[llvm] r200067 - [LPM] Make LCSSA a utility with a FunctionPass that applies it to all
Chandler Carruth
chandlerc at gmail.com
Fri Jan 24 20:07:24 PST 2014
Author: chandlerc
Date: Fri Jan 24 22:07:24 2014
New Revision: 200067
URL: http://llvm.org/viewvc/llvm-project?rev=200067&view=rev
Log:
[LPM] Make LCSSA a utility with a FunctionPass that applies it to all
the loops in a function, and teach LICM to work in the presance of
LCSSA.
Previously, LCSSA was a loop pass. That made passes requiring it also be
loop passes and unable to depend on function analysis passes easily. It
also caused outer loops to have a different "canonical" form from inner
loops during analysis. Instead, we go into LCSSA form and preserve it
through the loop pass manager run.
Note that this has the same problem as LoopSimplify that prevents
enabling its verification -- loop passes which run at the end of the loop
pass manager and don't preserve these are valid, but the subsequent loop
pass runs of outer loops that do preserve this pass trigger too much
verification and fail because the inner loop no longer verifies.
The other problem this exposed is that LICM was completely unable to
handle LCSSA form. It didn't preserve it and it actually would give up
on moving instructions in many cases when they were used by an LCSSA phi
node. I've taught LICM to support detecting LCSSA-form PHI nodes and to
hoist and sink around them. This may actually let LICM fire
significantly more because we put everything into LCSSA form to rotate
the loop before running LICM. =/ Now LICM should handle that fine and
preserve it correctly. The down side is that LICM has to require LCSSA
in order to preserve it. This is just a fact of life for LCSSA. It's
entirely possible we should completely remove LCSSA from the optimizer.
The test updates are essentially accomodating LCSSA phi nodes in the
output of LICM, and the fact that we now completely sink every
instruction in ashr-crash below the loop bodies prior to unrolling.
With this change, LCSSA is computed only three times in the pass
pipeline. One of them could be removed (and potentially a SCEV run and
a separate LoopPassManager entirely!) if we had a LoopPass variant of
InstCombine that ran InstCombine on the loop body but refused to combine
away LCSSA PHI nodes. Currently, this also prevents loop unrolling from
being in the same loop pass manager is rotate, LICM, and unswitch.
There is one thing that I *really* don't like -- preserving LCSSA in
LICM is quite expensive. We end up having to re-run LCSSA twice for some
loops after LICM runs because LICM can undo LCSSA both in the current
loop and the parent loop. I don't really see good solutions to this
other than to completely move away from LCSSA and using tools like
SSAUpdater instead.
Modified:
llvm/trunk/include/llvm/Transforms/Utils/LoopUtils.h
llvm/trunk/lib/Transforms/Scalar/LICM.cpp
llvm/trunk/lib/Transforms/Utils/LCSSA.cpp
llvm/trunk/test/Transforms/LICM/scalar_promote.ll
llvm/trunk/test/Transforms/LICM/sinking.ll
llvm/trunk/test/Transforms/LoopSimplify/ashr-crash.ll
Modified: llvm/trunk/include/llvm/Transforms/Utils/LoopUtils.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Transforms/Utils/LoopUtils.h?rev=200067&r1=200066&r2=200067&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Transforms/Utils/LoopUtils.h (original)
+++ llvm/trunk/include/llvm/Transforms/Utils/LoopUtils.h Fri Jan 24 22:07:24 2014
@@ -34,6 +34,19 @@ BasicBlock *InsertPreheaderForLoop(Loop
bool simplifyLoop(Loop *L, DominatorTree *DT, LoopInfo *LI, Pass *PP,
AliasAnalysis *AA = 0, ScalarEvolution *SE = 0);
+/// \brief Put loop into LCSSA form.
+///
+/// Looks at all instructions in the loop which have uses outside of the
+/// current loop. For each, an LCSSA PHI node is inserted and the uses outside
+/// the loop are rewritten to use this node.
+///
+/// LoopInfo and DominatorTree are required and preserved.
