When clearing a SmallPtrSet, if the set had a huge capacity, but the

contents of the set were small, deallocate and shrink the set.  This
avoids having us to memset as much data, significantly speeding up
some pathological cases.  For example, this speeds up the verifier
from 0.3899s to 0.0763 (5.1x) on the testcase from PR1432 in a
release build.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@40837 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/ADT/DenseMap.h b/include/llvm/ADT/DenseMap.h
index 78caba52a51c24b078a5b0d894bf9e1716117ed3..8b25a82e6ac69b5d6954a3d4ddd9e394decd4b25 100644 (file)
--- a/include/llvm/ADT/DenseMap.h
+++ b/include/llvm/ADT/DenseMap.h
@@ -91,6 +91,8 @@ public:
   unsigned size() const { return NumEntries; }
   
   void clear() {
+    // If the capacity of the array is huge, and the # elements used is small,
+    // shrink the array.
     if (NumEntries * 4 < NumBuckets && NumBuckets > 64) {
       shrink_and_clear();
       return;

diff --git a/include/llvm/ADT/SmallPtrSet.h b/include/llvm/ADT/SmallPtrSet.h
index e39a4fe70643df3805c252240a9a4830f8112a6a..2ff7de448fd2859bcf3730b22e7f0a436cb1064d 100644 (file)
--- a/include/llvm/ADT/SmallPtrSet.h
+++ b/include/llvm/ADT/SmallPtrSet.h
@@ -80,6 +80,11 @@ public:
   }
   
   void clear() {
+    // If the capacity of the array is huge, and the # elements used is small,
+    // shrink the array.
+    if (!isSmall() && NumElements*4 < CurArraySize && CurArraySize > 32)
+      return shrink_and_clear();
+    
     // Fill the array with empty markers.
     memset(CurArray, -1, CurArraySize*sizeof(void*));
     NumElements = 0;
@@ -103,8 +108,8 @@ public:
   bool count(void * const Ptr) const {
     if (isSmall()) {
       // Linear search for the item.
-      for (const void *const *APtr = SmallArray, *const *E = SmallArray+NumElements;
-           APtr != E; ++APtr)
+      for (const void *const *APtr = SmallArray,
+                      *const *E = SmallArray+NumElements; APtr != E; ++APtr)
         if (*APtr == Ptr)
           return true;
       return false;
@@ -121,6 +126,7 @@ private:
     return ((uintptr_t)Ptr >> 4) & (CurArraySize-1);
   }
   const void * const *FindBucketFor(const void *Ptr) const;
+  void shrink_and_clear();
   
   /// Grow - Allocate a larger backing store for the buckets and move it over.
   void Grow();

diff --git a/lib/Support/SmallPtrSet.cpp b/lib/Support/SmallPtrSet.cpp
index 1507059f386b764178f46c764a2628fce8726e39..ba00d903658ffe83c11fcd1970f91709126c3ecc 100644 (file)
--- a/lib/Support/SmallPtrSet.cpp
+++ b/lib/Support/SmallPtrSet.cpp
@@ -18,6 +18,24 @@
 
 using namespace llvm;
 
+void SmallPtrSetImpl::shrink_and_clear() {
+  assert(!isSmall() && "Can't shrink a small set!");
+  free(CurArray);
+
+  // Reduce the number of buckets.
+  CurArraySize = NumElements > 16 ? 1 << (Log2_32_Ceil(NumElements) + 1) : 32;
+  NumElements = NumTombstones = 0;
+
+  // Install the new array.  Clear all the buckets to empty.
+  CurArray = (const void**)malloc(sizeof(void*) * (CurArraySize+1));
+  assert(CurArray && "Failed to allocate memory?");
+  memset(CurArray, -1, CurArraySize*sizeof(void*));
+  
+  // The end pointer, always valid, is set to a valid element to help the
+  // iterator.
+  CurArray[CurArraySize] = 0;
+}
+
 bool SmallPtrSetImpl::insert(const void * Ptr) {
   if (isSmall()) {
     // Check to see if it is already in the set.