2003-10-13 11:32:08 +08:00
|
|
|
//===- LoopInfo.cpp - Natural Loop Calculator -----------------------------===//
|
2005-04-22 05:13:18 +08:00
|
|
|
//
|
2003-10-21 03:43:21 +08:00
|
|
|
// The LLVM Compiler Infrastructure
|
|
|
|
//
|
2007-12-30 04:36:04 +08:00
|
|
|
// This file is distributed under the University of Illinois Open Source
|
|
|
|
// License. See LICENSE.TXT for details.
|
2005-04-22 05:13:18 +08:00
|
|
|
//
|
2003-10-21 03:43:21 +08:00
|
|
|
//===----------------------------------------------------------------------===//
|
2001-11-27 02:41:20 +08:00
|
|
|
//
|
|
|
|
// 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.
|
|
|
|
//
|
|
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
|
2004-01-31 01:26:24 +08:00
|
|
|
#include "llvm/Analysis/LoopInfo.h"
|
2004-04-15 23:16:02 +08:00
|
|
|
#include "llvm/Constants.h"
|
|
|
|
#include "llvm/Instructions.h"
|
|
|
|
#include "llvm/Analysis/Dominators.h"
|
2011-08-10 09:59:05 +08:00
|
|
|
#include "llvm/Analysis/LoopIterator.h"
|
2002-07-27 09:12:17 +08:00
|
|
|
#include "llvm/Assembly/Writer.h"
|
2004-01-31 01:26:24 +08:00
|
|
|
#include "llvm/Support/CFG.h"
|
2009-09-28 08:27:48 +08:00
|
|
|
#include "llvm/Support/CommandLine.h"
|
2010-01-06 05:08:02 +08:00
|
|
|
#include "llvm/Support/Debug.h"
|
2004-09-02 06:55:40 +08:00
|
|
|
#include "llvm/ADT/DepthFirstIterator.h"
|
2007-03-04 12:06:39 +08:00
|
|
|
#include "llvm/ADT/SmallPtrSet.h"
|
2001-11-27 02:41:20 +08:00
|
|
|
#include <algorithm>
|
2004-04-13 04:26:17 +08:00
|
|
|
using namespace llvm;
|
2003-11-12 06:41:34 +08:00
|
|
|
|
2009-09-28 08:27:48 +08:00
|
|
|
// Always verify loopinfo if expensive checking is enabled.
|
|
|
|
#ifdef XDEBUG
|
2010-04-16 01:08:50 +08:00
|
|
|
static bool VerifyLoopInfo = true;
|
2009-09-28 08:27:48 +08:00
|
|
|
#else
|
2010-04-16 01:08:50 +08:00
|
|
|
static bool VerifyLoopInfo = false;
|
2009-09-28 08:27:48 +08:00
|
|
|
#endif
|
|
|
|
static cl::opt<bool,true>
|
|
|
|
VerifyLoopInfoX("verify-loop-info", cl::location(VerifyLoopInfo),
|
|
|
|
cl::desc("Verify loop info (time consuming)"));
|
|
|
|
|
2007-05-03 09:11:54 +08:00
|
|
|
char LoopInfo::ID = 0;
|
2010-10-13 03:48:12 +08:00
|
|
|
INITIALIZE_PASS_BEGIN(LoopInfo, "loops", "Natural Loop Information", true, true)
|
|
|
|
INITIALIZE_PASS_DEPENDENCY(DominatorTree)
|
|
|
|
INITIALIZE_PASS_END(LoopInfo, "loops", "Natural Loop Information", true, true)
|
2002-01-31 08:42:27 +08:00
|
|
|
|
|
|
|
//===----------------------------------------------------------------------===//
|
2002-04-29 00:21:30 +08:00
|
|
|
// Loop implementation
|
2002-01-31 08:42:27 +08:00
|
|
|
//
|
2002-10-11 13:31:10 +08:00
|
|
|
|
2009-07-14 06:02:44 +08:00
|
|
|
/// isLoopInvariant - Return true if the specified value is loop invariant
|
|
|
|
///
|
|
|
|
bool Loop::isLoopInvariant(Value *V) const {
|
|
|
|
if (Instruction *I = dyn_cast<Instruction>(V))
|
2010-09-06 09:05:37 +08:00
|
|
|
return !contains(I);
|
2009-07-14 06:02:44 +08:00
|
|
|
return true; // All non-instructions are loop invariant
|
|
|
|
}
|
|
|
|
|
2010-09-06 09:05:37 +08:00
|
|
|
/// hasLoopInvariantOperands - Return true if all the operands of the
|
2011-08-04 07:45:50 +08:00
|
|
|
/// specified instruction are loop invariant.
