Rollup merge of rust-lang#78361 - DevJPM:master, r=workingjubilee

Updated the list of white-listed target features for x86

This PR both adds in-source documentation on what to look out for when adding a new (X86) feature set and [adds all that are detectable at run-time in Rust stable as of 1.27.0](https://github.com/rust-lang/stdarch/blob/master/crates/std_detect/src/detect/arch/x86.rs).

This should only enable the use of the corresponding LLVM intrinsics.
Actual intrinsics need to be added separately in rust-lang/stdarch.

It also re-orders the run-time-detect test statements to be more consistent
with the actual list of intrinsics whitelisted and removes underscores not present
in the actual names (which might be mistaken as being part of the name)

The reference for LLVM's feature names used is [this file](https://github.com/llvm/llvm-project/blob/master/llvm/include/llvm/Support/X86TargetParser.def).

This PR was motivated as the compiler end's part for allowing rust-lang#67329 to be adressed over on rust-lang/stdarch

Author: m-ou-se

std/tests/run-time-detect.rs

@@ -54,42 +54,62 @@ fn powerpc64_linux() {
 #[test]
 #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
 fn x86_all() {
+    // the below is the set of features we can test at runtime, but don't actually
+    // use to gate anything and are thus not part of the X86_ALLOWED_FEATURES list
+
+    println!("abm: {:?}", is_x86_feature_detected!("abm")); // this is a synonym for lzcnt but we test it anyways
+    println!("mmx: {:?}", is_x86_feature_detected!("mmx"));
+    println!("tsc: {:?}", is_x86_feature_detected!("tsc"));
+
+    // the below is in alphabetical order and matches
+    // the order of X86_ALLOWED_FEATURES in rustc_codegen_ssa's target_features.rs
+
+    println!("adx: {:?}", is_x86_feature_detected!("adx"));
     println!("aes: {:?}", is_x86_feature_detected!("aes"));
-    println!("pcmulqdq: {:?}", is_x86_feature_detected!("pclmulqdq"));
+    println!("avx: {:?}", is_x86_feature_detected!("avx"));
+    println!("avx2: {:?}", is_x86_feature_detected!("avx2"));
+    println!("avx512bf16: {:?}", is_x86_feature_detected!("avx512bf16"));
+    println!("avx512bitalg: {:?}", is_x86_feature_detected!("avx512bitalg"));
+    println!("avx512bw: {:?}", is_x86_feature_detected!("avx512bw"));
+    println!("avx512cd: {:?}", is_x86_feature_detected!("avx512cd"));
+    println!("avx512dq: {:?}", is_x86_feature_detected!("avx512dq"));
+    println!("avx512er: {:?}", is_x86_feature_detected!("avx512er"));
+    println!("avx512f: {:?}", is_x86_feature_detected!("avx512f"));
+    println!("avx512gfni: {:?}", is_x86_feature_detected!("avx512gfni"));
+    println!("avx512ifma: {:?}", is_x86_feature_detected!("avx512ifma"));
+    println!("avx512pf: {:?}", is_x86_feature_detected!("avx512pf"));
+    println!("avx512vaes: {:?}", is_x86_feature_detected!("avx512vaes"));
+    println!("avx512vbmi: {:?}", is_x86_feature_detected!("avx512vbmi"));
+    println!("avx512vbmi2: {:?}", is_x86_feature_detected!("avx512vbmi2"));
+    println!("avx512vl: {:?}", is_x86_feature_detected!("avx512vl"));
+    println!("avx512vnni: {:?}", is_x86_feature_detected!("avx512vnni"));
+    println!("avx512vp2intersect: {:?}", is_x86_feature_detected!("avx512vp2intersect"));
+    println!("avx512vpclmulqdq: {:?}", is_x86_feature_detected!("avx512vpclmulqdq"));
