[llvm-commits] [llvm] r122120 - /llvm/trunk/lib/Analysis/LazyValueInfo.cpp
Nick Lewycky
nicholas at mxc.ca
Fri Dec 17 17:00:40 PST 2010
Author: nicholas
Date: Fri Dec 17 19:00:40 2010
New Revision: 122120
URL: http://llvm.org/viewvc/llvm-project?rev=122120&view=rev
Log:
Make LazyValueInfo non-recursive.
Modified:
llvm/trunk/lib/Analysis/LazyValueInfo.cpp
Modified: llvm/trunk/lib/Analysis/LazyValueInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/LazyValueInfo.cpp?rev=122120&r1=122119&r2=122120&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/LazyValueInfo.cpp (original)
+++ llvm/trunk/lib/Analysis/LazyValueInfo.cpp Fri Dec 17 19:00:40 2010
@@ -29,6 +29,7 @@
#include "llvm/ADT/STLExtras.h"
#include <map>
#include <set>
+#include <stack>
using namespace llvm;
char LazyValueInfo::ID = 0;
@@ -296,8 +297,8 @@
typedef std::map<AssertingVH<BasicBlock>, LVILatticeVal> ValueCacheEntryTy;
private:
- /// LVIValueHandle - A callback value handle update the cache when
- /// values are erased.
+ /// LVIValueHandle - A callback value handle update the cache when
+ /// values are erased.
struct LVIValueHandle : public CallbackVH {
LazyValueInfoCache *Parent;
@@ -319,9 +320,20 @@
/// for cache updating.
std::set<std::pair<AssertingVH<BasicBlock>, Value*> > OverDefinedCache;
- LVILatticeVal &getCachedEntryForBlock(Value *Val, BasicBlock *BB);
LVILatticeVal getBlockValue(Value *Val, BasicBlock *BB);
- LVILatticeVal getEdgeValue(Value *V, BasicBlock *F, BasicBlock *T);
+ bool getEdgeValue(Value *V, BasicBlock *F, BasicBlock *T,
+ LVILatticeVal &Result);
+ bool hasBlockValue(Value *Val, BasicBlock *BB);
+
+ // These methods process one work item and may add more. A false value
+ // returned means that the work item was not completely processed and must
+ // be revisited after going through the new items.
+ bool solveBlockValue(Value *Val, BasicBlock *BB);
+ bool solveBlockValueNonLocal(Value *Val, BasicBlock *BB);
+ bool solveBlockValuePHINode(PHINode *PN, BasicBlock *BB);
+ bool solveBlockValueConstantRange(Instruction *BBI, BasicBlock *BB);
+
+ void solve();
ValueCacheEntryTy &lookup(Value *V) {
return ValueCache[LVIValueHandle(V, this)];
@@ -332,7 +344,17 @@
if (L.isOverdefined()) OverDefinedCache.insert(std::make_pair(BB, V));
return Cache[BB] = L;
}
+ LVILatticeVal setBlockValue(Value *V, BasicBlock *BB, LVILatticeVal L) {
+ return setBlockValue(V, BB, L, lookup(V));
+ }
+ struct BlockStackEntry {
+ BlockStackEntry(Value *Val, BasicBlock *BB) : Val(Val), BB(BB) {}
+ Value *Val;
+ BasicBlock *BB;
+ };
+ std::stack<BlockStackEntry> block_value_stack;
+
public:
/// getValueInBlock - This is the query interface to determine the lattice
/// value for the specified Value* at the end of the specified block.
@@ -389,14 +411,41 @@
I->second.erase(BB);
}
+void LazyValueInfoCache::solve() {
+ while (!block_value_stack.empty()) {
+ BlockStackEntry &e = block_value_stack.top();
+ if (solveBlockValue(e.Val, e.BB))
+ block_value_stack.pop();
+ }
+}
+
+bool LazyValueInfoCache::hasBlockValue(Value *Val, BasicBlock *BB) {
+ // If already a constant, there is nothing to compute.
+ if (isa<Constant>(Val))
+ return true;
+
+ return lookup(Val).count(BB);
+}
+
LVILatticeVal LazyValueInfoCache::getBlockValue(Value *Val, BasicBlock *BB) {
+ // If already a constant, there is nothing to compute.