|
2010-09-06 09:05:37 +08:00
|
|
|
bool Loop::hasLoopInvariantOperands(Instruction *I) const {
|
|
|
|
for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
|
|
|
|
if (!isLoopInvariant(I->getOperand(i)))
|
|
|
|
return false;
|
2011-08-04 07:45:50 +08:00
|
|
|
|
2010-09-06 09:05:37 +08:00
|
|
|
return true;
|
2009-07-14 09:06:29 +08:00
|
|
|
}
|
|
|
|
|
|
|
|
/// makeLoopInvariant - If the given value is an instruciton inside of the
|
|
|
|
/// loop and it can be hoisted, do so to make it trivially loop-invariant.
|
|
|
|
/// Return true if the value after any hoisting is loop invariant. This
|
|
|
|
/// function can be used as a slightly more aggressive replacement for
|
|
|
|
/// isLoopInvariant.
|
|
|
|
///
|
|
|
|
/// If InsertPt is specified, it is the point to hoist instructions to.
|
|
|
|
/// If null, the terminator of the loop preheader is used.
|
|
|
|
///
|
2009-07-15 09:25:43 +08:00
|
|
|
bool Loop::makeLoopInvariant(Value *V, bool &Changed,
|
|
|
|
Instruction *InsertPt) const {
|
2009-07-14 09:06:29 +08:00
|
|
|
if (Instruction *I = dyn_cast<Instruction>(V))
|
2009-07-15 09:25:43 +08:00
|
|
|
return makeLoopInvariant(I, Changed, InsertPt);
|
2009-07-14 09:06:29 +08:00
|
|
|
return true; // All non-instructions are loop-invariant.
|
|
|
|
}
|
|
|
|
|
|
|
|
/// makeLoopInvariant - If the given instruction is inside of the
|
|
|
|
/// loop and it can be hoisted, do so to make it trivially loop-invariant.
|
|
|
|
/// Return true if the instruction after any hoisting is loop invariant. This
|
|
|
|
/// function can be used as a slightly more aggressive replacement for
|
|
|
|
/// isLoopInvariant.
|
|
|
|
///
|
|
|
|
/// If InsertPt is specified, it is the point to hoist instructions to.
|
|
|
|
/// If null, the terminator of the loop preheader is used.
|
|
|
|
///
|
2009-07-15 09:25:43 +08:00
|
|
|
bool Loop::makeLoopInvariant(Instruction *I, bool &Changed,
|
|
|
|
Instruction *InsertPt) const {
|
2009-07-14 09:06:29 +08:00
|
|
|
// Test if the value is already loop-invariant.
|
|
|
|
if (isLoopInvariant(I))
|
|
|
|
return true;
|
2009-07-17 12:28:42 +08:00
|
|
|
if (!I->isSafeToSpeculativelyExecute())
|
2009-07-14 09:06:29 +08:00
|
|
|
return false;
|
2009-07-17 12:28:42 +08:00
|
|
|
if (I->mayReadFromMemory())
|
2009-07-14 09:06:29 +08:00
|
|
|
return false;
|
|
|
|
// Determine the insertion point, unless one was given.
|
|
|
|
if (!InsertPt) {
|
|
|
|
BasicBlock *Preheader = getLoopPreheader();
|
|
|
|
// Without a preheader, hoisting is not feasible.
|
|
|
|
if (!Preheader)
|
|
|
|
return false;
|
|
|
|
InsertPt = Preheader->getTerminator();
|
|
|
|
}
|
|
|
|
// Don't hoist instructions with loop-variant operands.
|
|
|
|
for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
|
2009-07-15 09:25:43 +08:00
|
|
|
if (!makeLoopInvariant(I->getOperand(i), Changed, InsertPt))
|
2009-07-14 09:06:29 +08:00
|
|
|
return false;
|
2011-08-04 07:45:50 +08:00
|
|
|
|
2009-07-14 09:06:29 +08:00
|
|
|
// Hoist.
|
|
|
|
I->moveBefore(InsertPt);
|
2009-07-15 09:25:43 +08:00
|
|
|
Changed = true;
|
2009-07-14 09:06:29 +08:00
|
|
|
return true;
|
|
|
|
}
|
|
|
|
|
2009-07-14 06:02:44 +08:00
|
|
|
/// getCanonicalInductionVariable - Check to see if the loop has a canonical
|
|
|
|
/// induction variable: an integer recurrence that starts at 0 and increments
|
|
|
|
/// by one each time through the loop. If so, return the phi node that
|
|
|
|
/// corresponds to it.
|
|
|
|
///
|
|
|
|
/// The IndVarSimplify pass transforms loops to have a canonical induction
|
|
|
|
/// variable.
|
|
|
|
///
|
|
|
|
PHINode *Loop::getCanonicalInductionVariable() const {
|
|
|
|
BasicBlock *H = getHeader();
|
|
|
|
|
|
|
|
BasicBlock *Incoming = 0, *Backedge = 0;
|
2010-07-24 05:25:16 +08:00
|
|
|
pred_iterator PI = pred_begin(H);
|
|
|
|
assert(PI != pred_end(H) &&
|
2009-07-14 06:02:44 +08:00
|
|
|
"Loop must have at least one backedge!");
|
|
|
|
Backedge = *PI++;
|
2010-07-24 05:25:16 +08:00
|
|
|
if (PI == pred_end(H)) return 0; // dead loop
|
2009-07-14 06:02:44 +08:00
|
|
|
Incoming = *PI++;
|
2010-07-24 05:25:16 +08:00
|
|
|
if (PI != pred_end(H)) return 0; // multiple backedges?