+    println!("avx512vpopcntdq: {:?}", is_x86_feature_detected!("avx512vpopcntdq"));
+    println!("bmi1: {:?}", is_x86_feature_detected!("bmi1"));
+    println!("bmi2: {:?}", is_x86_feature_detected!("bmi2"));
+    println!("cmpxchg16b: {:?}", is_x86_feature_detected!("cmpxchg16b"));
+    println!("f16c: {:?}", is_x86_feature_detected!("f16c"));
+    println!("fma: {:?}", is_x86_feature_detected!("fma"));
+    println!("fxsr: {:?}", is_x86_feature_detected!("fxsr"));
+    println!("lzcnt: {:?}", is_x86_feature_detected!("lzcnt"));
+    //println!("movbe: {:?}", is_x86_feature_detected!("movbe")); // movbe is unsupported as a target feature
+    println!("pclmulqdq: {:?}", is_x86_feature_detected!("pclmulqdq"));
+    println!("popcnt: {:?}", is_x86_feature_detected!("popcnt"));
     println!("rdrand: {:?}", is_x86_feature_detected!("rdrand"));
     println!("rdseed: {:?}", is_x86_feature_detected!("rdseed"));
-    println!("tsc: {:?}", is_x86_feature_detected!("tsc"));
-    println!("mmx: {:?}", is_x86_feature_detected!("mmx"));
+    println!("rtm: {:?}", is_x86_feature_detected!("rtm"));
+    println!("sha: {:?}", is_x86_feature_detected!("sha"));
     println!("sse: {:?}", is_x86_feature_detected!("sse"));
     println!("sse2: {:?}", is_x86_feature_detected!("sse2"));
     println!("sse3: {:?}", is_x86_feature_detected!("sse3"));
-    println!("ssse3: {:?}", is_x86_feature_detected!("ssse3"));
     println!("sse4.1: {:?}", is_x86_feature_detected!("sse4.1"));
     println!("sse4.2: {:?}", is_x86_feature_detected!("sse4.2"));
     println!("sse4a: {:?}", is_x86_feature_detected!("sse4a"));
-    println!("sha: {:?}", is_x86_feature_detected!("sha"));
-    println!("avx: {:?}", is_x86_feature_detected!("avx"));
-    println!("avx2: {:?}", is_x86_feature_detected!("avx2"));
-    println!("avx512f {:?}", is_x86_feature_detected!("avx512f"));
-    println!("avx512cd {:?}", is_x86_feature_detected!("avx512cd"));
-    println!("avx512er {:?}", is_x86_feature_detected!("avx512er"));
-    println!("avx512pf {:?}", is_x86_feature_detected!("avx512pf"));
-    println!("avx512bw {:?}", is_x86_feature_detected!("avx512bw"));
-    println!("avx512dq {:?}", is_x86_feature_detected!("avx512dq"));
-    println!("avx512vl {:?}", is_x86_feature_detected!("avx512vl"));
-    println!("avx512_ifma {:?}", is_x86_feature_detected!("avx512ifma"));
-    println!("avx512_vbmi {:?}", is_x86_feature_detected!("avx512vbmi"));
-    println!("avx512_vpopcntdq {:?}", is_x86_feature_detected!("avx512vpopcntdq"));
-    println!("fma: {:?}", is_x86_feature_detected!("fma"));
-    println!("bmi1: {:?}", is_x86_feature_detected!("bmi1"));
-    println!("bmi2: {:?}", is_x86_feature_detected!("bmi2"));
-    println!("abm: {:?}", is_x86_feature_detected!("abm"));
-    println!("lzcnt: {:?}", is_x86_feature_detected!("lzcnt"));
+    println!("ssse3: {:?}", is_x86_feature_detected!("ssse3"));
     println!("tbm: {:?}", is_x86_feature_detected!("tbm"));
-    println!("popcnt: {:?}", is_x86_feature_detected!("popcnt"));
-    println!("fxsr: {:?}", is_x86_feature_detected!("fxsr"));
     println!("xsave: {:?}", is_x86_feature_detected!("xsave"));
+    println!("xsavec: {:?}", is_x86_feature_detected!("xsavec"));
     println!("xsaveopt: {:?}", is_x86_feature_detected!("xsaveopt"));
     println!("xsaves: {:?}", is_x86_feature_detected!("xsaves"));
-    println!("xsavec: {:?}", is_x86_feature_detected!("xsavec"));
 }