+///
+/// If ScalarEvolution is passed in, it will be preserved.
+///
+/// Returns true if any modifications are made to the loop.
+bool formLCSSA(Loop &L, DominatorTree &DT, ScalarEvolution *SE = 0);
+
}
#endif
Modified: llvm/trunk/lib/Transforms/Scalar/LICM.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LICM.cpp?rev=200067&r1=200066&r2=200067&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LICM.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LICM.cpp Fri Jan 24 22:07:24 2014
@@ -54,6 +54,7 @@
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetLibraryInfo.h"
#include "llvm/Transforms/Utils/Local.h"
+#include "llvm/Transforms/Utils/LoopUtils.h"
#include "llvm/Transforms/Utils/SSAUpdater.h"
#include <algorithm>
using namespace llvm;
@@ -85,10 +86,12 @@ namespace {
AU.addRequired<DominatorTreeWrapperPass>();
AU.addRequired<LoopInfo>();
AU.addRequiredID(LoopSimplifyID);
+ AU.addPreservedID(LoopSimplifyID);
+ AU.addRequiredID(LCSSAID);
+ AU.addPreservedID(LCSSAID);
AU.addRequired<AliasAnalysis>();
AU.addPreserved<AliasAnalysis>();
AU.addPreserved<ScalarEvolution>();
- AU.addPreservedID(LoopSimplifyID);
AU.addRequired<TargetLibraryInfo>();
}
@@ -193,6 +196,8 @@ INITIALIZE_PASS_BEGIN(LICM, "licm", "Loo
INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
INITIALIZE_PASS_DEPENDENCY(LoopInfo)
INITIALIZE_PASS_DEPENDENCY(LoopSimplify)
+INITIALIZE_PASS_DEPENDENCY(LCSSA)
+INITIALIZE_PASS_DEPENDENCY(ScalarEvolution)
INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfo)
INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
INITIALIZE_PASS_END(LICM, "licm", "Loop Invariant Code Motion", false, false)
@@ -283,6 +288,14 @@ bool LICM::runOnLoop(Loop *L, LPPassMana
PromoteAliasSet(*I, ExitBlocks, InsertPts);
}
+ // If we have successfully changed the loop, re-form LCSSA and also re-form
+ // LCSSA in the parent loop as hoisting or sinking may have broken it.
+ if (Changed) {
+ formLCSSA(*L, *DT, getAnalysisIfAvailable<ScalarEvolution>());
+ if (Loop *ParentL = L->getParentLoop())
+ formLCSSA(*ParentL, *DT, getAnalysisIfAvailable<ScalarEvolution>());
+ }
+
// Clear out loops state information for the next iteration
CurLoop = 0;
Preheader = 0;
@@ -451,6 +464,19 @@ bool LICM::canSinkOrHoistInst(Instructio
return isSafeToExecuteUnconditionally(I);
}
+/// \brief Returns true if a PHINode is a trivially replaceable with an
+/// Instruction.
+///
+/// This is true when all incoming values are that instruction. This pattern
+/// occurs most often with LCSSA PHI nodes.
+static bool isTriviallyReplacablePHI(PHINode &PN, Instruction &I) {
+ for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
+ if (PN.getIncomingValue(i) != &I)
+ return false;
+
+ return true;
+}
+
/// isNotUsedInLoop - Return true if the only users of this instruction are
/// outside of the loop. If this is true, we can sink the instruction to the
/// exit blocks of the loop.
@@ -459,18 +485,48 @@ bool LICM::isNotUsedInLoop(Instruction &
for (Value::use_iterator UI = I.use_begin(), E = I.use_end(); UI != E; ++UI) {
Instruction *User = cast<Instruction>(*UI);
if (PHINode *PN = dyn_cast<PHINode>(User)) {
- // PHI node uses occur in predecessor blocks!
+ // A PHI node where all of the incoming values are this instruction are
+ // special -- they can just be RAUW'ed with the instruction and thus
+ // don't require a use in the predecessor. This is a particular important
+ // special case because it is the pattern found in LCSSA form.