|
2009-07-14 06:02:44 +08:00
|
|
|
|
|
|
|
if (contains(Incoming)) {
|
|
|
|
if (contains(Backedge))
|
|
|
|
return 0;
|
|
|
|
std::swap(Incoming, Backedge);
|
|
|
|
} else if (!contains(Backedge))
|
|
|
|
return 0;
|
|
|
|
|
|
|
|
// Loop over all of the PHI nodes, looking for a canonical indvar.
|
|
|
|
for (BasicBlock::iterator I = H->begin(); isa<PHINode>(I); ++I) {
|
|
|
|
PHINode *PN = cast<PHINode>(I);
|
|
|
|
if (ConstantInt *CI =
|
|
|
|
dyn_cast<ConstantInt>(PN->getIncomingValueForBlock(Incoming)))
|
|
|
|
if (CI->isNullValue())
|
|
|
|
if (Instruction *Inc =
|
|
|
|
dyn_cast<Instruction>(PN->getIncomingValueForBlock(Backedge)))
|
|
|
|
if (Inc->getOpcode() == Instruction::Add &&
|
|
|
|
Inc->getOperand(0) == PN)
|
|
|
|
if (ConstantInt *CI = dyn_cast<ConstantInt>(Inc->getOperand(1)))
|
|
|
|
if (CI->equalsInt(1))
|
|
|
|
return PN;
|
|
|
|
}
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
|
|
|
/// getTripCount - Return a loop-invariant LLVM value indicating the number of
|
|
|
|
/// times the loop will be executed. Note that this means that the backedge
|
|
|
|
/// of the loop executes N-1 times. If the trip-count cannot be determined,
|
|
|
|
/// this returns null.
|
|
|
|
///
|
|
|
|
/// The IndVarSimplify pass transforms loops to have a form that this
|
|
|
|
/// function easily understands.
|
|
|
|
///
|
|
|
|
Value *Loop::getTripCount() const {
|
|
|
|
// Canonical loops will end with a 'cmp ne I, V', where I is the incremented
|
|
|
|
// canonical induction variable and V is the trip count of the loop.
|
2010-07-24 05:34:51 +08:00
|
|
|
PHINode *IV = getCanonicalInductionVariable();
|
|
|
|
if (IV == 0 || IV->getNumIncomingValues() != 2) return 0;
|
2009-07-14 06:02:44 +08:00
|
|
|
|
2010-07-24 05:34:51 +08:00
|
|
|
bool P0InLoop = contains(IV->getIncomingBlock(0));
|
|
|
|
Value *Inc = IV->getIncomingValue(!P0InLoop);
|
|
|
|
BasicBlock *BackedgeBlock = IV->getIncomingBlock(!P0InLoop);
|
2009-07-14 06:02:44 +08:00
|
|
|
|
|
|
|
if (BranchInst *BI = dyn_cast<BranchInst>(BackedgeBlock->getTerminator()))
|
|
|
|
if (BI->isConditional()) {
|
|
|
|
if (ICmpInst *ICI = dyn_cast<ICmpInst>(BI->getCondition())) {
|
|
|
|
if (ICI->getOperand(0) == Inc) {
|
|
|
|
if (BI->getSuccessor(0) == getHeader()) {
|
|
|
|
if (ICI->getPredicate() == ICmpInst::ICMP_NE)
|
|
|
|
return ICI->getOperand(1);
|
|
|
|
} else if (ICI->getPredicate() == ICmpInst::ICMP_EQ) {
|
|
|
|
return ICI->getOperand(1);
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
|
|
|
/// getSmallConstantTripCount - Returns the trip count of this loop as a
|
|
|
|
/// normal unsigned value, if possible. Returns 0 if the trip count is unknown
|
2010-11-13 20:16:27 +08:00
|
|
|
/// or not constant. Will also return 0 if the trip count is very large
|
2009-07-14 06:02:44 +08:00
|
|
|
/// (>= 2^32)
|
|
|
|
unsigned Loop::getSmallConstantTripCount() const {
|
|
|
|
Value* TripCount = this->getTripCount();
|
|
|
|
if (TripCount) {
|
|
|
|
if (ConstantInt *TripCountC = dyn_cast<ConstantInt>(TripCount)) {
|
|
|
|
// Guard against huge trip counts.
|
|
|
|
if (TripCountC->getValue().getActiveBits() <= 32) {
|
|
|
|
return (unsigned)TripCountC->getZExtValue();
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
|
|
|
/// getSmallConstantTripMultiple - Returns the largest constant divisor of the
|
|
|
|
/// trip count of this loop as a normal unsigned value, if possible. This
|
|
|
|
/// means that the actual trip count is always a multiple of the returned
|
|
|
|
/// value (don't forget the trip count could very well be zero as well!).
