2003-10-13 11:32:08 +08:00
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//===- LoopInfo.cpp - Natural Loop Calculator -----------------------------===//
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2005-04-22 05:13:18 +08:00
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//
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2003-10-21 03:43:21 +08:00
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// The LLVM Compiler Infrastructure
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//
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2007-12-30 04:36:04 +08:00
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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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2005-04-22 05:13:18 +08:00
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//
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2003-10-21 03:43:21 +08:00
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//===----------------------------------------------------------------------===//
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2001-11-27 02:41:20 +08:00
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//
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// This file defines the LoopInfo class that is used to identify natural loops
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// and determine the loop depth of various nodes of the CFG. Note that the
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// loops identified may actually be several natural loops that share the same
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// header node... not just a single natural loop.
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//
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//===----------------------------------------------------------------------===//
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2004-01-31 01:26:24 +08:00
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#include "llvm/Analysis/LoopInfo.h"
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2012-12-04 00:50:05 +08:00
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#include "llvm/ADT/DepthFirstIterator.h"
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#include "llvm/ADT/SmallPtrSet.h"
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2004-04-15 23:16:02 +08:00
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#include "llvm/Analysis/Dominators.h"
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2012-06-20 11:42:09 +08:00
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#include "llvm/Analysis/LoopInfoImpl.h"
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2011-08-10 09:59:05 +08:00
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#include "llvm/Analysis/LoopIterator.h"
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2011-12-15 07:49:11 +08:00
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#include "llvm/Analysis/ValueTracking.h"
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2002-07-27 09:12:17 +08:00
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#include "llvm/Assembly/Writer.h"
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2013-01-02 19:36:10 +08:00
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#include "llvm/IR/Constants.h"
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#include "llvm/IR/Instructions.h"
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2013-02-14 02:08:57 +08:00
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#include "llvm/IR/Metadata.h"
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2004-01-31 01:26:24 +08:00
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#include "llvm/Support/CFG.h"
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2009-09-28 08:27:48 +08:00
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#include "llvm/Support/CommandLine.h"
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2010-01-06 05:08:02 +08:00
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#include "llvm/Support/Debug.h"
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2001-11-27 02:41:20 +08:00
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#include <algorithm>
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2004-04-13 04:26:17 +08:00
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using namespace llvm;
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2003-11-12 06:41:34 +08:00
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2012-06-20 11:42:09 +08:00
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// Explicitly instantiate methods in LoopInfoImpl.h for IR-level Loops.
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template class llvm::LoopBase<BasicBlock, Loop>;
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template class llvm::LoopInfoBase<BasicBlock, Loop>;
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2009-09-28 08:27:48 +08:00
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// Always verify loopinfo if expensive checking is enabled.
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#ifdef XDEBUG
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2010-04-16 01:08:50 +08:00
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static bool VerifyLoopInfo = true;
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2009-09-28 08:27:48 +08:00
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#else
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2010-04-16 01:08:50 +08:00
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static bool VerifyLoopInfo = false;
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2009-09-28 08:27:48 +08:00
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#endif
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static cl::opt<bool,true>
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VerifyLoopInfoX("verify-loop-info", cl::location(VerifyLoopInfo),
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cl::desc("Verify loop info (time consuming)"));
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2007-05-03 09:11:54 +08:00
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char LoopInfo::ID = 0;
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2010-10-13 03:48:12 +08:00
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INITIALIZE_PASS_BEGIN(LoopInfo, "loops", "Natural Loop Information", true, true)
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INITIALIZE_PASS_DEPENDENCY(DominatorTree)
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INITIALIZE_PASS_END(LoopInfo, "loops", "Natural Loop Information", true, true)
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2002-01-31 08:42:27 +08:00
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2013-05-29 04:00:34 +08:00
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// Loop identifier metadata name.
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2013-07-16 09:17:10 +08:00
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static const char *const LoopMDName = "llvm.loop";
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2013-05-29 04:00:34 +08:00
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2002-01-31 08:42:27 +08:00
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//===----------------------------------------------------------------------===//
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2002-04-29 00:21:30 +08:00
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// Loop implementation
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2002-01-31 08:42:27 +08:00
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//
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2002-10-11 13:31:10 +08:00
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2009-07-14 06:02:44 +08:00
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/// isLoopInvariant - Return true if the specified value is loop invariant
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///
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bool Loop::isLoopInvariant(Value *V) const {
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if (Instruction *I = dyn_cast<Instruction>(V))
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2010-09-06 09:05:37 +08:00
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return !contains(I);
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2009-07-14 06:02:44 +08:00
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return true; // All non-instructions are loop invariant
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}
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2010-09-06 09:05:37 +08:00
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/// hasLoopInvariantOperands - Return true if all the operands of the
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2011-08-04 07:45:50 +08:00
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/// specified instruction are loop invariant.
