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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: 83790
This commit is contained in:
Chris Lattner 2009-10-11 21:04:37 +00:00
parent 8525f5df9a
commit aafa929524
1 changed files with 14 additions and 1 deletions
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15
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -12681,6 +12681,9 @@ 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();
@ -12727,7 +12730,7 @@ 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
@ -12759,6 +12762,16 @@ 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.
for (std::vector<Instruction*>::reverse_iterator
I = InstrsForInstCombineWorklist.rbegin(),
E = InstrsForInstCombineWorklist.rend(); I != E; ++I)
IC.Worklist.Add(*I);
}
bool InstCombiner::DoOneIteration(Function &F, unsigned Iteration) {