|
|
|
|
///
|
|
|
|
/// Returns 1 if the trip count is unknown or not guaranteed to be the
|
|
|
|
/// multiple of a constant (which is also the case if the trip count is simply
|
|
|
|
/// constant, use getSmallConstantTripCount for that case), Will also return 1
|
|
|
|
/// if the trip count is very large (>= 2^32).
|
|
|
|
unsigned Loop::getSmallConstantTripMultiple() const {
|
|
|
|
Value* TripCount = this->getTripCount();
|
|
|
|
// This will hold the ConstantInt result, if any
|
|
|
|
ConstantInt *Result = NULL;
|
|
|
|
if (TripCount) {
|
|
|
|
// See if the trip count is constant itself
|
|
|
|
Result = dyn_cast<ConstantInt>(TripCount);
|
|
|
|
// if not, see if it is a multiplication
|
|
|
|
if (!Result)
|
|
|
|
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TripCount)) {
|
|
|
|
switch (BO->getOpcode()) {
|
|
|
|
case BinaryOperator::Mul:
|
|
|
|
Result = dyn_cast<ConstantInt>(BO->getOperand(1));
|
|
|
|
break;
|
2009-11-20 09:09:34 +08:00
|
|
|
case BinaryOperator::Shl:
|
|
|
|
if (ConstantInt *CI = dyn_cast<ConstantInt>(BO->getOperand(1)))
|
|
|
|
if (CI->getValue().getActiveBits() <= 5)
|
|
|
|
return 1u << CI->getZExtValue();
|
|
|
|
break;
|
2009-07-14 06:02:44 +08:00
|
|
|
default:
|
|
|
|
break;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
// Guard against huge trip counts.
|
|
|
|
if (Result && Result->getValue().getActiveBits() <= 32) {
|
|
|
|
return (unsigned)Result->getZExtValue();
|
|
|
|
} else {
|
|
|
|
return 1;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
/// isLCSSAForm - Return true if the Loop is in LCSSA form
|
2010-03-11 03:38:49 +08:00
|
|
|
bool Loop::isLCSSAForm(DominatorTree &DT) const {
|
2009-07-14 06:02:44 +08:00
|
|
|
// Sort the blocks vector so that we can use binary search to do quick
|
|
|
|
// lookups.
|
2010-07-09 22:28:41 +08:00
|
|
|
SmallPtrSet<BasicBlock*, 16> LoopBBs(block_begin(), block_end());
|
2009-07-14 06:02:44 +08:00
|
|
|
|
|
|
|
for (block_iterator BI = block_begin(), E = block_end(); BI != E; ++BI) {
|
2009-11-10 02:19:43 +08:00
|
|
|
BasicBlock *BB = *BI;
|
|
|
|
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E;++I)
|
2009-07-14 06:02:44 +08:00
|
|
|
for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E;
|
|
|
|
++UI) {
|
2010-07-09 22:28:41 +08:00
|
|
|
User *U = *UI;
|
|
|
|
BasicBlock *UserBB = cast<Instruction>(U)->getParent();
|
|
|
|
if (PHINode *P = dyn_cast<PHINode>(U))
|
2009-07-14 06:02:44 +08:00
|
|
|
UserBB = P->getIncomingBlock(UI);
|
|
|
|
|
2010-03-09 09:53:33 +08:00
|
|
|
// 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) &&
|
2010-03-11 03:38:49 +08:00
|
|
|
DT.isReachableFromEntry(UserBB))
|
2009-07-14 06:02:44 +08:00
|
|
|
return false;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
return true;
|
|
|
|
}
|
2009-07-17 00:16:23 +08:00
|
|
|
|
|
|
|
/// isLoopSimplifyForm - Return true if the Loop is in the form that
|
|
|
|
/// the LoopSimplify form transforms loops to, which is sometimes called
|
|
|
|
/// normal form.
|
|
|
|
bool Loop::isLoopSimplifyForm() const {
|
2009-11-06 03:21:41 +08:00
|
|
|
// 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 {
|
2009-10-21 04:41:13 +08:00
|
|
|
// Sort the blocks vector so that we can use binary search to do quick
|
|
|
|
// lookups.
|
|
|
|
SmallPtrSet<BasicBlock *, 16> LoopBBs(block_begin(), block_end());
|
2009-07-17 00:16:23 +08:00
|
|
|
// Each predecessor of each exit block of a normal loop is contained
|
|
|
|
// within the loop.
|
|
|
|
SmallVector<BasicBlock *, 4> ExitBlocks;
|
|
|
|
getExitBlocks(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)
|
2009-10-21 04:41:13 +08:00
|
|
|
if (!LoopBBs.count(*PI))
|
2009-07-17 00:16:23 +08:00
|
|
|
return false;
|
|
|
|
// All the requirements are met.
