Replace the ugly FindValue method with STL-like find methods.
llvm-svn: 34183
diff --git a/llvm/lib/Support/StringMap.cpp b/llvm/lib/Support/StringMap.cpp
index 5a38964..02d42b9 100644
--- a/llvm/lib/Support/StringMap.cpp
+++ b/llvm/lib/Support/StringMap.cpp
@@ -91,6 +91,49 @@
}
}
+
+/// FindKey - Look up the bucket that contains the specified key. If it exists
+/// in the map, return the bucket number of the key. Otherwise return -1.
+/// This does not modify the map.
+int StringMapImpl::FindKey(const char *KeyStart, const char *KeyEnd) const {
+ unsigned HTSize = NumBuckets;
+ unsigned FullHashValue = HashString(KeyStart, KeyEnd);
+ unsigned BucketNo = FullHashValue & (HTSize-1);
+
+ unsigned ProbeAmt = 1;
+ while (1) {
+ ItemBucket &Bucket = TheTable[BucketNo];
+ StringMapEntryBase *BucketItem = Bucket.Item;
+ // If we found an empty bucket, this key isn't in the table yet, return.
+ if (BucketItem == 0)
+ return -1;
+
+ // If the full hash value matches, check deeply for a match. The common
+ // case here is that we are only looking at the buckets (for item info
+ // being non-null and for the full hash value) not at the items. This
+ // is important for cache locality.
+ if (Bucket.FullHashValue == FullHashValue) {
+ // Do the comparison like this because NameStart isn't necessarily
+ // null-terminated!
+ char *ItemStr = (char*)BucketItem+ItemSize;
+ unsigned ItemStrLen = BucketItem->getKeyLength();
+ if (unsigned(KeyEnd-KeyStart) == ItemStrLen &&
+ memcmp(ItemStr, KeyStart, ItemStrLen) == 0) {
+ // We found a match!
+ return BucketNo;
+ }
+ }
+
+ // Okay, we didn't find the item. Probe to the next bucket.
+ BucketNo = (BucketNo+ProbeAmt) & (HTSize-1);
+
+ // Use quadratic probing, it has fewer clumping artifacts than linear
+ // probing and has good cache behavior in the common case.
+ ++ProbeAmt;
+ }
+}
+
+
/// RehashTable - Grow the table, redistributing values into the buckets with
/// the appropriate mod-of-hashtable-size.
void StringMapImpl::RehashTable() {