+ if (isTriviallyReplacablePHI(*PN, I)) {
+ if (CurLoop->contains(PN))
+ return false;
+ else
+ continue;
+ }
+
+ // Otherwise, PHI node uses occur in predecessor blocks if the incoming
+ // values. Check for such a use being inside the loop.
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
if (PN->getIncomingValue(i) == &I)
if (CurLoop->contains(PN->getIncomingBlock(i)))
return false;
- } else if (CurLoop->contains(User)) {
- return false;
+
+ continue;
}
+
+ if (CurLoop->contains(User))
+ return false;
}
return true;
}
+static BasicBlock::iterator
+replaceTrivialPHIsAndGetInsertionPt(BasicBlock &BB, Instruction &I) {
+ BasicBlock::iterator II = BB.begin();
+ while (PHINode *PN = dyn_cast<PHINode>(II)) {
+ ++II;
+ if (isTriviallyReplacablePHI(*PN, I)) {
+ PN->replaceAllUsesWith(&I);
+ PN->eraseFromParent();
+ }
+ }
+ if (isa<LandingPadInst>(II))
+ ++II;
+
+ return II;
+}
/// sink - When an instruction is found to only be used outside of the loop,
/// this function moves it to the exit blocks and patches up SSA form as needed.
@@ -502,9 +558,14 @@ void LICM::sink(Instruction &I) {
I.replaceAllUsesWith(UndefValue::get(I.getType()));
I.eraseFromParent();
} else {
+ // Look for any LCSSA PHI nodes for this instruction in the exit blocks
+ // and replace them.
+ BasicBlock::iterator II =
+ replaceTrivialPHIsAndGetInsertionPt(*ExitBlocks[0], I);
+
// Move the instruction to the start of the exit block, after any PHI
// nodes in it.
- I.moveBefore(ExitBlocks[0]->getFirstInsertionPt());
+ I.moveBefore(II);
// This instruction is no longer in the AST for the current loop, because
// we just sunk it out of the loop. If we just sunk it into an outer
@@ -546,8 +607,10 @@ void LICM::sink(Instruction &I) {
if (!DT->dominates(InstOrigBB, ExitBlock))
continue;
- // Insert the code after the last PHI node.
- BasicBlock::iterator InsertPt = ExitBlock->getFirstInsertionPt();
+ // Look for any LCSSA PHI nodes for this instruction in the exit blocks
+ // and replace them. Then get the insertion point after the last PHI.
+ BasicBlock::iterator InsertPt =
+ replaceTrivialPHIsAndGetInsertionPt(*ExitBlock, I);
// If this is the first exit block processed, just move the original
// instruction, otherwise clone the original instruction and insert
Modified: llvm/trunk/lib/Transforms/Utils/LCSSA.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/LCSSA.cpp?rev=200067&r1=200066&r2=200067&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/LCSSA.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/LCSSA.cpp Fri Jan 24 22:07:24 2014
@@ -39,208 +39,95 @@
#include "llvm/IR/Instructions.h"
#include "llvm/Pass.h"
#include "llvm/Support/PredIteratorCache.h"
+#include "llvm/Transforms/Utils/LoopUtils.h"
#include "llvm/Transforms/Utils/SSAUpdater.h"
using namespace llvm;
STATISTIC(NumLCSSA, "Number of live out of a loop variables");
-namespace {
- struct LCSSA : public LoopPass {
- static char ID; // Pass identification, replacement for typeid
- LCSSA() : LoopPass(ID) {
- initializeLCSSAPass(*PassRegistry::getPassRegistry());
- }
-
- // Cached analysis information for the current function.
- DominatorTree *DT;
- LoopInfo *LI;
- ScalarEvolution *SE;
- PredIteratorCache PredCache;
- Loop *L;
-
- virtual bool runOnLoop(Loop *L, LPPassManager &LPM);
-
- /// This transformation requires natural loop information & requires that
- /// loop preheaders be inserted into the CFG. It maintains both of these,
- /// as well as the CFG. It also requires dominator information.