|
|
|
|
return true;
|
|
|
|
}
|
|
|
|
|
2009-09-04 00:10:48 +08:00
|
|
|
/// getUniqueExitBlocks - Return all unique successor blocks of this loop.
|
|
|
|
/// These are the blocks _outside of the current loop_ which are branched to.
|
2009-12-12 04:05:23 +08:00
|
|
|
/// This assumes that loop exits are in canonical form.
|
2009-09-04 00:10:48 +08:00
|
|
|
///
|
|
|
|
void
|
|
|
|
Loop::getUniqueExitBlocks(SmallVectorImpl<BasicBlock *> &ExitBlocks) const {
|
2009-12-12 04:05:23 +08:00
|
|
|
assert(hasDedicatedExits() &&
|
|
|
|
"getUniqueExitBlocks assumes the loop has canonical form exits!");
|
2009-09-08 23:45:00 +08:00
|
|
|
|
2009-09-04 00:10:48 +08:00
|
|
|
// 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());
|
|
|
|
|
2009-09-04 04:36:13 +08:00
|
|
|
SmallVector<BasicBlock *, 32> switchExitBlocks;
|
2009-09-04 00:10:48 +08:00
|
|
|
|
|
|
|
for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) {
|
|
|
|
|
|
|
|
BasicBlock *current = *BI;
|
|
|
|
switchExitBlocks.clear();
|
|
|
|
|
2010-07-24 05:25:16 +08:00
|
|
|
for (succ_iterator I = succ_begin(*BI), E = succ_end(*BI); I != E; ++I) {
|
2009-09-04 00:10:48 +08:00
|
|
|
// If block is inside the loop then it is not a exit block.
|
|
|
|
if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I))
|
|
|
|
continue;
|
|
|
|
|
2010-07-24 05:25:16 +08:00
|
|
|
pred_iterator PI = pred_begin(*I);
|
2009-09-04 00:10:48 +08:00
|
|
|
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.
|
2010-07-24 05:25:16 +08:00
|
|
|
if (std::distance(succ_begin(current), succ_end(current)) <= 2) {
|
2009-09-04 00:10:48 +08:00
|
|
|
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;
|
|
|
|
}
|
|
|
|
|
2010-01-06 05:08:02 +08:00
|
|
|
void Loop::dump() const {
|
|
|
|
print(dbgs());
|
|
|
|
}
|
|
|
|
|
2011-08-11 07:22:57 +08:00
|
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
// UnloopUpdater implementation
|
|
|
|
//
|
|
|
|
|
|
|
|
/// Find the new parent loop for all blocks within the "unloop" whose last
|
|
|
|
/// backedges has just been removed.
|
|
|
|
class UnloopUpdater {
|
|
|
|
Loop *Unloop;
|
|
|
|
LoopInfo *LI;
|
|
|
|
|
|
|
|
LoopBlocksDFS DFS;
|
|
|
|
|
|
|
|
// Map unloop's immediate subloops to their nearest reachable parents. Nested
|
|
|
|
// loops within these subloops will not change parents. However, an immediate
|
|
|
|
// subloop's new parent will be the nearest loop reachable from either its own
|
|
|
|
// exits *or* any of its nested loop's exits.
|
|
|
|
DenseMap<Loop*, Loop*> SubloopParents;
|
|
|
|
|
|
|
|
// Flag the presence of an irreducible backedge whose destination is a block
|
|
|
|
// directly contained by the original unloop.
|
|
|
|
bool FoundIB;
|
|
|
|
|
|
|
|
public:
|
|
|
|
UnloopUpdater(Loop *UL, LoopInfo *LInfo) :
|
|
|
|
Unloop(UL), LI(LInfo), DFS(UL), FoundIB(false) {}
|
|
|
|
|
|
|
|
void updateBlockParents();
|
|
|
|
|
2011-08-12 04:27:32 +08:00
|
|
|
void removeBlocksFromAncestors();
|
|
|
|
|
2011-08-11 07:22:57 +08:00
|
|
|
void updateSubloopParents();
|
|
|
|
|
|
|
|
protected:
|
|
|
|
Loop *getNearestLoop(BasicBlock *BB, Loop *BBLoop);
|
|
|
|
};
|
|
|
|
|
|
|
|
/// updateBlockParents - Update the parent loop for all blocks that are directly
|
|
|
|
/// contained within the original "unloop".
|
|
|
|
void UnloopUpdater::updateBlockParents() {
|
|
|
|
if (Unloop->getNumBlocks()) {
|
|
|
|
// Perform a post order CFG traversal of all blocks within this loop,
|
|
|
|
// propagating the nearest loop from sucessors to predecessors.
