1 files changed, 76 insertions, 0 deletions

diff --git a/contrib/llvm-project/llvm/lib/Support/IntEqClasses.cpp b/contrib/llvm-project/llvm/lib/Support/IntEqClasses.cpp
new file mode 100644
index 000000000000..4a976dcefc65
--- /dev/null
+++ b/contrib/llvm-project/llvm/lib/Support/IntEqClasses.cpp
@@ -0,0 +1,76 @@
+//===-- llvm/ADT/IntEqClasses.cpp - Equivalence Classes of Integers -------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Equivalence classes for small integers. This is a mapping of the integers
+// 0 .. N-1 into M equivalence classes numbered 0 .. M-1.
+//
+// Initially each integer has its own equivalence class. Classes are joined by
+// passing a representative member of each class to join().
+//
+// Once the classes are built, compress() will number them 0 .. M-1 and prevent
+// further changes.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/IntEqClasses.h"
+
+using namespace llvm;
+
+void IntEqClasses::grow(unsigned N) {
+  assert(NumClasses == 0 && "grow() called after compress().");
+  EC.reserve(N);
+  while (EC.size() < N)
+    EC.push_back(EC.size());
+}
+
+unsigned IntEqClasses::join(unsigned a, unsigned b) {
+  assert(NumClasses == 0 && "join() called after compress().");
+  unsigned eca = EC[a];
+  unsigned ecb = EC[b];
+  // Update pointers while searching for the leaders, compressing the paths
+  // incrementally. The larger leader will eventually be updated, joining the
+  // classes.
+  while (eca != ecb)
+    if (eca < ecb) {
+      EC[b] = eca;
+      b = ecb;
+      ecb = EC[b];
+    } else {
+      EC[a] = ecb;
+      a = eca;
+      eca = EC[a];
+    }
+
+  return eca;
+}
+
+unsigned IntEqClasses::findLeader(unsigned a) const {
+  assert(NumClasses == 0 && "findLeader() called after compress().");
+  while (a != EC[a])
+    a = EC[a];
+  return a;
+}
+
+void IntEqClasses::compress() {
+  if (NumClasses)
+    return;
+  for (unsigned i = 0, e = EC.size(); i != e; ++i)
+    EC[i] = (EC[i] == i) ? NumClasses++ : EC[EC[i]];
+}
+
+void IntEqClasses::uncompress() {
+  if (!NumClasses)
+    return;
+  SmallVector<unsigned, 8> Leader;
+  for (unsigned i = 0, e = EC.size(); i != e; ++i)
+    if (EC[i] < Leader.size())
+      EC[i] = Leader[EC[i]];
+    else
+      Leader.push_back(EC[i] = i);
+  NumClasses = 0;
+}