[TableGen] Avoid repeated map lookups (NFC)

[kazutakahirata]

This patch avoids repeated map lookups and constructions of temporary
std::string instances by switching to DenseSet.

[llvmbot]

@llvm/pr-subscribers-clang

Author: Kazu Hirata (kazutakahirata)

Changes

This patch avoids repeated map lookups and constructions of temporary
std::string instances by switching to StringMap.

---

Full diff: https://github.com/llvm/llvm-project/pull/124448.diff

1 Files Affected:

• (modified) clang/utils/TableGen/MveEmitter.cpp (+3-3)

diff --git a/clang/utils/TableGen/MveEmitter.cpp b/clang/utils/TableGen/MveEmitter.cpp
index 8ebd0bb800feff..7f298d1cbd4376 100644
--- a/clang/utils/TableGen/MveEmitter.cpp
+++ b/clang/utils/TableGen/MveEmitter.cpp
@@ -60,6 +60,7 @@
 
 #include "llvm/ADT/APInt.h"
 #include "llvm/ADT/StringRef.h"
+#include "llvm/ADT/StringSet.h"
 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/raw_ostream.h"
@@ -1955,18 +1956,17 @@ void MveEmitter::EmitBuiltinDef(raw_ostream &OS) {
        << ", \"\", \"n\")\n";
   }
 
-  std::set<std::string> ShortNamesSeen;
+  StringSet<> ShortNamesSeen;
 
   for (const auto &kv : ACLEIntrinsics) {
     const ACLEIntrinsic &Int = *kv.second;
     if (Int.polymorphic()) {
       StringRef Name = Int.shortName();
-      if (ShortNamesSeen.find(std::string(Name)) == ShortNamesSeen.end()) {
+      if (ShortNamesSeen.insert(Name).second) {
         OS << "BUILTIN(__builtin_arm_mve_" << Name << ", \"vi.\", \"nt";
         if (Int.nonEvaluating())
           OS << "u"; // indicate that this builtin doesn't evaluate its args
         OS << "\")\n";
-        ShortNamesSeen.insert(std::string(Name));
       }
     }
   }

[nikic]

Can't this use DenseSet? It looks like the names here live for the lifetime of the set.

[kazutakahirata]

Can't this use DenseSet? It looks like the names here live for the lifetime of the set.

Good idea! Revised.