|
|
|
|
LoopBlocksTraversal Traversal(DFS, LI);
|
|
|
|
for (LoopBlocksTraversal::POTIterator POI = Traversal.begin(),
|
|
|
|
POE = Traversal.end(); POI != POE; ++POI) {
|
|
|
|
|
|
|
|
Loop *L = LI->getLoopFor(*POI);
|
|
|
|
Loop *NL = getNearestLoop(*POI, L);
|
|
|
|
|
|
|
|
if (NL != L) {
|
|
|
|
// For reducible loops, NL is now an ancestor of Unloop.
|
|
|
|
assert((NL != Unloop && (!NL || NL->contains(Unloop))) &&
|
|
|
|
"uninitialized successor");
|
|
|
|
LI->changeLoopFor(*POI, NL);
|
|
|
|
}
|
|
|
|
else {
|
|
|
|
// Or the current block is part of a subloop, in which case its parent
|
|
|
|
// is unchanged.
|
|
|
|
assert((FoundIB || Unloop->contains(L)) && "uninitialized successor");
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
// Each irreducible loop within the unloop induces a round of iteration using
|
|
|
|
// the DFS result cached by Traversal.
|
|
|
|
bool Changed = FoundIB;
|
|
|
|
for (unsigned NIters = 0; Changed; ++NIters) {
|
|
|
|
assert(NIters < Unloop->getNumBlocks() && "runaway iterative algorithm");
|
|
|
|
|
|
|
|
// Iterate over the postorder list of blocks, propagating the nearest loop
|
|
|
|
// from successors to predecessors as before.
|
|
|
|
Changed = false;
|
|
|
|
for (LoopBlocksDFS::POIterator POI = DFS.beginPostorder(),
|
|
|
|
POE = DFS.endPostorder(); POI != POE; ++POI) {
|
|
|
|
|
|
|
|
Loop *L = LI->getLoopFor(*POI);
|
|
|
|
Loop *NL = getNearestLoop(*POI, L);
|
|
|
|
if (NL != L) {
|
|
|
|
assert(NL != Unloop && (!NL || NL->contains(Unloop)) &&
|
|
|
|
"uninitialized successor");
|
|
|
|
LI->changeLoopFor(*POI, NL);
|
|
|
|
Changed = true;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
2011-08-12 04:27:32 +08:00
|
|
|
/// removeBlocksFromAncestors - Remove unloop's blocks from all ancestors below
|
|
|
|
/// their new parents.
|
|
|
|
void UnloopUpdater::removeBlocksFromAncestors() {
|
|
|
|
// Remove unloop's blocks from all ancestors below their new parents.
|
|
|
|
for (Loop::block_iterator BI = Unloop->block_begin(),
|
|
|
|
BE = Unloop->block_end(); BI != BE; ++BI) {
|
|
|
|
Loop *NewParent = LI->getLoopFor(*BI);
|
|
|
|
// If this block is an immediate subloop, remove all blocks (including
|
|
|
|
// nested subloops) from ancestors below the new parent loop.
|
|
|
|
// Otherwise, if this block is in a nested subloop, skip it.
|
|
|
|
if (SubloopParents.count(NewParent))
|
|
|
|
NewParent = SubloopParents[NewParent];
|
|
|
|
else if (Unloop->contains(NewParent))
|
|
|
|
continue;
|
|
|
|
|
|
|
|
// Remove blocks from former Ancestors except Unloop itself which will be
|
|
|
|
// deleted.
|
|
|
|
for (Loop *OldParent = Unloop->getParentLoop(); OldParent != NewParent;
|
|
|
|
OldParent = OldParent->getParentLoop()) {
|
|
|
|
assert(OldParent && "new loop is not an ancestor of the original");
|
|
|
|
OldParent->removeBlockFromLoop(*BI);
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
2011-08-11 07:22:57 +08:00
|
|
|
/// updateSubloopParents - Update the parent loop for all subloops directly
|
|
|
|
/// nested within unloop.
|
|
|
|
void UnloopUpdater::updateSubloopParents() {
|
|
|
|
while (!Unloop->empty()) {
|
2011-08-12 01:54:58 +08:00
|
|
|
Loop *Subloop = *llvm::prior(Unloop->end());
|
|
|
|
Unloop->removeChildLoop(llvm::prior(Unloop->end()));
|
2011-08-11 07:22:57 +08:00
|
|
|
|
|
|
|
assert(SubloopParents.count(Subloop) && "DFS failed to visit subloop");
|
|
|
|
if (SubloopParents[Subloop])
|
|
|
|
SubloopParents[Subloop]->addChildLoop(Subloop);
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
/// getNearestLoop - Return the nearest parent loop among this block's
|
|
|
|
/// successors. If a successor is a subloop header, consider its parent to be
|
|
|
|
/// the nearest parent of the subloop's exits.
|
|
|
|
///
|
|
|
|
/// For subloop blocks, simply update SubloopParents and return NULL.
|
|
|
|
Loop *UnloopUpdater::getNearestLoop(BasicBlock *BB, Loop *BBLoop) {
|
|
|
|
|
2011-08-12 01:54:58 +08:00
|
|
|
// Initially for blocks directly contained by Unloop, NearLoop == Unloop and
|
|
|
|
// is considered uninitialized.