- ///
- virtual void getAnalysisUsage(AnalysisUsage &AU) const {
- AU.setPreservesCFG();
-
- AU.addRequired<DominatorTreeWrapperPass>();
- AU.addRequired<LoopInfo>();
- AU.addPreservedID(LoopSimplifyID);
- AU.addPreserved<ScalarEvolution>();
- }
- private:
- bool ProcessInstruction(Instruction *Inst,
- const SmallVectorImpl<BasicBlock*> &ExitBlocks);
-
- /// verifyAnalysis() - Verify loop nest.
- virtual void verifyAnalysis() const {
- // Check the special guarantees that LCSSA makes.
- assert(L->isLCSSAForm(*DT) && "LCSSA form not preserved!");
- }
- };
-}
-
-char LCSSA::ID = 0;
-INITIALIZE_PASS_BEGIN(LCSSA, "lcssa", "Loop-Closed SSA Form Pass", false, false)
-INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
-INITIALIZE_PASS_DEPENDENCY(LoopInfo)
-INITIALIZE_PASS_END(LCSSA, "lcssa", "Loop-Closed SSA Form Pass", false, false)
-
-Pass *llvm::createLCSSAPass() { return new LCSSA(); }
-char &llvm::LCSSAID = LCSSA::ID;
-
-
-/// BlockDominatesAnExit - Return true if the specified block dominates at least
-/// one of the blocks in the specified list.
-static bool BlockDominatesAnExit(BasicBlock *BB,
- const SmallVectorImpl<BasicBlock*> &ExitBlocks,
- DominatorTree *DT) {
- DomTreeNode *DomNode = DT->getNode(BB);
- for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i)
- if (DT->dominates(DomNode, DT->getNode(ExitBlocks[i])))
- return true;
-
- return false;
-}
-
-
-/// runOnFunction - Process all loops in the function, inner-most out.
-bool LCSSA::runOnLoop(Loop *TheLoop, LPPassManager &LPM) {
- L = TheLoop;
-
- DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
- LI = &getAnalysis<LoopInfo>();
- SE = getAnalysisIfAvailable<ScalarEvolution>();
-
- // Get the set of exiting blocks.
- SmallVector<BasicBlock*, 8> ExitBlocks;
- L->getExitBlocks(ExitBlocks);
-
- if (ExitBlocks.empty())
- return false;
-
- // 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;
-}
-
-/// isExitBlock - Return true if the specified block is in the list.
+/// Return true if the specified block is in the list.
static bool isExitBlock(BasicBlock *BB,
- const SmallVectorImpl<BasicBlock*> &ExitBlocks) {
+ const SmallVectorImpl<BasicBlock *> &ExitBlocks) {
for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i)
if (ExitBlocks[i] == BB)
return true;
return false;
}
-/// ProcessInstruction - Given an instruction in the loop, check to see if it
-/// has any uses that are outside the current loop. If so, insert LCSSA PHI
-/// nodes and rewrite the uses.
-bool LCSSA::ProcessInstruction(Instruction *Inst,
- const SmallVectorImpl<BasicBlock*> &ExitBlocks) {
- SmallVector<Use*, 16> UsesToRewrite;
-
- BasicBlock *InstBB = Inst->getParent();
-
- for (Value::use_iterator UI = Inst->use_begin(), E = Inst->use_end();
- UI != E; ++UI) {
+/// Given an instruction in the loop, check to see if it has any uses that are
+/// outside the current loop. If so, insert LCSSA PHI nodes and rewrite the
+/// uses.
+static bool processInstruction(Loop &L, Instruction &Inst, DominatorTree &DT,
+ const SmallVectorImpl<BasicBlock *> &ExitBlocks,
+ PredIteratorCache &PredCache) {
+ SmallVector<Use *, 16> UsesToRewrite;
+
+ BasicBlock *InstBB = Inst.getParent();
+
+ for (Value::use_iterator UI = Inst.use_begin(), E = Inst.use_end(); UI != E;
+ ++UI) {
User *U = *UI;
BasicBlock *UserBB = cast<Instruction>(U)->getParent();
if (PHINode *PN = dyn_cast<PHINode>(U))
UserBB = PN->getIncomingBlock(UI);
-
- if (InstBB != UserBB && !L->contains(UserBB))
+
+ if (InstBB != UserBB && !L.contains(UserBB))
UsesToRewrite.push_back(&UI.getUse());
}
// If there are no uses outside the loop, exit with no change.
