diff --git a/compiler/rustc_codegen_llvm/src/context.rs b/compiler/rustc_codegen_llvm/src/context.rs index 01aae24ab56c2..73c2c15717fc1 100644 --- a/compiler/rustc_codegen_llvm/src/context.rs +++ b/compiler/rustc_codegen_llvm/src/context.rs @@ -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 diff --git a/compiler/rustc_codegen_llvm/src/llvm_util.rs b/compiler/rustc_codegen_llvm/src/llvm_util.rs index 6e4ddbb6f3b6a..29afe6f6bfc7f 100644 --- a/compiler/rustc_codegen_llvm/src/llvm_util.rs +++ b/compiler/rustc_codegen_llvm/src/llvm_util.rs @@ -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 { diff --git a/compiler/rustc_interface/src/tests.rs b/compiler/rustc_interface/src/tests.rs index 50422df8ee648..baeac6c32f939 100644 --- a/compiler/rustc_interface/src/tests.rs +++ b/compiler/rustc_interface/src/tests.rs @@ -847,6 +847,7 @@ fn test_unstable_options_tracking_hash() { tracked!(share_generics, Some(true)); tracked!(show_span, Some(String::from("abc"))); tracked!(simulate_remapped_rust_src_base, Some(PathBuf::from("/rustc/abc"))); + tracked!(small_data_threshold, Some(16)); tracked!(split_lto_unit, Some(true)); tracked!(src_hash_algorithm, Some(SourceFileHashAlgorithm::Sha1)); tracked!(stack_protector, StackProtector::All); diff --git a/compiler/rustc_session/messages.ftl b/compiler/rustc_session/messages.ftl index 01c371ee49884..a4fbab8477b13 100644 --- a/compiler/rustc_session/messages.ftl +++ b/compiler/rustc_session/messages.ftl @@ -113,6 +113,8 @@ session_split_lto_unit_requires_lto = `-Zsplit-lto-unit` requires `-Clto`, `-Clt session_target_requires_unwind_tables = target requires unwind tables, they cannot be disabled with `-C force-unwind-tables=no` +session_target_small_data_threshold_not_supported = `-Z small-data-threshold` is not supported for target {$target_triple} and will be ignored + session_target_stack_protector_not_supported = `-Z stack-protector={$stack_protector}` is not supported for target {$target_triple} and will be ignored session_unleashed_feature_help_named = skipping check for `{$gate}` feature diff --git a/compiler/rustc_session/src/errors.rs b/compiler/rustc_session/src/errors.rs index 15bbd4ff7bf4b..462e2a97c33da 100644 --- a/compiler/rustc_session/src/errors.rs +++ b/compiler/rustc_session/src/errors.rs @@ -182,6 +182,12 @@ pub(crate) struct StackProtectorNotSupportedForTarget<'a> { pub(crate) target_triple: &'a TargetTriple, } +#[derive(Diagnostic)] +#[diag(session_target_small_data_threshold_not_supported)] +pub(crate) struct SmallDataThresholdNotSupportedForTarget<'a> { + pub(crate) target_triple: &'a TargetTriple, +} + #[derive(Diagnostic)] #[diag(session_branch_protection_requires_aarch64)] pub(crate) struct BranchProtectionRequiresAArch64; diff --git a/compiler/rustc_session/src/options.rs b/compiler/rustc_session/src/options.rs index 982a3d5cf110d..106628ec8f6c6 100644 --- a/compiler/rustc_session/src/options.rs +++ b/compiler/rustc_session/src/options.rs @@ -2014,6 +2014,8 @@ written to standard error output)"), simulate_remapped_rust_src_base: Option = (None, parse_opt_pathbuf, [TRACKED], "simulate the effect of remap-debuginfo = true at bootstrapping by remapping path \ to rust's source base directory. only meant for testing purposes"), + small_data_threshold: Option = (None, parse_opt_number, [TRACKED], + "Set the threshold for objects to be stored in a \"small data\" section"), span_debug: bool = (false, parse_bool, [UNTRACKED], "forward proc_macro::Span's `Debug` impl to `Span`"), /// o/w tests have closure@path diff --git a/compiler/rustc_session/src/session.rs b/compiler/rustc_session/src/session.rs index 70430d82ab55b..387ae1b78c480 100644 --- a/compiler/rustc_session/src/session.rs +++ b/compiler/rustc_session/src/session.rs @@ -30,8 +30,8 @@ use rustc_span::source_map::{FilePathMapping, SourceMap}; use rustc_span::{FileNameDisplayPreference, RealFileName, Span, Symbol}; use rustc_target::asm::InlineAsmArch; use rustc_target::spec::{ - CodeModel, DebuginfoKind, PanicStrategy, RelocModel, RelroLevel, SanitizerSet, SplitDebuginfo, - StackProtector, Target, TargetTriple, TlsModel, + CodeModel, DebuginfoKind, PanicStrategy, RelocModel, RelroLevel, SanitizerSet, + SmallDataThresholdSupport, SplitDebuginfo, StackProtector, Target, TargetTriple, TlsModel, }; use