|
2011-08-11 07:22:57 +08:00
|
|
|
Loop *NearLoop = BBLoop;
|
|
|
|
|
|
|
|
Loop *Subloop = 0;
|
|
|
|
if (NearLoop != Unloop && Unloop->contains(NearLoop)) {
|
|
|
|
Subloop = NearLoop;
|
|
|
|
// Find the subloop ancestor that is directly contained within Unloop.
|
|
|
|
while (Subloop->getParentLoop() != Unloop) {
|
|
|
|
Subloop = Subloop->getParentLoop();
|
|
|
|
assert(Subloop && "subloop is not an ancestor of the original loop");
|
|
|
|
}
|
|
|
|
// Get the current nearest parent of the Subloop exits, initially Unloop.
|
|
|
|
if (!SubloopParents.count(Subloop))
|
|
|
|
SubloopParents[Subloop] = Unloop;
|
|
|
|
NearLoop = SubloopParents[Subloop];
|
|
|
|
}
|
|
|
|
|
|
|
|
succ_iterator I = succ_begin(BB), E = succ_end(BB);
|
|
|
|
if (I == E) {
|
|
|
|
assert(!Subloop && "subloop blocks must have a successor");
|
|
|
|
NearLoop = 0; // unloop blocks may now exit the function.
|
|
|
|
}
|
|
|
|
for (; I != E; ++I) {
|
|
|
|
if (*I == BB)
|
|
|
|
continue; // self loops are uninteresting
|
|
|
|
|
|
|
|
Loop *L = LI->getLoopFor(*I);
|
|
|
|
if (L == Unloop) {
|
|
|
|
// This successor has not been processed. This path must lead to an
|
|
|
|
// irreducible backedge.
|
|
|
|
assert((FoundIB || !DFS.hasPostorder(*I)) && "should have seen IB");
|
|
|
|
FoundIB = true;
|
|
|
|
}
|
|
|
|
if (L != Unloop && Unloop->contains(L)) {
|
|
|
|
// Successor is in a subloop.
|
|
|
|
if (Subloop)
|
|
|
|
continue; // Branching within subloops. Ignore it.
|
|
|
|
|
|
|
|
// BB branches from the original into a subloop header.
|
|
|
|
assert(L->getParentLoop() == Unloop && "cannot skip into nested loops");
|
|
|
|
|
|
|
|
// Get the current nearest parent of the Subloop's exits.
|
|
|
|
L = SubloopParents[L];
|
|
|
|
// L could be Unloop if the only exit was an irreducible backedge.
|
|
|
|
}
|
|
|
|
if (L == Unloop) {
|
|
|
|
continue;
|
|
|
|
}
|
|
|
|
// Handle critical edges from Unloop into a sibling loop.
|
|
|
|
if (L && !L->contains(Unloop)) {
|
|
|
|
L = L->getParentLoop();
|
|
|
|
}
|
|
|
|
// Remember the nearest parent loop among successors or subloop exits.
|
|
|
|
if (NearLoop == Unloop || !NearLoop || NearLoop->contains(L))
|
|
|
|
NearLoop = L;
|
|
|
|
}
|
|
|
|
if (Subloop) {
|
|
|
|
SubloopParents[Subloop] = NearLoop;
|
|
|
|
return BBLoop;
|
|
|
|
}
|
|
|
|
return NearLoop;
|
|
|
|
}
|
|
|
|
|
2002-01-31 08:42:27 +08:00
|
|
|
//===----------------------------------------------------------------------===//
|
2002-04-29 00:21:30 +08:00
|
|
|
// LoopInfo implementation
|
2002-01-31 08:42:27 +08:00
|
|
|
//
|
2002-06-26 00:13:24 +08:00
|
|
|
bool LoopInfo::runOnFunction(Function &) {
|
2002-04-09 13:43:19 +08:00
|
|
|
releaseMemory();
|
2009-06-28 05:22:48 +08:00
|
|
|
LI.Calculate(getAnalysis<DominatorTree>().getBase()); // Update
|
2002-01-31 08:42:27 +08:00
|
|
|
return false;
|
|
|
|
}
|
|
|
|
|
2011-08-11 07:22:57 +08:00
|
|
|
/// updateUnloop - The last backedge has been removed from a loop--now the
|
|
|
|
/// "unloop". Find a new parent for the blocks contained within unloop and
|
2011-08-12 01:54:58 +08:00
|
|
|
/// update the loop tree. We don't necessarily have valid dominators at this
|
2011-08-11 07:22:57 +08:00
|
|
|
/// point, but LoopInfo is still valid except for the removal of this loop.
|
|
|
|
///
|
|
|
|
/// Note that Unloop may now be an empty loop. Calling Loop::getHeader without
|
|
|
|
/// checking first is illegal.
|
|
|
|
void LoopInfo::updateUnloop(Loop *Unloop) {
|
|
|
|
|
|
|
|
// First handle the special case of no parent loop to simplify the algorithm.