+ if (Constant *VC = dyn_cast<Constant>(Val))
+ return LVILatticeVal::get(VC);
+
+ return lookup(Val)[BB];
+}
+
+bool LazyValueInfoCache::solveBlockValue(Value *Val, BasicBlock *BB) {
+ if (isa<Constant>(Val))
+ return true;
+
ValueCacheEntryTy &Cache = lookup(Val);
LVILatticeVal &BBLV = Cache[BB];
-
+
// If we've already computed this block's value, return it.
if (!BBLV.isUndefined()) {
DEBUG(dbgs() << " reuse BB '" << BB->getName() << "' val=" << BBLV <<'\n');
- return BBLV;
+ return true;
}
// Otherwise, this is the first time we're seeing this block. Reset the
@@ -406,88 +455,13 @@
Instruction *BBI = dyn_cast<Instruction>(Val);
if (BBI == 0 || BBI->getParent() != BB) {
- LVILatticeVal Result; // Start Undefined.
-
- // If this is a pointer, and there's a load from that pointer in this BB,
- // then we know that the pointer can't be NULL.
- bool NotNull = false;
- if (Val->getType()->isPointerTy()) {
- for (BasicBlock::iterator BI = BB->begin(), BE = BB->end();BI != BE;++BI){
- LoadInst *L = dyn_cast<LoadInst>(BI);
- if (L && L->getPointerAddressSpace() == 0 &&
- GetUnderlyingObject(L->getPointerOperand()) ==
- GetUnderlyingObject(Val)) {
- NotNull = true;
- break;
- }
- }
- }
-
- unsigned NumPreds = 0;
- // Loop over all of our predecessors, merging what we know from them into
- // result.
- for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
- Result.mergeIn(getEdgeValue(Val, *PI, BB));
-
- // If we hit overdefined, exit early. The BlockVals entry is already set
- // to overdefined.
- if (Result.isOverdefined()) {
- DEBUG(dbgs() << " compute BB '" << BB->getName()
- << "' - overdefined because of pred.\n");
- // If we previously determined that this is a pointer that can't be null
- // then return that rather than giving up entirely.
- if (NotNull) {
- const PointerType *PTy = cast<PointerType>(Val->getType());
- Result = LVILatticeVal::getNot(ConstantPointerNull::get(PTy));
- }
-
- return setBlockValue(Val, BB, Result, Cache);
- }
- ++NumPreds;
- }
-
-
- // If this is the entry block, we must be asking about an argument. The
- // value is overdefined.
- if (NumPreds == 0 && BB == &BB->getParent()->front()) {
- assert(isa<Argument>(Val) && "Unknown live-in to the entry block");
- Result.markOverdefined();
- return setBlockValue(Val, BB, Result, Cache);
- }
-
- // Return the merged value, which is more precise than 'overdefined'.
- assert(!Result.isOverdefined());
- return setBlockValue(Val, BB, Result, Cache);
+ return solveBlockValueNonLocal(Val, BB);
}
-
- // If this value is defined by an instruction in this block, we have to
- // process it here somehow or return overdefined.
+
if (PHINode *PN = dyn_cast<PHINode>(BBI)) {
- LVILatticeVal Result; // Start Undefined.
-
- // Loop over all of our predecessors, merging what we know from them into
- // result.
- for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
- Value *PhiVal = PN->getIncomingValueForBlock(*PI);
- Result.mergeIn(getValueOnEdge(PhiVal, *PI, BB));
-
- // If we hit overdefined, exit early. The BlockVals entry is already set
- // to overdefined.
- if (Result.isOverdefined()) {
- DEBUG(dbgs() << " compute BB '" << BB->getName()
- << "' - overdefined because of pred.\n");
- return setBlockValue(Val, BB, Result, Cache);
- }
- }
-
- // Return the merged value, which is more precise than 'overdefined'.
- assert(!Result.isOverdefined());
- return setBlockValue(Val, BB, Result, Cache);
+ return solveBlockValuePHINode(PN, BB);
}
- assert(Cache[BB].isOverdefined() &&
- "Recursive query changed our cache?");
-
// We can only analyze the definitions of certain classes of instructions
// (integral binops and casts at the moment), so bail if this isn't one.
LVILatticeVal Result;
@@ -496,9 +470,10 @@
DEBUG(dbgs() << " compute BB '" << BB->getName()
<< "' - overdefined because inst def found.\n");
Result.markOverdefined();
- return setBlockValue(Val, BB, Result, Cache);
+ setBlockValue(Val, BB, Result, Cache);
+ return true;
}
-
+
// FIXME: We're currently limited to binops with a constant RHS. This should
// be improved.
