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abc5f825d6
The new leader is known anyway so we can return it for some micro optimization in code where it is easy to pass along the result to the next join(). llvm-svn: 257130
73 lines
2.1 KiB
C++
73 lines
2.1 KiB
C++
//===-- llvm/ADT/IntEqClasses.cpp - Equivalence Classes of Integers -------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// Equivalence classes for small integers. This is a mapping of the integers
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// 0 .. N-1 into M equivalence classes numbered 0 .. M-1.
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//
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// Initially each integer has its own equivalence class. Classes are joined by
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// passing a representative member of each class to join().
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//
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// Once the classes are built, compress() will number them 0 .. M-1 and prevent
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// further changes.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/ADT/IntEqClasses.h"
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using namespace llvm;
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void IntEqClasses::grow(unsigned N) {
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assert(NumClasses == 0 && "grow() called after compress().");
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EC.reserve(N);
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while (EC.size() < N)
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EC.push_back(EC.size());
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}
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unsigned IntEqClasses::join(unsigned a, unsigned b) {
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assert(NumClasses == 0 && "join() called after compress().");
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unsigned eca = EC[a];
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unsigned ecb = EC[b];
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// Update pointers while searching for the leaders, compressing the paths
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// incrementally. The larger leader will eventually be updated, joining the
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// classes.
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while (eca != ecb)
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if (eca < ecb)
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EC[b] = eca, b = ecb, ecb = EC[b];
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else
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EC[a] = ecb, a = eca, eca = EC[a];
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return eca;
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}
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unsigned IntEqClasses::findLeader(unsigned a) const {
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assert(NumClasses == 0 && "findLeader() called after compress().");
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while (a != EC[a])
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a = EC[a];
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return a;
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}
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void IntEqClasses::compress() {
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if (NumClasses)
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return;
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for (unsigned i = 0, e = EC.size(); i != e; ++i)
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EC[i] = (EC[i] == i) ? NumClasses++ : EC[EC[i]];
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}
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void IntEqClasses::uncompress() {
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if (!NumClasses)
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return;
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SmallVector<unsigned, 8> Leader;
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for (unsigned i = 0, e = EC.size(); i != e; ++i)
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if (EC[i] < Leader.size())
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EC[i] = Leader[EC[i]];
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else
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Leader.push_back(EC[i] = i);
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NumClasses = 0;
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}
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