel, r=compiler-errors

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.

Relands [2]:  rust-lang#120661

[1]: https://github.com/loongson/la-abi-specs/blob/v2.30/laelf.adoc#code-models
[2]: rust-lang#121289 (comment)

Author: matthiaskrgr

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(crate) fn target() -> Target {
     Target {
@@ -13,6 +13,7 @@ pub(crate) fn target() -> Target {
         data_layout: "e-m:e-p:64:64-i64:64-i128:128-n32:64-S128".into(),
         arch: "loongarch64".into(),
         options: TargetOptions {
+            code_model: Some(CodeModel::Medium),
             cpu: "generic".into(),
             features: "+f,+d".into(),
             llvm_abiname: "lp64d".into(),

compiler/rustc_target/src/spec/targets/loongarch64_unknown_linux_musl.rs

@@ -1,4 +1,4 @@
-use crate::spec::{base, Target, TargetOptions};
+use crate::spec::{base, CodeModel, Target, TargetOptions};
 
 pub(crate) fn target() -> Target {
     Target {
@@ -13,6 +13,7 @@ pub(crate) fn target() -> Target {
         data_layout: "e-m:e-p:64:64-i64:64-i128:128-n32:64-S128".into(),
         arch: "loongarch64".into(),
         options: TargetOptions {
+            code_model: Some(CodeModel::Medium),
             cpu: "generic".into(),
             features: "+f,+d".into(),
             llvm_abiname: "lp64d".into(),

compiler/rustc_target/src/spec/targets/loongarch64_unknown_none.rs

@@ -23,7 +23,7 @@ pub(crate) 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()
         },
     }

compiler/rustc_target/src/spec/targets/loongarch64_unknown_none_softfloat.rs

@@ -24,7 +24,7 @@ pub(crate) 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()
         },
     }