Auto merge of rust-lang#117680 - matthiaskrgr:rollup-kgaa4ma, r=matthiaskrgr

Rollup of 4 pull requests

Successful merges:

 - rust-lang#115485 (Format macro const literals with pretty printer)
 - rust-lang#117616 (warn when using an unstable feature with -Ctarget-feature)
 - rust-lang#117639 (Update books)
 - rust-lang#117675 (llvm-wrapper: Remove include of non-existant Vectorize.h)

r? `@ghost`
`@rustbot` modify labels: rollup

Author: bors

compiler/rustc_codegen_llvm/messages.ftl

@@ -76,8 +76,8 @@ codegen_llvm_target_machine = could not create LLVM TargetMachine for triple: {$
 codegen_llvm_target_machine_with_llvm_err = could not create LLVM TargetMachine for triple: {$triple}: {$llvm_err}
 
 codegen_llvm_unknown_ctarget_feature =
-    unknown feature specified for `-Ctarget-feature`: `{$feature}`
-    .note = it is still passed through to the codegen backend
+    unknown and unstable feature specified for `-Ctarget-feature`: `{$feature}`
+    .note = it is still passed through to the codegen backend, but use of this feature might be unsound and the behavior of this feature can change in the future
     .possible_feature = you might have meant: `{$rust_feature}`
     .consider_filing_feature_request = consider filing a feature request
 
@@ -87,6 +87,10 @@ codegen_llvm_unknown_ctarget_feature_prefix =
 
 codegen_llvm_unknown_debuginfo_compression = unknown debuginfo compression algorithm {$algorithm} - will fall back to uncompressed debuginfo
 
+codegen_llvm_unstable_ctarget_feature =
+    unstable feature specified for `-Ctarget-feature`: `{$feature}`
+    .note = this feature is not stably supported; its behavior can change in the future
+
 codegen_llvm_write_bytecode = failed to write bytecode to {$path}: {$err}
 
 codegen_llvm_write_ir = failed to write LLVM IR to {$path}

compiler/rustc_codegen_llvm/src/errors.rs

@@ -26,6 +26,13 @@ pub(crate) struct UnknownCTargetFeature<'a> {
     pub rust_feature: PossibleFeature<'a>,
 }
 
+#[derive(Diagnostic)]
+#[diag(codegen_llvm_unstable_ctarget_feature)]
+#[note]
+pub(crate) struct UnstableCTargetFeature<'a> {
+    pub feature: &'a str,
+}
+
 #[derive(Subdiagnostic)]
 pub(crate) enum PossibleFeature<'a> {
     #[help(codegen_llvm_possible_feature)]

compiler/rustc_codegen_llvm/src/llvm_util.rs

@@ -1,7 +1,7 @@
 use crate::back::write::create_informational_target_machine;
 use crate::errors::{
     PossibleFeature, TargetFeatureDisableOrEnable, UnknownCTargetFeature,
-    UnknownCTargetFeaturePrefix,
+    UnknownCTargetFeaturePrefix, UnstableCTargetFeature,
 };
 use crate::llvm;
 use libc::c_int;
@@ -531,25 +531,34 @@ pub(crate) fn global_llvm_features(sess: &Session, diagnostics: bool) -> Vec<Str
             };
 
             let feature = backend_feature_name(s)?;
-            // Warn against use of LLVM specific feature names on the CLI.
-            if diagnostics && !supported_features.iter().any(|&(v, _)| v == feature) {
-                let rust_feature = supported_features.iter().find_map(|&(rust_feature, _)| {
-                    let llvm_features = to_llvm_features(sess, rust_feature);
-                    if llvm_features.contains(&feature) && !llvm_features.contains(&rust_feature) {
-                        Some(rust_feature)
+            // Warn against use of LLVM specific feature names and unstable features on the CLI.
+            if diagnostics {
+                let feature_state = supported_features.iter().find(|&&(v, _)| v == feature);
+                if feature_state.is_none() {
+                    let rust_feature = supported_features.iter().find_map(|&(rust_feature, _)| {
+                        let llvm_features = to_llvm_features(sess, rust_feature);
+                        if llvm_features.contains(&feature)
+                            && !llvm_features.contains(&rust_feature)
+                        {
+                            Some(rust_feature)
+                        } else {
+                            None
+                        }
+                    });
+                    let unknown_feature = if let Some(rust_feature) = rust_feature {
+                        UnknownCTargetFeature {
+                            feature,
+                            rust_feature: PossibleFeature::Some { rust_feature },
+                        }
                     } else {
-                        None
-                    }
-                });
-                let unknown_feature = if let Some(rust_feature) = rust_feature {
-                    UnknownCTargetFeature {
-                        feature,
-                        rust_feature: PossibleFeature::Some { rust_feature },
-                    }
-                } else {
-                    UnknownCTargetFeature { feature, rust_feature: PossibleFeature::None }
-                };
-                sess.emit_warning(unknown_feature);
+                        UnknownCTargetFeature { feature, rust_feature: PossibleFeature::None }
+                    };
+                    sess.emit_warning(unknown_feature);
+                } else if feature_state.is_some_and(|(_name, feature_gate)| feature_gate.is_some())
+                {
+                    // An unstable feature. Warn about using it.
+                    sess.emit_warning(UnstableCTargetFeature { feature });
+                }
             }
 
