#define DEBUG_TYPE "gvn"
#include "llvm/Transforms/Scalar.h"
-#include "llvm/Constants.h"
-#include "llvm/DerivedTypes.h"
#include "llvm/GlobalVariable.h"
-#include "llvm/Function.h"
#include "llvm/IntrinsicInst.h"
#include "llvm/LLVMContext.h"
-#include "llvm/Operator.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Assembly/Writer.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
-#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Utils/SSAUpdater.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DepthFirstIterator.h"
-#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Support/Allocator.h"
-#include "llvm/Support/CFG.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
-#include "llvm/Support/ErrorHandling.h"
-#include "llvm/Support/GetElementPtrTypeIterator.h"
#include "llvm/Support/IRBuilder.h"
-#include <list>
using namespace llvm;
STATISTIC(NumGVNInstr, "Number of instructions deleted");
ValueTable VN;
- /// NumberTable - A mapping from value numers to lists of Value*'s that
- /// have that value number. Use lookupNumber to query it.
- struct NumberTableEntry {
+ /// LeaderTable - A mapping from value numbers to lists of Value*'s that
+ /// have that value number. Use findLeader to query it.
+ struct LeaderTableEntry {
Value *Val;
BasicBlock *BB;
- NumberTableEntry *Next;
+ LeaderTableEntry *Next;
};
- DenseMap<uint32_t, NumberTableEntry> NumberTable;
+ DenseMap<uint32_t, LeaderTableEntry> LeaderTable;
BumpPtrAllocator TableAllocator;
- /// insert_table - Push a new Value to the NumberTable onto the list for
+ /// addToLeaderTable - Push a new Value to the LeaderTable onto the list for
/// its value number.
- void insert_table(uint32_t N, Value *V, BasicBlock *BB) {
- NumberTableEntry& Curr = NumberTable[N];
+ void addToLeaderTable(uint32_t N, Value *V, BasicBlock *BB) {
+ LeaderTableEntry& Curr = LeaderTable[N];
if (!Curr.Val) {
Curr.Val = V;
Curr.BB = BB;
return;
}
- NumberTableEntry* Node = TableAllocator.Allocate<NumberTableEntry>();
+ LeaderTableEntry* Node = TableAllocator.Allocate<LeaderTableEntry>();
Node->Val = V;
Node->BB = BB;
Node->Next = Curr.Next;
Curr.Next = Node;
}
- /// erase_table - Scan the list of values corresponding to a given value
- /// number, and remove the given value if encountered.
- void erase_table(uint32_t N, Value *V, BasicBlock *BB) {
- NumberTableEntry* Prev = 0;
- NumberTableEntry* Curr = &NumberTable[N];
+ /// removeFromLeaderTable - Scan the list of values corresponding to a given
+ /// value number, and remove the given value if encountered.
+ void removeFromLeaderTable(uint32_t N, Value *V, BasicBlock *BB) {
+ LeaderTableEntry* Prev = 0;
+ LeaderTableEntry* Curr = &LeaderTable[N];
while (Curr->Val != V || Curr->BB != BB) {
Prev = Curr;
Curr->Val = 0;
Curr->BB = 0;
} else {
- NumberTableEntry* Next = Curr->Next;
+ LeaderTableEntry* Next = Curr->Next;
Curr->Val = Next->Val;
Curr->BB = Next->BB;
+ Curr->Next = Next->Next;
}
}
}
void dump(DenseMap<uint32_t, Value*>& d);
bool iterateOnFunction(Function &F);
bool performPRE(Function& F);
- Value *lookupNumber(BasicBlock *BB, uint32_t num);
+ Value *findLeader(BasicBlock *BB, uint32_t num);
void cleanupGlobalSets();
void verifyRemoved(const Instruction *I) const;
bool splitCriticalEdges();
// @1 = getelementptr (i8* p, ...
// test p and branch if == 0
// load @1
- // It is valid to have the getelementptr before the test, even if p can be 0,
- // as getelementptr only does address arithmetic.
+ // It is valid to have the getelementptr before the test, even if p can
+ // be 0, as getelementptr only does address arithmetic.
// If we are not pushing the value through any multiple-successor blocks
// we do not have this case. Otherwise, check that the load is safe to
// put anywhere; this can be improved, but should be conservatively safe.
return false;
}
-// lookupNumber - In order to find a leader for a given value number at a
+// findLeader - In order to find a leader for a given value number at a
// specific basic block, we first obtain the list of all Values for that number,
// and then scan the list to find one whose block dominates the block in
// question. This is fast because dominator tree queries consist of only
// a few comparisons of DFS numbers.