BinaryOperator *BO = dyn_cast<BinaryOperator>(BBI);
@@ -507,30 +482,155 @@
<< "' - overdefined because inst def found.\n");
Result.markOverdefined();
- return setBlockValue(Val, BB, Result, Cache);
- }
+ setBlockValue(Val, BB, Result, Cache);
+ return true;
+ }
+
+ return solveBlockValueConstantRange(BBI, BB);
+}
+
+static bool InstructionDereferencesPointer(Instruction *I, Value *Ptr) {
+ if (LoadInst *L = dyn_cast<LoadInst>(I)) {
+ return L->getPointerAddressSpace() == 0 &&
+ GetUnderlyingObject(L->getPointerOperand()) ==
+ GetUnderlyingObject(Ptr);
+ }
+ if (StoreInst *S = dyn_cast<StoreInst>(I)) {
+ return S->getPointerAddressSpace() == 0 &&
+ GetUnderlyingObject(S->getPointerOperand()) ==
+ GetUnderlyingObject(Ptr);
+ }
+ // FIXME: llvm.memset, etc.
+ return false;
+}
+
+bool LazyValueInfoCache::solveBlockValueNonLocal(Value *Val, BasicBlock *BB) {
+ LVILatticeVal Result; // Start Undefined.
+
+ // If this is a pointer, and there's a load from that pointer in this BB,
+ // then we know that the pointer can't be NULL.
+ bool NotNull = false;
+ if (Val->getType()->isPointerTy()) {
+ for (BasicBlock::iterator BI = BB->begin(), BE = BB->end();BI != BE;++BI){
+ if (InstructionDereferencesPointer(BI, Val)) {
+ NotNull = true;
+ break;
+ }
+ }
+ }
+
+ // If this is the entry block, we must be asking about an argument. The
+ // value is overdefined.
+ if (BB == &BB->getParent()->getEntryBlock()) {
+ assert(isa<Argument>(Val) && "Unknown live-in to the entry block");
+ if (NotNull) {
+ const PointerType *PTy = cast<PointerType>(Val->getType());
+ Result = LVILatticeVal::getNot(ConstantPointerNull::get(PTy));
+ } else {
+ Result.markOverdefined();
+ }
+ setBlockValue(Val, BB, Result);
+ return true;
+ }
+ // Loop over all of our predecessors, merging what we know from them into
+ // result.
+ bool EdgesMissing = false;
+ for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
+ LVILatticeVal EdgeResult;
+ EdgesMissing |= !getEdgeValue(Val, *PI, BB, EdgeResult);
+ if (EdgesMissing)
+ continue;
+
+ Result.mergeIn(EdgeResult);
+
+ // If we hit overdefined, exit early. The BlockVals entry is already set
+ // to overdefined.
+ if (Result.isOverdefined()) {
+ DEBUG(dbgs() << " compute BB '" << BB->getName()
+ << "' - overdefined because of pred.\n");
+ // If we previously determined that this is a pointer that can't be null
+ // then return that rather than giving up entirely.
+ if (NotNull) {
+ const PointerType *PTy = cast<PointerType>(Val->getType());
+ Result = LVILatticeVal::getNot(ConstantPointerNull::get(PTy));
+ }
+ setBlockValue(Val, BB, Result);
+ return true;
+ }
+ }
+ if (EdgesMissing)
+ return false;
+
+ // Return the merged value, which is more precise than 'overdefined'.
+ assert(!Result.isOverdefined());
+ setBlockValue(Val, BB, Result);
+ return true;
+}
+
+bool LazyValueInfoCache::solveBlockValuePHINode(PHINode *PN, BasicBlock *BB) {
+ LVILatticeVal Result; // Start Undefined.
+
+ // Loop over all of our predecessors, merging what we know from them into
+ // result.
+ bool EdgesMissing = false;
+ for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
+ BasicBlock *PhiBB = PN->getIncomingBlock(i);
+ Value *PhiVal = PN->getIncomingValue(i);
+ LVILatticeVal EdgeResult;
+ EdgesMissing |= !getEdgeValue(PhiVal, PhiBB, BB, EdgeResult);
+ if (EdgesMissing)
+ continue;
+
+ Result.mergeIn(EdgeResult);
+
+ // If we hit overdefined, exit early. The BlockVals entry is already set
+ // to overdefined.