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2010-09-06 09:05:37 +08:00
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bool Loop::hasLoopInvariantOperands(Instruction *I) const {
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for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
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if (!isLoopInvariant(I->getOperand(i)))
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return false;
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2011-08-04 07:45:50 +08:00
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2010-09-06 09:05:37 +08:00
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return true;
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2009-07-14 09:06:29 +08:00
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}
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/// makeLoopInvariant - If the given value is an instruciton inside of the
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/// loop and it can be hoisted, do so to make it trivially loop-invariant.
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/// Return true if the value after any hoisting is loop invariant. This
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/// function can be used as a slightly more aggressive replacement for
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/// isLoopInvariant.
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///
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/// If InsertPt is specified, it is the point to hoist instructions to.
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/// If null, the terminator of the loop preheader is used.
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///
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2009-07-15 09:25:43 +08:00
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bool Loop::makeLoopInvariant(Value *V, bool &Changed,
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Instruction *InsertPt) const {
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2009-07-14 09:06:29 +08:00
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if (Instruction *I = dyn_cast<Instruction>(V))
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2009-07-15 09:25:43 +08:00
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return makeLoopInvariant(I, Changed, InsertPt);
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2009-07-14 09:06:29 +08:00
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return true; // All non-instructions are loop-invariant.
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}
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/// makeLoopInvariant - If the given instruction is inside of the
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/// loop and it can be hoisted, do so to make it trivially loop-invariant.
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/// Return true if the instruction after any hoisting is loop invariant. This
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/// function can be used as a slightly more aggressive replacement for
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/// isLoopInvariant.
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///
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/// If InsertPt is specified, it is the point to hoist instructions to.
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/// If null, the terminator of the loop preheader is used.
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///
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2009-07-15 09:25:43 +08:00
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bool Loop::makeLoopInvariant(Instruction *I, bool &Changed,
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Instruction *InsertPt) const {
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2009-07-14 09:06:29 +08:00
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// Test if the value is already loop-invariant.
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if (isLoopInvariant(I))
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return true;
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2011-12-15 07:49:11 +08:00
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if (!isSafeToSpeculativelyExecute(I))
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2009-07-14 09:06:29 +08:00
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return false;
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2009-07-17 12:28:42 +08:00
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if (I->mayReadFromMemory())
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2009-07-14 09:06:29 +08:00
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return false;
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2011-08-18 04:36:44 +08:00
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// The landingpad instruction is immobile.
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if (isa<LandingPadInst>(I))
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return false;
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2009-07-14 09:06:29 +08:00
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// Determine the insertion point, unless one was given.
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if (!InsertPt) {
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BasicBlock *Preheader = getLoopPreheader();
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// Without a preheader, hoisting is not feasible.
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if (!Preheader)
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return false;
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InsertPt = Preheader->getTerminator();
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}
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// Don't hoist instructions with loop-variant operands.
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for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
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2009-07-15 09:25:43 +08:00
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if (!makeLoopInvariant(I->getOperand(i), Changed, InsertPt))
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2009-07-14 09:06:29 +08:00
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return false;
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2011-08-04 07:45:50 +08:00
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2009-07-14 09:06:29 +08:00
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// Hoist.
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I->moveBefore(InsertPt);
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2009-07-15 09:25:43 +08:00
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Changed = true;
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2009-07-14 09:06:29 +08:00
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return true;
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}
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2009-07-14 06:02:44 +08:00
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/// getCanonicalInductionVariable - Check to see if the loop has a canonical
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/// induction variable: an integer recurrence that starts at 0 and increments
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/// by one each time through the loop. If so, return the phi node that
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/// corresponds to it.
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///
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/// The IndVarSimplify pass transforms loops to have a canonical induction
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/// variable.
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///
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PHINode *Loop::getCanonicalInductionVariable() const {
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BasicBlock *H = getHeader();
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BasicBlock *Incoming = 0, *Backedge = 0;
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2010-07-24 05:25:16 +08:00
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pred_iterator PI = pred_begin(H);
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assert(PI != pred_end(H) &&
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2009-07-14 06:02:44 +08:00
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"Loop must have at least one backedge!");
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Backedge = *PI++;
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2010-07-24 05:25:16 +08:00
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if (PI == pred_end(H)) return 0; // dead loop
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2009-07-14 06:02:44 +08:00
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Incoming = *PI++;
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2010-07-24 05:25:16 +08:00
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if (PI != pred_end(H)) return 0; // multiple backedges?
