[llvm-commits] [llvm] r85016 - /llvm/trunk/lib/Transforms/Scalar/LoopRotation.cpp
Dan Gohman
gohman at apple.com
Sat Oct 24 16:19:53 PDT 2009
Author: djg
Date: Sat Oct 24 18:19:52 2009
New Revision: 85016
URL: http://llvm.org/viewvc/llvm-project?rev=85016&view=rev
Log:
Rewrite LoopRotation's SSA updating code using SSAUpdater.
Modified:
llvm/trunk/lib/Transforms/Scalar/LoopRotation.cpp
Modified: llvm/trunk/lib/Transforms/Scalar/LoopRotation.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopRotation.cpp?rev=85016&r1=85015&r2=85016&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LoopRotation.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LoopRotation.cpp Sat Oct 24 18:19:52 2009
@@ -21,6 +21,7 @@
#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
+#include "llvm/Transforms/Utils/SSAUpdater.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/ADT/Statistic.h"
@@ -32,16 +33,6 @@
STATISTIC(NumRotated, "Number of loops rotated");
namespace {
- class RenameData {
- public:
- RenameData(Instruction *O, Value *P, Instruction *H)
- : Original(O), PreHeader(P), Header(H) { }
- public:
- Instruction *Original; // Original instruction
- Value *PreHeader; // Original pre-header replacement
- Instruction *Header; // New header replacement
- };
-
class LoopRotate : public LoopPass {
public:
static char ID; // Pass ID, replacement for typeid
@@ -71,25 +62,12 @@
/// Initialize local data
void initialize();
- /// Make sure all Exit block PHINodes have required incoming values.
- /// If incoming value is constant or defined outside the loop then
- /// PHINode may not have an entry for original pre-header.
- void updateExitBlock();
-
- /// Return true if this instruction is used outside original header.
- bool usedOutsideOriginalHeader(Instruction *In);
-
- /// Find Replacement information for instruction. Return NULL if it is
- /// not available.
- const RenameData *findReplacementData(Instruction *I);
-
/// After loop rotation, loop pre-header has multiple sucessors.
/// Insert one forwarding basic block to ensure that loop pre-header
/// has only one successor.
void preserveCanonicalLoopForm(LPPassManager &LPM);
private:
-
Loop *L;
BasicBlock *OrigHeader;
BasicBlock *OrigPreHeader;
@@ -97,7 +75,6 @@
BasicBlock *NewHeader;
BasicBlock *Exit;
LPPassManager *LPM_Ptr;
- SmallVector<RenameData, MAX_HEADER_SIZE> LoopHeaderInfo;
};
}
@@ -199,168 +176,88 @@
"New header doesn't have one pred!");
FoldSingleEntryPHINodes(NewHeader);
- // Copy PHI nodes and other instructions from the original header
- // into the original pre-header. Unlike the original header, the original
- // pre-header is not a member of the loop.
- //
- // The new loop header is the one and only successor of original header that
- // is inside the loop. All other original header successors are outside
- // the loop. Copy PHI Nodes from the original header into the new loop header.
- // Add second incoming value, from original loop pre-header into these phi
- // nodes. If a value defined in original header is used outside original
- // header then new loop header will need new phi nodes with two incoming
- // values, one definition from original header and second definition is
- // from original loop pre-header.
-
- // Remove terminator from Original pre-header. Original pre-header will
- // receive a clone of original header terminator as a new terminator.
- OrigPreHeader->getInstList().pop_back();
+ // Begin by walking OrigHeader and populating ValueMap with an entry for
+ // each Instruction.
BasicBlock::iterator I = OrigHeader->begin(), E = OrigHeader->end();
- PHINode *PN = 0;
- for (; (PN = dyn_cast<PHINode>(I)); ++I) {
- // PHI nodes are not copied into original pre-header. Instead their values
- // are directly propagated.
- Value *NPV = PN->getIncomingValueForBlock(OrigPreHeader);
-
- // Create a new PHI node with two incoming values for NewHeader.