-Value *GVN::lookupNumber(BasicBlock *BB, uint32_t num) {
- NumberTableEntry Vals = NumberTable[num];
+Value *GVN::findLeader(BasicBlock *BB, uint32_t num) {
+ LeaderTableEntry Vals = LeaderTable[num];
if (!Vals.Val) return 0;
Value *Val = 0;
if (isa<Constant>(Val)) return Val;
}
- NumberTableEntry* Next = Vals.Next;
+ LeaderTableEntry* Next = Vals.Next;
while (Next) {
if (DT->dominates(Next->BB, BB)) {
if (isa<Constant>(Next->Val)) return Next->Val;
if (!Changed) {
unsigned Num = VN.lookup_or_add(LI);
- insert_table(Num, LI, LI->getParent());
+ addToLeaderTable(Num, LI, LI->getParent());
}
return Changed;
}
- uint32_t NextNum = VN.getNextUnusedValueNumber();
- unsigned Num = VN.lookup_or_add(I);
-
// For conditions branches, we can perform simple conditional propagation on
// the condition value itself.
if (BranchInst *BI = dyn_cast<BranchInst>(I)) {
- insert_table(Num, I, I->getParent());
-
if (!BI->isConditional() || isa<Constant>(BI->getCondition()))
return false;
BasicBlock *FalseSucc = BI->getSuccessor(1);
if (TrueSucc->getSinglePredecessor())
- insert_table(CondVN,
+ addToLeaderTable(CondVN,
ConstantInt::getTrue(TrueSucc->getContext()),
TrueSucc);
if (FalseSucc->getSinglePredecessor())
- insert_table(CondVN,
+ addToLeaderTable(CondVN,
ConstantInt::getFalse(TrueSucc->getContext()),
FalseSucc);
return false;
}
+
+ // Instructions with void type don't return a value, so there's
+ // no point in trying to find redudancies in them.
+ if (I->getType()->isVoidTy()) return false;
+
+ uint32_t NextNum = VN.getNextUnusedValueNumber();
+ unsigned Num = VN.lookup_or_add(I);
// Allocations are always uniquely numbered, so we can save time and memory
// by fast failing them.
if (isa<AllocaInst>(I) || isa<TerminatorInst>(I) || isa<PHINode>(I)) {
- insert_table(Num, I, I->getParent());
+ addToLeaderTable(Num, I, I->getParent());
return false;
}
// need to do a lookup to see if the number already exists
// somewhere in the domtree: it can't!
if (Num == NextNum) {
- insert_table(Num, I, I->getParent());
+ addToLeaderTable(Num, I, I->getParent());
return false;
}
// Perform fast-path value-number based elimination of values inherited from
// dominators.
- Value *repl = lookupNumber(I->getParent(), Num);
+ Value *repl = findLeader(I->getParent(), Num);
if (repl == 0) {
// Failure, just remember this instance for future use.
- insert_table(Num, I, I->getParent());
+ addToLeaderTable(Num, I, I->getParent());
return false;
}
break;
}
- Value* predV = lookupNumber(P, ValNo);
+ Value* predV = findLeader(P, ValNo);
if (predV == 0) {
PREPred = P;
++NumWithout;
if (isa<Argument>(Op) || isa<Constant>(Op) || isa<GlobalValue>(Op))
continue;
- if (Value *V = lookupNumber(PREPred, VN.lookup(Op))) {
+ if (Value *V = findLeader(PREPred, VN.lookup(Op))) {
PREInstr->setOperand(i, V);
} else {
success = false;
++NumGVNPRE;
// Update the availability map to include the new instruction.
- insert_table(ValNo, PREInstr, PREPred);
+ addToLeaderTable(ValNo, PREInstr, PREPred);
// Create a PHI to make the value available in this block.
PHINode* Phi = PHINode::Create(CurInst->getType(),
}
VN.add(Phi, ValNo);
- insert_table(ValNo, Phi, CurrentBlock);
+ addToLeaderTable(ValNo, Phi, CurrentBlock);
CurInst->replaceAllUsesWith(Phi);
if (Phi->getType()->isPointerTy()) {
MD->invalidateCachedPointerInfo(Phi);
}
VN.erase(CurInst);
- erase_table(ValNo, CurInst, CurrentBlock);
+ removeFromLeaderTable(ValNo, CurInst, CurrentBlock);
DEBUG(dbgs() << "GVN PRE removed: " << *CurInst << '\n');
if (MD) MD->removeInstruction(CurInst);
void GVN::cleanupGlobalSets() {
VN.clear();
- NumberTable.clear();
+ LeaderTable.clear();
TableAllocator.Reset();
}
// Walk through the value number scope to make sure the instruction isn't
// ferreted away in it.
- for (DenseMap<uint32_t, NumberTableEntry>::const_iterator
- I = NumberTable.begin(), E = NumberTable.end(); I != E; ++I) {
- const NumberTableEntry *Node = &I->second;
+ for (DenseMap<uint32_t, LeaderTableEntry>::const_iterator
+ I = LeaderTable.begin(), E = LeaderTable.end(); I != E; ++I) {
+ const LeaderTableEntry *Node = &I->second;
assert(Node->Val != Inst && "Inst still in value numbering scope!");
while (Node->Next) {
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