bjoernager/rust
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Auto merge of #87402 - nagisa:nagisa/request-feature-requests-for-features, r=estebank

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Direct users towards using Rust target feature names in CLI

This PR consists of a couple of changes on how we handle target features.

In particular there is a bug-fix wherein we avoid passing through features that aren't prefixed by `+` or `-` to LLVM. These appear to be causing LLVM to assert, which is pretty poor a behaviour (and also makes it pretty clear we expect feature names to be prefixed).

The other commit, I anticipate to be somewhat more controversial is outputting a warning when users specify a LLVM-specific, or otherwise unknown, feature name on the CLI. In those situations we request users to either replace it with a known Rust feature name (e.g. `bmi` -> `bmi1`) or file a feature request. I've a couple motivations for this: first of all, if users are specifying these features on the command line, I'm pretty confident there is also a need for these features to be usable via `#[cfg(target_feature)]` machinery.  And second, we're growing a fair number of backends recently and having ability to provide some sort of unified-ish interface in this place seems pretty useful to me.

Sponsored by: standard.ai
This commit is contained in:
bors 2022-03-02 03:03:22 +00:00
commit 39a3b52767
22 changed files with 253 additions and 108 deletions
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17
compiler/rustc_codegen_llvm/src/back/write.rs
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@ -100,7 +100,10 @@ pub fn write_output_file<'ll>(
pub fn create_informational_target_machine(sess: &Session) -> &'static mut llvm::TargetMachine {
let config = TargetMachineFactoryConfig { split_dwarf_file: None };
target_machine_factory(sess, config::OptLevel::No)(config)
// Can't use query system here quite yet because this function is invoked before the query
// system/tcx is set up.
let features = llvm_util::global_llvm_features(sess, false);
target_machine_factory(sess, config::OptLevel::No, &features)(config)
.unwrap_or_else(|err| llvm_err(sess.diagnostic(), &err).raise())
}
@ -115,8 +118,12 @@ pub fn create_target_machine(tcx: TyCtxt<'_>, mod_name: &str) -> &'static mut ll
None
};
let config = TargetMachineFactoryConfig { split_dwarf_file };
target_machine_factory(tcx.sess, tcx.backend_optimization_level(()))(config)
.unwrap_or_else(|err| llvm_err(tcx.sess.diagnostic(), &err).raise())
target_machine_factory(
&tcx.sess,
tcx.backend_optimization_level(()),
tcx.global_backend_features(()),
)(config)
.unwrap_or_else(|err| llvm_err(tcx.sess.diagnostic(), &err).raise())
}
pub fn to_llvm_opt_settings(
@ -171,6 +178,7 @@ pub(crate) fn to_llvm_code_model(code_model: Option<CodeModel>) -> llvm::CodeMod
pub fn target_machine_factory(
sess: &Session,
optlvl: config::OptLevel,
target_features: &[String],
) -> TargetMachineFactoryFn<LlvmCodegenBackend> {
let reloc_model = to_llvm_relocation_model(sess.relocation_model());
@ -195,8 +203,7 @@ pub fn target_machine_factory(
let triple = SmallCStr::new(&sess.target.llvm_target);
let cpu = SmallCStr::new(llvm_util::target_cpu(sess));
let features = llvm_util::llvm_global_features(sess).join(",");
let features = CString::new(features).unwrap();
let features = CString::new(target_features.join(",")).unwrap();
let abi = SmallCStr::new(&sess.target.llvm_abiname);
let trap_unreachable =
sess.opts.debugging_opts.trap_unreachable.unwrap_or(sess.target.trap_unreachable);