- // One incoming value is from OrigLatch (through OrigHeader) and the
- // second incoming value is from original pre-header.
- PHINode *NH = PHINode::Create(PN->getType(), PN->getName(),
- NewHeader->begin());
- NH->addIncoming(PN->getIncomingValueForBlock(OrigLatch), OrigHeader);
- NH->addIncoming(NPV, OrigPreHeader);
-
- // "In" can be replaced by NH at various places.
- LoopHeaderInfo.push_back(RenameData(PN, NPV, NH));
- }
+ DenseMap<const Value *, Value *> ValueMap;
- // Now, handle non-phi instructions.
- for (; I != E; ++I) {
- Instruction *In = I;
- assert(!isa<PHINode>(In) && "PHINode is not expected here");
-
- // This is not a PHI instruction. Insert its clone into original pre-header.
- // If this instruction is using a value from same basic block then
- // update it to use value from cloned instruction.
- Instruction *C = In->clone();
- C->setName(In->getName());
- OrigPreHeader->getInstList().push_back(C);
-
- for (unsigned opi = 0, e = In->getNumOperands(); opi != e; ++opi) {
- Instruction *OpInsn = dyn_cast<Instruction>(In->getOperand(opi));
- if (!OpInsn) continue; // Ignore non-instruction values.
- if (const RenameData *D = findReplacementData(OpInsn))
- C->setOperand(opi, D->PreHeader);
- }
+ // For PHI nodes, the value available in OldPreHeader is just the
+ // incoming value from OldPreHeader.
+ for (; PHINode *PN = dyn_cast<PHINode>(I); ++I)
+ ValueMap[PN] = PN->getIncomingValue(PN->getBasicBlockIndex(OrigPreHeader));
- // If this instruction is used outside this basic block then
- // create new PHINode for this instruction.
- Instruction *NewHeaderReplacement = NULL;
- if (usedOutsideOriginalHeader(In)) {
- PHINode *PN = PHINode::Create(In->getType(), In->getName(),
- NewHeader->begin());
- PN->addIncoming(In, OrigHeader);
- PN->addIncoming(C, OrigPreHeader);
- NewHeaderReplacement = PN;
- }
- LoopHeaderInfo.push_back(RenameData(In, C, NewHeaderReplacement));
- }
-
- // Rename uses of original header instructions to reflect their new
- // definitions (either from original pre-header node or from newly created
- // new header PHINodes.
- //
- // Original header instructions are used in
- // 1) Original header:
- //
- // If instruction is used in non-phi instructions then it is using
- // defintion from original heder iteself. Do not replace this use
- // with definition from new header or original pre-header.
- //
- // If instruction is used in phi node then it is an incoming
- // value. Rename its use to reflect new definition from new-preheader
- // or new header.
- //
- // 2) Inside loop but not in original header
- //
- // Replace this use to reflect definition from new header.
- for (unsigned LHI = 0, LHI_E = LoopHeaderInfo.size(); LHI != LHI_E; ++LHI) {
- const RenameData &ILoopHeaderInfo = LoopHeaderInfo[LHI];
-
- if (!ILoopHeaderInfo.Header)
- continue;
-
- Instruction *OldPhi = ILoopHeaderInfo.Original;
- Instruction *NewPhi = ILoopHeaderInfo.Header;
-
- // Before replacing uses, collect them first, so that iterator is
- // not invalidated.
- SmallVector<Instruction *, 16> AllUses;
- for (Value::use_iterator UI = OldPhi->use_begin(), UE = OldPhi->use_end();
- UI != UE; ++UI)
- AllUses.push_back(cast<Instruction>(UI));
-
- for (SmallVector<Instruction *, 16>::iterator UI = AllUses.begin(),
- UE = AllUses.end(); UI != UE; ++UI) {
- Instruction *U = *UI;
- BasicBlock *Parent = U->getParent();
-
- // Used inside original header
- if (Parent == OrigHeader) {
- // Do not rename uses inside original header non-phi instructions.
