#include "llvm/Analysis/Dominators.h"
#include "llvm/Assembly/Writer.h"
#include "llvm/Support/CFG.h"
-#include "llvm/Support/Streams.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Debug.h"
#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/ADT/SmallPtrSet.h"
#include <algorithm>
using namespace llvm;
+// Always verify loopinfo if expensive checking is enabled.
+#ifdef XDEBUG
+static bool VerifyLoopInfo = true;
+#else
+static bool VerifyLoopInfo = false;
+#endif
+static cl::opt<bool,true>
+VerifyLoopInfoX("verify-loop-info", cl::location(VerifyLoopInfo),
+ cl::desc("Verify loop info (time consuming)"));
+
char LoopInfo::ID = 0;
static RegisterPass<LoopInfo>
X("loops", "Natural Loop Information", true, true);
/// loop-invariant.
///
bool Loop::isLoopInvariant(Instruction *I) const {
- return !contains(I->getParent());
+ return !contains(I);
}
/// makeLoopInvariant - If the given value is an instruciton inside of the
case BinaryOperator::Mul:
Result = dyn_cast<ConstantInt>(BO->getOperand(1));
break;
+ case BinaryOperator::Shl:
+ if (ConstantInt *CI = dyn_cast<ConstantInt>(BO->getOperand(1)))
+ if (CI->getValue().getActiveBits() <= 5)
+ return 1u << CI->getZExtValue();
+ break;
default:
break;
}
}
/// isLCSSAForm - Return true if the Loop is in LCSSA form
-bool Loop::isLCSSAForm() const {
+bool Loop::isLCSSAForm(DominatorTree &DT) const {
// Sort the blocks vector so that we can use binary search to do quick
// lookups.
- SmallPtrSet<BasicBlock *, 16> LoopBBs(block_begin(), block_end());
+ SmallPtrSet<BasicBlock*, 16> LoopBBs(block_begin(), block_end());
for (block_iterator BI = block_begin(), E = block_end(); BI != E; ++BI) {
- BasicBlock *BB = *BI;
- for (BasicBlock ::iterator I = BB->begin(), E = BB->end(); I != E;++I)
+ BasicBlock *BB = *BI;
+ for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E;++I)
for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E;
++UI) {
- BasicBlock *UserBB = cast<Instruction>(*UI)->getParent();
- if (PHINode *P = dyn_cast<PHINode>(*UI)) {
+ User *U = *UI;
+ BasicBlock *UserBB = cast<Instruction>(U)->getParent();
+ if (PHINode *P = dyn_cast<PHINode>(U))
UserBB = P->getIncomingBlock(UI);
- }
- // Check the current block, as a fast-path. Most values are used in
- // the same block they are defined in.
- if (UserBB != BB && !LoopBBs.count(UserBB))
+ // Check the current block, as a fast-path, before checking whether
+ // the use is anywhere in the loop. Most values are used in the same
+ // block they are defined in. Also, blocks not reachable from the
+ // entry are special; uses in them don't need to go through PHIs.
+ if (UserBB != BB &&
+ !LoopBBs.count(UserBB) &&
+ DT.isReachableFromEntry(UserBB))
return false;
}
}
/// the LoopSimplify form transforms loops to, which is sometimes called
/// normal form.
bool Loop::isLoopSimplifyForm() const {
- // Normal-form loops have a preheader.
- if (!getLoopPreheader())
- return false;
- // Normal-form loops have a single backedge.
- if (!getLoopLatch())
- return false;
+ // Normal-form loops have a preheader, a single backedge, and all of their
+ // exits have all their predecessors inside the loop.
+ return getLoopPreheader() && getLoopLatch() && hasDedicatedExits();
+}
+
+/// hasDedicatedExits - Return true if no exit block for the loop
+/// has a predecessor that is outside the loop.
+bool Loop::hasDedicatedExits() const {
+ // Sort the blocks vector so that we can use binary search to do quick
+ // lookups.
+ SmallPtrSet<BasicBlock *, 16> LoopBBs(block_begin(), block_end());
// Each predecessor of each exit block of a normal loop is contained
// within the loop.