             if diagnostics {

compiler/rustc_codegen_ssa/src/target_features.rs

@@ -23,6 +23,15 @@ pub const RUSTC_SPECIFIC_FEATURES: &[&str] = &["crt-static"];
 // check whether they're named already elsewhere in rust
 // e.g. in stdarch and whether the given name matches LLVM's
 // if it doesn't, to_llvm_feature in llvm_util in rustc_codegen_llvm needs to be adapted
+//
+// When adding a new feature, be particularly mindful of features that affect function ABIs. Those
+// need to be treated very carefully to avoid introducing unsoundness! This often affects features
+// that enable/disable hardfloat support (see https://github.com/rust-lang/rust/issues/116344 for an
+// example of this going wrong), but features enabling new SIMD registers are also a concern (see
+// https://github.com/rust-lang/rust/issues/116558 for an example of this going wrong).
+//
+// Stabilizing a target feature (setting the 2nd component of the pair to `None`) requires t-lang
+// approval.
 
 const ARM_ALLOWED_FEATURES: &[(&str, Option<Symbol>)] = &[
     // tidy-alphabetical-start

compiler/rustc_llvm/llvm-wrapper/LLVMWrapper.h

@@ -25,7 +25,6 @@
 #include "llvm/Transforms/IPO.h"
 #include "llvm/Transforms/Instrumentation.h"
 #include "llvm/Transforms/Scalar.h"
-#include "llvm/Transforms/Vectorize.h"
 
 #define LLVM_VERSION_GE(major, minor)                                          \
   (LLVM_VERSION_MAJOR > (major) ||                                             \

compiler/rustc_metadata/src/lib.rs

@@ -8,6 +8,7 @@
 #![cfg_attr(not(bootstrap), feature(coroutines))]
 #![feature(iter_from_coroutine)]
 #![feature(let_chains)]
+#![feature(if_let_guard)]
 #![feature(proc_macro_internals)]
 #![feature(macro_metavar_expr)]
 #![feature(min_specialization)]

compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -2386,31 +2386,32 @@ pub fn rendered_const<'tcx>(tcx: TyCtxt<'tcx>, body: hir::BodyId) -> String {
         }
     }
 
-    let classification = classify(value);
-
-    if classification == Literal
-        && !value.span.from_expansion()
-        && let Ok(snippet) = tcx.sess.source_map().span_to_snippet(value.span)
-    {
-        // For literals, we avoid invoking the pretty-printer and use the source snippet instead to
-        // preserve certain stylistic choices the user likely made for the sake legibility like
+    match classify(value) {
+        // For non-macro literals, we avoid invoking the pretty-printer and use the source snippet
+        // instead to preserve certain stylistic choices the user likely made for the sake of
+        // legibility, like:
         //
         // * hexadecimal notation
         // * underscores
         // * character escapes
         //
         // FIXME: This passes through `-/*spacer*/0` verbatim.
-        snippet
-    } else if classification == Simple {
+        Literal if !value.span.from_expansion()
+            && let Ok(snippet) = tcx.sess.source_map().span_to_snippet(value.span) => {
+            snippet
+        }
+
         // Otherwise we prefer pretty-printing to get rid of extraneous whitespace, comments and
         // other formatting artifacts.
-        id_to_string(&hir, body.hir_id)
-    } else if tcx.def_kind(hir.body_owner_def_id(body).to_def_id()) == DefKind::AnonConst {
+        Literal | Simple => id_to_string(&hir, body.hir_id),
+
         // FIXME: Omit the curly braces if the enclosing expression is an array literal
         //        with a repeated element (an `ExprKind::Repeat`) as in such case it
         //        would not actually need any disambiguation.
-        "{ _ }".to_owned()
-    } else {
-        "_".to_owned()
+        Complex => if tcx.def_kind(hir.body_owner_def_id(body).to_def_id()) == DefKind::AnonConst {
+            "{ _ }".to_owned()
+        } else {
+            "_".to_owned()
+        }
     }
 }