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2009-07-14 06:02:44 +08:00
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if (contains(Incoming)) {
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if (contains(Backedge))
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return 0;
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std::swap(Incoming, Backedge);
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} else if (!contains(Backedge))
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return 0;
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// Loop over all of the PHI nodes, looking for a canonical indvar.
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for (BasicBlock::iterator I = H->begin(); isa<PHINode>(I); ++I) {
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PHINode *PN = cast<PHINode>(I);
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if (ConstantInt *CI =
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dyn_cast<ConstantInt>(PN->getIncomingValueForBlock(Incoming)))
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if (CI->isNullValue())
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if (Instruction *Inc =
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dyn_cast<Instruction>(PN->getIncomingValueForBlock(Backedge)))
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if (Inc->getOpcode() == Instruction::Add &&
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Inc->getOperand(0) == PN)
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if (ConstantInt *CI = dyn_cast<ConstantInt>(Inc->getOperand(1)))
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if (CI->equalsInt(1))
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return PN;
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}
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return 0;
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}
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/// isLCSSAForm - Return true if the Loop is in LCSSA form
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2010-03-11 03:38:49 +08:00
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bool Loop::isLCSSAForm(DominatorTree &DT) const {
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2009-07-14 06:02:44 +08:00
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for (block_iterator BI = block_begin(), E = block_end(); BI != E; ++BI) {
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2009-11-10 02:19:43 +08:00
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BasicBlock *BB = *BI;
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for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E;++I)
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2009-07-14 06:02:44 +08:00
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for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E;
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++UI) {
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2010-07-09 22:28:41 +08:00
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User *U = *UI;
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BasicBlock *UserBB = cast<Instruction>(U)->getParent();
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if (PHINode *P = dyn_cast<PHINode>(U))
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2009-07-14 06:02:44 +08:00
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UserBB = P->getIncomingBlock(UI);
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2010-03-09 09:53:33 +08:00
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// Check the current block, as a fast-path, before checking whether
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// the use is anywhere in the loop. Most values are used in the same
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// block they are defined in. Also, blocks not reachable from the
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// entry are special; uses in them don't need to go through PHIs.
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if (UserBB != BB &&
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2013-10-26 11:08:02 +08:00
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!contains(UserBB) &&
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2010-03-11 03:38:49 +08:00
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DT.isReachableFromEntry(UserBB))
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2009-07-14 06:02:44 +08:00
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return false;
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}
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}
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return true;
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}
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2009-07-17 00:16:23 +08:00
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/// isLoopSimplifyForm - Return true if the Loop is in the form that
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/// the LoopSimplify form transforms loops to, which is sometimes called
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/// normal form.
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bool Loop::isLoopSimplifyForm() const {
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2009-11-06 03:21:41 +08:00
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// Normal-form loops have a preheader, a single backedge, and all of their
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// exits have all their predecessors inside the loop.
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return getLoopPreheader() && getLoopLatch() && hasDedicatedExits();
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}
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2012-04-10 13:14:42 +08:00
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/// isSafeToClone - Return true if the loop body is safe to clone in practice.
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/// Routines that reform the loop CFG and split edges often fail on indirectbr.
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bool Loop::isSafeToClone() const {
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2012-12-21 00:04:27 +08:00
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// Return false if any loop blocks contain indirectbrs, or there are any calls
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// to noduplicate functions.
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2012-04-10 13:14:42 +08:00
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for (Loop::block_iterator I = block_begin(), E = block_end(); I != E; ++I) {
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2012-12-21 00:04:27 +08:00
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if (isa<IndirectBrInst>((*I)->getTerminator())) {
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2012-04-10 13:14:42 +08:00
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return false;
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2012-12-21 00:04:27 +08:00
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} else if (const InvokeInst *II = dyn_cast<InvokeInst>((*I)->getTerminator())) {
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if (II->hasFnAttr(Attribute::NoDuplicate))
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return false;
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}
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for (BasicBlock::iterator BI = (*I)->begin(), BE = (*I)->end(); BI != BE; ++BI) {
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if (const CallInst *CI = dyn_cast<CallInst>(BI)) {
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if (CI->hasFnAttr(Attribute::NoDuplicate))
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return false;
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}
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}
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2012-04-10 13:14:42 +08:00
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}
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return true;
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}
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2013-05-29 04:00:34 +08:00
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MDNode *Loop::getLoopID() const {
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MDNode *LoopID = 0;
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if (isLoopSimplifyForm()) {
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LoopID = getLoopLatch()->getTerminator()->getMetadata(LoopMDName);
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} else {
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// Go through each predecessor of the loop header and check the
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// terminator for the metadata.