+ if (Result.isOverdefined()) {
+ DEBUG(dbgs() << " compute BB '" << BB->getName()
+ << "' - overdefined because of pred.\n");
+ setBlockValue(PN, BB, Result);
+ return true;
+ }
+ }
+ if (EdgesMissing)
+ return false;
+
+ // Return the merged value, which is more precise than 'overdefined'.
+ assert(!Result.isOverdefined() && "Possible PHI in entry block?");
+ setBlockValue(PN, BB, Result);
+ return true;
+}
+
+bool LazyValueInfoCache::solveBlockValueConstantRange(Instruction *BBI,
+ BasicBlock *BB) {
// Figure out the range of the LHS. If that fails, bail.
- LVILatticeVal LHSVal = getValueInBlock(BBI->getOperand(0), BB);
+ if (!hasBlockValue(BBI->getOperand(0), BB)) {
+ block_value_stack.push(BlockStackEntry(BBI->getOperand(0), BB));
+ return false;
+ }
+
+ LVILatticeVal Result;
+ LVILatticeVal LHSVal = getBlockValue(BBI->getOperand(0), BB);
if (!LHSVal.isConstantRange()) {
Result.markOverdefined();
- return setBlockValue(Val, BB, Result, Cache);
+ setBlockValue(BBI, BB, Result);
+ return true;
}
- ConstantInt *RHS = 0;
ConstantRange LHSRange = LHSVal.getConstantRange();
ConstantRange RHSRange(1);
const IntegerType *ResultTy = cast<IntegerType>(BBI->getType());
if (isa<BinaryOperator>(BBI)) {
- RHS = dyn_cast<ConstantInt>(BBI->getOperand(1));
- if (!RHS) {
+ if (ConstantInt *RHS = dyn_cast<ConstantInt>(BBI->getOperand(1))) {
+ RHSRange = ConstantRange(RHS->getValue());
+ } else {
Result.markOverdefined();
- return setBlockValue(Val, BB, Result, Cache);
+ setBlockValue(BBI, BB, Result);
+ return true;
}
-
- RHSRange = ConstantRange(RHS->getValue(), RHS->getValue()+1);
}
-
+
// NOTE: We're currently limited by the set of operations that ConstantRange
// can evaluate symbolically. Enhancing that set will allows us to analyze
// more definitions.
@@ -580,14 +680,19 @@
break;
}
- return setBlockValue(Val, BB, Result, Cache);
+ setBlockValue(BBI, BB, Result);
+ return true;
}
-
/// getEdgeValue - This method attempts to infer more complex
-LVILatticeVal LazyValueInfoCache::getEdgeValue(Value *Val,
- BasicBlock *BBFrom,
- BasicBlock *BBTo) {
+bool LazyValueInfoCache::getEdgeValue(Value *Val, BasicBlock *BBFrom,
+ BasicBlock *BBTo, LVILatticeVal &Result) {
+ // If already a constant, there is nothing to compute.
+ if (Constant *VC = dyn_cast<Constant>(Val)) {
+ Result = LVILatticeVal::get(VC);
+ return true;
+ }
+
// TODO: Handle more complex conditionals. If (v == 0 || v2 < 1) is false, we
// know that v != 0.
if (BranchInst *BI = dyn_cast<BranchInst>(BBFrom->getTerminator())) {
@@ -601,9 +706,11 @@
// If V is the condition of the branch itself, then we know exactly what
// it is.
- if (BI->getCondition() == Val)
- return LVILatticeVal::get(ConstantInt::get(
+ if (BI->getCondition() == Val) {
+ Result = LVILatticeVal::get(ConstantInt::get(
Type::getInt1Ty(Val->getContext()), isTrueDest));
+ return true;
+ }
// If the condition of the branch is an equality comparison, we may be
// able to infer the value.
@@ -614,30 +721,35 @@
// We know that V has the RHS constant if this is a true SETEQ or
// false SETNE.
if (isTrueDest == (ICI->getPredicate() == ICmpInst::ICMP_EQ))
- return LVILatticeVal::get(cast<Constant>(ICI->getOperand(1)));
- return LVILatticeVal::getNot(cast<Constant>(ICI->getOperand(1)));
+ Result = LVILatticeVal::get(cast<Constant>(ICI->getOperand(1)));
+ else
+ Result = LVILatticeVal::getNot(cast<Constant>(ICI->getOperand(1)));
+ return true;
}
-
+
if (ConstantInt *CI = dyn_cast<ConstantInt>(ICI->getOperand(1))) {
// Calculate the range of values that would satisfy the comparison.