SmallVector<BasicBlock *, 4> ExitBlocks;
for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i)
for (pred_iterator PI = pred_begin(ExitBlocks[i]),
PE = pred_end(ExitBlocks[i]); PI != PE; ++PI)
- if (!contains(*PI))
+ if (!LoopBBs.count(*PI))
return false;
// All the requirements are met.
return true;
}
+/// getUniqueExitBlocks - Return all unique successor blocks of this loop.
+/// These are the blocks _outside of the current loop_ which are branched to.
+/// This assumes that loop exits are in canonical form.
+///
+void
+Loop::getUniqueExitBlocks(SmallVectorImpl<BasicBlock *> &ExitBlocks) const {
+ assert(hasDedicatedExits() &&
+ "getUniqueExitBlocks assumes the loop has canonical form exits!");
+
+ // Sort the blocks vector so that we can use binary search to do quick
+ // lookups.
+ SmallVector<BasicBlock *, 128> LoopBBs(block_begin(), block_end());
+ std::sort(LoopBBs.begin(), LoopBBs.end());
+
+ SmallVector<BasicBlock *, 32> switchExitBlocks;
+
+ for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) {
+
+ BasicBlock *current = *BI;
+ switchExitBlocks.clear();
+
+ typedef GraphTraits<BasicBlock *> BlockTraits;
+ typedef GraphTraits<Inverse<BasicBlock *> > InvBlockTraits;
+ for (BlockTraits::ChildIteratorType I =
+ BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI);
+ I != E; ++I) {
+ // If block is inside the loop then it is not a exit block.
+ if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I))
+ continue;
+
+ InvBlockTraits::ChildIteratorType PI = InvBlockTraits::child_begin(*I);
+ BasicBlock *firstPred = *PI;
+
+ // If current basic block is this exit block's first predecessor
+ // then only insert exit block in to the output ExitBlocks vector.
+ // This ensures that same exit block is not inserted twice into
+ // ExitBlocks vector.
+ if (current != firstPred)
+ continue;
+
+ // If a terminator has more then two successors, for example SwitchInst,
+ // then it is possible that there are multiple edges from current block
+ // to one exit block.
+ if (std::distance(BlockTraits::child_begin(current),
+ BlockTraits::child_end(current)) <= 2) {
+ ExitBlocks.push_back(*I);
+ continue;
+ }
+
+ // In case of multiple edges from current block to exit block, collect
+ // only one edge in ExitBlocks. Use switchExitBlocks to keep track of
+ // duplicate edges.
+ if (std::find(switchExitBlocks.begin(), switchExitBlocks.end(), *I)
+ == switchExitBlocks.end()) {
+ switchExitBlocks.push_back(*I);
+ ExitBlocks.push_back(*I);
+ }
+ }
+ }
+}
+
+/// getUniqueExitBlock - If getUniqueExitBlocks would return exactly one
+/// block, return that block. Otherwise return null.
+BasicBlock *Loop::getUniqueExitBlock() const {
+ SmallVector<BasicBlock *, 8> UniqueExitBlocks;
+ getUniqueExitBlocks(UniqueExitBlocks);
+ if (UniqueExitBlocks.size() == 1)
+ return UniqueExitBlocks[0];
+ return 0;
+}
+
+void Loop::dump() const {
+ print(dbgs());
+}
+
//===----------------------------------------------------------------------===//
// LoopInfo implementation
//
return false;
}
+void LoopInfo::verifyAnalysis() const {
+ // LoopInfo is a FunctionPass, but verifying every loop in the function
+ // each time verifyAnalysis is called is very expensive. The
+ // -verify-loop-info option can enable this. In order to perform some
+ // checking by default, LoopPass has been taught to call verifyLoop
+ // manually during loop pass sequences.
+
+ if (!VerifyLoopInfo) return;
+
+ for (iterator I = begin(), E = end(); I != E; ++I) {
+ assert(!(*I)->getParentLoop() && "Top-level loop has a parent!");
+ (*I)->verifyLoopNest();
+ }
+
+ // TODO: check BBMap consistency.
+}
+
void LoopInfo::getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesAll();
AU.addRequired<DominatorTree>();
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