fixup! Avoid while (true) during index generation

Author: cachemeifyoucan

llvm/lib/Support/TrieHashIndexGenerator.h

@@ -45,18 +45,19 @@ struct IndexGenerator {
 
   // Get the index of the object in the next level of trie.
   size_t next() {
-    size_t Index;
     if (!StartBit) {
       // Compute index for root when StartBit is not set.
       StartBit = 0;
-      Index = getIndex(Bytes, *StartBit, NumRootBits);
-    } else {
+      return getIndex(Bytes, *StartBit, NumRootBits);
+    }
+    if (*StartBit < Bytes.size() * 8) {
       // Compute index for sub-trie.
       *StartBit += *StartBit ? NumSubtrieBits : NumRootBits;
       assert((*StartBit - NumRootBits) % NumSubtrieBits == 0);
-      Index = getIndex(Bytes, *StartBit, NumSubtrieBits);
+      return getIndex(Bytes, *StartBit, NumSubtrieBits);
     }
-    return Index;
+    // All the bits are consumed.
+    return end();
   }
 
   // Provide a hint to speed up the index generation by providing the
@@ -79,6 +80,8 @@ struct IndexGenerator {
     return getIndex(CollidingBits, *StartBit, NumSubtrieBits);
   }
 
+  size_t end() const { return SIZE_MAX; }
+
   // Compute the index for the object from its hash, current start bits, and
   // the number of bits used for current level.
   static size_t getIndex(ArrayRef<uint8_t> Bytes, size_t StartBit,

llvm/lib/Support/TrieRawHashMap.cpp

@@ -224,7 +224,7 @@ ThreadSafeTrieRawHashMapBase::find(ArrayRef<uint8_t> Hash) const {
   TrieSubtrie *S = &Impl->Root;
   IndexGenerator IndexGen{NumRootBits, NumSubtrieBits, Hash};
   size_t Index = IndexGen.next();
-  while (true) {
+  while (Index != IndexGen.end()) {
     // Try to set the content.
     TrieNode *Existing = S->get(Index);
     if (!Existing)
@@ -239,6 +239,7 @@ ThreadSafeTrieRawHashMapBase::find(ArrayRef<uint8_t> Hash) const {
     Index = IndexGen.next();
     S = cast<TrieSubtrie>(Existing);
   }
+  llvm_unreachable("failed to locate the node after consuming all hash bytes");
 }
 
 ThreadSafeTrieRawHashMapBase::PointerBase ThreadSafeTrieRawHashMapBase::insert(
@@ -258,7 +259,7 @@ ThreadSafeTrieRawHashMapBase::PointerBase ThreadSafeTrieRawHashMapBase::insert(
     Index = IndexGen.next();
   }
 
-  while (true) {
+  while (Index != IndexGen.end()) {
     // Load the node from the slot, allocating and calling the constructor if
     // the slot is empty.
     bool Generated = false;
@@ -292,8 +293,8 @@ ThreadSafeTrieRawHashMapBase::PointerBase ThreadSafeTrieRawHashMapBase::insert(
       return PointerBase(ExistingContent.getValuePointer());
 
     // Sink the existing content as long as the indexes match.
-    while (true) {
-      size_t NextIndex = IndexGen.next();
+    size_t NextIndex = IndexGen.next();
+    while (NextIndex != IndexGen.end()) {
       size_t NewIndexForExistingContent =
           IndexGen.getCollidingBits(ExistingContent.getHash());
       S = S->sink(Index, ExistingContent, IndexGen.getNumBits(),
@@ -306,8 +307,11 @@ ThreadSafeTrieRawHashMapBase::PointerBase ThreadSafeTrieRawHashMapBase::insert(
       // Found the difference.
       if (NextIndex != NewIndexForExistingContent)
         break;
+
+      NextIndex = IndexGen.next();
     }
   }
+  llvm_unreachable("failed to insert the node after consuming all hash bytes");
 }
 
 ThreadSafeTrieRawHashMapBase::ThreadSafeTrieRawHashMapBase(