- if (UsesToRewrite.empty()) return false;
-
+ if (UsesToRewrite.empty())
+ return false;
+
++NumLCSSA; // We are applying the transformation
// Invoke instructions are special in that their result value is not available
- // along their unwind edge. The code below tests to see whether DomBB dominates
+ // along their unwind edge. The code below tests to see whether DomBB
+ // dominates
// the value, so adjust DomBB to the normal destination block, which is
// effectively where the value is first usable.
- BasicBlock *DomBB = Inst->getParent();
- if (InvokeInst *Inv = dyn_cast<InvokeInst>(Inst))
+ BasicBlock *DomBB = Inst.getParent();
+ if (InvokeInst *Inv = dyn_cast<InvokeInst>(&Inst))
DomBB = Inv->getNormalDest();
- DomTreeNode *DomNode = DT->getNode(DomBB);
+ DomTreeNode *DomNode = DT.getNode(DomBB);
- SmallVector<PHINode*, 16> AddedPHIs;
+ SmallVector<PHINode *, 16> AddedPHIs;
SSAUpdater SSAUpdate;
- SSAUpdate.Initialize(Inst->getType(), Inst->getName());
-
+ SSAUpdate.Initialize(Inst.getType(), Inst.getName());
+
// Insert the LCSSA phi's into all of the exit blocks dominated by the
// value, and add them to the Phi's map.
- for (SmallVectorImpl<BasicBlock*>::const_iterator BBI = ExitBlocks.begin(),
- BBE = ExitBlocks.end(); BBI != BBE; ++BBI) {
+ for (SmallVectorImpl<BasicBlock *>::const_iterator BBI = ExitBlocks.begin(),
+ BBE = ExitBlocks.end();
+ BBI != BBE; ++BBI) {
BasicBlock *ExitBB = *BBI;
- if (!DT->dominates(DomNode, DT->getNode(ExitBB))) continue;
-
+ if (!DT.dominates(DomNode, DT.getNode(ExitBB)))
+ continue;
+
// If we already inserted something for this BB, don't reprocess it.
- if (SSAUpdate.HasValueForBlock(ExitBB)) continue;
-
- PHINode *PN = PHINode::Create(Inst->getType(),
- PredCache.GetNumPreds(ExitBB),
- Inst->getName()+".lcssa",
- ExitBB->begin());
+ if (SSAUpdate.HasValueForBlock(ExitBB))
+ continue;
+
+ PHINode *PN = PHINode::Create(Inst.getType(), PredCache.GetNumPreds(ExitBB),
+ Inst.getName() + ".lcssa", ExitBB->begin());
// Add inputs from inside the loop for this PHI.
for (BasicBlock **PI = PredCache.GetPreds(ExitBB); *PI; ++PI) {
- PN->addIncoming(Inst, *PI);
+ PN->addIncoming(&Inst, *PI);
// If the exit block has a predecessor not within the loop, arrange for
// the incoming value use corresponding to that predecessor to be
// rewritten in terms of a different LCSSA PHI.
- if (!L->contains(*PI))
+ if (!L.contains(*PI))
UsesToRewrite.push_back(
- &PN->getOperandUse(
- PN->getOperandNumForIncomingValue(PN->getNumIncomingValues()-1)));
+ &PN->getOperandUse(PN->getOperandNumForIncomingValue(
+ PN->getNumIncomingValues() - 1)));
}
AddedPHIs.push_back(PN);
-
+
// Remember that this phi makes the value alive in this block.
