vendor/llvm/llvm-r72732

1 files changed, 234 insertions, 0 deletions

diff --git a/lib/Support/StringMap.cpp b/lib/Support/StringMap.cpp
new file mode 100644
index 000000000000..0c61732a61b3
--- /dev/null
+++ b/lib/Support/StringMap.cpp
@@ -0,0 +1,234 @@
+//===--- StringMap.cpp - String Hash table map implementation -------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the StringMap class.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/StringMap.h"
+#include <cassert>
+using namespace llvm;
+
+StringMapImpl::StringMapImpl(unsigned InitSize, unsigned itemSize) {
+  ItemSize = itemSize;
+  
+  // If a size is specified, initialize the table with that many buckets.
+  if (InitSize) {
+    init(InitSize);
+    return;
+  }
+  
+  // Otherwise, initialize it with zero buckets to avoid the allocation.
+  TheTable = 0;
+  NumBuckets = 0;
+  NumItems = 0;
+  NumTombstones = 0;
+}
+
+void StringMapImpl::init(unsigned InitSize) {
+  assert((InitSize & (InitSize-1)) == 0 &&
+         "Init Size must be a power of 2 or zero!");
+  NumBuckets = InitSize ? InitSize : 16;
+  NumItems = 0;
+  NumTombstones = 0;
+  
+  TheTable = (ItemBucket*)calloc(NumBuckets+1, sizeof(ItemBucket));
+  
+  // Allocate one extra bucket, set it to look filled so the iterators stop at
+  // end.
+  TheTable[NumBuckets].Item = (StringMapEntryBase*)2;
+}
+
+
+/// HashString - Compute a hash code for the specified string.
+///
+static unsigned HashString(const char *Start, const char *End) {
+  // Bernstein hash function.
+  unsigned int Result = 0;
+  // TODO: investigate whether a modified bernstein hash function performs
+  // better: http://eternallyconfuzzled.com/tuts/algorithms/jsw_tut_hashing.aspx
+  //   X*33+c -> X*33^c
+  while (Start != End)
+    Result = Result * 33 + *Start++;
+  Result = Result + (Result >> 5);
+  return Result;
+}
+
+/// LookupBucketFor - Look up the bucket that the specified string should end
+/// up in.  If it already exists as a key in the map, the Item pointer for the
+/// specified bucket will be non-null.  Otherwise, it will be null.  In either
+/// case, the FullHashValue field of the bucket will be set to the hash value
+/// of the string.
+unsigned StringMapImpl::LookupBucketFor(const char *NameStart,
+                                        const char *NameEnd) {
+  unsigned HTSize = NumBuckets;
+  if (HTSize == 0) {  // Hash table unallocated so far?
+    init(16);
+    HTSize = NumBuckets;
+  }
+  unsigned FullHashValue = HashString(NameStart, NameEnd);
+  unsigned BucketNo = FullHashValue & (HTSize-1);
+  
+  unsigned ProbeAmt = 1;
+  int FirstTombstone = -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 it.
+    if (BucketItem == 0) {
+      // If we found a tombstone, we want to reuse the tombstone instead of an
+      // empty bucket.  This reduces probing.
+      if (FirstTombstone != -1) {
+        TheTable[FirstTombstone].FullHashValue = FullHashValue;
+        return FirstTombstone;
+      }
+      
+      Bucket.FullHashValue = FullHashValue;
+      return BucketNo;
+    }
+    
+    if (BucketItem == getTombstoneVal()) {
+      // Skip over tombstones.  However, remember the first one we see.
+      if (FirstTombstone == -1) FirstTombstone = BucketNo;
+    } else if (Bucket.FullHashValue == FullHashValue) {
+      // 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.
+      
+      // Do the comparison like this because NameStart isn't necessarily
+      // null-terminated!
+      char *ItemStr = (char*)BucketItem+ItemSize;
+      unsigned ItemStrLen = BucketItem->getKeyLength();
+      if (unsigned(NameEnd-NameStart) == ItemStrLen &&
+          memcmp(ItemStr, NameStart, 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;
+  }
+}
+
+
+/// 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;
+  if (HTSize == 0) return -1;  // Really empty table?
+  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 (BucketItem == getTombstoneVal()) {
+      // Ignore tombstones.
+    } else if (Bucket.FullHashValue == FullHashValue) {
+      // 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.
+      
+      // 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;
+  }
+}
+
+/// RemoveKey - Remove the specified StringMapEntry from the table, but do not
+/// delete it.  This aborts if the value isn't in the table.
+void StringMapImpl::RemoveKey(StringMapEntryBase *V) {
+  const char *VStr = (char*)V + ItemSize;
+  StringMapEntryBase *V2 = RemoveKey(VStr, VStr+V->getKeyLength());
+  V2 = V2;
+  assert(V == V2 && "Didn't find key?");
+}
+
+/// RemoveKey - Remove the StringMapEntry for the specified key from the
+/// table, returning it.  If the key is not in the table, this returns null.
+StringMapEntryBase *StringMapImpl::RemoveKey(const char *KeyStart,
+                                             const char *KeyEnd) {
+  int Bucket = FindKey(KeyStart, KeyEnd);
+  if (Bucket == -1) return 0;
+  
+  StringMapEntryBase *Result = TheTable[Bucket].Item;
+  TheTable[Bucket].Item = getTombstoneVal();
+  --NumItems;
+  ++NumTombstones;
+  return Result;
+}
+
+
+
+/// RehashTable - Grow the table, redistributing values into the buckets with
+/// the appropriate mod-of-hashtable-size.
+void StringMapImpl::RehashTable() {
+  unsigned NewSize = NumBuckets*2;
+  // Allocate one extra bucket which will always be non-empty.  This allows the
+  // iterators to stop at end.
+  ItemBucket *NewTableArray =(ItemBucket*)calloc(NewSize+1, sizeof(ItemBucket));
+  NewTableArray[NewSize].Item = (StringMapEntryBase*)2;
+  
+  // Rehash all the items into their new buckets.  Luckily :) we already have
+  // the hash values available, so we don't have to rehash any strings.
+  for (ItemBucket *IB = TheTable, *E = TheTable+NumBuckets; IB != E; ++IB) {
+    if (IB->Item && IB->Item != getTombstoneVal()) {
+      // Fast case, bucket available.
+      unsigned FullHash = IB->FullHashValue;
+      unsigned NewBucket = FullHash & (NewSize-1);
+      if (NewTableArray[NewBucket].Item == 0) {
+        NewTableArray[FullHash & (NewSize-1)].Item = IB->Item;
+        NewTableArray[FullHash & (NewSize-1)].FullHashValue = FullHash;
+        continue;
+      }
+      
+      // Otherwise probe for a spot.
+      unsigned ProbeSize = 1;
+      do {
+        NewBucket = (NewBucket + ProbeSize++) & (NewSize-1);
+      } while (NewTableArray[NewBucket].Item);
+      
+      // Finally found a slot.  Fill it in.
+      NewTableArray[NewBucket].Item = IB->Item;
+      NewTableArray[NewBucket].FullHashValue = FullHash;
+    }
+  }
+  
+  free(TheTable);
+  
+  TheTable = NewTableArray;
+  NumBuckets = NewSize;
+}