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BasicBlock *H = getHeader();
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for (block_iterator I = block_begin(), IE = block_end(); I != IE; ++I) {
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TerminatorInst *TI = (*I)->getTerminator();
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MDNode *MD = 0;
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2013-02-14 02:08:57 +08:00
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2013-05-29 04:00:34 +08:00
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// Check if this terminator branches to the loop header.
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for (unsigned i = 0, ie = TI->getNumSuccessors(); i != ie; ++i) {
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if (TI->getSuccessor(i) == H) {
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MD = TI->getMetadata(LoopMDName);
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break;
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}
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}
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if (!MD)
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return 0;
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if (!LoopID)
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LoopID = MD;
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else if (MD != LoopID)
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return 0;
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}
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}
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if (!LoopID || LoopID->getNumOperands() == 0 ||
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LoopID->getOperand(0) != LoopID)
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return 0;
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return LoopID;
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}
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2013-02-14 02:08:57 +08:00
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2013-05-29 04:00:34 +08:00
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void Loop::setLoopID(MDNode *LoopID) const {
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assert(LoopID && "Loop ID should not be null");
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assert(LoopID->getNumOperands() > 0 && "Loop ID needs at least one operand");
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assert(LoopID->getOperand(0) == LoopID && "Loop ID should refer to itself");
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if (isLoopSimplifyForm()) {
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getLoopLatch()->getTerminator()->setMetadata(LoopMDName, LoopID);
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return;
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}
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BasicBlock *H = getHeader();
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for (block_iterator I = block_begin(), IE = block_end(); I != IE; ++I) {
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TerminatorInst *TI = (*I)->getTerminator();
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for (unsigned i = 0, ie = TI->getNumSuccessors(); i != ie; ++i) {
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if (TI->getSuccessor(i) == H)
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TI->setMetadata(LoopMDName, LoopID);
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}
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}
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}
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|
|
bool Loop::isAnnotatedParallel() const {
|
|
|
|
MDNode *desiredLoopIdMetadata = getLoopID();
|
2013-02-14 02:08:57 +08:00
|
|
|
|
|
|
|
if (!desiredLoopIdMetadata)
|
|
|
|
return false;
|
|
|
|
|
|
|
|
// The loop branch contains the parallel loop metadata. In order to ensure
|
|
|
|
// that any parallel-loop-unaware optimization pass hasn't added loop-carried
|
|
|
|
// dependencies (thus converted the loop back to a sequential loop), check
|
|
|
|
// that all the memory instructions in the loop contain parallelism metadata
|
|
|
|
// that point to the same unique "loop id metadata" the loop branch does.
|
|
|
|
for (block_iterator BB = block_begin(), BE = block_end(); BB != BE; ++BB) {
|
|
|
|
for (BasicBlock::iterator II = (*BB)->begin(), EE = (*BB)->end();
|
|
|
|
II != EE; II++) {
|
|
|
|
|
|
|
|
if (!II->mayReadOrWriteMemory())
|
|
|
|
continue;
|
|
|
|
|
|
|
|
if (!II->getMetadata("llvm.mem.parallel_loop_access"))
|
|
|
|
return false;
|
|
|
|
|
|
|
|
// The memory instruction can refer to the loop identifier metadata
|
|
|
|
// directly or indirectly through another list metadata (in case of
|
|
|
|
// nested parallel loops). The loop identifier metadata refers to
|
|
|
|
// itself so we can check both cases with the same routine.
|
|
|
|
MDNode *loopIdMD =
|
|
|
|
dyn_cast<MDNode>(II->getMetadata("llvm.mem.parallel_loop_access"));
|
|
|
|
bool loopIdMDFound = false;
|
|
|
|
for (unsigned i = 0, e = loopIdMD->getNumOperands(); i < e; ++i) {
|
|
|
|
if (loopIdMD->getOperand(i) == desiredLoopIdMetadata) {
|
|
|
|
loopIdMDFound = true;
|
|
|
|
break;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
if (!loopIdMDFound)
|
|
|
|
return false;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
return true;
|
|
|
|
}
|
|
|
|
|
|
|
|
|
2009-11-06 03:21:41 +08:00
|
|
|
/// hasDedicatedExits - Return true if no exit block for the loop
|
|
|
|
/// has a predecessor that is outside the loop.
|
|
|
|
bool Loop::hasDedicatedExits() const {
|
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)
|
2013-10-26 11:08:02 +08:00
|
|
|
if (!contains(*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 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.
