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Rewrite part of the SSAUpdater to be more careful about inserting redundant

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PHIs.  The previous algorithm was unable to reliably detect when existing
PHIs in a cycle can be reused.  I'm still working on reducing a testcase.
Radar 7711900.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@100047 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Bob Wilson
2010-03-31 20:51:00 +00:00
parent 536d31b5b3
commit a0c6057061
2 changed files with 291 additions and 164 deletions
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32
include/llvm/Transforms/Utils/SSAUpdater.h
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@@ -27,22 +27,28 @@ namespace llvm {
/// transformation wants to rewrite a set of uses of one value with uses of a
/// set of values.
class SSAUpdater {
public:
class BBInfo;
private:
/// AvailableVals - This keeps track of which value to use on a per-block
/// basis. When we insert PHI nodes, we keep track of them here. We use
/// TrackingVH's for the value of the map because we RAUW PHI nodes when we
/// eliminate them, and want the TrackingVH's to track this.
//typedef DenseMap<BasicBlock*, TrackingVH<Value> > AvailableValsTy;
/// basis. When we insert PHI nodes, we keep track of them here.
//typedef DenseMap<BasicBlock*, Value*> AvailableValsTy;
void *AV;
/// PrototypeValue is an arbitrary representative value, which we derive names
/// and a type for PHI nodes.
Value *PrototypeValue;
/// IncomingPredInfo - We use this as scratch space when doing our recursive
/// walk. This should only be used in GetValueInBlockInternal, normally it
/// should be empty.
//std::vector<std::pair<BasicBlock*, TrackingVH<Value> > > IncomingPredInfo;
void *IPI;
/// BBMap - The GetValueAtEndOfBlock method maintains this mapping from
/// basic blocks to BBInfo structures.
/// typedef DenseMap<BasicBlock*, BBInfo*> BBMapTy;
void *BM;
/// Allocator - The GetValueAtEndOfBlock method uses this BumpPtrAllocator to
/// hold its internal data. The allocator and its storage is created and
/// discarded for each invocation of GetValueAtEndOfBlock.
void *BPA;
/// InsertedPHIs - If this is non-null, the SSAUpdater adds all PHI nodes that
/// it creates to the vector.
@@ -99,6 +105,14 @@ public:
private:
Value *GetValueAtEndOfBlockInternal(BasicBlock *BB);
void FindPHIPlacement(BasicBlock *BB, BBInfo *Info, bool &Changed,
unsigned Counter);
void FindAvailableVal(BasicBlock *BB, BBInfo *Info, unsigned Counter);
void FindExistingPHI(BasicBlock *BB, BBInfo *Info);
bool CheckIfPHIMatches(BasicBlock *BB, BBInfo *Info, Value *Val);
void RecordMatchingPHI(BasicBlock *BB, BBInfo *Info, PHINode *PHI);
void ClearPHITags(BasicBlock *BB, BBInfo *Info, PHINode *PHI);
void operator=(const SSAUpdater&); // DO NOT IMPLEMENT
SSAUpdater(const SSAUpdater&); // DO NOT IMPLEMENT
};