- PHINode *PU = dyn_cast<PHINode>(U);
- if (!PU)
+ // For the rest of the instructions, create a clone in the OldPreHeader.
+ TerminatorInst *LoopEntryBranch = OrigPreHeader->getTerminator();
+ for (; I != E; ++I) {
+ Instruction *C = I->clone();
+ C->setName(I->getName());
+ C->insertBefore(LoopEntryBranch);
+ ValueMap[I] = C;
+ }
+
+ // Along with all the other instructions, we just cloned OrigHeader's
+ // terminator into OrigPreHeader. Fix up the PHI nodes in each of OrigHeader's
+ // successors by duplicating their incoming values for OrigHeader.
+ TerminatorInst *TI = OrigHeader->getTerminator();
+ for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
+ for (BasicBlock::iterator BI = TI->getSuccessor(i)->begin();
+ PHINode *PN = dyn_cast<PHINode>(BI); ++BI)
+ PN->addIncoming(PN->getIncomingValueForBlock(OrigHeader), OrigPreHeader);
+
+ // Now that OrigPreHeader has a clone of OrigHeader's terminator, remove
+ // OrigPreHeader's old terminator (the original branch into the loop), and
+ // remove the corresponding incoming values from the PHI nodes in OrigHeader.
+ LoopEntryBranch->eraseFromParent();
+ for (I = OrigHeader->begin(); PHINode *PN = dyn_cast<PHINode>(I); ++I)
+ PN->removeIncomingValue(PN->getBasicBlockIndex(OrigPreHeader));
+
+ // Now fix up users of the instructions in OrigHeader, insertting PHI nodes
+ // as necessary.
+ SSAUpdater SSA;
+ for (I = OrigHeader->begin(); I != E; ++I) {
+ Value *OrigHeaderVal = I;
+ Value *OrigPreHeaderVal = ValueMap[OrigHeaderVal];
+
+ // The value now exits in two versions: the initial value in the preheader
+ // and the loop "next" value in the original header.
+ SSA.Initialize(OrigHeaderVal);
+ SSA.AddAvailableValue(OrigHeader, OrigHeaderVal);
+ SSA.AddAvailableValue(OrigPreHeader, OrigPreHeaderVal);
+
+ // Visit each use of the OrigHeader instruction.
+ for (Value::use_iterator UI = OrigHeaderVal->use_begin(),
+ UE = OrigHeaderVal->use_end(); UI != UE; ) {
+ // Grab the use before incrementing the iterator.
+ Use &U = UI.getUse();
+
+ // Increment the iterator before removing the use from the list.
+ ++UI;
+
+ // SSAUpdater can't handle a non-PHI use in the same block as an
+ // earlier def. We can easily handle those cases manually.
+ Instruction *UserInst = cast<Instruction>(U.getUser());
+ if (!isa<PHINode>(UserInst)) {
+ BasicBlock *UserBB = UserInst->getParent();
+
+ // The original users in the OrigHeader are already using the
+ // original definitions.
+ if (UserBB == OrigHeader)
continue;
- // Do not rename uses inside original header phi nodes, if the
- // incoming value is for new header.
- if (PU->getBasicBlockIndex(NewHeader) != -1
- && PU->getIncomingValueForBlock(NewHeader) == U)
+ // Users in the OrigPreHeader need to use the value to which the
+ // original definitions are mapped.
+ if (UserBB == OrigPreHeader) {
+ U = OrigPreHeaderVal;
continue;
-
- U->replaceUsesOfWith(OldPhi, NewPhi);
- continue;
+ }
}
- // Used inside loop, but not in original header.
- if (L->contains(U->getParent())) {
- if (U != NewPhi)
- U->replaceUsesOfWith(OldPhi, NewPhi);
- continue;
- }
-
- // Used inside Exit Block. Since we are in LCSSA form, U must be PHINode.
