[RISCV] Minor improvements/cleanup to target attribute handling. NFC

[topperc]

Use ArrayRef to avoid a vector copy.
Replace a push_back loop with a call to std::vector::insert.

[llvmbot]

@llvm/pr-subscribers-backend-risc-v

@llvm/pr-subscribers-clang

Author: Craig Topper (topperc)

Changes

Use ArrayRef to avoid a vector copy.
Replace a push_back loop with a call to std::vector::insert.

---

Full diff: https://github.com/llvm/llvm-project/pull/73851.diff

1 Files Affected:

• (modified) clang/lib/Basic/Targets/RISCV.cpp (+4-6)

diff --git a/clang/lib/Basic/Targets/RISCV.cpp b/clang/lib/Basic/Targets/RISCV.cpp
index d1d9cc1c770e361..2e9ce468b5d3e36 100644
--- a/clang/lib/Basic/Targets/RISCV.cpp
+++ b/clang/lib/Basic/Targets/RISCV.cpp
@@ -236,8 +236,7 @@ ArrayRef<Builtin::Info> RISCVTargetInfo::getTargetBuiltins() const {
 }
 
 static std::vector<std::string>
-collectNonISAExtFeature(const std::vector<std::string> &FeaturesNeedOverride,
-                        int XLen) {
+collectNonISAExtFeature(ArrayRef<std::string> FeaturesNeedOverride, int XLen) {
   auto ParseResult =
       llvm::RISCVISAInfo::parseFeatures(XLen, FeaturesNeedOverride);
 
@@ -265,11 +264,11 @@ resolveTargetAttrOverride(const std::vector<std::string> &FeaturesVec,
   if (I == FeaturesVec.end())
     return FeaturesVec;
 
-  const std::vector<std::string> FeaturesNeedOverride(FeaturesVec.begin(), I);
+  ArrayRef<std::string> FeaturesNeedOverride(&*FeaturesVec.begin(), &*I);
   std::vector<std::string> NonISAExtFeature =
       collectNonISAExtFeature(FeaturesNeedOverride, XLen);
 
-  auto ResolvedFeature = std::vector<std::string>(++I, FeaturesVec.end());
+  std::vector<std::string> ResolvedFeature(++I, FeaturesVec.end());
   ResolvedFeature.insert(ResolvedFeature.end(), NonISAExtFeature.begin(),
                          NonISAExtFeature.end());
 
@@ -415,8 +414,7 @@ static void handleFullArchString(StringRef FullArchStr,
     Features.push_back("+" + FullArchStr.str());
   } else {
     std::vector<std::string> FeatStrings = (*RII)->toFeatureVector();
-    for (auto FeatString : FeatStrings)
-      Features.push_back(FeatString);
+    Features.insert(Features.end(), FeatStrings.begin(), FeatStrings.end());
   }
 }
 

[topperc]

The &* are here to convert from the std::vector pointer wrappers to raw pointers.

[asb]

LGTM.