|
2013-10-26 11:08:02 +08:00
|
|
|
if (contains(*I))
|
2009-09-04 00:10:48 +08:00
|
|
|
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;
|
|
|
|
}
|
|
|
|
|
2012-09-12 13:06:18 +08:00
|
|
|
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
|
2010-01-06 05:08:02 +08:00
|
|
|
void Loop::dump() const {
|
|
|
|
print(dbgs());
|
|
|
|
}
|
2012-09-07 03:55:56 +08:00
|
|
|
#endif
|
2010-01-06 05:08:02 +08:00
|
|
|
|
2011-08-11 07:22:57 +08:00
|
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
// UnloopUpdater implementation
|
|
|
|
//
|
|
|
|
|
2011-08-19 09:42:18 +08:00
|
|
|
namespace {
|
2011-08-11 07:22:57 +08:00
|
|
|
/// 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);
|
|
|
|
};
|
2011-08-19 09:42:18 +08:00
|
|
|
} // end anonymous namespace
|
2011-08-11 07:22:57 +08:00
|
|
|
|
|
|
|
/// 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() {
|
2011-11-18 11:42:41 +08:00
|
|
|
// Remove all unloop's blocks (including those in nested subloops) from
|
|
|
|
// ancestors below the new parent loop.
|
2011-08-12 04:27:32 +08:00
|
|
|
for (Loop::block_iterator BI = Unloop->block_begin(),
|
|
|
|
BE = Unloop->block_end(); BI != BE; ++BI) {
|
2011-11-18 11:42:41 +08:00
|
|
|
Loop *OuterParent = LI->getLoopFor(*BI);
|
|
|
|
if (Unloop->contains(OuterParent)) {
|
|
|
|
while (OuterParent->getParentLoop() != Unloop)
|
|
|
|
OuterParent = OuterParent->getParentLoop();
|
|
|
|
OuterParent = SubloopParents[OuterParent];
|
|
|
|
}
|
2011-08-12 04:27:32 +08:00
|
|
|
// Remove blocks from former Ancestors except Unloop itself which will be
|
|
|
|
// deleted.
|
2011-11-18 11:42:41 +08:00
|
|
|
for (Loop *OldParent = Unloop->getParentLoop(); OldParent != OuterParent;
|
2011-08-12 04:27:32 +08:00
|
|
|
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");
|
2012-08-22 23:37:57 +08:00
|
|
|
if (Loop *Parent = SubloopParents[Subloop])
|
|
|
|
Parent->addChildLoop(Subloop);
|
2011-08-26 11:06:34 +08:00
|
|
|
else
|
|
|
|
LI->addTopLevelLoop(Subloop);
|
2011-08-11 07:22:57 +08:00
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
/// 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.
|
2012-08-22 23:37:57 +08:00
|
|
|
NearLoop =
|
|
|
|
SubloopParents.insert(std::make_pair(Subloop, Unloop)).first->second;
|
2011-08-11 07:22:57 +08:00
|
|
|
}
|
|
|
|
|
|
|
|
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();
|
2012-06-26 12:11:38 +08:00
|
|
|
LI.Analyze(getAnalysis<DominatorTree>().getBase());
|
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.
|
2011-08-12 22:54:45 +08:00
|
|
|
for (LoopInfo::iterator I = LI.begin();; ++I) {
|
|
|
|
assert(I != LI.end() && "Couldn't find loop");
|
2011-08-11 07:22:57 +08:00
|
|
|
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();
|
2011-08-12 22:54:45 +08:00
|
|
|
for (Loop::iterator I = ParentLoop->begin();; ++I) {
|
|
|
|
assert(I != ParentLoop->end() && "Couldn't find loop");
|
2011-08-11 07:22:57 +08:00
|
|
|
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;
|
|
|
|
|
2011-08-26 11:06:34 +08:00
|
|
|
DenseSet<const Loop*> Loops;
|
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!");
|
2011-08-26 11:06:34 +08:00
|
|
|
(*I)->verifyLoopNest(&Loops);
|
2009-09-08 23:45:00 +08:00
|
|
|
}
|
2009-09-28 08:27:48 +08:00
|
|
|
|
2011-08-26 11:06:34 +08:00
|
|
|
// Verify that blocks are mapped to valid loops.
|
|
|
|
for (DenseMap<BasicBlock*, Loop*>::const_iterator I = LI.BBMap.begin(),
|
|
|
|
E = LI.BBMap.end(); I != E; ++I) {
|
|
|
|
assert(Loops.count(I->second) && "orphaned loop");
|
|
|
|
assert(I->second->contains(I->first) && "orphaned block");
|
|
|
|
}
|
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) ;
|
|
|
|
}
|