llvm-6502/lib/Analysis/LoopInfo.cpp
Chris Lattner cee8f9ae67 Create a new #include "Support/..." directory structure to move things
from "llvm/Support/..." that are not llvm dependant.

Move files and fix #includes


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@1400 91177308-0d34-0410-b5e6-96231b3b80d8
2001-11-27 00:03:19 +00:00

82 lines
2.7 KiB
C++

//===- LoopInfo.cpp - Natural Loop Calculator -------------------------------=//
//
// This file defines the LoopInfo class that is used to identify natural loops
// and determine the loop depth of various nodes of the CFG. Note that the
// loops identified may actually be several natural loops that share the same
// header node... not just a single natural loop.
//
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/BasicBlock.h"
#include "Support/DepthFirstIterator.h"
#include <algorithm>
bool cfg::Loop::contains(const BasicBlock *BB) const {
return find(Blocks.begin(), Blocks.end(), BB) != Blocks.end();
}
cfg::LoopInfo::LoopInfo(const DominatorSet &DS) {
const BasicBlock *RootNode = DS.getRoot();
for (df_iterator<const BasicBlock*> NI = df_begin(RootNode),
NE = df_end(RootNode); NI != NE; ++NI)
if (Loop *L = ConsiderForLoop(*NI, DS))
TopLevelLoops.push_back(L);
for (unsigned i = 0; i < TopLevelLoops.size(); ++i)
TopLevelLoops[i]->setLoopDepth(1);
}
cfg::Loop *cfg::LoopInfo::ConsiderForLoop(const BasicBlock *BB,
const DominatorSet &DS) {
if (BBMap.find(BB) != BBMap.end()) return 0; // Havn't processed this node?
vector<const BasicBlock *> TodoStack;
// Scan the predecessors of BB, checking to see if BB dominates any of
// them.
for (BasicBlock::pred_const_iterator I = BB->pred_begin(),
E = BB->pred_end(); I != E; ++I)
if (DS.dominates(BB, *I)) // If BB dominates it's predecessor...
TodoStack.push_back(*I);
if (TodoStack.empty()) return 0; // Doesn't dominate any predecessors...
// Create a new loop to represent this basic block...
Loop *L = new Loop(BB);
BBMap[BB] = L;
while (!TodoStack.empty()) { // Process all the nodes in the loop
const BasicBlock *X = TodoStack.back();
TodoStack.pop_back();
if (!L->contains(X)) { // As of yet unprocessed??
L->Blocks.push_back(X);
// Add all of the predecessors of X to the end of the work stack...
TodoStack.insert(TodoStack.end(), X->pred_begin(), X->pred_end());
}
}
// Add the basic blocks that comprise this loop to the BBMap so that this
// loop can be found for them. Also check subsidary basic blocks to see if
// they start subloops of their own.
//
for (vector<const BasicBlock*>::reverse_iterator I = L->Blocks.rbegin(),
E = L->Blocks.rend(); I != E; ++I) {
// Check to see if this block starts a new loop
if (Loop *NewLoop = ConsiderForLoop(*I, DS)) {
L->SubLoops.push_back(NewLoop);
NewLoop->ParentLoop = L;
}
if (BBMap.find(*I) == BBMap.end())
BBMap.insert(make_pair(*I, L));
}
return L;
}