feat: Added capability to add multiple dependencies for an LLVMFeature

Author: madhav-madhusoodanan

compiler/rustc_codegen_llvm/src/llvm_util.rs

@@ -19,6 +19,7 @@ use rustc_session::config::{PrintKind, PrintRequest};
 use rustc_span::Symbol;
 use rustc_target::spec::{MergeFunctions,PanicStrategy,SmallDataThresholdSupport};
 use rustc_target::target_features::{RUSTC_SPECIAL_FEATURES,RUSTC_SPECIFIC_FEATURES};
+use smallvec::{SmallVec, smallvec};
 
 usecrate::back::write::create_informational_target_machine;
 usecrate::errors::{
@@ -180,27 +181,27 @@ impl<'a> TargetFeatureFoldStrength<'a> {
 
 pub(crate)structLLVMFeature<'a>{
 llvm_feature_name:&'astr,
-dependency:Option<TargetFeatureFoldStrength<'a>>,
+dependencies:SmallVec<[TargetFeatureFoldStrength<'a>;1]>,
 }
 
 impl<'a>LLVMFeature<'a>{
 fnnew(llvm_feature_name:&'astr) -> Self{
-Self{ llvm_feature_name,dependency:None}
+Self{ llvm_feature_name,dependencies:SmallVec::new()}
 }
 
-fnwith_dependency(
+fnwith_dependencies(
 llvm_feature_name:&'astr,
-dependency:TargetFeatureFoldStrength<'a>,
+dependencies:SmallVec<[TargetFeatureFoldStrength<'a>;1]>,
 ) -> Self{
-Self{ llvm_feature_name,dependency:Some(dependency)}
+Self{ llvm_feature_name,dependencies}
 }
 
-fncontains(&self,feat:&str) -> bool{
+fncontains(&'aself,feat:&str) -> bool{
 self.iter().any(|dep| dep == feat)
 }
 
 fniter(&'aself) -> implIterator<Item = &'astr>{
-let dependencies = self.dependency.iter().map(|feat| feat.as_str());
+let dependencies = self.dependencies.iter().map(|feat| feat.as_str());
  std::iter::once(self.llvm_feature_name).chain(dependencies)
 }
 }
@@ -210,7 +211,7 @@ impl<'a> IntoIterator for LLVMFeature<'a> {
 typeIntoIter = implIterator<Item = &'astr>;
 
 fninto_iter(self) -> Self::IntoIter{
-let dependencies = self.dependency.into_iter().map(|feat| feat.as_str());
+let dependencies = self.dependencies.into_iter().map(|feat| feat.as_str());
  std::iter::once(self.llvm_feature_name).chain(dependencies)
 }
 }
@@ -240,9 +241,9 @@ pub(crate) fn to_llvm_features<'a>(sess: &Session, s: &'a str) -> Option<LLVMFea
 &*sess.target.arch
 };
 match(arch, s){
-("x86","sse4.2") => Some(LLVMFeature::with_dependency(
+("x86","sse4.2") => Some(LLVMFeature::with_dependencies(
 "sse4.2",
-TargetFeatureFoldStrength::EnableOnly("crc32"),
+smallvec![TargetFeatureFoldStrength::EnableOnly("crc32")],
 )),
 ("x86","pclmulqdq") => Some(LLVMFeature::new("pclmul")),
 ("x86","rdrand") => Some(LLVMFeature::new("rdrnd")),
@@ -262,9 +263,10 @@ pub(crate) fn to_llvm_features<'a>(sess: &Session, s: &'a str) -> Option<LLVMFea
 ("aarch64","sme-b16b16")ifget_version().0 < 20 => Some(LLVMFeature::new("b16b16")),
 ("aarch64","flagm2") => Some(LLVMFeature::new("altnzcv")),
 // Rust ties fp and neon together.
-("aarch64","neon") => {
-Some(LLVMFeature::with_dependency("neon",TargetFeatureFoldStrength::Both("fp-armv8")))
-}
+("aarch64","neon") => Some(LLVMFeature::with_dependencies(
+"neon",
+smallvec![TargetFeatureFoldStrength::Both("fp-armv8")],
+)),
 // In LLVM neon implicitly enables fp, but we manually enable
 // neon when a feature only implicitly enables fp
 ("aarch64","fhm") => Some(LLVMFeature::new("fp16fml")),
@@ -281,9 +283,10 @@ pub(crate) fn to_llvm_features<'a>(sess: &Session, s: &'a str) -> Option<LLVMFea
 // Filter out features that are not supported by the current LLVM version
 ("riscv32" | "riscv64","zacas")ifget_version().0 < 20 => None,
 // Enable the evex512 target feature if an avx512 target feature is enabled.
-("x86", s)if s.starts_with("avx512") => {
-Some(LLVMFeature::with_dependency(s,TargetFeatureFoldStrength::EnableOnly("evex512")))
-}
+("x86", s)if s.starts_with("avx512") => Some(LLVMFeature::with_dependencies(
+ s,
+smallvec![TargetFeatureFoldStrength::EnableOnly("evex512")],
+)),
 // Support for `wide-arithmetic` will first land in LLVM 20 as part of
 // llvm/llvm-project#111598
 ("wasm32" | "wasm64","wide-arithmetic")ifget_version() < (20,0,0) => None,
@@ -853,7 +856,7 @@ pub(crate) fn global_llvm_features(
 "{}{}",
  enable_disable, llvm_feature.llvm_feature_name
 ))
-.chain(llvm_feature.dependency.into_iter().filter_map(
+.chain(llvm_feature.dependencies.into_iter().filter_map(
 move |feat| match(enable, feat){
 (_,TargetFeatureFoldStrength::Both(f))
  | (true,TargetFeatureFoldStrength::EnableOnly(f)) => {