crate::code_stats::CodeStats; @@ -1278,6 +1278,14 @@ fn validate_commandline_args_with_session_available(sess: &Session) { } } + if sess.opts.unstable_opts.small_data_threshold.is_some() { + if sess.target.small_data_threshold_support() == SmallDataThresholdSupport::None { + sess.dcx().emit_warn(errors::SmallDataThresholdNotSupportedForTarget { + target_triple: &sess.opts.target_triple, + }) + } + } + if sess.opts.unstable_opts.branch_protection.is_some() && sess.target.arch != "aarch64" { sess.dcx().emit_err(errors::BranchProtectionRequiresAArch64); } diff --git a/compiler/rustc_target/src/spec/mod.rs b/compiler/rustc_target/src/spec/mod.rs index c3e7f74c56410..f12e3e595adf6 100644 --- a/compiler/rustc_target/src/spec/mod.rs +++ b/compiler/rustc_target/src/spec/mod.rs @@ -855,6 +855,43 @@ impl ToJson for RelroLevel { } } +#[derive(Clone, Debug, PartialEq, Hash)] +pub enum SmallDataThresholdSupport { + None, + DefaultForArch, + LlvmModuleFlag(StaticCow), + LlvmArg(StaticCow), +} + +impl FromStr for SmallDataThresholdSupport { + type Err = (); + + fn from_str(s: &str) -> Result { + if s == "none" { + Ok(Self::None) + } else if s == "default-for-arch" { + Ok(Self::DefaultForArch) + } else if let Some(flag) = s.strip_prefix("llvm-module-flag=") { + Ok(Self::LlvmModuleFlag(flag.to_string().into())) + } else if let Some(arg) = s.strip_prefix("llvm-arg=") { + Ok(Self::LlvmArg(arg.to_string().into())) + } else { + Err(()) + } + } +} + +impl ToJson for SmallDataThresholdSupport { + fn to_json(&self) -> Value { + match self { + Self::None => "none".to_json(), + Self::DefaultForArch => "default-for-arch".to_json(), + Self::LlvmModuleFlag(flag) => format!("llvm-module-flag={flag}").to_json(), + Self::LlvmArg(arg) => format!("llvm-arg={arg}").to_json(), + } + } +} + #[derive(Clone, Copy, Debug, PartialEq, Hash)] pub enum MergeFunctions { Disabled, @@ -2392,6 +2429,9 @@ pub struct TargetOptions { /// Whether the target supports XRay instrumentation. pub supports_xray: bool, + + /// Whether the targets supports -Z small-data-threshold + small_data_threshold_support: SmallDataThresholdSupport, } /// Add arguments for the given flavor and also for its "twin" flavors @@ -2609,6 +2649,7 @@ impl Default for TargetOptions { entry_name: "main".into(), entry_abi: Conv::C, supports_xray: false, + small_data_threshold_support: SmallDataThresholdSupport::DefaultForArch, } } } @@ -2884,6 +2925,15 @@ impl Target { Some(Ok(())) })).unwrap_or(Ok(())) } ); + ($key_name:ident, SmallDataThresholdSupport) => ( { + obj.remove("small-data-threshold-support").and_then(|o| o.as_str().and_then(|s| { + match s.parse::() { + Ok(support) => base.small_data_threshold_support = support, + _ => return Some(Err(format!("'{s}' is not a valid value for small-data-threshold-support."))), + } + Some(Ok(())) + })).unwrap_or(Ok(())) + } ); ($key_name:ident, PanicStrategy) => ( { let name = (stringify!($key_name)).replace("_", "-"); obj.remove(&name).and_then(|o| o.as_str().and_then(|s| { @@ -3321,6 +3371,7 @@ impl Target { key!(supported_sanitizers, SanitizerSet)?; key!(generate_arange_section, bool); key!(supports_stack_protector, bool); + key!(small_data_threshold_support, SmallDataThresholdSupport)?; key!(entry_name); key!(entry_abi, Conv)?; key!(supports_xray, bool); @@ -3415,6 +3466,30 @@ impl Target { } } } + + /// Return the target's small data threshold support, converting + /// `DefaultForArch` into a concrete value. + pub fn small_data_threshold_support(&self) -> SmallDataThresholdSupport { + match &self.options.small_data_threshold_support { + // Avoid having to duplicate the small data support in every + // target file by supporting a default value for each + // architecture. + SmallDataThresholdSupport::DefaultForArch => match self.arch.as_ref() { + "mips" | "mips64" | "mips32r6" => { + SmallDataThresholdSupport::LlvmArg("mips-ssection-threshold".into()) + } + "hexagon" => { + SmallDataThresholdSupport::LlvmArg("hexagon-small-data-threshold".into()) + } + "m68k" => SmallDataThresholdSupport::LlvmArg("m68k-ssection-threshold".into()), + "riscv32" | "riscv64" => { + SmallDataThresholdSupport::LlvmModuleFlag("SmallDataLimit".into()) + } + _ => SmallDataThresholdSupport::None, + }, + s => s.clone(), + } + } } impl ToJson for Target { @@ -3577,6 +3652,7 @@ impl ToJson for Target { target_option_val!