- if (U->getParent() == Exit) {
- assert(isa<PHINode>(U) && "Use in Exit Block that is not PHINode");
-
- PHINode *UPhi = cast<PHINode>(U);
- // UPhi already has one incoming argument from original header.
- // Add second incoming argument from new Pre header.
- UPhi->addIncoming(ILoopHeaderInfo.PreHeader, OrigPreHeader);
- } else {
- // Used outside Exit block. Create a new PHI node in the exit block
- // to receive the value from the new header and pre-header.
- PHINode *PN = PHINode::Create(U->getType(), U->getName(),
- Exit->begin());
- PN->addIncoming(ILoopHeaderInfo.PreHeader, OrigPreHeader);
- PN->addIncoming(OldPhi, OrigHeader);
- U->replaceUsesOfWith(OldPhi, PN);
- }
+ // Anything else can be handled by SSAUpdater.
+ SSA.RewriteUse(U);
}
}
-
- /// Make sure all Exit block PHINodes have required incoming values.
- updateExitBlock();
- // Update CFG
-
- // Removing incoming branch from loop preheader to original header.
- // Now original header is inside the loop.
- for (BasicBlock::iterator I = OrigHeader->begin();
- (PN = dyn_cast<PHINode>(I)); ++I)
- PN->removeIncomingValue(OrigPreHeader);
-
- // Make NewHeader as the new header for the loop.
+ // NewHeader is now the header of the loop.
L->moveToHeader(NewHeader);
preserveCanonicalLoopForm(LPM);
@@ -369,31 +266,6 @@
return true;
}
-/// Make sure all Exit block PHINodes have required incoming values.
-/// If an incoming value is constant or defined outside the loop then
-/// PHINode may not have an entry for the original pre-header.
-void LoopRotate::updateExitBlock() {
-
- PHINode *PN;
- for (BasicBlock::iterator I = Exit->begin();
- (PN = dyn_cast<PHINode>(I)); ++I) {
-
- // There is already one incoming value from original pre-header block.
- if (PN->getBasicBlockIndex(OrigPreHeader) != -1)
- continue;
-
- const RenameData *ILoopHeaderInfo;
- Value *V = PN->getIncomingValueForBlock(OrigHeader);
- if (isa<Instruction>(V) &&
- (ILoopHeaderInfo = findReplacementData(cast<Instruction>(V)))) {
- assert(ILoopHeaderInfo->PreHeader && "Missing New Preheader Instruction");
- PN->addIncoming(ILoopHeaderInfo->PreHeader, OrigPreHeader);
- } else {
- PN->addIncoming(V, OrigPreHeader);
- }
- }
-}
-
/// Initialize local data
void LoopRotate::initialize() {
L = NULL;
@@ -401,34 +273,6 @@
OrigPreHeader = NULL;
NewHeader = NULL;
Exit = NULL;
-
- LoopHeaderInfo.clear();
-}
-
-/// Return true if this instruction is used by any instructions in the loop that
-/// aren't in original header.
-bool LoopRotate::usedOutsideOriginalHeader(Instruction *In) {
- for (Value::use_iterator UI = In->use_begin(), UE = In->use_end();
- UI != UE; ++UI) {
- BasicBlock *UserBB = cast<Instruction>(UI)->getParent();
- if (UserBB != OrigHeader && L->contains(UserBB))
- return true;
- }
-
- return false;
-}
-
-/// Find Replacement information for instruction. Return NULL if it is
-/// not available.
-const RenameData *LoopRotate::findReplacementData(Instruction *In) {
-
- // Since LoopHeaderInfo is small, linear walk is OK.
- for (unsigned LHI = 0, LHI_E = LoopHeaderInfo.size(); LHI != LHI_E; ++LHI) {
- const RenameData &ILoopHeaderInfo = LoopHeaderInfo[LHI];
- if (ILoopHeaderInfo.Original == In)
- return &ILoopHeaderInfo;
- }
- return NULL;
}
/// After loop rotation, loop pre-header has multiple sucessors.
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