[ADT][NFC] Refactor/optimize DenseMap::copyFrom

[marcauberer]

Simplify code, constexpr-ify if with constexpr condition

[llvmbot]

@llvm/pr-subscribers-llvm-adt

Author: Marc Auberer (marcauberer)

Changes

Simplify code constexpr-ify if with constexpr condition

---

Full diff: https://github.com/llvm/llvm-project/pull/108377.diff

1 Files Affected:

• (modified) llvm/include/llvm/ADT/DenseMap.h (+15-12)

diff --git a/llvm/include/llvm/ADT/DenseMap.h b/llvm/include/llvm/ADT/DenseMap.h
index 083d5c9388f7c8..8951ecfeb4720d 100644
--- a/llvm/include/llvm/ADT/DenseMap.h
+++ b/llvm/include/llvm/ADT/DenseMap.h
@@ -471,19 +471,22 @@ class DenseMapBase : public DebugEpochBase {
     setNumEntries(other.getNumEntries());
     setNumTombstones(other.getNumTombstones());
 
-    if (std::is_trivially_copyable<KeyT>::value &&
-        std::is_trivially_copyable<ValueT>::value)
-      memcpy(reinterpret_cast<void *>(getBuckets()), other.getBuckets(),
+    BucketT *Buckets = getBuckets();
+    const BucketT *OtherBuckets = other.getBuckets();
+    if constexpr (std::is_trivially_copyable_v<KeyT> &&
+                  std::is_trivially_copyable_v<ValueT>) {
+      memcpy(reinterpret_cast<void *>(Buckets), OtherBuckets,
              getNumBuckets() * sizeof(BucketT));
-    else
-      for (size_t i = 0; i < getNumBuckets(); ++i) {
-        ::new (&getBuckets()[i].getFirst())
-            KeyT(other.getBuckets()[i].getFirst());
-        if (!KeyInfoT::isEqual(getBuckets()[i].getFirst(), getEmptyKey()) &&
-            !KeyInfoT::isEqual(getBuckets()[i].getFirst(), getTombstoneKey()))
-          ::new (&getBuckets()[i].getSecond())
-              ValueT(other.getBuckets()[i].getSecond());
+    } else {
+      const KeyT EmptyKey = getEmptyKey();
+      const KeyT TombstoneKey = getTombstoneKey();
+      for (size_t I = 0; I < getNumBuckets(); ++I) {
+        ::new (&Buckets[I].getFirst()) KeyT(OtherBuckets[I].getFirst());
+        if (!KeyInfoT::isEqual(Buckets[I].getFirst(), EmptyKey) &&
+            !KeyInfoT::isEqual(Buckets[I].getFirst(), TombstoneKey))
+          ::new (&Buckets[I].getSecond()) ValueT(OtherBuckets[I].getSecond());
       }
+    }
   }
 
   static unsigned getHashValue(const KeyT &Val) {
@@ -496,7 +499,7 @@ class DenseMapBase : public DebugEpochBase {
   }
 
   static const KeyT getEmptyKey() {
-    static_assert(std::is_base_of<DenseMapBase, DerivedT>::value,
+    static_assert(std::is_base_of_v<DenseMapBase, DerivedT>,
                   "Must pass the derived type to this template!");
     return KeyInfoT::getEmptyKey();
   }

[kazutakahirata]

LGTM. Thanks!