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Auto merge of #117465 - paulmenage:small-data-limit, r=compiler-errors

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Add -Z small-data-threshold

This flag allows specifying the threshold size above which LLVM should not consider placing small objects in a `.sdata` or `.sbss` section.

Support is indicated in the target options via the
small-data-threshold-support target option, which can indicate either an
LLVM argument or an LLVM module flag.  To avoid duplicate specifications
in a large number of targets, the default value for support is
DefaultForArch, which is translated to a concrete value according to the
target's architecture.
This commit is contained in:
bors 2024-09-12 04:27:08 +00:00
commit 1f51450c68
10 changed files with 241 additions and 4 deletions
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20
compiler/rustc_codegen_llvm/src/context.rs
View file

@ -27,7 +27,7 @@ use rustc_span::source_map::Spanned;
use rustc_span::{Span, DUMMY_SP};
use rustc_target::abi::call::FnAbi;
use rustc_target::abi::{HasDataLayout, TargetDataLayout, VariantIdx};
use rustc_target::spec::{HasTargetSpec, RelocModel, Target, TlsModel};
use rustc_target::spec::{HasTargetSpec, RelocModel, SmallDataThresholdSupport, Target, TlsModel};
use smallvec::SmallVec;
use crate::back::write::to_llvm_code_model;
@ -387,6 +387,24 @@ pub(crate) unsafe fn create_module<'ll>(
}
}
match (sess.opts.unstable_opts.small_data_threshold, sess.target.small_data_threshold_support())
{
// Set up the small-data optimization limit for architectures that use
// an LLVM module flag to control this.
(Some(threshold), SmallDataThresholdSupport::LlvmModuleFlag(flag)) => {
let flag = SmallCStr::new(flag.as_ref());
unsafe {
llvm::LLVMRustAddModuleFlagU32(
llmod,
llvm::LLVMModFlagBehavior::Error,
flag.as_c_str().as_ptr(),
threshold as u32,
)
}
}
_ => (),
};
// Insert `llvm.ident` metadata.
//
// On the wasm targets it will get hooked up to the "producer" sections

14
compiler/rustc_codegen_llvm/src/llvm_util.rs
View file

@ -14,7 +14,7 @@ use rustc_middle::bug;
use rustc_session::config::{PrintKind, PrintRequest};
use rustc_session::Session;
use rustc_span::symbol::Symbol;
use rustc_target::spec::{MergeFunctions, PanicStrategy};
use rustc_target::spec::{MergeFunctions, PanicStrategy, SmallDataThresholdSupport};
use rustc_target::target_features::{RUSTC_SPECIAL_FEATURES, RUSTC_SPECIFIC_FEATURES};
use crate::back::write::create_informational_target_machine;
@ -125,6 +125,18 @@ unsafe fn configure_llvm(sess: &Session) {
for arg in sess_args {
add(&(*arg), true);
}
match (
sess.opts.unstable_opts.small_data_threshold,
sess.target.small_data_threshold_support(),
) {
// Set up the small-data optimization limit for architectures that use
// an LLVM argument to control this.
(Some(threshold), SmallDataThresholdSupport::LlvmArg(arg)) => {
add(&format!("--{arg}={threshold}"), false)
}
_ => (),
};
}
if sess.opts.unstable_opts.llvm_time_trace {