SSAUpdate.AddAvailableValue(ExitBB, PN);
}
@@ -257,15 +144,14 @@ bool LCSSA::ProcessInstruction(Instructi
if (PHINode *PN = dyn_cast<PHINode>(User))
UserBB = PN->getIncomingBlock(*UsesToRewrite[i]);
- if (isa<PHINode>(UserBB->begin()) &&
- isExitBlock(UserBB, ExitBlocks)) {
+ if (isa<PHINode>(UserBB->begin()) && isExitBlock(UserBB, ExitBlocks)) {
// Tell the VHs that the uses changed. This updates SCEV's caches.
if (UsesToRewrite[i]->get()->hasValueHandle())
ValueHandleBase::ValueIsRAUWd(*UsesToRewrite[i], UserBB->begin());
UsesToRewrite[i]->set(UserBB->begin());
continue;
}
-
+
// Otherwise, do full PHI insertion.
SSAUpdate.RewriteUse(*UsesToRewrite[i]);
}
@@ -275,7 +161,152 @@ bool LCSSA::ProcessInstruction(Instructi
if (AddedPHIs[i]->use_empty())
AddedPHIs[i]->eraseFromParent();
}
-
+
return true;
}
+/// Return true if the specified block dominates at least
+/// one of the blocks in the specified list.
+static bool
+blockDominatesAnExit(BasicBlock *BB,
+ DominatorTree &DT,
+ const SmallVectorImpl<BasicBlock *> &ExitBlocks) {
+ DomTreeNode *DomNode = DT.getNode(BB);
+ for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i)
+ if (DT.dominates(DomNode, DT.getNode(ExitBlocks[i])))
+ return true;
+
+ return false;
+}
+
+bool llvm::formLCSSA(Loop &L, DominatorTree &DT, ScalarEvolution *SE) {
+ bool Changed = false;
+
+ // Get the set of exiting blocks.
+ SmallVector<BasicBlock *, 8> ExitBlocks;
+ L.getExitBlocks(ExitBlocks);
+
+ if (ExitBlocks.empty())
+ return false;
+
+ PredIteratorCache PredCache;
+
+ // Look at all the instructions in the loop, checking to see if they have uses
+ // outside the loop. If so, rewrite those uses.
+ for (Loop::block_iterator BBI = L.block_begin(), BBE = L.block_end();
+ BBI != BBE; ++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, DT, ExitBlocks))
+ 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;
+
+ Changed |= processInstruction(L, *I, DT, ExitBlocks, PredCache);
+ }
+ }
+
+ // 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 && Changed)
+ SE->forgetLoop(&L);
+
+ assert(L.isLCSSAForm(DT));
+
+ return Changed;
+}
+
+namespace {
+struct LCSSA : public FunctionPass {
+ static char ID; // Pass identification, replacement for typeid
+ LCSSA() : FunctionPass(ID) {
+ initializeLCSSAPass(*PassRegistry::getPassRegistry());
+ }
+
+ // Cached analysis information for the current function.
+ DominatorTree *DT;
+ LoopInfo *LI;
+ ScalarEvolution *SE;
+
+ virtual bool runOnFunction(Function &F);
+
+ /// This transformation requires natural loop information & requires that
+ /// loop preheaders be inserted into the CFG. It maintains both of these,
+ /// as well as the CFG. It also requires dominator information.
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.setPreservesCFG();
+
+ AU.addRequired<DominatorTreeWrapperPass>();
+ AU.addRequired<LoopInfo>();
+ AU.addPreservedID(LoopSimplifyID);
+ AU.addPreserved<ScalarEvolution>();
+ }
+
+private:
+ bool processLoop(Loop &L);
+
+ virtual void verifyAnalysis() const;
+};
+}
+
+char LCSSA::ID = 0;
+INITIALIZE_PASS_BEGIN(LCSSA, "lcssa", "Loop-Closed SSA Form Pass", false, false)
+INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
+INITIALIZE_PASS_DEPENDENCY(LoopInfo)
+INITIALIZE_PASS_END(LCSSA, "lcssa", "Loop-Closed SSA Form Pass", false, false)
+
+Pass *llvm::createLCSSAPass() { return new LCSSA(); }
+char &llvm::LCSSAID = LCSSA::ID;
+
+
+/// Process all loops in the function, inner-most out.
