From 102a5d867c9b82df79ff7465eb8287b700af3bce Mon Sep 17 00:00:00 2001
From: Caleb Zulawski <caleb.zulawski@gmail.com>
Date: Sat, 19 Nov 2022 21:22:17 -0500
Subject: [PATCH] Print all features with --print target-features, including
 aliases and tied features

---
 compiler/rustc_codegen_llvm/src/llvm_util.rs | 35 +++++++++++---------
 1 file changed, 19 insertions(+), 16 deletions(-)

diff --git a/compiler/rustc_codegen_llvm/src/llvm_util.rs b/compiler/rustc_codegen_llvm/src/llvm_util.rs
index 4af1aaec0a112..8383a9c853556 100644
--- a/compiler/rustc_codegen_llvm/src/llvm_util.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm_util.rs
@@ -292,30 +292,33 @@ fn llvm_target_features(tm: &llvm::TargetMachine) -> Vec<(&str, &str)> {
 }
 
 fn print_target_features(sess: &Session, tm: &llvm::TargetMachine) {
-    let mut target_features = llvm_target_features(tm);
+    let mut llvm_target_features = llvm_target_features(tm);
+    let mut known_llvm_target_features = FxHashSet::<&'static str>::default();
     let mut rustc_target_features = supported_target_features(sess)
         .iter()
-        .filter_map(|(feature, _gate)| {
-            for llvm_feature in to_llvm_features(sess, *feature) {
+        .map(|(feature, _gate)| {
+            let desc = if let Some(llvm_feature) = to_llvm_features(sess, *feature).first() {
                 // LLVM asserts that these are sorted. LLVM and Rust both use byte comparison for these strings.
-                match target_features.binary_search_by_key(&llvm_feature, |(f, _d)| f).ok().map(
-                    |index| {
-                        let (_f, desc) = target_features.remove(index);
-                        (*feature, desc)
-                    },
-                ) {
-                    Some(v) => return Some(v),
-                    None => {}
+                match llvm_target_features.binary_search_by_key(&llvm_feature, |(f, _d)| f).ok() {
+                    Some(index) => {
+                        known_llvm_target_features.insert(llvm_feature);
+                        llvm_target_features[index].1
+                    }
+                    None => "",
                 }
-            }
-            None
+            } else {
+                ""
+            };
+            (*feature, desc)
         })
         .collect::<Vec<_>>();
     rustc_target_features.extend_from_slice(&[(
         "crt-static",
         "Enables C Run-time Libraries to be statically linked",
     )]);
-    let max_feature_len = target_features
+    llvm_target_features.retain(|(f, _d)| !known_llvm_target_features.contains(f));
+
+    let max_feature_len = llvm_target_features
         .iter()
         .chain(rustc_target_features.iter())
         .map(|(feature, _desc)| feature.len())
@@ -327,10 +330,10 @@ fn print_target_features(sess: &Session, tm: &llvm::TargetMachine) {
         println!("    {1:0$} - {2}.", max_feature_len, feature, desc);
     }
     println!("\nCode-generation features supported by LLVM for this target:");
-    for (feature, desc) in &target_features {
+    for (feature, desc) in &llvm_target_features {
         println!("    {1:0$} - {2}.", max_feature_len, feature, desc);
     }
-    if target_features.is_empty() {
+    if llvm_target_features.is_empty() {
         println!("    Target features listing is not supported by this LLVM version.");
     }
     println!("\nUse +feature to enable a feature, or -feature to disable it.");