|
|
|
|
if (!Unloop->getParentLoop()) {
|
|
|
|
// Since BBLoop had no parent, Unloop blocks are no longer in a loop.
|
|
|
|
for (Loop::block_iterator I = Unloop->block_begin(),
|
|
|
|
E = Unloop->block_end(); I != E; ++I) {
|
|
|
|
|
|
|
|
// Don't reparent blocks in subloops.
|
|
|
|
if (getLoopFor(*I) != Unloop)
|
|
|
|
continue;
|
|
|
|
|
|
|
|
// Blocks no longer have a parent but are still referenced by Unloop until
|
|
|
|
// the Unloop object is deleted.
|
|
|
|
LI.changeLoopFor(*I, 0);
|
|
|
|
}
|
|
|
|
|
|
|
|
// Remove the loop from the top-level LoopInfo object.
|
|
|
|
for (LoopInfo::iterator I = LI.begin(), E = LI.end();; ++I) {
|
|
|
|
assert(I != E && "Couldn't find loop");
|
|
|
|
if (*I == Unloop) {
|
|
|
|
LI.removeLoop(I);
|
|
|
|
break;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
// Move all of the subloops to the top-level.
|
|
|
|
while (!Unloop->empty())
|
2011-08-12 01:54:58 +08:00
|
|
|
LI.addTopLevelLoop(Unloop->removeChildLoop(llvm::prior(Unloop->end())));
|
2011-08-11 07:22:57 +08:00
|
|
|
|
|
|
|
return;
|
|
|
|
}
|
|
|
|
|
|
|
|
// Update the parent loop for all blocks within the loop. Blocks within
|
|
|
|
// subloops will not change parents.
|
|
|
|
UnloopUpdater Updater(Unloop, this);
|
|
|
|
Updater.updateBlockParents();
|
|
|
|
|
2011-08-12 04:27:32 +08:00
|
|
|
// Remove blocks from former ancestor loops.
|
|
|
|
Updater.removeBlocksFromAncestors();
|
2011-08-11 07:22:57 +08:00
|
|
|
|
|
|
|
// Add direct subloops as children in their new parent loop.
|
|
|
|
Updater.updateSubloopParents();
|
|
|
|
|
|
|
|
// Remove unloop from its parent loop.
|
|
|
|
Loop *ParentLoop = Unloop->getParentLoop();
|
|
|
|
for (Loop::iterator I = ParentLoop->begin(), E = ParentLoop->end();; ++I) {
|
|
|
|
assert(I != E && "Couldn't find loop");
|
|
|
|
if (*I == Unloop) {
|
|
|
|
ParentLoop->removeChildLoop(I);
|
|
|
|
break;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
2009-09-08 23:45:00 +08:00
|
|
|
void LoopInfo::verifyAnalysis() const {
|
2009-09-28 08:27:48 +08:00
|
|
|
// 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;
|
|
|
|
|
2009-09-08 23:45:00 +08:00
|
|
|
for (iterator I = begin(), E = end(); I != E; ++I) {
|
|
|
|
assert(!(*I)->getParentLoop() && "Top-level loop has a parent!");
|
|
|
|
(*I)->verifyLoopNest();
|
|
|
|
}
|
2009-09-28 08:27:48 +08:00
|
|
|
|
|
|
|
// TODO: check BBMap consistency.
|
2009-09-08 23:45:00 +08:00
|
|
|
}
|
|
|
|
|
2002-04-29 00:21:30 +08:00
|
|
|
void LoopInfo::getAnalysisUsage(AnalysisUsage &AU) const {
|
2002-04-27 14:56:12 +08:00
|
|
|
AU.setPreservesAll();
|
2007-06-08 08:17:13 +08:00
|
|
|
AU.addRequired<DominatorTree>();
|
2002-01-31 08:42:27 +08:00
|
|
|
}
|
2009-08-23 13:17:37 +08:00
|
|
|
|
2009-08-23 14:03:38 +08:00
|
|
|
void LoopInfo::print(raw_ostream &OS, const Module*) const {
|
|
|
|
LI.print(OS);
|
2009-08-23 13:17:37 +08:00
|
|
|
}
|
|
|
|
|
2011-08-10 09:59:05 +08:00
|
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
// LoopBlocksDFS implementation
|
|
|
|
//
|
|
|
|
|
|
|
|
/// Traverse the loop blocks and store the DFS result.
|
|
|
|
/// Useful for clients that just want the final DFS result and don't need to
|
|
|
|
/// visit blocks during the initial traversal.
|
|
|
|
void LoopBlocksDFS::perform(LoopInfo *LI) {
|
|
|
|
LoopBlocksTraversal Traversal(*this, LI);
|
|
|
|
for (LoopBlocksTraversal::POTIterator POI = Traversal.begin(),
|
|
|
|
POE = Traversal.end(); POI != POE; ++POI) ;
|
|
|
|
}
|