+bool LCSSA::runOnFunction(Function &F) {
+ bool Changed = false;
+ LI = &getAnalysis<LoopInfo>();
+ DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
+ SE = getAnalysisIfAvailable<ScalarEvolution>();
+
+ // Simplify each loop nest in the function.
+ for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I)
+ Changed |= processLoop(**I);
+
+ return Changed;
+}
+
+/// Process a loop nest depth first.
+bool LCSSA::processLoop(Loop &L) {
+ bool Changed = false;
+
+ // Recurse depth-first through inner loops.
+ for (Loop::iterator LI = L.begin(), LE = L.end(); LI != LE; ++LI)
+ Changed |= processLoop(**LI);
+
+ Changed |= formLCSSA(L, *DT, SE);
+ return Changed;
+}
+
+static void verifyLoop(Loop &L, DominatorTree &DT) {
+ // Recurse depth-first through inner loops.
+ for (Loop::iterator LI = L.begin(), LE = L.end(); LI != LE; ++LI)
+ verifyLoop(**LI, DT);
+
+ // Check the special guarantees that LCSSA makes.
+ //assert(L.isLCSSAForm(DT) && "LCSSA form not preserved!");
+}
+
+void LCSSA::verifyAnalysis() const {
+ // Verify each loop nest in the function, assuming LI still points at that
+ // function's loop info.
+ for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I)
+ verifyLoop(**I, *DT);
+}
Modified: llvm/trunk/test/Transforms/LICM/scalar_promote.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LICM/scalar_promote.ll?rev=200067&r1=200066&r2=200067&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/LICM/scalar_promote.ll (original)
+++ llvm/trunk/test/Transforms/LICM/scalar_promote.ll Fri Jan 24 22:07:24 2014
@@ -24,7 +24,8 @@ Loop: ; preds = %Loop, %0
Out:
ret void
; CHECK: Out:
-; CHECK-NEXT: store i32 %x2, i32* @X
+; CHECK-NEXT: %[[LCSSAPHI:.*]] = phi i32 [ %x2
+; CHECK-NEXT: store i32 %[[LCSSAPHI]], i32* @X
; CHECK-NEXT: ret void
}
@@ -48,7 +49,8 @@ Loop: ; preds = %Loop, %0
Exit: ; preds = %Loop
ret void
; CHECK: Exit:
-; CHECK-NEXT: store i32 %V, i32* getelementptr inbounds (i32* @X, i64 1)
+; CHECK-NEXT: %[[LCSSAPHI:.*]] = phi i32 [ %V
+; CHECK-NEXT: store i32 %[[LCSSAPHI]], i32* getelementptr inbounds (i32* @X, i64 1)
; CHECK-NEXT: ret void
}
@@ -142,7 +144,8 @@ Loop: ; preds = %Loop, %0
Out:
ret void
; CHECK: Out:
-; CHECK-NEXT: store i32 %x2, i32* @X
+; CHECK-NEXT: %[[LCSSAPHI:.*]] = phi i32 [ %x2
+; CHECK-NEXT: store i32 %[[LCSSAPHI]], i32* @X
; CHECK-NEXT: ret void
}
@@ -178,7 +181,8 @@ for.end:
; CHECK: for.body.lr.ph:
; CHECK-NEXT: %gi.promoted = load i32* %gi, align 4, !tbaa !0
; CHECK: for.cond.for.end_crit_edge:
-; CHECK-NEXT: store i32 %inc, i32* %gi, align 4, !tbaa !0
+; CHECK-NEXT: %[[LCSSAPHI:.*]] = phi i32 [ %inc
+; CHECK-NEXT: store i32 %[[LCSSAPHI]], i32* %gi, align 4, !tbaa !0