(c_enum_min_bits); target_option_val!(generate_arange_section); target_option_val!(supports_stack_protector); + target_option_val!(small_data_threshold_support); target_option_val!(entry_name); target_option_val!(entry_abi); target_option_val!(supports_xray); diff --git a/src/doc/unstable-book/src/compiler-flags/small-data-threshold.md b/src/doc/unstable-book/src/compiler-flags/small-data-threshold.md new file mode 100644 index 0000000000000..1734433181e38 --- /dev/null +++ b/src/doc/unstable-book/src/compiler-flags/small-data-threshold.md @@ -0,0 +1,20 @@ +# `small-data-threshold` + +----------------------- + +This flag controls the maximum static variable size that may be included in the +"small data sections" (.sdata, .sbss) supported by some architectures (RISCV, +MIPS, M68K, Hexagon). Can be set to `0` to disable the use of small data +sections. + +Target support is indicated by the `small_data_threshold_support` target +option which can be: + +- `none` (`SmallDataThresholdSupport::None`) for no support +- `default-for-arch` (`SmallDataThresholdSupport::DefaultForArch`) which + is automatically translated into an appropriate value for the target. +- `llvm-module-flag=` + (`SmallDataThresholdSupport::LlvmModuleFlag`) for specifying the + threshold via an LLVM module flag +- `llvm-arg=` (`SmallDataThresholdSupport::LlvmArg`) for + specifying the threshold via an LLVM argument. diff --git a/tests/assembly/small_data_threshold.rs b/tests/assembly/small_data_threshold.rs new file mode 100644 index 0000000000000..b0c0a63ca492d --- /dev/null +++ b/tests/assembly/small_data_threshold.rs @@ -0,0 +1,92 @@ +// Test for -Z small_data_threshold=... +//@ revisions: RISCV MIPS HEXAGON M68K +//@ assembly-output: emit-asm +//@ compile-flags: -Z small_data_threshold=4 +//@ [RISCV] compile-flags: --target=riscv32im-unknown-none-elf +//@ [RISCV] needs-llvm-components: riscv +//@ [MIPS] compile-flags: --target=mips-unknown-linux-uclibc -C relocation-model=static +//@ [MIPS] compile-flags: -C llvm-args=-mgpopt -C llvm-args=-mlocal-sdata +//@ [MIPS] compile-flags: -C target-feature=+noabicalls +//@ [MIPS] needs-llvm-components: mips +//@ [HEXAGON] compile-flags: --target=hexagon-unknown-linux-musl -C target-feature=+small-data +//@ [HEXAGON] compile-flags: -C llvm-args=--hexagon-statics-in-small-data +//@ [HEXAGON] needs-llvm-components: hexagon +//@ [M68K] compile-flags: --target=m68k-unknown-linux-gnu +//@ [M68K] needs-llvm-components: m68k + +#![feature(no_core, lang_items)] +#![no_std] +#![no_core] +#![crate_type = "lib"] + +#[lang = "sized"] +trait Sized {} + +#[lang = "drop_in_place"] +fn drop_in_place(_: *mut T) {} + +#[used] +#[no_mangle] +// U is below the threshold, should be in sdata +static mut U: u16 = 123; + +#[used] +#[no_mangle] +// V is below the threshold, should be in sbss +static mut V: u16 = 0; + +#[used] +#[no_mangle] +// W is at the threshold, should be in sdata +static mut W: u32 = 123; + +#[used] +#[no_mangle] +// X is at the threshold, should be in sbss +static mut X: u32 = 0; + +#[used] +#[no_mangle] +// Y is over the threshold, should be in its own .data section +static mut Y: u64 = 123; + +#[used] +#[no_mangle] +// Z is over the threshold, should be in its own .bss section +static mut Z: u64 = 0; + +// Currently, only MIPS and RISCV successfully put any objects in the small data +// sections so the U/V/W/X tests are skipped on Hexagon and M68K + +//@ RISCV: .section .sdata, +//@ RISCV-NOT: .section +//@ RISCV: U: +//@ RISCV: .section .sbss +//@ RISCV-NOT: .section +//@ RISCV: V: +//@ RISCV: .section .sdata +//@ RISCV-NOT: .section +//@ RISCV: W: +//@ RISCV: .section .sbss +//@ RISCV-NOT: .section +//@ RISCV: X: + +//@ MIPS: .section .sdata, +//@ MIPS-NOT: .section +//@ MIPS: U: +//@ MIPS: .section .sbss +//@ MIPS-NOT: .section +//@ MIPS: V: +//@ MIPS: .section .sdata +//@ MIPS-NOT: .section +//@ MIPS: W: +//@ MIPS: .section .sbss +//@ MIPS-NOT: .section +//@ MIPS: X: + +//@ CHECK: .section .data.Y, +//@ CHECK-NOT: .section +//@ CHECK: Y: +//@ CHECK: .section .bss.Z, +//@ CHECK-NOT: .section +//@ CHECK: Z: