/// runOnFunction - Process all loops in the function, inner-most out.
bool LCSSA::runOnLoop(Loop *TheLoop, LPPassManager &LPM) {
L = TheLoop;
DT = &getAnalysis<DominatorTree>();
LI = &getAnalysis<LoopInfo>();
SE = getAnalysisIfAvailable<ScalarEvolution>();
// Get the set of exiting blocks.
SmallVector<BasicBlock*, 8> ExitBlocks;
L->getExitBlocks(ExitBlocks);
if (ExitBlocks.empty())
return false;
// Speed up queries by creating a sorted vector of blocks.
LoopBlocks.clear();
LoopBlocks.insert(LoopBlocks.end(), L->block_begin(), L->block_end());
array_pod_sort(LoopBlocks.begin(), LoopBlocks.end());
// Look at all the instructions in the loop, checking to see if they have uses
// outside the loop. If so, rewrite those uses.
bool MadeChange = false;
for (Loop::block_iterator BBI = L->block_begin(), E = L->block_end();
BBI != E; ++BBI) {
BasicBlock *BB = *BBI;
// For large loops, avoid use-scanning by using dominance information: In
// particular, if a block does not dominate any of the loop exits, then none
// of the values defined in the block could be used outside the loop.
if (!BlockDominatesAnExit(BB, ExitBlocks, DT))
continue;
for (BasicBlock::iterator I = BB->begin(), E = BB->end();
I != E; ++I) {
// Reject two common cases fast: instructions with no uses (like stores)
// and instructions with one use that is in the same block as this.
if (I->use_empty() ||
(I->hasOneUse() && I->use_back()->getParent() == BB &&
!isa<PHINode>(I->use_back())))
continue;
MadeChange |= ProcessInstruction(I, ExitBlocks);
}
}
// If we modified the code, remove any caches about the loop from SCEV to
// avoid dangling entries.
// FIXME: This is a big hammer, can we clear the cache more selectively?
if (SE && MadeChange)
SE->forgetLoop(L);
assert(L->isLCSSAForm(*DT));
PredCache.clear();
return MadeChange;
}
/// ApproximateLoopSize - Approximate the size of the loop after it has been
/// unrolled.
static unsigned ApproximateLoopSize(const Loop *L) {
unsigned Size = 0;
for (unsigned i = 0, e = L->getBlocks().size(); i != e; ++i) {
BasicBlock *BB = L->getBlocks()[i];
Instruction *Term = BB->getTerminator();
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
if (isa<PHINode>(I) && BB == L->getHeader()) {
// Ignore PHI nodes in the header.
} else if (I->hasOneUse() && I->use_back() == Term) {
// Ignore instructions only used by the loop terminator.
} else {
++Size;
}
// TODO: Ignore expressions derived from PHI and constants if inval of phi
// is a constant, or if operation is associative. This will get induction
// variables.
}
}
return Size;
}