ConstantRange CmpRange(CI->getValue(), CI->getValue()+1);
ConstantRange TrueValues =
ConstantRange::makeICmpRegion(ICI->getPredicate(), CmpRange);
-
+
// If we're interested in the false dest, invert the condition.
if (!isTrueDest) TrueValues = TrueValues.inverse();
// Figure out the possible values of the query BEFORE this branch.
LVILatticeVal InBlock = getBlockValue(Val, BBFrom);
- if (!InBlock.isConstantRange())
- return LVILatticeVal::getRange(TrueValues);
-
+ if (!InBlock.isConstantRange()) {
+ Result = LVILatticeVal::getRange(TrueValues);
+ return true;
+ }
+
// Find all potential values that satisfy both the input and output
// conditions.
ConstantRange PossibleValues =
TrueValues.intersectWith(InBlock.getConstantRange());
-
- return LVILatticeVal::getRange(PossibleValues);
+
+ Result = LVILatticeVal::getRange(PossibleValues);
+ return true;
}
}
}
@@ -649,9 +761,8 @@
if (SI->getCondition() == Val) {
// We don't know anything in the default case.
if (SI->getDefaultDest() == BBTo) {
- LVILatticeVal Result;
Result.markOverdefined();
- return Result;
+ return true;
}
// We only know something if there is exactly one value that goes from
@@ -664,42 +775,48 @@
EdgeVal = SI->getCaseValue(i);
}
assert(EdgeVal && "Missing successor?");
- if (NumEdges == 1)
- return LVILatticeVal::get(EdgeVal);
+ if (NumEdges == 1) {
+ Result = LVILatticeVal::get(EdgeVal);
+ return true;
+ }
}
}
// Otherwise see if the value is known in the block.
- return getBlockValue(Val, BBFrom);
+ if (hasBlockValue(Val, BBFrom)) {
+ Result = getBlockValue(Val, BBFrom);
+ return true;
+ }
+ block_value_stack.push(BlockStackEntry(Val, BBFrom));
+ return false;
}
LVILatticeVal LazyValueInfoCache::getValueInBlock(Value *V, BasicBlock *BB) {
- // If already a constant, there is nothing to compute.
- if (Constant *VC = dyn_cast<Constant>(V))
- return LVILatticeVal::get(VC);
-
DEBUG(dbgs() << "LVI Getting block end value " << *V << " at '"
<< BB->getName() << "'\n");
+ block_value_stack.push(BlockStackEntry(V, BB));
+ solve();
LVILatticeVal Result = getBlockValue(V, BB);
-
+
DEBUG(dbgs() << " Result = " << Result << "\n");
return Result;
}
LVILatticeVal LazyValueInfoCache::
getValueOnEdge(Value *V, BasicBlock *FromBB, BasicBlock *ToBB) {
- // If already a constant, there is nothing to compute.
- if (Constant *VC = dyn_cast<Constant>(V))
- return LVILatticeVal::get(VC);
-
DEBUG(dbgs() << "LVI Getting edge value " << *V << " from '"
<< FromBB->getName() << "' to '" << ToBB->getName() << "'\n");
- LVILatticeVal Result = getEdgeValue(V, FromBB, ToBB);
-
+ LVILatticeVal Result;
+ if (!getEdgeValue(V, FromBB, ToBB, Result)) {
+ solve();
+ bool WasFastQuery = getEdgeValue(V, FromBB, ToBB, Result);
+ (void)WasFastQuery;
+ assert(WasFastQuery && "More work to do after problem solved?");
+ }
+
DEBUG(dbgs() << " Result = " << Result << "\n");
-
return Result;
}
@@ -747,7 +864,7 @@
// Remove it from the caches.
ValueCacheEntryTy &Entry = ValueCache[LVIValueHandle(*I, this)];
ValueCacheEntryTy::iterator CI = Entry.find(ToUpdate);
-
+
assert(CI != Entry.end() && "Couldn't find entry to update?");
Entry.erase(CI);
OverDefinedCache.erase(OI);
@@ -756,7 +873,7 @@
// blocks successors too.
changed = true;
}
-
+
if (!changed) continue;
worklist.insert(worklist.end(), succ_begin(ToUpdate), succ_end(ToUpdate));
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