}
!0 = metadata !{metadata !4, metadata !4, i64 0}
Modified: llvm/trunk/test/Transforms/LICM/sinking.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LICM/sinking.ll?rev=200067&r1=200066&r2=200067&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/LICM/sinking.ll (original)
+++ llvm/trunk/test/Transforms/LICM/sinking.ll Fri Jan 24 22:07:24 2014
@@ -76,7 +76,8 @@ Out: ; preds = %Loop
ret i32 %tmp.7
; CHECK-LABEL: @test4(
; CHECK: Out:
-; CHECK-NEXT: mul i32 %N, %N_addr.0.pn
+; CHECK-NEXT: %[[LCSSAPHI:.*]] = phi i32 [ %N_addr.0.pn
+; CHECK-NEXT: mul i32 %N, %[[LCSSAPHI]]
; CHECK-NEXT: sub i32 %tmp.6, %N
; CHECK-NEXT: ret i32
}
@@ -152,12 +153,14 @@ Out2: ; preds = %ContLoop
ret i32 %tmp.7
; CHECK-LABEL: @test7(
; CHECK: Out1:
-; CHECK-NEXT: mul i32 %N, %N_addr.0.pn
+; CHECK-NEXT: %[[LCSSAPHI:.*]] = phi i32 [ %N_addr.0.pn
+; CHECK-NEXT: mul i32 %N, %[[LCSSAPHI]]
; CHECK-NEXT: sub i32 %tmp.6, %N
; CHECK-NEXT: ret
; CHECK: Out2:
-; CHECK-NEXT: mul i32 %N, %N_addr.0.pn
-; CHECK-NEXT: sub i32 %tmp.6
+; CHECK-NEXT: %[[LCSSAPHI:.*]] = phi i32 [ %N_addr.0.pn
+; CHECK-NEXT: mul i32 %N, %[[LCSSAPHI]]
+; CHECK-NEXT: sub i32 %tmp.6.le, %N
; CHECK-NEXT: ret
}
@@ -183,7 +186,8 @@ exit2: ; preds = %Cont
; CHECK: exit1:
; CHECK-NEXT: ret i32 0
; CHECK: exit2:
-; CHECK-NEXT: %V = add i32 %X, 1
+; CHECK-NEXT: %[[LCSSAPHI:.*]] = phi i32 [ %X
+; CHECK-NEXT: %V = add i32 %[[LCSSAPHI]], 1
; CHECK-NEXT: ret i32 %V
}
@@ -229,7 +233,8 @@ Out: ; preds = %Loop
; CHECK-LABEL: @test10(
; CHECK: Out:
-; CHECK-NEXT: %tmp.6 = sdiv i32 %N, %N_addr.0.pn
+; CHECK-NEXT: %[[LCSSAPHI:.*]] = phi i32 [ %N_addr.0.pn
+; CHECK-NEXT: %tmp.6 = sdiv i32 %N, %[[LCSSAPHI]]
; CHECK-NEXT: ret i32 %tmp.6
}
Modified: llvm/trunk/test/Transforms/LoopSimplify/ashr-crash.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopSimplify/ashr-crash.ll?rev=200067&r1=200066&r2=200067&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/LoopSimplify/ashr-crash.ll (original)
+++ llvm/trunk/test/Transforms/LoopSimplify/ashr-crash.ll Fri Jan 24 22:07:24 2014
@@ -23,15 +23,15 @@ target triple = "x86_64-apple-macosx"
@b = common global i32 0, align 4
; Check that the def-use chain that leads to the bad SCEV is still
-; there, and part of it is hoisted to the entry block.
+; there.
;
; CHECK-LABEL: @foo
; CHECK-LABEL: entry:
-; CHECK: %cmp4
; CHECK-LABEL: for.cond1.preheader:
; CHECK-LABEL: for.body3:
-; CHECK: %1 = zext i1 %cmp4 to i32
-; CHECK: %xor = xor i32 %1, 1
+; CHECK: %cmp4
+; CHECK: %conv = zext i1 %cmp4 to i32
+; CHECK: %xor = xor i32 %conv6, 1
define void @foo() {
entry:
br label %for.cond
More information about the llvm-commits
mailing list