From 7f840870c727ca7037111600768b057baa2387a0 Mon Sep 17 00:00:00 2001
From: Alex Crichton <alex@alexcrichton.com>
Date: Tue, 26 Jan 2021 16:42:11 -0600
Subject: [PATCH] cranelift-native: Use libstd feature detection (#2607)

This commit switches cranelift-native to useing the
`is_x86_feature_detected!` macro in the standard library instead of the
`raw-cpuid` crate.
---
 Cargo.lock                  | 10 -----
 cranelift/native/Cargo.toml |  3 --
 cranelift/native/src/lib.rs | 74 ++++++++++++++++---------------------
 3 files changed, 31 insertions(+), 56 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 86cbcb9f6b..ead0ab8413 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -607,7 +607,6 @@ name = "cranelift-native"
 version = "0.69.0"
 dependencies = [
  "cranelift-codegen",
- "raw-cpuid",
  "target-lexicon",
 ]
 
@@ -2145,15 +2144,6 @@ dependencies = [
  "rand_core 0.5.1",
 ]
 
-[[package]]
-name = "raw-cpuid"
-version = "9.0.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c27cb5785b85bd05d4eb171556c9a1a514552e26123aeae6bb7d811353148026"
-dependencies = [
- "bitflags",
-]
-
 [[package]]
 name = "rawbytes"
 version = "0.1.1"
diff --git a/cranelift/native/Cargo.toml b/cranelift/native/Cargo.toml
index 047d21261a..3bcd72d699 100644
--- a/cranelift/native/Cargo.toml
+++ b/cranelift/native/Cargo.toml
@@ -14,9 +14,6 @@ edition = "2018"
 cranelift-codegen = { path = "../codegen", version = "0.69.0", default-features = false }
 target-lexicon = "0.11"
 
-[target.'cfg(any(target_arch = "x86", target_arch = "x86_64"))'.dependencies]
-raw-cpuid = "9.0.0"
-
 [features]
 default = ["std"]
 std = ["cranelift-codegen/std"]
diff --git a/cranelift/native/src/lib.rs b/cranelift/native/src/lib.rs
index 8dffd8ff79..43938bd97e 100644
--- a/cranelift/native/src/lib.rs
+++ b/cranelift/native/src/lib.rs
@@ -22,14 +22,10 @@
         clippy::use_self
     )
 )]
-#![no_std]
 
 use cranelift_codegen::isa;
 use target_lexicon::Triple;
 
-#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
-use raw_cpuid::CpuId;
-
 /// Return an `isa` builder configured for the current host
 /// machine, or `Err(())` if the host machine is not supported
 /// in the current configuration.
@@ -56,72 +52,64 @@ pub fn builder_with_options(
             isa::LookupError::Unsupported => "unsupported architecture",
         })?;
 
-    if infer_native_flags && cfg!(any(target_arch = "x86", target_arch = "x86_64")) {
-        parse_x86_cpuid(&mut isa_builder)?;
-    }
+    #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
+    {
+        use cranelift_codegen::settings::Configurable;
 
-    Ok(isa_builder)
-}
-
-#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
-fn parse_x86_cpuid(isa_builder: &mut isa::Builder) -> Result<(), &'static str> {
-    use cranelift_codegen::settings::Configurable;
-    let cpuid = CpuId::new();
-
-    if let Some(info) = cpuid.get_feature_info() {
-        if !info.has_sse2() {
+        if !std::is_x86_feature_detected!("sse2") {
             return Err("x86 support requires SSE2");
         }
-        if info.has_sse3() {
+
+        if !infer_native_flags {
+            return Ok(isa_builder);
+        }
+
+        if std::is_x86_feature_detected!("sse3") {
             isa_builder.enable("has_sse3").unwrap();
         }
-        if info.has_ssse3() {
+        if std::is_x86_feature_detected!("ssse3") {
             isa_builder.enable("has_ssse3").unwrap();
         }
-        if info.has_sse41() {
+        if std::is_x86_feature_detected!("sse4.1") {
             isa_builder.enable("has_sse41").unwrap();
         }
-        if info.has_sse42() {
+        if std::is_x86_feature_detected!("sse4.2") {
             isa_builder.enable("has_sse42").unwrap();
         }
-        if info.has_popcnt() {
+        if std::is_x86_feature_detected!("popcnt") {
             isa_builder.enable("has_popcnt").unwrap();
         }
-        if info.has_avx() {
+        if std::is_x86_feature_detected!("avx") {
             isa_builder.enable("has_avx").unwrap();
         }
-    }
-    if let Some(info) = cpuid.get_extended_feature_info() {
-        if info.has_bmi1() {
-            isa_builder.enable("has_bmi1").unwrap();
-        }
-        if info.has_bmi2() {
-            isa_builder.enable("has_bmi2").unwrap();
-        }
-        if info.has_avx2() {
+        if std::is_x86_feature_detected!("avx2") {
             isa_builder.enable("has_avx2").unwrap();
         }
-        if info.has_avx512dq() {
+        if std::is_x86_feature_detected!("bmi1") {
+            isa_builder.enable("has_bmi1").unwrap();
+        }
+        if std::is_x86_feature_detected!("bmi2") {
+            isa_builder.enable("has_bmi2").unwrap();
+        }
+        if std::is_x86_feature_detected!("avx512dq") {
             isa_builder.enable("has_avx512dq").unwrap();
         }
-        if info.has_avx512vl() {
+        if std::is_x86_feature_detected!("avx512vl") {
             isa_builder.enable("has_avx512vl").unwrap();
         }
-        if info.has_avx512f() {
+        if std::is_x86_feature_detected!("avx512f") {
             isa_builder.enable("has_avx512f").unwrap();
         }
-    }
-    if let Some(info) = cpuid.get_extended_function_info() {
-        if info.has_lzcnt() {
+        if std::is_x86_feature_detected!("lzcnt") {
             isa_builder.enable("has_lzcnt").unwrap();
         }
     }
-    Ok(())
-}
 
-#[cfg(not(any(target_arch = "x86", target_arch = "x86_64")))]
-fn parse_x86_cpuid(_isa_builder: &mut isa::Builder) -> Result<(), &'static str> {
-    unreachable!();
+    // squelch warnings about unused mut/variables on some platforms.
+    drop(&mut isa_builder);
+    drop(infer_native_flags);
+
+    Ok(isa_builder)
 }
 
 #[cfg(test)]