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populate instcombine's initial worklist more carefully, causing

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it to visit instructions from the start of the function to the
end of the function in the first path.  This greatly speeds up
some pathological cases (e.g. PR5150). 

llvm-svn: 83814
This commit is contained in:
Chris Lattner 2009-10-11 23:17:43 +00:00
parent 4c87d257a4
commit 1a6fbd067a
1 changed files with 26 additions and 1 deletions
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27
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -101,6 +101,20 @@ namespace {
Add(I);
}
/// AddInitialGroup - Add the specified batch of stuff in reverse order.
/// which should only be done when the worklist is empty and when the group
/// has no duplicates.
void AddInitialGroup(Instruction *const *List, unsigned NumEntries) {
assert(Worklist.empty() && "Worklist must be empty to add initial group");
Worklist.reserve(NumEntries+16);
DEBUG(errs() << "IC: ADDING: " << NumEntries << " instrs to worklist\n");
for (; NumEntries; --NumEntries) {
Instruction *I = List[NumEntries-1];
WorklistMap.insert(std::make_pair(I, Worklist.size()));
Worklist.push_back(I);
}
}
// Remove - remove I from the worklist if it exists.
void Remove(Instruction *I) {
DenseMap<Instruction*, unsigned>::iterator It = WorklistMap.find(I);
@ -12663,6 +12677,9 @@ static void AddReachableCodeToWorklist(BasicBlock *BB,
const TargetData *TD) {
SmallVector<BasicBlock*, 256> Worklist;
Worklist.push_back(BB);
std::vector<Instruction*> InstrsForInstCombineWorklist;
InstrsForInstCombineWorklist.reserve(128);
while (!Worklist.empty()) {
BB = Worklist.back();
@ -12709,7 +12726,7 @@ static void AddReachableCodeToWorklist(BasicBlock *BB,
DBI_Prev = 0;
}
IC.Worklist.Add(Inst);
InstrsForInstCombineWorklist.push_back(Inst);
}
// Recursively visit successors. If this is a branch or switch on a
@ -12741,6 +12758,14 @@ static void AddReachableCodeToWorklist(BasicBlock *BB,
for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
Worklist.push_back(TI->getSuccessor(i));
}
// Once we've found all of the instructions to add to instcombine's worklist,
// add them in reverse order. This way instcombine will visit from the top
// of the function down. This jives well with the way that it adds all uses
// of instructions to the worklist after doing a transformation, thus avoiding
// some N^2 behavior in pathological cases.
IC.Worklist.AddInitialGroup(&InstrsForInstCombineWorklist[0],
InstrsForInstCombineWorklist.size());
}
bool InstCombiner::DoOneIteration(Function &F, unsigned Iteration) {